Search

A novel postcolumn photooxidation reactor with remarkably high efficiency was developed. It was installed into a system of liquid chromatography (LC) combined with inductively coupled plasma mass spectrometry (ICPMS) using a hydride generation (HG) technique to enable sensitive speciation of organic arsenicals. An LC eluent was passed into a reaction tube that runs through a low-pressure mercury lamp of a high-efficiency photooxidation (HEPO) reactor. It provided efficient irradiation with vacuum ultraviolet light at 185 nm, which induced oxidative decomposition of persistent organic arsenicals, for example, arsenobetaine, to the final product, arsenate, for an extremely short time, 3.5 s, without using any oxidizing agents. That arsenate was subsequently detectable by HG-ICPMS. In contrast, conventional photooxidation reactors require more than 100 s for completion, even when using a peroxodisulfate solution as an oxidizing agent. Because of the absence of broadening and dilution of the LC-separated peaks caused by mixing with the oxidant solution, the detection limits for 10 arsenic species including the persistent organic arsenicals by the proposed LC-HEPO-HG-ICPMS ranged from 2.3 to 18 ng of As/L, which were about one-tenth as low as those by LC-ICPMS. The proposed method revealed for the first time the occurrence of 20 arsenic species, including the unknown trace species, which were undetectable by LC-ICPMS and LC-HG-ICPMS, in human urine.

A sensitive method for the determination of ultratrace organotin species in seawater is described. The merits and demerits of derivatization methods using Grignard reagent or sodium tetracethylborate (NaBEt(sub 4) were evaluated in terms of derivatigation efficiency, applicability to the programmed temperature vaporization (PTV) method, and procedural blanks. The sensitivity of the gas chromatography/inductively coupled plasma mass spectrometry (GC/ICPMS) was improved by more than 100-fold by operating the shield torch at normal plasma conditions, compared with that obtained without using it. The absolute detection limit as tin reached subfemtogram (fg) levels. Furthermore, the detection limit in terms of relative concentration was improved 100-fold by using the PTV method, which enabled the injection of a large sample volume of as much as 100 mu L without loss of analyte. When the organotin species in seawater were extracted into hexane with a preconcentration factor of 1000 after ethylation with NaBEt(sub 4) and 100 mu L aliquot of the extract was injected into the GC, the instrumental detection limit in relative concentration reached 0.01 pg/L in original seawater. Sources of contamination of organotin species during the sample preparation were examined, and a purification method of NaBEt(sub 4) was developed. Finally, the method was successfully applied to open ocean seawater samples containing organotin species at the level of 1-100 pg/L.

High-performance liquid chromatography was used in combination with a photodiode array detector to determine and measure extremely small amounts of monofluorophosphate (MFP) and other phosphate contaminants. Similarly, P nuclear magnetic resonance spectroscopy gave quantitation and structural results that were identical with those of the chromatographic technique. Both techniques had presented analytical procedures which could prove valuable in the isolation of MFP chemicals from biological samples.