AN ANALYTICAL METHOD FOR TRIFLUOROACETIC-ACID IN WATER AND AIR SAMPLES USING HEADSPACE GAS-CHROMATOGRAPHIC DETERMINATION OF THE METHYL-ESTER

An analytical method has been developed for the determination of trace levels of trifluoroacetic acid (TFA), an atmospheric breakdown produc t of several of the hydrofluorocarbon (HFC) and hydrochlorofluorocarbo n (HCFC) replacements for the chlorofluorocarbon (CFC) refrigerants, i n water and air. TFA is derivatized to the volatile methyl trifluoroac etate (MTFA) and determined by automated headspace gas chromatography (HSGC) with electron-capture detection or manual HSGC using GC/MS in t he selected ion monitoring (Srm) mode. The method is based on the reac tion of an aqueous sample containing TFA with dimethyl sulfate (DMS) i n concentrated sulfuric acid in a sealed headspace vial under conditio ns favoring distribution of MFTA to the vapor phase, Water samples are prepared by evaporative concentration, during which TFA is retained a s the anion, followed by extraction with diethyl. ether of the acidifi ed sample and then back-extraction of TFA (as the anion) in aqueous bi carbonate solution. The extraction step is required for samples with a relatively high background of other salts and organic materials, Air samples are collected in sodium bicarbonate-glycerin-coated glass denu der tubes and prepared by rinsing the denuder contents with water to f orm an aqueous sample for derivatization and analysis, Recoveries of T FA from spiked water, with and without evaporative concentration, and from spiked air were quantitative, with estimated detection limits of 10 ng/mL (unconcentrated) and 25 pg/mL (concentrated 250 mL:1 mL) for water and 1 ng/m(3) (72 h at 5 L/min) for air, Several environmental a ir, fogwater, rainwater, and surface water samples were successfully a nalyzed; many showed the presence of TFA.