Beautiful Florianópolis in Santa Catarina, Brazil, was the site of this year’s Congresso Latino Americano de Cromatografia e Técnicas Relacionadas (COLACRO). Perhaps the most influential meeting on chromatography in South America, this biannual event was originally scheduled to be in Chile two years ago, but a devastating earthquake forced a cancellation. Thankfully, under the leadership of Professor Fernando Lanҫas, attendees had no trouble making up for lost time in 2012.
Restek’s Jaap de Zeeuw, Chris Denicola, and Mark Badger made the trip south and staffed the booth with our Brazilian distributor Cromatec. Restek contributed seven posters to the 500+ on display at COLACRO. In addition, Jaap was invited to speak in the main program, where he gave advice on gaining faster GC analysis times using existing instrumentation, and he offered a short course in trace-level analysis as part of the GC-MS workshop organized by Elena Stashenko. Not to be missed, Restek also held a vendor seminar where Jaap and Chris delved into choosing the best phases for both GC and LC.
Continue reading to learn more about our presentations at COLACRO XIV. For more information on COLACRO, you can visit their website at www.colacro.org
Practical Ways to Reduce Analysis Time in Gas Chromatography
Jaap de Zeeuw (presenter)
Abstract: There is always an interest in reducing the analysis time as this increases throughput and reduces cost per analysis. Especially for laboratories with high sample load, the time per analysis is becoming a concern. Analysis time can be reduced in many ways.
In case of enough separation, the options are:
• Use a shorter column length. (Take 15 m instead of 30 m, or 30 m instead of 60 m.)
• If the injection technique allows it, start at a higher temperature or use a faster oven program rate to elute the components.
• Operate the column at a higher flow rate or use flow programming to elute late-eluting compounds.
In case we require the same efficiency, our options are:
• Use a faster carrier gas: use hydrogen instead of helium. This is the easiest way to reduce analysis time, and implementation can be quite fast. At our lab, all columns and applications are run using hydrogen. Hydrogen has about twice the optimum velocity of helium, meaning analysis times are 2x faster. Of course, we need to deal with safety procedures, and because of safety risks, for some labs, hydrogen is not an option. One needs to be aware that helium will become more expensive, as the supply will not last forever. Using hydrogen, the supply is guaranteed.
• Use a shorter capillary with a smaller bore. This produces similar efficiency, but run times will be shorter.
In this presentation, we will discuss the different options we have to reduce the run time using the existing instrumentation. Important in all cases is to adjust chromatographic settings the right way to make sure the separations are kept as similar as possible. Several examples will be shared and discussed.
Workshop: Recent Developments in Capillary GC-MS
Hosted by: Elena Stashenko
Improving Trace Analysis: Maximizing Sensitivity by Minimizing the Noise and Background in GC and GC-MS
Jaap de Zeeuw (presenter)
Abstract: Increased background signal is one of the most common problems in GC. Especially for detection of low levels as is requested for many applications, the signal/noise (S/N) must be optimized. Sources for background will be discussed and solutions will be given to practical problems. Also the eluting peak must be symmetrical, which only happens if the system has sufficient inertness.
This talk includes many practical tips for maximizing signal/noise in daily operation of GC instrumentation.
Degradation of Certain Organochlorine, Organophosphorus, Organonitrogen, and Carbamate Pesticides During Hot Splitless GC Injection of QuEChERS Extracts of Canola Seed
Jaap de Zeeuw (presenter), Julie Kowalski, Michelle Misselwitz, Sharon Lupo, Jack Cochran
Abstract: Recently, we noticed low response factors for certain pesticides with hot splitless injection GC in EN QuEChERS extracts of canola seeds when compared with those same pesticides in EN QuEChERS extracts of tobacco. An experiment was designed to quantify and attempt to explain the losses. A single taper with wool liner was used for hot splitless injection in an Agilent GC at 250 °C. Duplicate samples from EN QuEChERS extracts of tobacco leaf and canola seeds (cleaned with 150 mg MgSO4 / 25 mg PSA / 7.5 mg GCB) were created by adding 50 μL of pesticide standard to 50 μL extract. A pesticide standard in acetonitrile only was also created. Samples were analyzed by hot splitless injection GC in the order: tobacco, canola seed, acetonitrile, tobacco, canola seed, acetonitrile. The analyzed concentration level was relatively high at 5 ng/μL for each pesticide to minimize any matrix-enhanced response effect for acetonitrile-only standards. DCPA was used as an internal standard to calculate response factors, as its response was extremely stable in extracts and solvent, and average response factors for pesticides in each matrix were calculated from the duplicate GC analyses. Samples were also analyzed using LC-MS/MS after 50x H2O dilution.
The pesticides acephate, omethoate, dimethoate, carbaryl, methiocarb, dichlofluanid, malathion, phosalone, azinphos methyl, coumaphos, deltamethrin, chlorothalonil, delta-BHC, captan, and folpet were heavily degraded in the GC inlet during hot splitless injection of a canola seed extract, as was confirmed when LC-MS/MS analysis of the same canola seed extract showed good response factors comparable to those from tobacco extracts and solvent-only standards analyzed by LC-MS/MS.
Degradation may have been caused by a high concentration of sulfur-containing compounds in the canola seed extract that reacted with pesticides during hot splitless GC injection.
A New Capillary GC Column for Highly Efficient Separation of Polycyclic Aromatic Hydrocarbons, Including the EFSA PAH4
Jaap de Zeeuw (presenter), Amanda Rigdon, Steve Allison, Shawn Reese, Roy Lautamo, Julie Kowalski, Jack Cochran
Abstract: Polycyclic aromatic hydrocarbons (PAHs) are toxic (carcinogenic, mutagenic, teratogenic, etc.) compounds sometimes found in food, and they require monitoring by capillary gas chromatography with mass spectrometry (MS), often at very low levels. Many of these PAHs are isobaric, so MS will not be sufficient to quantify them in an unbiased fashion, which means they must be separated by GC prior to detection. Some are more toxic than others, including the PAH4 noted by EFSA: benz[a]anthracene, chrysene, benzo[b]fluoranthene, and benzo[a]pyrene. Possible GC coelutions that would lead to qualitative and quantitative bias include triphenylene and chrysene (m/z 228), benzo[b]fluoranthene and benzo[k]fluoranthene (m/z 252), and benzo[e]- and benzo[a]pyrene (m/z 252). The triphenylene and chrysene coelution can be particularly difficult to resolve.
A new, high-phenyl-content, thermally stable GC stationary phase has been developed that separates the PAH4, the PAH8, and many more PAHs that can be present in food samples. Chromatograms that detail the PAH4 separations will be shown, and column ruggedness will be explored with QuEChERS oyster and smoked paprika spice extracts.
Is It Better to Use an Empty or Glass Wool–Packed Liner for Hot Splitless GC Injection? A Case Study with a QuEChERS Extract for Pesticides in Tobacco
Jaap de Zeeuw (presenter), Michelle Misselwitz, Julie Kowalski, Scott Grossman, Jack Cochran
Abstract: Gas chromatographers analyzing pesticides typically avoid using wool-packed liners for hot splitless injection for multiple reasons, including irreversible sorptive loss of lower levels of active pesticides (e.g., acephate, omethoate, etc.), thermal degradation of sensitive pesticides (e.g., carbaryl, captan, iprodione, etc.), and poor transfer of lower volatility pesticides to the GC column (e.g., azoxystrobin, deltamethrin, etc.). But a wool-packed liner can provide better sample homogenization, resulting in better repeatability and more accurate results. And wool protects the expensive GC column from non-volatile “dirt.” Properly deactivated wool does not necessarily lead to loss of active pesticides, even at low levels, and a judicious choice of purge valve times will result in complete transfer of relatively involatile pesticides.
In the work presented here, a selection of organophosphorus, organochlorine, organonitrogen, carbamate, and pyrethroid pesticides in a tobacco extract was analyzed using hot splitless injection GC for wool-packed and empty single-taper liners. Average response factors were comparable from 40 back-to-back injections for each liner type, except for the sensitive pesticide, dicofol, which fared better when the liner was empty. More consistent transfer to the GC column for less volatile pesticides was noted for the wool-packed liner.
An Advanced Base Deactivated Capillary Column for Analysis of Volatile Amines, Ammonia, and Alcohols
Jaap de Zeeuw (presenter), Ron Stricek, Gary Stidsen
Abstract: To analyze basic compounds at nanogram levels using gas chromatography, a basic surface modification is often required to reduce the impact of the acidic fused silica. Additionally, to separate volatile components, retention and efficiency at lower temperatures is also required. Base-modified polyethylene glycols have been available for some time, but they are not very stable and they lose efficiency when used below 60 °C. Siloxanes are more challenging for base modification as the stability siloxane polymer should not be compromised. There are some solutions available, but there is room for improvement as present phase technologies are not considered optimal, which translates into short column lifetimes and non-reproducibility in amine response.
An advanced base deactivation technology has been developed for designing a more stable column for volatile amines, not only by increasing the film thickness, but also by creating a direct link with the (basic) surface deactivation. Additionally, the number of cross-links (bridges) between polymer chains was optimized to make sure the polymer keeps efficiency as low as temperatures of 40 ºC. The higher degree of cross-linking was incorporated to make the column more resistant for amine/water mixtures.
The column, named Rtx®-Volatile Amine column, was evaluated at different test sites with a series of amine samples and water matrices to demonstrate performance. In this poster, several applications will be presented and discussed.
Activity in the FID Detection Port: A Big Problem if Underestimated
Jaap de Zeeuw (presenter)
Abstract: It is commonly known in gas chromatography that many problems can be traced to the injection system (e.g., sample, syringe, inlet), which is often a primary place to look at possible issues. This is a valid statement, as 90% of “trouble” is related to injection conditions.
One must also be aware that activity may be caused by other contributions. Especially if we look at non-symmetrical peaks, there are more important areas to look at.
Not only can the columns used be overloaded or poorly deactivated, but the contribution of the detector also has a huge impact on peak shape and response.
Here it is shown that flame tips can adsorb up to 90% of a component and cause tailing on polar as well as base/acidic compounds. Though it looks like columns are not performing, it’s the detector that is the problem.
Deactivation of Metal Capillary Columns: Moving From Trace Sulfur Applications to Stable and Inert High-Temperature GC Solutions
Jaap de Zeeuw (presenter)
Abstract: Metal has been used for a long time as capillary tubing. The big challenge was the high activity of the metal surface causing phase degradation and poor peak shapes. In 1987, a new way to deactivate metal columns was introduced by Restek. The original surface was shielded in such a way that the traditionally reactive metal surface was no longer impacting the chromatography. Later a secondary deactivation was applied, called “Siltek®” where the surface of the silicon layer was further passivated. This deactivation allowed not only columns to be deactivated, but also liners, tubing, cylinders, connectors, etc. Surfaces were especially inert towards reactive sulfur species. Volatile sulfur compounds like H2S and methyl mercaptan and even mercury are known to disappear when they are analyzed at trace levels or when they are stored for some time. The Siltek® technology fixed this issue.
Later the deactivation was found to also have a unique side effect that was not expected. The deactivation increased the stability of high-temperature columns like simulated distillation and biodiesel applications in a way that lifetime was increased typically by a factor 4. In this poster, the data is shared to show the inertness and stabilization effect off the silicon deactivation and what it means for the chromatography.
Understanding and Utilizing Chemical Interactions to Simplify Chromatographic Method Development
Ty Kahler, Rick Lake, Paul Connolly, Sharon Lupo, Mike Wittrig, Bruce Albright, Chris Denicola (presenter)
Vendor Seminar: Recent Developments in GC and LC Columns and Technology From Restek
Ultra Selective Liquid Chromatography™ Technology: Using Chemical Phases to Simplify Method Development in HPLC
Chris Denicola (presenter)
Abstract: In LC method development, it is very important to start with the right stationary phase because that is the best way to obtain the best possible separation in the shortest amount of time. C18 phases are the most common, but there are better phases available with which to start your development.
The Best GC Column Phases for Challenging Applications
Jaap de Zeeuw (presenter)
Abstract: An overview of recent advances in GC column technology will be presented, focusing on the trace analysis of compounds using sensitive detection techniques such as MS. New applications and specific adsorption columns are also discussed.