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Restek Technical Articles

Editorials

Using Guard Columns and Retention Gaps in GC (Part 2)

< Added, February, 2008

Guard columns & retention gaps are used widely in gas chromatography (GC) but the differences between them are not always understood. Part 2 of this two-part editorial by Jaap de Zeeuw discusses guard columns & introduces a new segment coating technology that allows retention gaps & guard columns to be built directly in the same piece of tubing as the analytical column.
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Using Guard Columns and Retention Gaps in GC (Part 1)

Guard columns & retention gaps are used widely in gas chromatography (GC) but the differences between them are not always understood. Part 1 of this two-part editorial by Jaap de Zeeuw reviews the use of retention gaps & discusses critical factors affecting performance. This sets the background for Part 2, which details guard columns & introduces a new segment coating technology that allows retention gaps & guard columns to be built directly in the same piece of tubing as the analytical column.
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Retention Cross-over Phenomenon in Gas Chromatography

Can the Mystery Be Revealed?

Dr. Werner Engewald discusses the phenomenon of cross-over, or changes in elution order following modification of the GC temperature program. This effect has been observed for decades but the physio-chemical background still is not well understood. In this article Dr. Engewald explores the theory and potential explanations for the cross-over phenomenon.
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Restek: A Company of Owners

By Paul Silvis, Restek Founder & former Head Coach

In this editorial, founder and former CEO Paul Silvis explains some of the reasons for Restek’s success as a provider of chromatography columns and supplies. Restek will continue to be successful because, as an employee-owned company, we hold our future in our own hands. Customers will benefit because we can continue to respond to their ideas for the products and services they need to make their work easier.
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Sample Preparation Techniques Used for Gas Chromatography

Guest Editorial by Robert L. Grob, Ph.D.

Sample preparation principles and techniques for gas chromatography are reviewed. Techniques include: static headspace, dynamic headspace, solid phase extraction and microextraction, distillation, stir bar sorptive extraction, Soxhlet, accelerated solvent extraction, pressurized liquid extraction, subcritical water extraction, microwave assisted extraction, ultrasonic extraction, and supercritical fluid extraction.
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Comprehensive 2D Gas Chromatography — Making GC Separations Work Harder

Guest editor Dr. Phil Marriott tells us the three primary contributions ascribed to GCxGC are greater separation capacity, greater sensitivity, and a data presentation that permits identification of related compounds based on the molecular properties that control retention. The most significant advantage is separation power: to be able to resolve many more compounds immediately enables a much more complete ‘picture’ of the composition of a sample.
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Preventive Maintenance for GC

Professor Jennings explains the consequences of ignoring those enclosures included with a new column, and offers simple, proven, preventive maintenance options that help avoid downtime.
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The "Replacement" Column, A Recurring Problem in Gas Chromatography

In his first contribution to the Restek Advantage Professor Walter Jennings discusses why analysts often encounter problems when replacing a capillary GC column, and provides a solution.
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Chemical/Petrochemical

Stable Sulfur & Mercury Sampling in Refineries

Using Siltek® and Sulfinert® Surface Treated Components

< Added, February, 2008

Refinery and natural gas samples often contain trace amounts of sulfur- and mercury-containing compounds, which can interfere with reactions, poison catalysts in petrochemical processes, and damage equipment. Because these compounds quickly react with stainless steel surfaces, accurate determination of these compounds is impossible when samples are collected and stored in untreated sample cylinders. Restek's Siltek® and Sulfinert® passivation techniques bond an inert layer into the surface of stainless steel, preventing active compounds from reacting with or adsorbing to the steel.
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Selecting a GC Column for Glycerin in Biodiesel

< Added, February, 2008

Fused silica columns traditionally have been used for analyzing glycerin in biodiesel, but metal columns offer significant performance advantages. How can analysts determine which column is best for their lab? Here we compare fused silica and metal column performance for total glycerin analysis of biodiesel and offer guidelines for column selection.
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Complete Resolution of Benzene from Ethanol in Spark Ignition Fuels

Using a Modified ASTM D3606-06e1 Method and Rt™-D3606 Column Set

If you have concerns about analyzing reformulated fuels containing ethanol, our new two-column set is the solution—it completely resolves benzene from ethanol. The aromatic compounds, too, are fully resolved, and can easily be quantified, using sec-butanol as an internal standard. The robust column set is ready to use after only a 10 minute carrier gas purge at ambient temperature, followed by a 30 minute hold at 165°C.
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How Good is Your PONA Column?

Data-Based Decisions Help Simplify the Choice

We evaluated our 100 meter x 0.25mm ID x 0.5df PONA column and equivalent columns from four other vendors, following ASTM D-6730 methodology (hydrogen carrier gas). Data and chromatograms presented here show that only the Restek PONA column performed to method specifications admirably. Column efficiency exceeded specification.
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Parker ChromGas® Hydrogen Generators

Relative to helium as the GC carrier gas, hydrogen from a gas generator reduces gas costs, cuts analysis time by 50%, and reduces temperatures needed for eluting analytes — which increases column lifetime. Parker ChromGas® hydrogen generators are safe, convenient, reliable, and easy to use.
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High Temp. Stability Problem Solved with New Metal Columns

Analysis of Total Glycerides in Biodiesel Oils by ASTM D-6584 Using the New MXT®-Biodiesel TG Capillary Column

The high temperatures required for biodiesel analysis by gas chromatography present a considerable challenge to analytical columns. Fused silica columns, even those rated for high-temperature tolerance, breakdown relatively quickly. Restek’s new MXT®-Biodiesel columns are more stable up to 430°C and offer excellent chromatography for glycerides. These columns are available in two configurations: factory-coupled to a 0.53mm retention gap, or with a built-in, leak-proof Integra-Gap™ retention gap.
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Fast, Accurate FAMEs Analyses of Biodiesel Fuel

Using a Stabilwax® Capillary GC Column

As biodiesel fuel continues to stimulate interest worldwide as an energy source, several gas chromatographic methods have been developed to determine the quality of B100 fuel. Here we show excellent peak symmetry, resolution, and reproducibility for determining the fatty acid methyl ester (FAME) and linolenic acid methyl ester content in B100 biodiesel fuel, using European standard method EN 14103 on a Stabilwax® fused silica GC column.
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Separate Argon from Oxygen Above Ambient Temperatures

Using an Rt-Msieve™ 5A PLOT Column

A Restek PLOT column can be your best solution for difficult separations of gaseous analytes. Rt-Msieve™ 5A PLOT columns offer fast, efficient separation of argon/oxygen, hydrogen/helium, and other permanent gases, including permanent gases in refinery or natural gas. You can make difficult separations without subambient temperatures, e.g.: separate oxygen from argon to baseline in approximately 4 minutes.
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Biodiesel Analysis by European Methodology

Exceptional Peak Symmetry, Using an Rtx®-Biodiesel GC Column

Glycerin is a notoriously difficult challenge in GC, particularly at the levels involved in biodiesel oil analysis, but an Rtx®-Biodiesel column provides a symmetric peak that makes quantification easier and more reliable. The column performs well at elevated temperatures: peaks for glycerin and glycerides exhibit minimal tailing, and bleed is low at 370°C, as specified in European method DIN EN14105.
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Analyze Biodiesel Oil for Glycerin

Using Restek’s Robust Rtx®-Biodiesel Capillary GC Column

We challenged our Rtx®-Biodiesel column with analysis for glycerin in biodiesel according to method ASTM D-6584-00. Excellent linearity was established for glycerin, triolein, monolein, and diolein, with r2 values exceeding the method criteria for all compounds. Mono-, di-, and triglycerides resolved well from other compounds in B100 biodiesel oil. Column performance was strong at high temperatures, with low bleed even at 380°C. An Alumaseal™ connector and guard column were used to extend column life.
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GC Analysis of Total Reduced Sulfurs at ppbv Levels Using an Rxi™-1ms Column and Sulfur Chemiluminescence Detection:

Ultra-low bleed and exceptional inertness assure complete separation of sulfur compounds (hydrogen sulfide, carbonyl sulfide, dimethyl sulfide, mercaptans) on our new column, with excellent peak shapes and reliable quantification at ppbv levels. A Sulfinert® treated sampling/transfer system assures no adsorption losses of these very reactive compounds.
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Sulfinert®-Treated Sample Cylinders Store Active Sulfur Compounds at ppb Levels:

Recovery of a 17ppbv test standard of hydrogen sulfide exceeded 85% after 54 hours in a Sulfinert®-treated cylinder; recoveries of methyl mercaptan, ethyl mercaptan, carbonyl sulfide, and dimethyl disulfide exceeded 90%. A Sulfinert®-treated sampling/transfer system can assure accurate sulfur content data for natural gas, beverage-grade carbon dioxide, or other samples.
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Analyze Hydrocarbons on OPN/Res-Sil™ C Bonded GC Packing:

In process GC analyses, this material offers unique selectivity for the difficult-to-separate saturated and unsaturated C4 hydrocarbons, eluting cis-2-butene before 1,3-butadiene. Innovative bonding chemistry assures batch-to-batch reproducibility, excellent thermal stability, and long column life.
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Res-Sil™ C Packings for Analyses of Light Hydrocarbons:

n-Octane on Res-Sil™ C packing provides excellent, reproducible separations of volatile hydrocarbons in petroleum products, including the difficult-to-separate saturated and unsaturated C4 compounds. An OPN on Res-Sil™ C column separates C1-C5 hydrocarbons in half the time required by alternative columns.
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Clinical/Forensics/Toxicology

Accurate, Reproducible Amphetamines Analysis

Clean Up Procedure Improves Chromatography and Reduces Maintenance

< Added, February, 2008

Analyzing amphetamines by GC/MS can be challenging whether they are derivatized or underivatized. Here we evaluate the effects of several sample pretreatment methods. The resulting method reported here produces symmetric peaks while reducing the amount of contamination that can enter the GC system. This method ensures accurate area count reproducibility, a clean GC system, and a stable baseline, even for GC/MS work.
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Fast, Sensitive Analysis of Benzodiazepines by LC/MS/MS

Quantify an Order of Magnitude below Typical Methods

< Added, February, 2008

An LC/MS/MS method for benzodiazepines was developed and offers several advantages over other techniques: minimal sample preparation, fast analysis times, multiple reaction monitoring transitions for quantification and confirmation, and sensitivity down to 0.10-10ng/mL. This method uses the Allure® PFP Propyl stationary phase, which retains compounds long enough to minimize matrix interferences and chromatographically separate compounds that share the same precursor ion.
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Simplify and Speed Up Opiates Analysis

Using LC/MS/MS & an Allure® PFP Propyl HPLC Column

The analysis of opiates typically requires derivatization when using gas chromatography/mass spectrometry (GC/MS), which leads to longer sample preparation time. An alternative liquid chromatography tandem mass spectrometry (LC/MS/MS) method presented here eliminates sample derivatization and offers fast analysis times, resulting in increased sample throughput. In addition, the Allure® PFP Propyl column used here produces baseline resolution for compounds that have very similar mass spectra.
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Why Derivatize?

Improve GC Separations with Derivatization

Derivatizing compounds is often necessary to obtain acceptable, reproducible results. Here we review reasons for derivatization and the three basic types of derivatization reactions for gas chromatography: silylation, acylation, and alkylation. An example procedure for derivatizing hormones, including chromatography, is given.
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GC Inlet Liner Deactivations for Basic Drug Analysis

Basic drugs can interact with active sites on the surface of the inlet liner, reducing responses. The combination of a base-deactivated liner and a base-deactivated Rtx®-5Amine column ensures the greatest responses in analyses for these compounds.
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Analyze and Confirm Cannabinoids by LC/MS/MS

Using an Allure® Biphenyl Column

Use an Allure® Biphenyl column, with a Shimadzu Prominence chromatograph and an API MS/MS 3200 detector, to quantify 1ng levels of cannabinoid analytes in underivatized sample and separate Δ9-THC and cannabidiol to baseline in less than 5 minutes. The unique separation mechanism, π-π interaction, greatly improves selectivity and retention, relative to C18 phases. If you use an electrospray interface, you can use higher amounts of methanol in the mobile phase, to increase sensitivity.
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Reliably Confirm Cannabinoids by GC/MS

Using a 12m x 0.20mm ID 0.33µm Rxi®-5ms Column

Screening for evidence of marijuana use is typically done using an immunoassay method to detect derivatives in urine, but confirmation of positive results requires GC/MS. Here we describe a GC/MS method, using an Rxi®-5ms column, that resolves all major cannabinoid metabolites to baseline and exhibits very low bleed, even at 300°C. We also prolonged column life by baking at 340°C to remove derivatization by-products.
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Fast Screening and Confirmation for Gamma-Hydroxybutyrate (GHB):

Using Restek Columns in Headspace GC or GC/MS Systems

We adapted Rtx®-BAC1 and Rtx®-BAC2 columns, with their proven performance in blood alcohol analysis, to a screening procedure for GHB, followed by confirmation and quantification on a highly inert Rxi®-5ms column. Use of a system and column already in use for blood alcohol analysis eliminates the need for additional equipment, reduces system maintenance, and allows rapid and reliable screening, confirmation, and quantification.
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Drugs of Abuse Analytical Reference Materials:

These exempted materials include amphetamine and methamphetamine, barbiturates, benzodiazepines, cannabidiol and cannabinol, cocaine/cocaine metabolites, methadone/methadone metabolites, opiates/opiate metabolites, and other drugs, a range of blood alcohol standards from 0.010g/dl to 0.4g/dl, and a blood alcohol resolution control standard.
Find out more about: Exempted Drug of Abuse Reference Materials Blood Alcohol Standards Blood Alcohol Mix Resolution Control Standard

Rapid Analysis of Steroid Hormones by GC/MS:

Using the New Rxi®-1ms Column

GC/MS analysis of urinary steroid hormones is a demanding application, and the Rxi®-1ms column meets the requirements for low bleed and inertness better than any column we have tested. We analyzed a variety of derivatized steroid sex hormones in less than 25 minutes, with excellent resolution and symmetric peaks. At 300°C or above, bleed from the Rxi®-1ms column was negligible.
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GC Inlet Liner Deactivations for Basic Drug Analysis:

Sensitive GC/MS Analysis for Drugs of Abuse:

An Rxi®-5ms column will resolve acidic/neutral or free basic drugs under one set of conditions. There is no interference from column bleed — not even at 330°C. This is one of the first published applications for our new family of Rxi® columns.
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Rapid, Sensitive HPLC/TOF-MS Analysis for Cocaine:

A high-organic mobile phase and an Allure™ PFP Propyl column offers adequate retention, short analysis times, and excellent sensitivity for cocaine and cocaine metabolites, without mobile phase modifiers. Target compounds are eluted within 3 minutes, with excellent sensitivity at 5.0pg on-column.
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Environmental

Fast, Simple Sample Cleanup

Using QuEChERS SPE Tubes

< Added, February, 2008

Quick, Easy, Cheap, Effective, Rugged, and Safe, the QuEChERS ("catchers") method for extracting pesticides from food is based on USDA research and employs a novel dispersive solid phase extraction cleanup (dSPE). QuEChERS methods are convenient, rugged methods that simplify extract cleanup, reduce material costs, and improve sample throughput. Here we demonstrate the effectiveness of QuEChERS sample cleanup using a multiresidue analysis of pesticides on strawberries.
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Enhancing Air Monitoring Methods with Thermal Desorption

< Added, February, 2008

The use of carbon disulfide (CS2) extraction as an air monitoring method for vapor-phase organic compounds (VOCs) is fundamentally limited with respect to detection limits. Thermal desorption (TD) is a complementary gas extraction technique whereby sorbent tubes are heated in a flow of carrier gas. Trapped vapors desorb from the sample tubes into the gas stream and are transferred into the GC/MS analyzer. Here, we summarize the key advantages of thermal desorption versus solvent extraction.
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13 Minute Chlorophenoxyacid Herbicides Analysis

On New Rtx®-CLPesticides & Rtx®-CLPesticides2 Columns

< Added, February, 2008

The Rtx®-CLPesticides and Rtx®-CLPesticides2 column pair is an excellent choice for chlorophenoxyacid herbicide analysis. Now, with an optimized film thickness for the 0.32mm ID version, this difficult analysis can be made in less than 13 minutes on both the primary and confirmation columns. Near baseline resolution is achieved for all analytes except for bentazon/picloram on the Rtx®-CLPesticides column; however, this pair is fully resolved on the Rtx®-CLPesticides2.
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Accurately Quantify PAHs Down to 5pg On-Column

GC/MS SIM Analysis with the New Rxi®-5Sil MS Column

< Added, February, 2008

Semivolatiles methods, such as EPA Method 8270, place stringent demands on gas chromatography (GC) columns. Here we demonstrate the performance of Rxi®-5Sil MS columns for semivolatiles analysis in terms of bleed, efficiency, and activity. Excellent sensitivity and resolution are seen, even for difficult PAHs such as benzo(b)fluoranthene & benzo(k)fluoranthene, and indeno(1,2,3-cd)pyrene and dibenzo(a,h)anthracene. Both basic and acidic compounds show good response even at low levels.
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Fast, Accurate Semivolatiles Analysis!

Using New Rxi®-5Sil MS GC Columns

Semivolatiles methods, such as EPA Method 8270, place stringent demands on gas chromatography (GC) columns. Here we evaluate the performance of Rxi®-5Sil MS columns for semivolatiles analysis in terms of bleed, efficiency, and activity. We demonstrate excellent sensitivity and resolution, even for difficult PAHs such as benzo(b)fluoranthene & benzo(k)fluoranthene, and indeno(1,2,3-cd)pyrene and dibenzo(a,h)anthracene. Both basic and acidic compounds show good response even at low levels.
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Complete Resolution of 13 Difficult Carbonyls

Using the New Allure® AK HPLC Column

The new Allure® AK HPLC column was developed specifically for the analysis of aldehydes and ketones, including the 13 carbonyl compounds specified in the California Air Resources Board (CARB) Method 1004. The data shown in this article demonstrate excellent resolution, even of buteraldehyde and methyl ethyl ketone (MEK), in less than 12 minutes using a 200mm Allure® AK HPLC column.
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Faster Organochlorine Pesticide Sample Throughput

On New Rtx®-CLPesticides & Rtx®-CLPesticides2 Columns

Increasing sample throughput is an effective way to reduce operating costs for environmental labs. Here we introduce new film thicknesses for the Rtx®-CLPesticide and Rtx®-CLPesticide2 GC columns, optimized for complete separations and short analysis times. Using these new columns, all US EPA Method 8081 organochlorine pesticides are resolved in <9 min. We also show complete separation of these compounds in <5 min. using these columns and a Gerstel MACH column heating system.
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Resolving the Benzo(j)fluoranthene Challenge

Separate New PAHs Quickly Using the Rxi®-17 GC Column

Polynuclear aromatic hydrocarbons are a significant, and wide-spread, source of pollution. The US EPA mandates testing of the 16 PAHs they designate as most hazardous; the target list in other countries is expanding and includes new compounds that are difficult to separate. Here we demonstrate the ability of the Rxi®-17 column to effectively resolve dibenzo pyrene isomers, as well as to separate benzo(j)fluoranthene from benzo(b)fluoranthene and benzo(k)fluoranthene.
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8-Minute Dual Column Analysis of Organochlorine Pesticides

Using Rtx®-CLPesticides / Rtx®-CLPesticides2 Columns

Unique selectivities make the Rtx®-CLPesticides / Rtx®-CLPesticides2 column pair an excellent choice for analyzing pesticides by US EPA Method 8081, or equivalent methods. A 0.53mm ID guard column allows sample injection onto high-efficiency 20m x 0.18mm ID thin film columns, for baseline resolution in greatly reduced analysis time. Sharp, symmetric peaks help assure reliable quantification data.
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Separate Explosives and Propellant Residues

Using Ultra C18 and Pinnacle™ II Biphenyl Columns

We recently reassessed the performance of our current column offerings relative to the recently revised explosives/propellants method, US EPA Method 8330B. Based on this study, we continue to recommend using the Ultra C18 and Pinnacle™ II Biphenyl column pair as primary and confirmation columns respectively. Both columns provide excellent resolution of all target analytes, including the new ones, and their differing selectivity provides a true confirmation analysis.
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Superior Chromatography for Semivolatile Organics

Using the Rtx®-5Sil MS Capillary GC Column

Combining an optimized stationary phase and deactivation that assures unsurpassed inertness and excellent responses for active analytes, Rtx®-5Sil MS columns address the challenging demands of semivolatiles analyses. Phenyl rings in the polymer backbone stiffen the siloxane chain, ensuring thermal stability and reducing bleed. Selectivity is similar to that of conventional 5% diphenyl phases, but improved, e.g.: separation of isomers benzo(b)- and benzo(k)fluoranthene is increased.
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8-Minute Dual Column Analysis of Organochlorine Pesticides

Using Rtx®-CLPesticides / Rtx®-CLPesticides2 Columns

High Throughput of Semivolatiles Samples by GC/MS

Using a 20m x 0.18mm x 0.30µm Rxi®-5ms Column

We developed the 20m x 0.18mm x 0.30µm Rxi®-5ms column to balance the demand for shorter analysis times with the need to maintain both column capacity and column efficiency. Here we establish conditions for eluting more than 90 semivolatiles, including 7 surrogates and 6 internal standards, in less than 12 minutes. Benzo(b) and benzo(k)fluoranthene were resolved well and sample throughput was improved by 75%. This highly inert, low bleed column is ideal for GC/MS analysis.
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Resolving Benzo(j)fluoranthene from Other PAHs

Using a Pinnacle™ II PAH Column

Nineteen polycyclic aromatic hydrocarbons (PAHs), including benzo(b) and benzo(j)fluoranthene, were fully resolved using a Pinnacle™ II PAH column. Greater sensitivity was achieved by coupling UV and fluorescence detection. This HPLC method offers improved resolution compared to standard GC techniques.
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Analysis of Brominated Flame Retardants on an Rxi®-5ms Column

Optimizing Method Conditions to Reliably Quantify BFRs

Brominated flame retardants are an analytical challenge because high temperatures are required to elute them from the GC column, but elevated temperatures can also can debrominate them, leading to extraneous peaks and poor peak shape. Excellent resolution and peak symmetry for BDE-209 and other EPA Method 527 BFRs were achieved using an Rxi®-5ms column below 300°C. Column bleed was low and chromatography was excellent — even for the comprehensive Wellington mix.
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Enhanced Resolution of Endocrine Disrupting Hormones:

Using an Allure™ Biphenyl Column and LC-TOFMS

An Allure™ Biphenyl column provides superior separations of endocrine-disrupting steroid sex hormones, based on π-π interactions. The secondary separation power of the Unique® TOFMS system and software allows column dimensions and run conditions to be optimized to reduce analysis time, while maintaining qualitative identification.
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New Rxi®-1ms Capillary GC Column:

For Low Level GC/MS Analyses

Our new, nonpolar, 100% dimethyl polysiloxane Rxi®-1ms column offers the same superior inertness, ultra-low bleed, and excellent batch to batch reproducibility exhibited by our Rxi®-5ms column. We analyzed a complex mixture of semivolatile analytes, including both acidic and basic compounds, at levels as low as 0.5ng on column. The selectivity, analyte breakdown, peak symmetry, and bleed results shown here are strong recommendations for the new column.
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Low-Level GC/MS for Semivolatiles in Drinking Water Excellent Responses at 10ng On Column, Using an Rxi®-5ms Column:

Using this new column, resolution and peak shapes for 88 semivolatile compounds commonly analyzed in drinking water are exceptionally good at 10ng each on column. Because the Rxi®-5ms column performs well with analytes in a diverse range of chemical classes, we highly recommend it for analyzing complex mixtures of semivolatiles.
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Fast, Sensitive LC/MS/MS Analysis of Paraquat and Diquat Using an API 3200™ Mass Spectrometer and an Ultra Quat HPLC Column:

Developed through collaboration with scientists at AB/MDS Sciex, this analysis allows complete resolution of paraquat and diquat with a simple, isocratic mobile phase. It is significantly faster than conventional methodologies and, with detection limits of 5ppb for paraquat or 0.1ppb for diquat, sensitivity is superior — without preconcentration.
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Analytical Reference Materials for Semivolatile Pollutants:

Drinking Water: US EPA Method 525.2

Listed reference mixes include organochlorine pesticides, organonitrogen pesticides, organophosphorus pesticides, PCB congeners, internal standards, surrogates, a performance check mix, and more.
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Reliable Quantification of Brominated Flame Retardants by GC/MS:

New Rxi®-5ms Column Minimizes PBDE Breakdown and Peak Skewing

Exceptionally inert, an Rxi®-5ms column separates thermally labile polybrominated diphenyl ethers (PBDEs) with minimal on-column breakdown or peak skewing. Of special interest is the column’s superior performance with BDE-209, a widely used PBDE particularly susceptible to debromination, whose analysis often is characterized by very poor peak shape and extraneous peaks from breakdown products.
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Excellent Responses in GC/MS Analysis of Semivolatiles:

The newest members of our new line of Rxi® columns, Rxi®-1ms columns, offer the same outstanding inertness, ultra-low bleed, and batch-to-batch reproducibility as our Rxi®-5ms columns. Rxi®-1ms columns provide excellent selectivity and symmetric peaks for the diverse chemicals that can make up a semivolatiles sample.
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Analysis of Semivolatile Organics:

Exceptional inertness and ultra-low bleed enable an Rxi®-5ms column to resolve sub-1ng quantities of acidic or basic analytes under a single set of conditions. In this example analysis, an Rxi®-5ms column separated 93 target analytes in US EPA Method 8270D in less than 18 minutes.
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Monitoring Petroleum Hydrocarbons by Solid Phase Extraction/GC:

New manufacturing processes for our Massachusetts TPH solid phase extraction cartridges reduce extractable contaminants almost to blank levels, and assure more reliable fractionation of aliphatics from aromatics. Large, uniform lots of silica reduce the frequency of verifying fractionation results.
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New Reference Mix of Canadian Drinking Water Volatiles:

This new mix includes all 19 volatile compounds on the Canadian Drinking Water List. We recommend using an Rtx®-VMS column for the analysis, to assure sharp peaks for early eluters and resolution of the heavier compounds.
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A 12-Minute Analysis for Volatiles:

An Rtx®-VMS column provides rapid, baseline resolution of most volatile analytes in the CLP OLM 04.1 analysis for groundwaters or drinking waters from Superfund sites. A particularly challenging stipulation of the method, 90% resolution of the gaseous components, is easily attained.
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Foods, Flavors & Fragrances

High Sensitivity Melamine GC/MS Analysis of Cat Food

Modified Conditions Save Costs and Reduce Maintenance

< Added, February, 2008

Melamine contamination was implicated in a large pet food recall that occurred in 2007 when animals died after eating contaminated pet food. Here, a modified GC/MS method, based on an FDA method, was used to analyze for melamine & related compounds cyanuric acid, ammelide, and ammeline in dry cat food. Analytes were easily identified by retention time matching and mass spectra.
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Rapid Characterization of Garlic Volatiles—No Sample Prep Requires!

Using Headspace GC/MS and an Rxi®-5ms Capillary Column

Chromatographic methods for garlic and garlic powder are used by the food and dietary supplement industries to monitor product quality. Here we present a headspace gas chromatography mass spectrometry (HS GC/MS) method for garlic flavor and odor components using an Rxi®-5ms column. This method eliminates sample preparation making the bench work simple and fast. The experimental set-up is ideal for both screening analysis and low-level trace analysis.
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Simple, Reliable HPLC Analyses of Organic Acids

Using Water-Compatible Allure® or Ultra C18 Columns

Commonly used organic acid methods (e.g. AOAC method 986.13) depend on reversed phase HPLC and C18 columns, however these columns are vulnerable to phase collapse when used with the aqueous mobile phases necessary for optimal organic acid analysis. Restek’s Ultra Aqueous C18, Allure® Aqueous C18, and Allure® Organic Acids columns all withstand phase collapse and resolve organic acids in a 100% aqueous mobile phase, compared to a conventional C18 column which shows a complete loss of retention.
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Analysis of Nitrofurans in Honey

Using LC/MS/MS and an Ultra C18 Column

Nitrofurans are a class of veterinary antibiotics used to increase growth rate and prevent or treat disease in animals. Determining levels of nitrofurans in animal tissue, or even products such as honey, is important in studying drug resistance and allergies in humans. The Ultra C18 HPLC column is an excellent choice for LC/MS/MS analysis of nitrofurans at low levels in complex matrices such as honey. Here we show excellent sensitivity, resolution, and peak shape at trace levels.
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Evaluating Undiluted Essential Oils

Essential oils are complex natural products containing many components across a wide concentration range. This complexity makes their analysis especially challenging. Many methods involve sample dilution to prevent syringes from clogging but this is not always necessary and can compromise analytical quality, especially for less abundant compounds near the solvent peak. Here we provide steps for optimizing your method to allow essential oils to be analyzed without dilution.
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Simplified LC/MS/MS Analysis of Fluoroquinolones

Using An Allure® PFP Propyl Column

When you need greater retention to achieve a desired selectivity, or in LC/MS analyses, an Allure® PFP Propyl column and a simple mobile phase are a better alternative than a C18 column and ion-pairing. An Allure® PFP Propyl column assures satisfactory retention, and no coelutions, with the water content in the mobile phase greatly reduced, relative to the requirements of a C18 or cyano column. In LC/MS analyses, this offers the potential for increasing sensitivity.
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Monitor Antioxidants in Tea Extract

Using an Ultra Aqueous C18 HPLC Column and Unique® TOFMS

An Ultra Aqueous C18 column enables you to use the conditions most effective for this analysis: gradient elution in high aqueous mobile phases. The C18 chains will not collapse in the presence of a high water content. Use this chromatographic system to extract data for specific compounds of interest and to manually inspect spectra for phenolic glycosides, esters of phenolic acid, or other compounds.
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Robust 9-Minute GC Analysis of Cholesterol

Excellent Sample Throughput with an Rxi™-5ms Column

Conditions are established for analyzing both derivatized and underivatized cholesterol on a highly inert Rxi™-5ms column. Methods described include both an isothermal analysis for use when interferences are minimal, but sample throughput is critical, and a temperature program for use when separation of analytes from contaminants or interfering compounds is the primary concern. Results for both derivatized and underivatized samples were highly reproducible.
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Rapid, Reproducible HPLC Analysis for Flavonoids in Cocoa:

Using a Leco Unique® LC-TOFMS Systemand an Ultra Aqueous C18 Column

We separated flavonoids in cacao or cocoa powder samples and returned conditions to the initial mobile phase composition in 15 minutes. For compounds common to both samples, retention times were equal to within 0.01 seconds. Flavonoid marker compound profiles for 38%, 49%, and 65% cacao were easily distinguished.
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80% Faster GC/MS Analysis of Essential Oils:

A 10-meter, 0.10mm ID, 0.10µm film Rtx®-5 column reduces analysis time for bergamot oil or patchouli oil by 80%, for five-fold greater sample throughput and sharply reduced cost per analysis. Sample resolution is unchanged for bergamot oil and is slightly improved for patchouli oil.
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trans Fat: Resolving cis and trans FAME Isomers by GC:

The highly polar Rt-2560 stationary phase has the selectivity needed for resolving cis and trans FAME isomers to comply with US FDA food labeling guidelines. Restek reference materials will help you accurately characterize your materials.
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Detecting Illegal Dyes in Foods: Identify Four Sudan Dyes in One HPLC Analysis:

Using an Ultra Aqueous C18 column, a simple, isocratic mobile phase, and detection at two UV wavelengths (488nm for Sudan I and II and 520nm for Sudan III and IV), the four dyes are separated and identified in approximately 20 minutes.
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Simple HPLC Analysis for Sudan Dyes:

Sudan dyes are illegal as food additives according to the US FDA and the EU. A reversed phase HPLC separation of Sudan I, Sudan II, Sudan III, and Sudan IV (Scarlet Red) is simple, yet efficient, requiring only a simple mobile phase, isocratic elution, and detection at two wavelengths. An Ultra Aqueous C18 column provides the selectivity needed to assure the separation.
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Malachite Green and Leucomalachite Green Analysis:

Illegal use of malachite green (MG), an inexpensive fungicide, can allow MG to enter water cycles, where it is easily absorbed by fish tissue, and thus enters the human food supply. Reversed phase HPLC often is used to analyze for MG and its stored metabolite, leucomalachite green. Methods that facilitate detection of both compounds are discussed.
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Pharmaceutical

How do intrinsically base-deactivated phases work?

< Added, February, 2008

Analyzing basic compounds can be somewhat troublesome on traditional alkyl stationary phases, namely conventional C18 columns. This is largely due to the interaction of analyte molecules with silanol groups present on the silica surface. To better understand the workings of silanol interactions, it is important to consider the composition of the support material. Silica is the most commonly used support in the production of HPLC columns, mainly because it is well-suited to high-pressure chromatographic separations, giving high efficiencies and good reproducibility. Silica offers bed and pressure stability and is highly porous, which ultimately gives rise to its large surface area, increased bonding capacity and high peak efficiencies. Silica also possesses widely-studied and effective bonding chemistries, making possible diverse analyte selectivities through a wide variety of bonded stationary phases.
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Multi-task with an Ultra IBD Column

A Versatile Column with Many Applications

< Added, February, 2008

The Ultra IBD HPLC column addresses the inherent problems attributed to linear alkyl phases, providing excellent peak shape for basic compounds and heightened retention of hydrophilic compounds. Here we demonstrate the versatility of this polar embedded column, and its ability to overcome some of the common limitations of conventional C18 columns. The versatility of the Ultra IBD makes it an excellent tool for the practicing method developer.
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Easy Transfer HPLC Methods to UHPLC

Using Fully Scalable Pinnacle™ DB Columns

Ultra High Pressure Liquid Chromatography (UHPLC) is a rapidly growing technique that can provide faster analysis times. Scaling conventional HPLC methods down to UHPLC can be an effective way to take advantage of shorter run times and increase sample throughput. Here we review the factors that must be considered when scaling down an existing method. A sulfonamides method transfer is used as an example; chromatograms and formulas for all required calculations are included.
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Explaining the Small Particle Advantage:

Faster Sample Throughput on a 1.9µm Pinnacle™ DB column

Small particle HPLC columns can offer faster analysis times but only if the particle size distribution is tightly controlled. Restek’s 1.9µm Pinnacle™ DB columns have tight, symmetric particle size distributions and contain no particles less than 1µm. Here we demonstrate how our stringent quality requirements translate into faster, more reproducible results compared to competitor columns. Greater column efficiency and reproducibility mean faster throughput and more consistent results.
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Revised USP 467 Residual Solvent Method

Satisfy New Method Requirements with Restek Columns and Standards

The United States Pharmacopeia recently revised the general chapter on residual solvent analysis, USP <467>, to mirror the International Conference on Harmonization (ICH) guidelines for the identification, control and quantification of residual solvents. This revision, effective July 1, 2007, replaces previous methods that were not consistent with the ICH guidelines. Here we provide an overview, chromatograms, and technical tips for successfully running the new procedure.
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Optimize Selectivity & Efficiency in UHPLC Separations

With More Stationary Phase Choices on 1.9µm Pinnacle™ DB HPLC Columns

Ultra-high pressure liquid chromatography (UHPLC) can significantly increase efficiency and produce faster separations. The small particle sizes used in UHPLC improve efficiency; however selectivity is still the most important factor affecting compound resolution. Here we demonstrate the importance of stationary phase choice in UHPLC separations. By optimizing selectivity for your analytes of interest, faster separations can be achieved without compromising resolution.
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New pHidelity™ pH-Stable HPLC Columns

For Analyses at Extreme pH Conditions

pHidelity™ columns give you more control over analyte retention and resolution: they can be used routinely up to pH 12 — a significant improvement over the pH 2.5 to 7.5 range typical for silica-based materials. You can increase mobile phase pH to enhance retention of basic analytes, without sacrificing column lifetime. True C18 selectivity helps assure simple and reproducible analyses.
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Separating NSAIDs through Aromatic Selectivity

Improve Retention by Using an Allure® Biphenyl HPLC Column

Non-steroidal anti-inflammatory drugs (NSAIDs) are typically separated on C18 phases. Separations on our Allure® Biphenyl HPLC column are based on pi-pi interactions, resulting in optimized retention and selectivity. Increased retention requires higher organic content in the mobile phase, increasing desolvation efficiency in LC/MS. Simple mobile phase changes enhance selectivity, making this column a great alternative to conventional phenyl phase columns, especially in method development.
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Assaying Local Anesthetics by GC/FID:

Optimizing System Suitability, Using an Rxi™-5ms Column

An Rxi™-5ms column and a wool-packed inlet liner provide the stability and inertness needed for these basic, active analytes. Chromatography from a six-replicate system suitability analysis was well within normal acceptance criteria. USP tailing factors were approximately 1.00 for all analytes; retention times and area responses were very stable.
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Optimized RP-HPLC Analysis of Hydroxybenzoic Acids:

An Ultra Aqueous C18 Column Provides the BestRetention of Polar and Weakly Polar Compounds

Among hydroxybenzoic acids, hydroxyl groups on the benzene ring vary by position and number, creating differences in overall polarity and solubility. The unique bonding chemistry of the Ultra Aqueous C18 phase assures high resolving power, the best separations across a broad range of analyte polarity, and compatibility with 100% aqueous mobile phases.
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Optimizing Difficult Separations of Steroids Using an Allure™ Biphenyl HPLC Column:

Steroids are structurally very similar, and separations on alkyl stationary phases can be difficult. Through a unique separation mechanism — π-π interactions between double bonds in the stationary phase and in the steroid molecules — an Allure™ Biphenyl column greatly enhances selectivity, and resolution. Two examples, sex hormones and corticosteroids, are shown here.
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8-Minute GC Analysis of Residual Solvents:

Single-injection, dual-column detection/confirmation assay is feasible for regulated solvents in pharmaceutical products, but no temperature program provides sufficient resolution on both columns. Using a Restek G43/G16 column pair and independent temperature programs in a Gerstel MACH column heating system, we analyzed and confirmed 23 Class 2 solvents in 8 minutes.
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Simple, Optimized HPLC Analysis of Catecholamines:

An Allure™ PFP Propyl column exhibits the retention needed to resolve these active, basic compounds, without derivatization or ion-pairing agents. Selectivity can be adjusted simply by changing the organic modifier in the mostly aqueous mobile phase.
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RP-HPLC Analysis of Selective Serotonin Reuptake Inhibitors:

Two Restek columns provide good retention, selectivity, and peak shape for SSRIs, without ion-pairing chromatography. Choose an Allure™ Basix column and neutral pH conditions, or an Ultra PFP column and acidic conditions — either will improve performance for these basic compounds, relative to alkyl phases.
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Developing a Simple, Rugged HPLC Assay for Tetracyclines:

Overall, three columns provide excellent repeatability in a simple analysis: Allure™ PFP Propyl, Ultra C18, and Allure™ Biphenyl. An Allure™ Biphenyl column employs π-π bonding with the ring structures of the tetracycline molecules to ensure good capacity, high selectivity, and the most symmetric peaks.
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Using π-π Interactions to Enhance Selectivity for Unsaturated Compounds: The Allure™ Biphenyl HPLC Column:

Relative to phases that separate via hydrophobic or polar interactions, the Allure™ Biphenyl stationary phase offers better retention, selectivity, and efficiency, when analyzing compounds with differences in the numbers and locations of unsaturated bonds in the hydrocarbon ring structure.
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Air Sampling

Sampling Volatile Organic Compounds in Air

Restek Sampling Equipment Helps Assure Accurate Data

TO-Can™ air sampling canisters are electropolished and extensively cleaned, to provide a high-quality, passivated surface for improved stability of analytes listed in USEPA Method TO-15 (ambient air monitoring). For reactive compounds, such as sulfur-containing components, SilcoCan™ canisters are your best choice — our exclusive Siltek® surface treatment ensures exceptional inertness and maximum sample stability, even for 1-20ppb sulfur compounds.
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Sample Preparation

Superior Fractionation of Extractable Petroleum Hydrocarbons

Get More Accurate Results Using Restek SPE Tubes

< Added, October, 2007

The Massachusetts Dept. of Environmental Protection’s “Method for the Determination of Extractable Petroleum Hydrocarbons” is a method commonly used for underground storage tank testing. Commercially available SPE tubes are convenient, but vary in quality and consistency. Here we show that Restek’s EPH SPE tubes have the highest silica activity and lowest overall level of coextractables among the tubes tested. These characteristics translate into more reliable and reproducible results.
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Faster Extraction and Cleanup of Pesticide Residue Samples

With QuEChERS Products

If you are frustrated by the time and cost involved with pesticide sample cleanup, we suggest you try the simple and economical QuEChERS method. Follow this approach to remove sugars, lipids, organic acids, sterols, proteins, pigments, and excess water, any of which often are present. To make your work even simpler, we offer QuEChERS extraction products in a variety of standard sizes and formats, and custom products by request.
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Bioanalytical

Improve Characterization of Complex Protein Digests:

A Viva C18 wide pore HPLC column resolves a tryptic digest of bovine serum albumin primarily into 1-2 peptide peaks, versus peaks of 3 or more peptides typically provided by conventional C18 columns. This superior resolution helps ensure more reliable identification of peptides in complex mixtures. Find out more.

Restek Performance Coatings

Sulfinert® Treated Systems Preserve ppb Levels of Active Sulfur Compounds

< Added, November, 2007

Many volatile sulfur compounds adsorb strongly to the metal surfaces encountered during sampling, transfer, and storage. This adsorption can cause falsely low sample results and also prolong analysis cycle times. Data shown here demonstrate the effectiveness of Sulfinert® treatment of system components. Sulfinert® treatment reduces adsorption, resulting in more accurate quantitation of sulfur compounds and reduced cycle times.
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Assure Accurate Sampling and Reliable Sample Purity

Restek Sampling System Treatments Prevent Adsorption, Protect Components

Siltek®/Sulfinert® surface treatments improve component performance by significantly reducing corrosion and adsorption problems in the sampling and sample transfer pathways. These treatments improve sampling accuracy, increase component lifetime, and cost less than super alloys. Treatments can be applied to cylinders, valves, fittings, tubing and more, and demonstrably improve detection of low-level sulfur, nitric oxide, and mercury compounds in a wide variety of applications and industries.
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Prevent Mercury Loss During Transport and Storage

Use Siltek® Surface Treatment on Steel Components

As concerns about mercury in the environment grow, new regulations and testing requirements emerge. To ensure accurate results, sample storage and transfer systems must be inert to elemental mercury. Here we demonstrate that Siltek® treatment provides an unreactive surface compared to stainless steel. Data shown demonstrate that Siltek® treatment of sampling systems will improve analytical accuracy. Siltek® treatment is available on many stock items and custom components can be treated upon request.
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Protect Sample Integrity and Prolong Sampling System Lifetime

Using Hydroguard™ Deactivated/Silcosteel® Treated Tubing

Tubing deactivated with Hydroguard™ and treated with Silcosteel® is preferred for situations in which water vaporization is encountered, such as in purge and trap systems. Hydroguard’s™ unique deactivation chemistry creates an outer surface that prevents water vapor from contacting the Silcosteel® treated stainless steel surface below. This protected inert surface allows active analytes to pass through the tubing without adsorbing to the surface.
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Extend Process Component Lifetime and Enhance Durability

Restek Surface Treatments ImproveSampling and Transfer Component Performance

In sampling or process stream pathways, Siltek®/Sulfinert® treated tubing reduces uptake of active (e.g., sulfur) compounds by orders of magnitude, relative to untreated tubing, for reliable data about stream composition. Silcosteel®-CR treated tubing improves corrosion resistance by up to 10X over untreated tubing, reducing the need for maintenance and helping to ensure the purity of the sample or process stream.
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Superior Protection Against Corrosion: Silcosteel®-CR

Treated Fittings and Tubing

Silcosteel®-CR treatment is highly effective protection for stainless steel exposed to hydrochloric acid, nitric acid, or marine environments: in independent tests, Silcosteel®-CR treatment upgraded the corrosion resistance of 300-grade stainless steel by an order of magnitude. Now, electropolished stainless steel tubing and a wide selection of world-renowned Swagelok® fittings are available with Silcosteel®-CR treatment, from stock. Custom treatment of system components also is available.
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LC Accessories

Genuine Restek Replacement Parts

For Agilent HPLC Systems

Use our Outlet Cap and Gold Seal Assembly Tool for Agilent 1100 HPLC Systems to easily install the seal into the cap. Also featured are preventive maintenance kits, a pump maintenance kit, pistons and piston seals, rotor seals, check valves, lamps, and more. All parts meet or exceed original equipment quality.
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HPLC Mobile Phase Accessories

An economical way to store and deliver your mobile phases.

An Opti-Cap™ Kit is the most economical way to helium-sparge mobile phases. The Opti-Cap™ top fits all standard GL-45 bottles, and Hub-Cap Bottle Tops and Adapters allow you to use the top with 4-liter solvent bottles. The Solvent Debubbler removes bubbles from the fluid stream before it enters the pump. Loosening the cap releases the trapped gas. The debubbler is fitted with universal connecting tips.
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Kromasil® HPLC Bulk Packing Materials:

Restek — Your One Source for Kromasil® Bulk Packing Materials
Kromasil® HPLC silica products consist of spherical, porous, mechanically strong particles in sizes from 3.5µm to 16µm or larger. The particles have large surface areas (330m2/g for 100Å silica) and minimal metal impurities. We supply these excellent bulk packings in a wide range of particle sizes and bonded phases.
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GC Accessories

Peak Performers

Replacement Parts for Agilent FID Detectors

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Cool Tools

Restek Innovations Save You Time and Money

Featured here are our MLE (Make Life Easier) capillary GC tool kits for column installation and general system maintenance. All kits have the many components that are needed with any instrument, but each kit has tools specific for one system: Agilent, PerkinElmer, Shimadzu, Thermo Scientific, or Varian.
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Supplies for Agilent Instrument Injection Ports

EZ Twist Top™ Split/Splitless Port for Agilent GCs

Using our unique EZ Twist Top™ Injection Port, Septum Nut Removal Tool, and Inlet Liner Removal Tool, you can reduce maintenance time and frustration, eliminate tangled gas lines that can lead to leaks, and avoid contact with hot surfaces. The gas lines are attached to the EZ Twist Top™ Shell Weldment, not to the weldment — they are under the GC cover and cannot interfere with routine injection port maintenance. Changing inlet liners becomes a quick and simple task.
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Restek’s Knowledgeable Technical Support

Real People, Real Time and Real Results for YOU!

Restek’s Technical Support group includes more than 64 individuals with extensive experience in chemistry, chromatography, engineering, and related fields. When you call Restek, you have access to the combined expertise of everyone in this group. With more than 110 international distributors and dealers in 81 countries, we can understand and respond to your lab’s unique challenges whether you are in North America, South America, Africa, Asia, Europe, the Pacific Rim or elsewhere.
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EZ No-Vent™ GC Column-Mass Spectrometer Connector

For Agilent, Thermo and Varian Instruments

Our EZ No-Vent™ GC column-mass spectrometer connector eliminates the need for purge gas and allows you to skip the lengthy vent and pump down cycle usually required when changing a column. This can save nearly a day of downtime per column change. It is simple to use and easily attaches to the MS source without special tools or extra plumbing. Features include an inert gold-plated body, deactivated transfer lines to focus analytes, and high-temperature polyimide ferrules to eliminate leaks.
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Peak Performers

Supplies for Agilent GC/MS Instruments

Featured items include an improved MSD conversion fitting that reduces the chance of leaks, an MSD source nut that permits easy removal of ferrules with a tapered needle file, an inert (gold-plated) transfer line for 5971/5972 MS systems, our capillary installation gauge that ensures correct and consistent installation distances and prevents crushed column ends, Alumaseal™ aluminum ferrules that do not need re-tightening, and more.
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Cool Tools

Restek Innovations Save You Time and Money
Our Inlet Liner Removal Tool lets you remove and replace the liner in a hot injector without burning your fingers. The Wool Puller/Inserter places wool plugs correctly and removes them easily. The Inlet Liner Packing Tool ensures reproducible positioning of wool plugs to a specific depth.
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Cool Tools:

For Thermo Instruments

Featured here are our new, innovative FID jet removing tool and injector liner cap removing tool, and our capillary installation gauge for easily and correctly seating a ferrule onto a column for installation into a TRACE™ or Focus SSL instrument.
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Peak Performers:

Injection Port Maintenance with FastPack™ Inlet Kits
Regular injection port maintenance helps ensure the best results from your analyses, and helps minimize downtime. Each FastPack™ inlet kit includes all the parts you need to perform routine maintenance — inlet liner (choose from four styles), O-ring, inlet seal and inlet seal washer, and septum — in a sealed Mylar® bag.
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Tech Tips

Preventing Septum Problems

Handy tips and tools for choosing the right septum for your application and instrument. Includes an overview of common septum problems including coring and bleed. Guidelines help you avoid extraneous peaks and optimize your system’s performance.
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How Hot is Your Septum?

Inlet design, including placement of the heating element, differs among manufacturers and as a result the temperature at the septum differs from the actual set point and the degree of this difference varies among manufacturers. Septa brands, however, are given a single maximum operating temperature. Here we demonstrate the temperature gradients within inlets for several popular GC models and discuss the pros and cons of hotter and cooler inlets.
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General Interest

Selecting the Right HPLC Guard Column

< Added, February, 2008

Understanding the significant factors that affect HPLC guard column performance can help you protect your analytical column and save money by extending analytical column lifetime. Here we review available options in packings, dimensions, cartridge holders, and filters to help you select the best guard column system for your application.
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The Forgotten Septum

How to Correctly Diagnose the Source of Bleed Contamination

< Added, February, 2008

Septum bleed is generally attributed to the injection port septum; however, the vial cap septum also can be a source. Bleed contamination from any septum can cause interfering peaks and lead to inaccurate results, so it is important to correctly identify the source and understand how to eliminate or minimize bleed level. Here we discuss how to diagnose the source of the bleed and review considerations that can reduce the amount of contamination.
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Warm-up Before You Run

Why Conditioning Your Inlet Parts After Maintenance Is Good Practice

Background noise in a gas chromatography system can be eliminated by conditioning the system prior to sample analysis. In this article, we discuss warm-up procedures and use liners and liner installation to demonstrate the importance of conditioning the system to remove background peaks. Investing a little time in warming-up the system pays big dividends by preventing costly coelutions and avoidable reanalyses.
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Affected by the Helium Shortage?

Switch Your GC Carrier Gas to Hydrogen

Faced with helium shortages and prices that continue to soar upwards like a runaway party balloon? Consider switching to hydrogen as your carrier gas. High-quality hydrogen is readily available from either high-pressure cylinders or hydrogen generators. It is cost-effective and provides shorter analysis times (by half if running isothermally) than helium and many times yields better separations.
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How to Maximize Column Oven Accuracy and Stability

Tips & Techniques for Long-term Instrument Performance

Simple tips and techniques are presented to improve the accuracy and precision of your data by keeping your column oven at peak performance. Details on reducing variation around the oven set point through calibration and maintenance are given.
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Choosing a Liner for Semivolatiles Analysis

Liner choice is a critical decision in semivolatiles analysis. Liners containing wool packing are recommended to minimize molecular weight discrimination. Attributes of different types of liners, including the Drilled Uniliner, are discussed.
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Get Connected!

Do you need to connect a GC analytical column to a guard column or transfer line? Or repair a broken column? How about connecting two columns for primary and confirmation analysis from a single injection? Restek’s extensive selection of GC connectors makes all of these connections possible. Here we review differences among our connectors and answer some frequently asked questions about our popular Press-Tight® connectors.
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Considerations for Adapting an HPLC Method for MS Detection

Most HPLC methods can be coupled with mass spectral detection provided appropriate attention is given to pump capabilities, column diameter, and system plumbing, and to sample matrix and mobile phase composition. Here we discuss these considerations and provide tips on adapting your method to include mass spectral detection using either electrospray ionization or atmospheric pressure chemical ionization.
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Using Micropacked Columns

Micropacked columns are 1-2 meter, 0.75-1.0mm ID packed stainless steel columns with performance characteristics intermediate between conventional packed columns and capillary columns. They are inexpensive, very durable, and easy to install and operate. They have a wide range of applications, but are especially useful for analyses of gas mixes, including sulfur compounds or light hydrocarbons, for which a packed column is needed to obtain baseline separations of sample components.
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Commonly Asked GC Questions:

The Restek Chromatography Information Services Group answers hundreds of questions each month. The answers provided here deal with inquiries about guard column chemistry, column temperature limits, ghost peaks in GC/MS analyses, pesticides breakdown on cyano-phase columns, and column cage options.
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How to Condition a New Capillary GC Column:

Proper conditioning is essential for optimal performance from a capillary GC column, but inexperienced chromatographers might not know the proper procedures for installing and conditioning a new column. Here, we summarize our recommendations for installation and conditioning procedures.
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Making Life Easier - Restek Technical Service:

When you want to discuss GC or HPLC column options, or have any other concern about chromatography, Restek Technical Service is just a toll-free phone call away. Our experienced, dedicated team provides expert, “Plus 1” service every time you call.
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Leak Checking a GC System:

Analysts should use an electronic leak detector when installing a new column or fitting, changing a cylinder, or troubleshooting the system. The portable, reliable, easy-to-use Restek Electronic Leak Detector reveals minute leaks without contaminating the system.
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