A reversed-phase ionpair chromatographic method with tetramethylene oxide as organic modifier has been developed for the simultaneous separation and detection of the sulfides NH2CSNH2, (NH4)2CS3, (NH4)2S, and NH4SCN. The optimized separation conditions were determined by means of a U7(76) uniform design experiment, and tetramethylene oxide played an important role in adjusting the retention behavior of(NH4)2S and NH4sSCN. The linearity of the calibration plots for the four components was investigated; correlation coefficients were from 0.9989-0.9999. The proposed method was successfully applied to the determination of NH2CSN H2, (NH4)2CS3, (NH4)2S, and NHSCN in synthesis and isomerization samples.

The species of Cr(III) and Cr(VI) in water samples were determined by flow injection on-line preconcentration and separation on two-microcolumn system-derivative flame atomic absorption spectrometry during a collaborative analysis for certification. The Cr(III) and Cr(VI) in water samples were retained on two microcolumns with ion exchange resin and were eluted directly to nebulizer by 15% HNO3 and 8% NH4NO3, respectively. The characteristic concentration (at the sensitivity grade of 2 mV min-1 for 1 min of preconcentration time) for Cr(III) and Cr(VI) were 0.130 and 0.0985 μg l-1, in the order which were 332- and 431-fold better than those of FAAS, and 45- and 47-fold better than those of FI-FAAS, respectively. The relative standard deviations were 3.27% and 3.66% with corresponding detection limits (3σ) of 0.244 and 0.235 μg l-1, respectively. The linear ranges of determinations for Cr(III) and Cr(VI) were 0~100 μgm l-1 with correlation coefficients of 0.9984 to 0.9996. The satisfactory recovery of 94.4%~106% for Cr(III) and Cr(VI) could be obtained from water samples.

A new method was developed for simultaneous determination of trace arsenic and antimony in Chinese herbal medicines by hydride generation-double channel atomic fluorescence spectrometry with a Soxhlet extraction system and an n-octanol-water extraction system, respectively. The effects of analytical conditions on the fluorescence intensity were investigated and optimized. A water-dissolving and methanol-water-dissolving capability were compared. The contents of different species in five Chinese herbal medicines and their decoctions were analyzed. The concentration ratios of n-octanol-soluble As or Sb to water-soluble As or Sb were related to the kinds of medicine and the acidity of the decoction. Soxhlet extraction was found to be an effective method for plants pretreatment for determination of arsenic and antimony species in Chinese herbs; the interferences of coexisting ions were evaluated. The proposed method has the advantages of simple operation, high sensitivity and high speed, with 3σ detection limits of 0.094µgg−1 for As(III), 0.056µgg−1 for total As, 0.063µgg−1 for Sb(III) and 0.019µgg−1 for total Sb in a 1.0g of the sample.

By HG-AFS, a new method was proposed for simultaneous determination of total arsenic and total selenium existed in the Chinese medicinal herbs in tartaric acid medium. The effects of analytical conditions and coexisting ions on the fluorescence signal intensity of analytes were investigated. The proposed method was provided with linear response ranges above 22µg l−1 for As and 44 µg l−1 for Se, and the detection limits of 0.13 and 0.12 µg l−1 were obtained for As and Se respectively. The recoveries of 93.8-96.1% for As and 95.3-99.1% for Se, and the precision of 1.2-3.8% and 2.4-5.3% (R.S.D., n=8) respectively, were obtained via simultaneous determined four samples of Chinese medicinal herbs and three certified botanic reference materials successfully. The proposed method has the advantages of simple operation, high sensitivity and high efficiency.

Hydride generation atomic fluorescence spectrometry (HG-AFS) has been used for determination of hydride-forming elements because of its high sensitivity, simplicity, and low costs, but most of such work has been concentrated on single element analysis, and reports dealing with multielement determination by HG-nondispersive (ND)AFS are rare. In this work, a sensitive HGNDAFS method was developed for simultaneous determination of trace cadmium and arsenic in biological materials. The conditions for the generation of volatile cadmium and arsenic species from the reaction with KBH4 in aqueous solution were investigated using a double-channel AFS integrated with an intermittent flow reactor. Like thiourea and Co(II), ascorbic acid was found to significantly enhance the generation efficiency of volatile Cd and As species. The interferences of coexisting ions were evaluated. Under optimal conditions, the detection limits for Cd and As were determined to be 10 and 150 ng L-1, respectively. The precision for 11 replicate determinations at the 1 μg L-1 Cd level and the 10 μg L-1 As level were 3.5 and 2.7% (RSD), respectively. The recoveries of spike analytes in the biological samples studied ranged from 94 to 109%. The proposed method was successfully applied to the simultaneous determination of Cd and As in a variety of biological samples.