CLEANUP AND CONFIRMATORY PROCEDURES FOR GAS-CHROMATOGRAPHIC ANALYSIS OF PESTICIDE-RESIDUES .2.

The behaviour of standard solutions of fourteen simple organohalogenat ed pesticides, nine individual polychlorinated biphenyls (PCBs) and Ar oclor 1242, 1248, 1254 and 1260 on treatment with sulphuric acid, pota ssium hydroxide and chromium(IV) oxide was studied by capillary gas-li quid chromatography (cGC) using electron-capture detection. These meth ods were applied to confirm the presence of organochlorine residues in river water and human milk. Positive confirmation with the three trea tments were in agreement with capillary GC(cGC)-MS determinations carr ied out in the electron impact and selected-ion monitoring mode. After cGC analyses, the extracts containing possible pesticides or Aroclors were treated with the three chemicals and re-analysed under the same cGC conditions. The new chromatographic profiles showed many missing a rtifact peaks, and some pesticides or PCBs were also destroyed. The pr esence or disappearance of the peaks after chemical attack makes it po ssible to identify the specific pesticides and PCBs analysed. PCBs res ist both acid and alkali attacks, but some low-chloride PCBs are total ly or partially destroyed by oxidative treatment. The methods studied are useful for intralaboratory purification and confirmation of residu es of pesticides and PCBs, although they can be insufficient for ident ifying organochlorine pesticide residues from some very polluted sampl es.