Haloacetic acid derivatization

[DNA]

I´m trying to use GC-ECD to detect haloacetic acids. My question is about the derivatization. There some papers were is used a methylation. But does anyone use a silylation or a acylation reaction? Is there a sgnificant diference in the results?

Thanks

[Steve Reimer]

I have only tried methylation of haloacetic acids, but even there the method and conditions can make a large difference in how reproducible the derivatization is. USEPA has updated its drinking water method for HHAs (552.3) to include the choice of a higher temperature methylation because laboratories were having problems with 2 hours at 50 degrees in MTBE.

552.3 is available at http://www.epa.gov/safewater/methods/sourcalt.html

[chhubert]

I have experience derivatizing some carboxylic acids using MTBSTFA and got good results. Not knowing whether it also works for haloacetic acid, silylation using MTBSTFA is presumably better than other common silylating reagent such as BSTFA 'cos the former contains bulky tert-butylsilyl group which hinders hydrolysis of the derivative. Of course, silylation has to be done in the absence of water.