Dear Paul,

You have to use GC metod （GC/MS/ MS）only for thermaly stable compound and those are soluble in organic solvent. otherwise It may be decompose ordeposited either in the inlet or colum befor the separation.

Also you have to use HPLC metod(HPLS/MS/MS) for the polar compound which are soluble in Aq. medium.

Those are the fundamentals to select GC or HPLC systemS.

For some pesticdes such As Mancozeb, both HPLC and GC may not applicable.

if you could provide a list we would help you futher.

Piyal Aravinna

You will need both GC-MS and LC-MS/MS to run the full USP list (561 list). You do not necessarily need GC-MS/MS although it is handy if you have it. Note that you also have to analyze for inorganic bromide, so you'll need a test method for that (titration, IC, etc).

Dear Paul,

In addition to the above, It is not possible to purchase all the standard from one supplier. Then, you have to contact several supplier to the task. Also, It is not required to be those in a common mixture. If possible It is good. You have to mix compound for the calibration avoiding the co-elution.

PiyalAravinna

Hi Mark and Piyal,

Thank you ALL for the advice!

Yes that is kind of the answer I assumed. I just found a Standard from "Chem Service" to run the USP (561) list For about $1700. Gentlemen, this begs the question though do I only have to run the 69 (and their isomers) on the USP list or do I need to run the entire gamut in EPA's method?

With intense respect.

Paul D. Dodson

USP compliance is based on their list. If you only run for USP compliance then you are fine with their list of compounds (and elements). Most labs that do pesticide residue work develop their own list, typically being a partial list of the 40 CFR 181 pesticides. For example, our standard list is roughly 300 pesticides. Restek has a great set of standards for a more complete screen than the USP list, but it does not include everything on the USP 561 list.

You can run the list so far as you can identify and differentiate each analyte in a method.

Again, as a general rule, you will have to run a normal gc-ms scan method on your system to determine the right conditions to apply first before you run gc-ms/ms even if, you have some literature to be sure of your system.

In addition, some suppliers of reference standards include in the pack a certificate of analysis on the analytes with the conditions when you purchase certified standards, at least I can say that for Dr. Ehrenstorfer GmbH which you can start with if you don't have a run method in-house already.

Thank you

Samuel and Mark,

Thank you immensely for those thorough answers. I absolutely could not get a straight answer from anyone at Restek, Shimadzu or past environmental labs I've worked with. Ironically Shimadzu and Restek are collaborating together on a pesticide list/program. Sincerely-Paul D. Dodson