Vapor Generation of Inorganic Anionic Species After Aqueous phase Alkylation with Trialkyloxonium Tetrafluoroborates

Aqueous phase reaction of trialkyloxonium tetrafluoroborates, R(3)O(+)BF(4)(-) (R=Me, Et) has been tested in the alkylation of simple inorganic anionic substrates such as halogen ions, cyanide, thiocyanate, sulphide and several oxoanions or their corresponding oxoacids. Gaseous products were separated and identified by gas chromatography mass spectrometry (GC-MS). Alkylated derivatives RI, RBr, RCl were obtained for iodide, bromide, and chloride, respectively, while for fluoride its conversion efficiency to RF is very poor. RCN and R(2)S were obtained for cyanide and sulphide, while thiocyanate gives RSCN as a main reaction product with a minor amount of alkylisothiocyanate, RNCS (<7%). Among tested oxoanions only nitrites and nitrates give volatile derivatives under the form of R-O-NO and R-O-NO(2), respectively. Reaction performed by adding Et(3)O(+)BF(4)(-) in CH(2)Cl(2) to aqueous sample with extraction in the organic phase of reaction products, failed to identify other less volatile reaction products. Using 2 mL sample in 4 mL reaction vial (T = 25 degrees C, 100 mu L of 2 M Et(3)O(+) BF(4)(-) and injecting 250 mu L of headspace into GC-MS, detection limits (3 s) are in the range of 1-280 ng mL(-1). Application to determination of bromide in groundwater certified reference material (BCR-612, 252 +/- 10 mu g kg(-1) of bromide) gave results in excellent agreement with certified values. The method, being not responsive to iodate, allows the selective determination of iodide in the presence of iodate. Total iodine can be determined after reduction of iodate to iodide by NaBH(4). Application of the method to iodide-iodate speciation in table salt gave results in excellent agreement with parallel analysis performed by ion chromatography as a reference method.