An Analytical Method for Trifluoroacetic Acid in Water and Air Samples Using Headspace Gas Chromatographic Determination of the Methyl Ester

Abstract

An analytical method has been developed for the determination of trace levels of trifluoroacetic acid (TFA), an atmospheric breakdown product of several of the hydrofluorocarbon (HFC) and hydrochlorofluorocarbon (HCFC) replacements for the chlorofluorocarbon (CFC) refrigerants, in water and air. TFA is derivatized to the volatile methyl trifluoroacetate (MTFA) and determined by automated headspace gas chromatography (HSGC) with electron-capture detection or manual HSGC using GC/MS in the selected ion monitoring (SIM) mode. The method is based on the reaction of an aqueous sample containing TFA with dimethyl sulfate (DMS) in concentrated sulfuric acid in a sealed headspace vial under conditions favoring distribution of MTFA to the vapor phase. Water samples are prepared by evaporative concentration, during which TFA is retained as the anion, followed by extraction with diethyl ether of the acidified sample and then back-extraction of TFA (as the anion) in aqueous bicarbonate 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 denuder tubes and prepared by rinsing the denuder contents with water to form an aqueous sample for derivatization and analysis. Recoveries of TFA 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 air, fogwater, rainwater, and surface water samples were successfully analyzed; many showed the presence of TFA.

Rainwater trifluoroacetic acid (TFA) in Guangzhou, South China: Levels, wet deposition fluxes and source implication

“…TFA has become a ubiquitous contaminant and has been detected in a variety of environmental media, such as air (Frank et al, 1996), precipitation (Jordan and Frank, 1999;Scott et al, 2006;Zehavi and Seiber, 1996), fog (Römpp et al, 2001), surface waters (Cahill and Seiber, 2000;Scott et al, 2000Scott et al, , 2002Zhang et al, 2005), soils and pine needles Scott et al, 2005b), oceans (Frank et al, 2002;Scott et al, 2005a) and even in the snow of the Arctic and Antarctica (Von Sydow et al, 2000). TFA is extremely stable in the ambient and highly resistant to chemical and biological degradation under normal environmental condition (Emptage et al, 1997;Boutonnet et al, 1999).…”

“…Although the observed TFA levels in aqueous environment were all below the safety level of 0.10 mg L −1 (Berends et al, 1999), high levels have been reported as early as in 1990s. For instance, TFA concentrations were reported as high as 40,900 ng L −1 in Pyramid Lake of the United States (Zehavi and Seiber, 1996); and the levels beyond 1000 ng L −1 were also recorded in rainwater around the world (Frank et al, 1995;Wujcik et al, 1998;Von Sydow et al, 2000;Berg et al, 2000;Scott et al, 2006). Due to the continual input to the environment and the accumulation in terminal water bodies, TFA levels in aqueous environment would keep increasing in the coming decades and more attention should be paid on its potential adverse effects (Berends et al, 1999;Boutonnet et al, 1999;Wiegand et al, 2000).…”

Changes in tropospheric composition and air quality due to stratospheric ozone depletion and climate change

“…80 Concentrations up to 350 ng L -1 in flowing surface waters have been reported from several locations. [81][82][83] However, in landlocked lakes, they may be as large as 40 000 ng L -1 . 81 Reports of TFA concentrations in oceans are generally less than or equal to 200 ng L -180, 81, 83 and much of this appears to have pre-industrial natural origins.…”

“…[81][82][83] However, in landlocked lakes, they may be as large as 40 000 ng L -1 . 81 Reports of TFA concentrations in oceans are generally less than or equal to 200 ng L -180, 81, 83 and much of this appears to have pre-industrial natural origins. 84 Based on historical production 85 of HFCs and HCFCs that are potential sources of TFA as well as projections of future uses, 77 an estimate of total production was made (Table 1).…”

Environmental effects of ozone depletion: 1998 assessment

“…Samples of rain and surface waters (oceans, rivers, lakes, and springs ) have been obtained from many geographical areas (USA, Canada, Australia, South Africa, Germany, Israel, Ireland, France, Switzerland, Finland) and show that TFA is a ubiquitous contaminant of the hydrosphere (Frank et al, 1996;Zehavi and Seiber, 1996;Grimvall et al, 1997;Wujcik et al, 1998), with values up to 40900 ng/l (Zehavi and Seiber, 1996). The average TFA concentration in rain water observed in Bayreuth during 1995 was 100 ng/l (Frank et al, 1996).…”