| Arsenic exists in the form of the inorganic and organic in nature, with different physic and chemical properly, migration and toxic. It is generally acknowledged that the toxic of inorganic arsenic will far outweigh the organic arsenic, while arsenobetaine, asenocholine and arsenic sugar were basicly thought as non-toxic. The total amount of arsenic research was not accurate assessment the toxic of the body, environment and biology. Therefore, the study of vary form arsenic is imperative. Based on the hydride generation-atomic fluorescence spectrometry detection and liquid chromatography separation, an analytical method for arsenic speciation in water, beers, lake sediment, seafood was developed. Specific details of the study are as follows:(1) Based on optimization conditions of the pre-treatment of arsenic speciations in water samples were developed. Four arsenic species, i.e., arsenite As (Ⅲ), dimethylarsinic acid (DMA), monomethylarsonic acid (MMA) and arsenate As (Ⅴ) were separated by anion-exchange chromatography with isocratic elution using 20 mmol/L KH2PO4/K2HPO4 with flow rate 1mL/min as mobile phase. The elution time were 2.80, 3.90, 5.42 and 12.01 min for As (Ⅲ), DMA, MMA and As(Ⅴ) respectively. Potassium borohydride (3.5% m/v) and hydrochloric acid (10%, m/v) were used as the reduction agents and the argon with a flow rate of 500 mL/min was used as the carrier gas to deliver the volatiled species. The detection limits of the As (Ⅲ), dimethylarsinic acid (DMA), monomethylarsonic acid (MMA) and As(Ⅴ) are 0.8, 1.6 , 0.8, 2.1μg/L respectively. The RSD values were between 1.62-2.19%. The linear respones for the four arsenic species were obtained in the range of the 10-200μg/L, and the recovery values were between 91.4-104%.(2) Based on microwave assisted extraction and the liquid chromatography-hydride generation-atomic fluorescence spectrometry determination, an analytical method for arsenic speciation (arsenite As(Ⅲ), dimethylarsinic acid (DMA), monomethylarsonic acid (MMA) and arsenate As(Ⅴ)) in the Tai lake sediment was developed. The experiment conditions were sysmetically optimized and 1 M phosphoric acid was selected as the extractant with microwave assisted extraction (power 60 W, time 12 min). The extraction rates of 79.8-91.6% were obtained and the linear respones for the four arsenic species were in the range of the 10-160μg/L. The detection limits were between 0.6-2.3μg/L for different species with the RSD in range of 1.62-2.19%. The recovery rates in the range of 94.8-107% were obtained for real sample analysis. It was found that the total As contents in the sediment of Tai lake were in the range of 8.37-13.1μg/L and arsenate As(Ⅴ) was the main species.(3) Seafood samples were extracted with accelerated solvent extraction(ASE) at 1500 Psi, 60℃for 5 min using a mixture of methanol and water (1:1,V/V) as the solvent. The experiment conditions were sysmetically optimized. Five arsenic species, i.e., arsenobetaine(AsB), arsenite As (Ⅲ), dimethylarsinic acid (DMA), monomethylarsonic acid (MMA) and arsenate As (Ⅴ) were separated by anion-exchange chromatography with isocratic elution using 20 mmol/L NH4HCO3 and 10 mmol/L K2SO4 as mobile phase with pH 9.00. Arseno-organic compounds were on-line digested by K2S2O8 (2% m/v) as digestion. The extraction rate was 83.4-93.5%, recovery rate 88.0-98.8%. Seafood arsenic content in 0.152-6.13μg/g, ultimately we measured arsenic betaine was the main form in the seafood. |
