Water vapor entering the gas chromatograph (GC) inlet, column, and, ultimately, the mass spectrometer (MS) can minimize the sensitivity of our early eluting compounds, including our gases. It can also cause poor peak shape, compounds to co-elude, and shift in retention time, even in compounds outside of the water peak. So, once the water is introduced into our system, it starts to wreak havoc on all our compounds. Some say water doesn’t affect column phase or lifespan, but some have seen an effect, especially if you’re running a lot of samples; water can shorten the column life of your GC column and can cause vacuum issues if you’re using a MS system, which could lead to shorter filament lifetime and having to clean the source more often.

Throughout this blog series, we’ve discussed ways to minimize the amount of water vapor introduced to the GC-MS, using Teledyne Tekmar’s moisture control fitting and application control. We can continue to control moisture not only through this hardware designed for the Purge and Trap, but also through method parameters we can adjust and using smart method parameters on the GC.

The last two Purge and Trap (P&T) settings we will discuss in this blog series might be the most important for moisture control in this volatile organic compound (VOC) analysis: desorb and bake settings.

We can adjust our desorb time to help reduce the amount of moisture we put onto the gas chromatograph (GC) and mass spectrometer (MS). A longer desorb time will remove more of compounds from the analytical trap and send them to the GC, but this includes water, leading to a longer water peak in the total ion chromatogram. If the desorb time is shortened, less of that analyte material is transferred to the GC, but we will have a much shorter water peak, giving the compound peaks better shape and resolution. This gives us an opportunity for method optimization with the desorb settings both in time and temperature.

In part one of this series, we learned why water vapor is bad for volatile organic compound (VOC) analysis. In part two, we will explore ways we can optimize moisture control in the Purge and Trap (P&T) system.

Hello all,

For those of you who are reading this from your office, or laboratory, please do be safe and thank you for the essential functions that you continue to serve, despite the risk to you and your family. We are all grateful for your efforts. However, if you’re like me right now, you are reading this from home. While it is certainly an adjustment (how is it possible that two toddlers can sound like a herd of elephants migrating through a bubble wrap factory!?), it is very important for those of us who can, to stay home and slow the spread of COVID-19. All the same, it is probably difficult being away from your instruments, even if this is a good time to catch up on other tasks. When all of this comes to an end, and eventually we return to work, in what kind of condition will we find our instruments?

Purge & Trap (P&T) concentration is a common technique used for the analysis of Volatile Organic Compounds. An analytical trap is the major component of any P&T system and is responsible for trapping the analytes purged from a sample, and then after heating, releasing them for further analysis.

An analytical trap choice for Purge and Trap concentration offers specific challenges for end users. Most standard methods define the dimensions of the trap, as well as recommend packing materials. There are several packing choices that can be substituted, however, provided they meet the analytical requirements of the method.

Fundamentals of Purge & Trap

Purge and Trap Background

When using a concentrator system, it is not essential to understand how it works. However, a good grasp of the fundamentals helps prevent problems and assists you when you are faced with tasks such as method development and troubleshooting.  The purpose of this blog is to help you develop an understanding of how and why compounds are concentrated.