SPECIATION OF MERCURY BY ICP-MS AFTER ONLINE CAPILLARY CRYOFOCUSING AND AMBIENT-TEMPERATURE MULTICAPILLARY GAS-CHROMATOGRAPHY

An automated, small and easily mountable/demountable accessory based o n a constant temperature multicapillary GC is proposed for time-resolv ed introduction of gaseous mercury species into an ICP-MS, The fast, n arrow-band injection was achieved by cryofocussing (-80 degrees C) of dimethyl-, methylethyl- and diethylmercury in an 11 cm capillary house d in a steel tube prior to desorption of the species (within 3-5 s) by rapid-pulse high intensity current. The highest chromatographic resol ution was achieved at ambient column temperatures; isothermal separati ons at higher temperatures offered increased sensitivity and speed of analysis controlled by the data acquisition rate of a quadrupole MS. T he compatibility of the operating variables with the ICP ionization co nditions (argon at 50-300 ml as the carrier gas) and negligible peak b roadening on the column and in the ICP-MS interface allow the sensitiv e (limit of detection 0.15 pg) isotope-selective speciation of mercury in biological and sediment samples.