Ion chromatographic determination of haloacetates in environmental samples

A method is reported for the sensitive, simultaneous determination of mono-, di-, and trifluoroacetates by ion chromatography. These species were separated using a Dionex AS17 anion-exchange column employed with a potassium hydroxide gradient (via a Dionex EG40 Eluent Generator) and suppressed conductivity detection. The fluoroacetates were successfully separated from a range of inorganic and organic species likely to be present in environmental samples, in a total analysis time of 35 min (including re-equilibration of the column). Detection limits for mono-, di- and trifluoroacetate were 21, 38 and 36 micrograms/L, respectively, determined using a signal to noise ratio of 3, and were obtained using a sample injection volume of 50 microlitres. Precision was less than 0.83% relative standard deviation for replicate injections performed over a period of 30 days. The method was applied to the determination of MFA, DFA and TFA in river water, carrot baits, urine samples and different kinds of plant material including Bilobum, Calvcinum and Spinosum, and found the concentration range of mono-(MFA), di-(DFA), tri-fluoroacetate (TFA) to be 11-788, 3.5-17 and 0.22-1.2 ppm in wet weight plant samples respectively. Further research was carried out using the Dionex equipment specified above. A comparative study was made of the chromatographic behaviour of nine haloacetic acids mono-(MFA), di-(DFA), tri-fluoroacetate (TFA); mono-(MCA), di-(DCA), trichloroacetate (TCA) and mono-(MBA), di-(DBA), tri-bromoacetate (TBA). The techniques included anion-exchange chromatography with suppressed conductivity and UV detection. All nine haloacetic acids were completely separated under the optimised gradient elution conditions. Using selective detection methods or by pretreating samples with a OnGuard II Ag cartridge, eliminated some interference. The procedure for the simultaneous determination of the nine haloacetic acids was simple and fast. The method detection limits for MFA, DFA, TFA, MCA, DCA, TCA, MBA, DBA, and TBA were 21, 40, 40, 48, 28, 86, 67, 55, and 160 ppb respectively, determined using a signal to noise ratio of 3. Applications of these methods for the determination of haloacetic acids in real soil samples are shown.