Speciation Analysis Of Arsenic In Vegetables And Its Application Research

Arsenic is one of the ordinary elements in the nature. It has a century-long reputation of being poisonous. Recently, as the development of investigating on arsenic, people know that the toxicity of arsenic is greatly dependent on its chemical form. So the total content of arsenic could not reflect the real influence of it on environment. It is qualitative and quantitative analysis of different arsenic species. Our study selects As(III),As(V),MMA,DMA, which have toxicity and universality, as analytical subject to establish speciation method of vegetables for the first time.Now, arsenic speciation analysis is achieved by High Pressure Liquid Chromatography-Inductively Coupled Plasma-Mass Spectrometry (HPLC-ICP-MS), Hydride Generation-Inductively Coupled Plasma-Atomic Absorption Spectroscopy (HG-ICP-AAS) and High Pressure Liquid Chromatography-Hydride Generation-Atomic Fluorescence Spectroscopy (HPLC-HG-AFS). HPLC-HG-AFS is the most reported and the most widely used. It has high accuracy, stability and sensitivity. We want to find a method that used to Arsenic Speciation Analysis of vegetables.Firstly, the object of study is established. We collect different types of vegetable samples and detect the total arsenic content of samples. Bracken is identified as research subjects, because it's higher arsenic content.Secondly, the equipment condition is optimized. Include three aspects: 1 .Optimization of separation system. The main study is for HPLC separation conditions. The concentration is 15 mmol/L, the pH is 6.0, and (NH₄)₂HPO₄ is used as mobile phase. The four arsenic species are baseline separated. 2. Optimization of HG. Carrier solution is 7 % (v/v) Hcl, reducing agent of HG is 1.5% (m/v) KBH₄ solution. 3. Optimization of detection system. The main study is for AFS detection system. The best conditions include that: the photomultiplier tube of negative high voltage is 290 V, lamp current is 100 mA, atomization temperate is 200℃, carrier gas's flow rate is 300 ml/min, and shielding gas's flow rate is 600 ml/min.Thirdly, pre-treatment method is chose. Extract is 1:1 (v/v) methanol-water solution. Ultrasound (20 min) - centrifugal (20 min) through 3 consecutive times extraction is the extraction method.Fourthly, the method is evaluated. Independently, the DL are: As(III) 2μg/L,DMA 4μg/L,MMA 4μg/L,As( V) 10μg/L, the recovery is between 82.3%-88.3%, and the RSD are: As(III) 1.01%, DMA 2.51%, MMA4.76%, As(V) 4.67%. It shows that the four arsenic species has good linearity, correlation coefficient> 0.999. It indicates that the method has the characteristic of high sensitivity, good accuracy, stability and wide range of linearity.Another part of the study is to make optimized method apply in the vegetables sample determination. Through investigation market in common terrestrial vegetables and aquatic vegetables, finally indicated: (1) The aquatic vegetables arsenic content is higher than the terrestrial vegetables general; (2) The terrestrial vegetables arsenic content is lower and mainly by inorganic arsenic shape primarily; (3) The aquatic vegetables arsenic content is higher, but by the non-toxic organic arsenic primarily, the inorganic arsenic content is mainly low; (4) The Arsenic-rich vegetables (such as bracken, rapes in contaminated areas, etc.) the arsenic content is very high and by toxic strongest inorganic arsenic forms existence.