GC Technical Tips
GAS CHROMATOGRAPHY
Preventing GC Septum Problems
Click here to view a PDF explaining common septa problems and solutions, including:
• Avoid extraneous peaks by proper septum handling and maintenance.
• Handy size chart and septum choice guidelines.
• Optimize performance by choosing the right septum for the job.
Protecting a GC Capillary Column from Matrix
If your chromatography degrades quickly after injecting samples (or standards) that contain matrix, the following suggestions may help increase the numbers of injections before routine maintenance (trimming the column, replacing the injection port liner, cleaning the injection port, etc.) is needed.
Just Because You Don’t Have a Leak Does Not Mean You Don’t Have a Leak
Identifying common GC inlet leaks chromatographically can be challenging since small leaks may result in subtle changes. In this article, the analyst was able to identify a small leak while running straight chained hydrocarbons (C10-C50). View the article to see how the problem was diagnosed and resolved.
GC Troubleshooting with an Electronic Flowmeter
One of the biggest reasons to have a standalone electronic flowmeter is for troubleshooting. Whether you’re seeing issues with an analysis you’ve performed hundreds of times or are developing a new method, it can be useful to have a separate, calibrated tool dedicated for measuring gas flow.
What are some specific applications for an electronic flowmeter?
Measuring Column Flow - Starting with the column, a great use for a flowmeter is measuring column flow. While this can be an excellent troubleshooting step for all columns -- packed and micropacked columns stand to benefit the most due to pressure drop variations.
Measuring Fuel Gases - Detectors like FIDs rely on specific gas ratios—in this case, air and hydrogen. These ratios have a limited range in which they can fluctuate in order to maintain proper function of the detector, and a flowmeter can help you monitor and stay within the ratio.
Calculating Split Ratios - By measuring the split and column flows, a flowmeter can help you calculate the split ratio. This can be useful when you want to verify that your ratio is correct—and that the traps, restrictions, and valves are functioning normally.
Verify Results- Handheld, calibrated electronic flowmeters can also be used to verify results obtained from onboard instrument software.
Whether you're performing troubleshooting or routine maintenance, being able to double-check your results is a great ability to have in your hand.
Using Guard Columns and Retention Gaps in GC (Part 1)
Guard columns and 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 and discusses critical factors affecting performance. This set the background for Part 2, which details guard columns and introduces a new segment coating technology that allows retention gaps and guard columns to be built directly in the same piece of tubing as the analytical column.
Using Guard Columns and Retention Gaps in GC (Part 2)
Guard columns and 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 and introduces a new segment coating technology that allows retention gaps and guard columns to be built directly in the same piece of tubing as the analytical column.
Many users have difficulty understanding the difference between these two products, even though there is a significant difference in application. In Part 1 of this article we reviewed retention gaps, which mainly are used for focusing the sample components when introducing a large (liquid) sample directly onto the column. In contrast, guard columns are used to protect the analytical column from contamination. Guard columns and retention gaps both must be coupled to the analytical column, and this connection introduces a potential point of risk.
Improve Trace Analyses by Optimizing Your Splitless Injections
Splitless injections excel at trace analyses, but to get the most out of a splitless analysis, it’s important to optimize your system. In this video, learn how liner selection, splitless hold times, and inlet and initial oven temperatures can be optimized to improve the performance of your analysis.
GC Inlet Maintenance: Restek’s Quick-Reference Guide
Implementing a rigorous and timely preventative GC inlet maintenance schedule, and choosing the right GC inlet supplies—Restek Topaz liners, septa, inlet seals—can help ensure optimum performance, maximum reproducibility, and minimized downtime for your lab.
How to Choose a GC Inlet Liner: Simplify Selection Based on Injection Type
When selecting an inlet liner, important decisions need to be made. Differences in liner configuration and design, volume, base material, deactivation, and presence or absence of packing material must be considered. Added to this challenge are the different styles of liners used depending on whether the samples are liquid or gas, and whether the injection method is split, splitless, on-column, or direct.
Fortunately, we’ve simplified this decision process for you based on the type of injection that is being used.
Keep Your GCs Running Reliably – Inlet Maintenance
Routine maintenance is an important step in getting the best performance from your gas chromatograph. There are numerous parts in the inlet that require regular replacement including inlet liners, liner O-rings, septa, ferrules, and, for some instruments, inlet seals. Replacement schedules can vary depending on samples and run conditions, but you will reduce your need for troubleshooting when you get your systems on a preventative maintenance schedule. Components and steps may vary based on the instrument or its configuration. Your instrument manual is always the definitive source of instructions.
Split vs. Splitless – Which Injection Mode Should I Use?
Split and splitless are the two most common GC injection techniques. But how do you know which to use? In this video, we follow a sample through split and splitless injections and compare the strengths of each technique to help you choose the right one for your analysis.
Optimizing Splitless Injections
Splitless injections excel at trace analyses, but to get to get the most out of a splitless analysis, it’s important to optimize your system. But what should you optimize and what are the benefits?
When performing a split injection, there are several considerations to keep in mind to improve the quality of your chromatography. But what should you change and why?
An Introduction to Low-Pressure GC-MS (LPGC-MS)
Recently we have demonstrated how low-pressure GC-MS can speed up pesticide analysis in food threefold. Today, we are sharing the background for this innovative technology and explaining how it works and why a new simplified setup makes it more accessible for routine analysis.
Is There a Gas Leak in Your GC? Here's What Can Go Wrong...
Gas leaks are one of the most prevalent and troublesome problems when doing gas chromatography. They can negatively affect your chromatography in a number of ways. This quick video details the headaches leaks can cause and explains why an electronic leak detector is the best way to prevent these problems.
Leak Checking a GC System, A Leak Free System Will Allow Greater Sample Throughput and Less Downtime
We recommend leak checking the system before beginning the column conditioning cycle and eliminating all leaks before proceeding with column conditioning and analytical work.
• Begin at the carrier gas source and regulator and carefully check each fitting and connection along the pathway to the GC.
• Turn off the oven fan and check all fittings, adaptors, and connections inside the oven as well.
• Don't forget to check all column and guard column connections, such as connectors or unions as well – often a leak can be traced to a column end that was crushed during installation.
Check These 10 Common GC Leak Locations
Even the smallest gas leak can cause a loss in sensitivity, contaminate samples, damage columns and instruments, and lead to a lot of wasted time. Grab your leak detector and check these 10 common leak locations now to keep your GC running smoothly.
Spring Cleaning Your GC System
Spring has sprung and now is a good time to give your GC system a thorough going over.
Importance of Inert GC Pathways
When measuring trace-level impurities, your GC system needs to be optimized and inert. If it is not, low-level compounds cannot be adequately distinguished from the baseline and accurate identification and quantification become difficult or impossible. Sensitivity is strongly influenced by column factors including inertness and bleed.
Carrier Gases: Hydrogen as an Alternative to Helium
As the Helium shortage continues to grow, Helium prices are rocketing sky high and in some cases companies are being told they can not get any. Switching to Hydrogen as a carrier gas offers some great advantages.
Tech Tip – How to Correctly Use a Press-Tight Connector
If you've ever attached a guard column, connected two columns together, or repaired a broken column, you know how essential it is to have a clean, reliable connection. In this Restek tip, we'll show you how to ensure a quality connection using a Press-Tight connector.
Guide to GC Column Selection and Optimizing Separations
You can improve lab productivity by assuring that speed and resolution are optimized. One of the best ways to do this is to use the resolution equation as the key to controlling your separations.
Rtx-200 GC Columns: Excellent Retention and Separation of Intermediate Polar Compounds
The distinctive polarity of Rtx-200 columns ensures separations that often cannot be achieved with either nonpolar or polar columns—making them suitable for a broad range of analyses.