Abstract: Two hydride generation manifold systems, utilizing flow injection and cryotrapping techniques for alkyl-metal(loid) speciation analysis in natural waters, are described in this paper. They provide shipboard capacity for simultaneous derivatization of analytes with NaBH4 and cryotrapping of the generated products in a field packed column at -196°C. The first system is a large-volume hydride generator, using a reagent-injection flow technique as a flow batch type, that has been fully optimized and applied to the simultaneous detection of alkylated species in estuarine waters. The technique permits the analysis of a large volume sample (0.5-11) at a sampling rate of 3 h-1. The second is an online continuous flow hydride generator. A sampling rate of 3-12 h-1 can be achieved with samples of 0.1-0.5 l. In addition, shipboard operation eliminates major problems related to sample pretreatment, transport and storage. Ultra-trace multi-element determination is finally performed in the laboratory by cryogenic GC hyphenated with ICP-MS. Routine detection limits of 0.5-10 pg (as metal) for 0.5 l water samples were achieved for the selected alkyl-metal(loid) species of arsenic, germanium, mercury and tin. Concentrations of various species, obtained from water samples taken from the Rhine estuary, are also presented. These species include alkylated arsenic compounds, other than methyl derivatives, that have been tentatively identified and are reported here for the first time.

Abstract: A novel semiautomatic dissolved elemental mercury analyzer (DEMA) was developed for investigating dissolved elemental Hg (DEM) in natural waters. This on-line setup couples the main analytical steps from sample introduction, gas-liquid separation, and Au amalgamation/separation to final detection/data acquisition using flow injection techniques. This approach provides ease of operation and high analytical performance and is suitable for shipboard use. The analyzer can be fully automated and also be modified to examine other Hg species (e.g., reactive and total Hg and monomethyl-Hg). Here, we present the results of laboratory performance tests and make a comparison with a traditional manual method. DEM measured by both manual and the DEMA show good agreement. Representative field DEM data from spring and summer 1999 in Long Island Sound, U.S.A. (LIS) are presented. Spatial and temporal DEM variations were evident. Rapid and accurate determinations of DEM are necessary to observe its distribution dynamics, evaluate emissions, and assess its role in the aquatic biogeochemical cycling of Hg.

Abstract: The precision and bias of monomethylmercury (MMHg) determinations in environmental samples can be improved by directly coupling and automating the numerous steps involved with analysis of this toxic Hg species. We developed a simple and robust mercury speciation analyzer (MSA) for measurement of MMHg in environmental matrixes. This on-line hyphenated system couples the main analytical steps, including sample introduction, aqueous-phase ethylation, Tenax pre-concentration, and gas chromatographic separation, to cold vapor atomic fluorescence detection and data acquisition. Here we describe the MMHg-MSA, present results of laboratory optimization and performance tests, and compare the reproducibility between dual analytical channels. With alternating sample concentration and analysis, a dual-channel system permits six high-accuracy MMHg determinations per hour. Additional advantages compared to the traditional manual method include ease of operation and high precision (<5% relative standard deviation). The MSA is applicable to the determination of MMHg in various environmental matrixes, and it can be fully automated. This method was validated by analysis of MMHg in certified reference materials of sediment and biological tissue. Estimated detection limits for MMHg with the MSA are ~0.01 ng g-1 for a 0.1-g sample of dry sediment or fish and ~0.01 ng L-1 for 0.15 L of water.