Arsenic Detection And Speciation In Complex Sample Matrixes

Arsenic is an abundant and ubiquitous element in nature and human living environment. It is the20th most abundant element in the earth crust,14th in the seawater,12th in human body. High concentration of arsenic in drinking water has been found in many countries, in-cluding USA, Chile, Bangladesh, Mexico, Argentina, Poland, Canada, Hungary, Japan, Nepal and India. In China, many places, e.g., Taiwan, Xinjiang, Inner Mongolia, Ningxia, Jilin, Qinghai are also suffering from serious arsenic pollution in drinking waters. Especially, the toxicity of arsenic has been recognized as one of the most serious problem for threatening human life and health. Therefore, it has become urgently for timely warning and accurate de-tection of arsenic pollution.It has been reported that arsenic has many species, and their toxicity depends closely on their chemical forms. The order of toxicity is generally as following:Arsine> arsenite> ar-senate> organic arsenic species. Thus, it is no longer sufficient to evaluate only the concen-tration of total arsenic. In this respect, arsenic speciation analysis brings in-depth information on the toxicity of the individual arsenic species.Currently, the commercially available methodologies for arsenic determination have pa-lyed an important role in the determination of arsenic. However, for the purpose of field anal-ysis, the commercial instrumentations provide better sensitivity but they are generally bulky and costly for routine running or with insufficient sensitivity for cheap devices. In this junc-ture, it is highly necessary to develop suitable analytical methods or instrumentations for this purpose. In this respect, light-emitting diode (LED) and photodiode are employed to build simple, sensitive and miniaturized arsenic detector. For arsenic speciation, we have modified the hydride generation approach for arsenic detection to improve the hydride generation effi-ciency and thus provided better sensitivity. In addition, solid phase extraction has been used for removing the sample matrix and further improved the sensitivity for arsenic speciation.The first chapter of the thesis introduces the general properties of arsenic and the current status of arsenic detection and speciation.The second chapter presents a simple arsenic detector for field arsenic detection in envi- ronmental water samples. The device used LED as the light source, photodiode as the detector and porous polypropylene membrane tube containing I-I3solution served as arsine capture medium.The third chapter studies the arsenic speciation by liquid chromatography hyphenated with gradient hydride generation with detection by flame atomic absorption spectrometry. The gradient hydride generation provides high conversion efficiency for all the arsenic species with optimal reactions conditions for each of the arsenic species, e.g., arsenite (As(III)), arse-nate (As(V)), monomethylarsonic acid (MMA), dimethylarsinic acid (DMA) and trimethylar-sine oxide (TMAO).The last chapter investigated the solid phase extraction of various arsenic species with MnO2particles as preconcentration medium. This helps to remove the sample matrix effect and further improves the detection sensitivity for arsenic species on the basis of gradient hy-dride generation with detection by flame atomic absorption spectrometry.