General Interest

The Global Advantage is a technical magazine covering industry news, chromatography applications, and guest editorials by leaders from a wide range of fields. Highlights from this issue include feature articles on marijuana potency testing, simplifying HPLC method development, large volume splitless injection with an unmodified GC inlet, and much more. (PDF - 2431kB)

Whether it’s a stock, off-the-shelf reference standard or a one-of-a-kind, custom-formulated solution, there are 10 critical steps that Restek takes in our ISO-accredited labs to separate our certified reference materials (CRMs) from the competition. (PDF - 549kB)

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.

What is derivatization and how can is improve your analyses? This note describes the advantages of derivatization and explains how to choose the correct reagent. Includes product information and an overview of silylation, acylation, and alkylation. (PDF - 312kB)

Hub-Cap bottle tops and adapters keep your mobile phase where it belongs and is the easiest, cleanest, safest way to deliver mobile phases for LC applications. (PDF - 871kB)

Product information for Restek capillary HPLC columns for micro-LC applications. (PDF - 245kB)

Wide range of options for HPLC systems and pumps. (PDF - 902kB)

Restek septa are precision molded from specially formulated silicone rubbers for minimal bleed, easy puncturability, and precise and consistent fit. Septa FAQs and product descriptions for standard septa, as well as Merlin Microseal mechanical septa, are included in this piece. (PDF - 519kB)

Restek USLC™ columns offer the widest range of selectivity available and are an integral part of successful method development. Ideal for column switching systems, these columns provide orthogonal separations to create optimal resolution and robust methods—all in a 4-column set. (PDF - 1813kB)

The Restek Advantage is a technical magazine covering industry news, chromatography applications, and guest editorials by leaders from a wide range of fields. Highlights from this issue include feature articles on analyzing complex marijuana samples, simplifying HPLC method development, large volume splitless injection with an unmodified GC inlet, and much more. (PDF - 2894kB)

Spotlight explores Restek's offering of gas chromatography (GC) accessories. This issue features Sky™ inlet liners, ProFLOW 6000 Flowmeter, Electronic Leak Detector, GC replacement parts, Flip Seal™ inlet seals, regulators, septa, gas generators, and more! (PDF - 1293kB)

Wondering why you are seeing differences in flowmeter readings or trying to change gas flow units? You’ll find answers to these and other frequently asked questions on our ProFLOW 6000 electronic flowmeter FAQ page.

A basic understanding of gas flow principles is fundamental to obtaining accurate flow measurements. This primer contrasts mass flow and volumetric flow regimes, and illustrates the effect of flow impedance and loading on the flow source in gas chromatography.

This article provides an introduction to control systems and discusses how control variables influence process variables. Topics include open loop, closed loop, and PID control systems. Simulations illustrate overshoot and undershoot around the setpoint during process control.

This 4-page product flyer details Restek’s line of quality laboratory glassware. Products offered include Kuderna-Danish evaporator concentrators, Soxhlet extraction apparatuses, Erlenmeyer flasks, volumetric flasks, micro volumetric flasks, burets, separatory funnels, impingers, and more. (PDF - 987kB)

The Trident Direct HPLC guard column system gives you 3 options for column protection: protection from particles, protection from particles and sample impurities, and protection from particles and heavy contamination. Cut costs by matching the level of column protection to your particular need. (PDF - 368kB)

Filtering sample extracts with syringe filters will greatly extend the life of costly chromatographic columns and replacement parts, particularly for HPLC systems. This 2-page fact sheet includes helpful membrane, porosity, and size selection guides. (PDF - 119kB)

Rxi® GC columns deliver more accurate, reliable trace-level results than any other fused silica column on the market. Take variation out of the equation and lower detection limits with highly inert, low bleed Rxi® gas chromatography columns. (PDF - 1929kB)

Rxi®-5Sil MS columns show lower bleed profiles and greater inertness than competitor columns, resulting in higher signal-to-noise ratios and lower detection limits. These silarylene GC columns are ideal for trace-level gas chromatography work and sensitive GC/MS applications. (PDF - 493kB)

Restek's fully documented reference standards will help you save worry, time, and money. Learn more about why you should rely on our chromatography standards as well as how you can save up to 75% by establishing a custom reference standards blanket order. (PDF - 305kB)

From full-day courses to one-hour webinars, The Restek Learning Network offers training on all things chromatography, including GC and HPLC analysis, intermediate GC/MS and LC/MS, advanced method development, and specific applications like environmental, petrochemical, or food safety. (PDF - 338kB)

Parker Balston® FID gas stations produce 99.9995% hydrogen from deionized water and UHP zero air (<0.1 ppm hydrocarbons) from house compressed air, eliminating inconvenient, costly, hazardous cylinders. The note describes models available from Restek. (PDF - 563kB)

Eliminate the inconveniences, costs, and hazards of gas cylinders – reliable Parker Balston® zero air generators produce UHP zero air (<0.1 ppm hydrocarbons) from house compressed air. This note describes all models available from Restek. (PDF - 473kB)

Replace inconvenient, costly, hazardous gas cylinders with a safe, reliable Parker Balston® hydrogen generator that produces 99.9995% pure hydrogen from deionized water at up to 510 cc/minute. This note describes all models available from Restek. (PDF - 655kB)

Eliminate inconvenient, costly, hazardous gas cylinders—reliable Parker Balston® Nitrogen Generators produce UHP (up to 99.9999%) or HP (99.99%) nitrogen from house compressed air. This note describes all models available from Restek. (PDF - 318kB)

Exceptionally inert, Sky™ inlet liners improve trace level analysis for a wide range of compounds. These blue liners have a new deactivation that allows analysts to increase accuracy and precision, lower detection limits, and use wool with confidence. (PDF - 517kB)

Our expertise, experience, and enthusiasm is your Advantage. (PDF - 3741kB)

The novel approach used here combines QuEChERS extraction, cartridge SPE cleanup, and GCxGC-TOFMS analysis, resulting in good recoveries for a wide range of pesticides in dietary supplements. Matrices include dandelion root, sage, and a multi-herb finished product.

Do you scratch notations or other marks into tubing? You shouldn’t—scratches can allow corrosion or stress to dangerously weaken the tubing. This guide includes many other things you should know to avoid installation problems, damage to system components, or leaks. (PDF - 1501kB)

Prevent expensive repairs with new UltraShield and UltraLine UHPLC filters. These 0.5 µm precolumn filters are available in standard and in-line configurations. Stainless steel bodies install easily and are leak tight up to 15,000 psi. (PDF - 180kB)

Screening methods for consumer product adulteration cases, such as the recent Tylenol recall, can benefit from fast QuEChERS-based sample preparation and sensitive, full mass-range GC/TOF-MS.

Learn what de-wetting is, and how to avoid it, by using an Aqueous C18 column, instead of a conventional C18, when analyzing polar compounds by HPLC.

Our expertise, experience, and enthusiasm is your Advantage. (PDF - 2090kB)

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.

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.

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.

Scaling HPLC methods down to UHPLC is an effective way to obtain of shorter analysis times and increase sample throughput. Here we review factors that must be considered when scaling down an existing method using a sulfonamides method as an example. (PDF - 221kB)

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.

QuEChERS dSPE methods 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. (PDF - 158kB)

Ultra-Clean resin is cleaned to meet or exceed US EPA Method TO-13 requirements for a sampling medium for airborne semivolatiles. Specifications and performance are equal to those of XAD®-2 resin, the standard for this purpose. Zero background for electroconductivity detection. The 2-page note details the material’s features and benefits. (PDF - 157kB)

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.

Restek has developed the first QuEChERS-based method for determining pesticide residues in dietary supplements. This simple, cost-effective procedure reduces matrix interferences as well as sample prep variation among technicians.

QuEChERS is a simple, effective approach to sample prep that can be applied to the analysis of pesticides in dietary supplements. Here we demonstrate a QuEChERS, cSPE, GC-TOFMS procedure that results in good recoveries for a wide range of pesticides in dandelion root. (PDF - 5523kB)

Biphenyl columns provide both high hydrophobic retention and aromatic selectivity in the same column. Orthogonal separations can be achieved with simple mobile phase changes, giving markedly better separations for a wide variety of molecules. (PDF - 531kB)

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.

Restek's Dual Vespel^® Ring inlet seal gives you a better seal with fewer parts. Data show that the soft Vespel^® material has a much lower leak rate than a metal seal. Also, since less torque is required for installation, user variability is reduced.

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.

Restek's Electronic Leak Detector is sensitive enough to find leaks below instrument pressure decay test levels and is available at a fraction of the cost of other hand-held units.

Scaling down column size is simple to do and can help reduce solvent use. Here is an easy-to-follow example that teaches you how to reduce column internal diameter.

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.

High pump pressures can be caused by heavily retained impurities building up in the head of the analytical column. Such contamination can cause poor chromatography, usually in the form of broad, split, or misshapen peaks, and ultimately can compromise results. Backflushing a contaminated analytical column, using the procedure outlined here, can help restore column performance and reduce pump pressure and system strain.

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.

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.

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.

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.

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.

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.

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.

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.

The multi-dynode approach of all ETP electron multipliers results in longer lifetimes and better sensitivity compared with channel multipliers. This 4-page note describes the features and benefits of ETP electron multipliers. (PDF - 399kB)

Thermal desorption is a convenient, fully automated alternative to solvent extraction for measuring residual volatiles. This 32-page publication from Markes International Ltd. details the testing of a wide variety of products using thermal desorption. (PDF - 1480kB)

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.

Genuine Restek Replacement Parts meet or exceed original equipment components. This 8-page publication lists a wide selection of Restek parts for Agilent, Beckman, Hitachi, PerkinElmer, Shimadzu, Thermo Separation Products, and Waters instruments. (PDF - 1040kB)

An extensive catalog of consumer-replaceable instrument parts, tools, accessories, and supplies needed to keep an Agilent 5890 GC running at top performance. Many items are designed to save time or improve results, and are exclusive to Restek. (PDF - 972kB)

Static headspace analysis will save you time and money when assaying a variety of sample matrices—and often is easier than alternative sampling approaches. This 20-page guide discusses basic principles, instrumentation, applications, and troubleshooting. Restek capillary GC columns and an extensive selection of accessories will simplify getting started. (PDF - 6234kB)

In some analyses, particularly with pharmaceutical or flavor and fragrance compounds, enantiomer pairs must be resolved for separate quantification. Five cyclodextrin-based Restek chiral capillary GC columns offer a unique range of selectivities, to enable you to accomplish these often-difficult separations. Many example chromatograms in this 24-page guide will help you find the best column—or columns—for your particular need. (PDF - 462kB)

This 72-page guide offers a concise, but thorough, overview to analyzing volatile organic compounds in environmental samples. Sections describe purge and trap theory, adsorbents and traps, troubleshooting purge and trap systems, GC system configurations for narrow-bore or wide-bore capillary columns, and detection systems and how they work. A large selection of chromatograms shows analyses obtained through various approaches and illustrates results of changing chromatographic parameters to achieve specific goals. Invaluable to new chromatographers; experienced analysts will find justification for updating methodology. (PDF - 2705kB)

Soaps, detergents, solvents, and many other components of household cleaners and personal care products are effectively monitored by GC and/or HPLC. Sometimes either approach can be used for the same purpose, but one will offer time, accuracy, or economic advantages over the other. Sometimes the approach is clear, but the choice involves alternative stationary phases. This 16-page guide presents numerous examples of GC and HPLC analyses of these diverse products. (PDF - 423kB)

Analyses of semivolatile organic compounds in environmental samples hold many challenges, particularly during sample preparation and injection onto the capillary GC column. At the same time, quality assurance/quality control requirements can be rigorous. This 28-page guide offers valuable information across the entire scope of the analysis: sample extraction and cleanup, column selection, GC analysis (including hints for reducing discrimination in the injection port), and quantification. (PDF - 6275kB)

A popular Restek guide revised, updated, and expanded What design of inlet liner is best for analyzing dirty samples by split injection? What design minimizes analyte breakdown in splitless injections? Learn about the advantages of these commonly used sample injection techniques – and their disadvantages – to obtain the best results and avoid problems. This 36-page guide is focused on system optimization, maintenance, and troubleshooting. An extensive selection of inlet liners and other products is included. (PDF - 473kB)

A better, simpler approach to analyses of trace-level compounds Compared to splitless injection, direct flash vaporization injection – direct injection – offers greater sensitivity, simpler operation, and reduced potential for adsorbing active compounds. This 24-page guide discusses the advantages and disadvantages of direct injection, compared to other techniques, and examines considerations such as modifying a splitless inlet, retrofitting a packed column injection port, and the need for make-up gas. Operating parameters such as flow rates and sample injection volume are reviewed. (PDF - 5608kB)

Confusion about “wax” columns resolved. Polyethylene glycol-based stationary phases are the most versatile and thermally stable polar GC phases, but PEG-based columns from different manufacturers can differ significantly in chemical makeup and performance. Restek PEG-based capillary columns are designed for specific categories of applications, for low bleed, excellent inertness, and unsurpassed column-to-column reproducibility. This 16-page guide discusses the performance characteristics of and applications for Restek PEG-based columns. (PDF - 701kB)