Restek’s Jack Cochran will be a featured speaker at both the 1st International Symposium on Recent Developments in Pesticide Analysis and the 10th International Symposium on Recent Developments in POPs Analysis. Both symposia are free, two-day events organized by Thermo Fisher Scientific. This year, the meetings will be held in late April in Prague, and they will offer exciting agendas focused on the analysis of persistent organic pollutants (POPs) and pesticides. Leading experts will present on analytical advances relevant to environmental and food testing and will also be available to discuss analytical challenges as well as state-of-the art methodology and instrumentation.
Jack is a recognized expert in GC and GCxGC for the analysis of pesticides and priority pollutants in food, soils, sediments, air, water, and other matrices. He uses his years of real-world experience in method development, sample preparation, and analysis to help chromatographers worldwide and is still a “hands-on” scientist, spending as much time in the laboratory as possible. As an invited speaker, he will give a presentation at each symposium as described in the following abstracts.
1st International Symposium on Recent Developments in Pesticide Analysis (April 27–28, 2015)
Shoot-and-Dilute GC-MS/MS for the Analysis of Pesticides in Food
“Shoot-and-dilute” GC-MS/MS uses split injection paired with a very sensitive triple-quadrupole mass spectrometer to alleviate matrix-related issues occurring in the GC inlet and column. There are well-known problems associated with splitless injection of dirty samples (e.g., QuEChERS extracts), most notably compound degradation and the loss of relatively active and nonvolatile pesticides. These issues lead to inaccurate quantification and, in some cases, completely missing the pesticide of interest. GC inlet problems can occur very quickly with real samples, sometimes with a single splitless injection of a particularly dirty sample. This leads to time-consuming inlet and column maintenance to restore instrument performance.
An easy way to mitigate the above problems is to use split injection when possible. If LOD and LOQ requirements are achievable using split injections, increased flow through the inlet minimizes residence time inside the inlet liner, which decreases the degradation of sensitive pesticides. In addition, the GC oven start temperature can be higher, thus reducing overall run time as well as the time needed to re-equilibrate the GC oven.
Shoot-and-dilute GC-MS/MS was tested using a screening method for multiclass pesticides in celery and orange QuEChERS extracts and compared to a splitless injection method.
10th International Symposium on Recent Developments in POPs Analysis (April 29–30, 2015)
Things You Can Do to Make GC Systems Stay Up Longer to Analyze More Samples
In GC-MS, most problems occur on the front end, at the GC inlet, where compounds can degrade during hot splitless injection, active compounds can be irreversibly adsorbed to inlet liner surfaces, and nonvolatile material from dirty samples can compromise the transfer of less volatile compounds of interest from the inlet to the GC column. These issues are magnified due to the very slow inlet flow during splitless injection, which is typically less than 2 mL/min. One way to mitigate them is to instead use split injection, what we term “shoot-and-dilute,” where the much higher flow rate through the inlet results in a substantially reduced residence time and a proportionately higher transfer for difficult compounds of interest. This technique is especially appropriate with ultra-sensitive detectors like electron capture detectors (ECD), magnetic sector high resolution mass spectrometers, and newly introduced GC-MS/MS systems.
Another way to suppress chromatography problems, especially in splitless injection GC, is through the use of “analyte protectants,” which are essentially masking agents such as sugars, diols, etc., that are co-injected with samples and standards to tie up active sites in GC inlet liners and columns. While this technique is somewhat common in the GC analysis of pesticides in food, its use is underexplored in environmental analytical work.
This paper will demonstrate the possibilities of using split injection and analyte protectants to keep GC systems up longer to analyze more samples. Better chromatographic peak shapes and more stable responses are the goals.
Register here for either or both symposia.