pesticide GCMS column

[Edde]

I am preparing to develop a GCMS method for multi-pesticides in biological samples for detection of poisoning cases. Therefore, my target coverage is as broad as possible. I'm just in the preliminary stage of literature review and choosing columns and other consumables.

Any idea which column is most suitable for broad pesticide screening? I refer to Shimadzu's method package which uses HP-5MSi, is it ok? What liner should be used?

Thanks.

[Don_Hilton]

The five percent phenyl columns are common in pesticide analysis.

Look at the list of pesticides you are likely to encounter. If you are looking to screen pesticides in an urban emergency room, the likely pesticides may differ from those sought in hazardous waste screening -- or from what would be more common in an agricultural community. There are customized columns for separation of particular types of compounds. While pesticides work is often done with an open liner, if your sample preparation leaves a fairly dirty extract, you may need glass wool or some kind of frit to catch non-volatile materials before they reach the column.

[Edde]

Don_Hilton,
Thanks for your comment. I found that for broad spectrum pesticide vegetable study, some other columns used are
1. DB-1701, 30 m, 0.25 mm, 0.25 m(J&W Scientific, Folsom, CA);
2. DB-35MS, 30m × 0.25mm i.d. capillary column with a 0.25m film (AT, Palo Alto, CA);
3. CP-Sil 8-ms (Varian,Middelburg, The Netherlands) capillary column (30 m, 0.25 mm id, 0.25 m film thickness)

Liners used:
1. Helix double taper deactivated
2. amino deactivated single gooseneck from Restek (Bellefonte, USA).
3. (single-gooseneck, 3.4mmid) contained a plug of Carbofrit (Restek; Bellefonte, PA).

Is it a good practice to experiment on each of these column and liners in the preliminary method development stage?

[Don_Hilton]

Edde,

You can take two approaches. The first is to look for something that meets minimum crieria and then move on. The second is to find what provides the best possible solution. In either case, you need to have a way to evaluate the performance of your system and to deal with the fact that a change may result in both gains and losses when you compare one chromatogram to another. The second approach - to fully evaluate every liner and column - gives a lot of detail - but only for the set of samples you use. So if you do this with standards, the answer may change when you begin to work wiht samples prepared in matrix.

Be aware of why people select each type of liner. Some are selected for split injection, others for splitless. Frits and glass wool are selected to collect nonvolatile materials from dirty samples.

I would suggest that you obtain the columns of interest to you and the liners. Install the set that looks the best from your review of vendor literature and published work. Check it out. If it seems to be able to separate the compunds of interst and give adequate sensitivity, start to work on the sample prepararation. If the column/liner combitation you have selected does not seem to meet your needs. Evaluate what is going on. Change one thing at a time. Columns are selected to provide separation. Liners provide for transofrmation of the sample from liquid to gas phase - with consideration of protection of the column from nonvolatile materials and protection of compunds from degredation or loss during evaporation. And choice of liner may be based on stabilty of measurement over a day's worth of injections.

Your most critical step will be sample preparation. The objective is to get rid of the stuff that gets in the way of analysis of your compunds of interst while retaining your compunds of interest. Look carefully at methods of sample preparation from materials similar to what you will be working with.

[Edde]

Many thanks to your directions. I think I am in a better position to start up.