Sampling and probing volatile metal(loid) species in natural waters by in-situ purge and cryogenic trapping followed by gas chromatography and inductively coupled plasma mass spectrometry (P-CT–GC–ICP/MS)

Abstract

An in situ purge and cryogenic trapping method for the pre-concentration of volatile metal and metalloid compounds dissolved in natural waters was developed. The analytes were collected in cryogenic trap stored at −196°C until analysis in the laboratory. Cryogenic traps were then introduced into a flash desorption, cryofocusing gas chromatography system hyphenated to an inductively coupled plasma mass spectrometer (ICP/MS). This multi-element detection technique allowed to determine volatile compounds of selected elements in aqueous solution simultaneously by scanning their corresponding stable isotopes. Blanks and recoveries for the whole analytical procedure of several volatile compounds of selected elements (Me 2Se, Me 2Se 2, Me 2Hg, Et 2Hg, Me 4Sn, Et 4Sn, Me 4Pb, Et 4Pb) were determined and are discussed. Method detection limits for 1 l water sample were estimated for Se, Hg, Sn and Pb volatile species to be as low as 10.0 (0.8), 1.0 (0.2), 0.4 (0.05) and 0.4 (0.08) fmol/l (pg/l), respectively. The occurrence of volatile compounds of selenium, tin, mercury and lead was evidenced and investigated in three major European estuaries such as the Gironde (F), the Rhine (NL) and the Scheldt (B/NL). The presence of these volatile species in natural waters seems to be related to both exchanges between environmental compartments and anthropogenic inputs.