Cherukurii Jyotsna, Anjaneyulu Y
Centre for Environment, Institute of Science &Technology, Jawaharlal Nehru Technological University, Kukatpally, Hyderabad-500072, India.
Int J Environ Res Public Health. 2005 Aug;2(2):322-7. doi: 10.3390/ijerph2005020018.
Arsenic is naturally found in surface and ground waters and the inorganic forms of arsenic are the most toxic forms. The adverse health effects of arsenic may involve the respiratory, gastrointestinal, cardiovascular, nervous, and haematopoietic systems. Arsenic contamination in drinking water is a global problem widely seen in Bangladesh and West Bengal of the Indian sub continent. As there is a great demand for field test kits due to the anticipated reduction of the US EPA arsenic standard from 50ppb to 10ppb a field kit which offers rapid, simple and safe method for precise estimation of arsenic at 10ppb in drinking water samples is developed. Field methods, based on the mercuric-bromide-stain, consist of three different major parts, which are carried out stepwise. The first part of the procedure is to remove serious interference caused by hydrogen sulphide. In commercially available kits either the sulphide is oxidized to sulphate and the excess oxidizing reagent removed prior to the hydride generation step or, the hydrogen sulphide is filtered out by passing the gas stream through a filter impregnated with lead acetate during the hydride generation step. The present method employs cupric chloride in combination with ferric chloride or Fentonis reagent for the removal of hydrogen sulphide, which is rapid, simple and more efficient. Other interferences at this step of the analyses are normally not expected for drinking water analysis. In the second step, the generation of the arsine gas involves the classical way of using zinc metal and hydrochloric acid, which produce the enascenti hydrogen, which is the actual reducing agent. Hydrochloric acid can be replaced by sulfamic acid, which is solid and avoids a major disadvantage of having to handle a corrosive liquid in the field. The arsine gas produces a yellowish spot on the reagent paper. Depending on the arsenic content, either, Yellow n H (HgBr)2 As (10-50ppb), Brown n (HgBr)3 As (50-100ppb) or Black n Hg3 As2 (>100ppb) are formed which can be precisely estimated by visual comparison with standard color chart. The results obtained by field kits agree well with the data obtained through I.C.P.AES methods. The most important characteristic for field measurement is that analytical results can be obtained on the site where the sample is taken with high precision and can be conveniently utilized for monitoring arsenic rapidly in a highly contaminated large geographical area.
砷天然存在于地表水和地下水中，无机形式的砷是毒性最强的形态。砷对健康的不良影响可能涉及呼吸、胃肠、心血管、神经和造血系统。饮用水中的砷污染是一个全球性问题，在印度次大陆的孟加拉国和西孟加拉邦广泛存在。由于预计美国环境保护局（US EPA）的砷标准将从50 ppb降至10 ppb，对现场检测试剂盒的需求很大，因此开发了一种能为饮用水样品中10 ppb的砷提供快速、简单且安全的精确估算方法的现场试剂盒。基于汞溴化物染色的现场方法由三个不同的主要部分组成，按步骤进行。该程序的第一部分是消除硫化氢引起的严重干扰。在市售试剂盒中，要么在氢化物发生步骤之前将硫化物氧化为硫酸盐并去除过量的氧化试剂，要么在氢化物发生步骤期间通过使气流通过浸渍有醋酸铅的过滤器滤出硫化氢。本方法采用氯化铜与氯化铁或芬顿试剂结合来去除硫化氢，该方法快速、简单且更有效。对于饮用水分析，在此分析步骤中的其他干扰通常是不存在的。在第二步中，砷化氢气体的产生采用经典方法，即使用锌金属和盐酸，它们产生初生态氢，这是实际的还原剂。盐酸可用氨基磺酸替代，氨基磺酸是固体，避免了在现场处理腐蚀性液体这一主要缺点。砷化氢气体在试剂纸上产生淡黄色斑点。根据砷含量，会形成黄色的nH(HgBr)2As（10 - 50 ppb）、棕色的n(HgBr)3As（50 - 100 ppb）或黑色的nHg3As2（>100 ppb），通过与标准色卡进行目视比较可精确估算。现场试剂盒获得的结果与通过电感耦合等离子体原子发射光谱法（I.C.P.AES）获得的数据非常吻合。现场测量最重要的特点是能够在采集样品的现场获得高精度的分析结果，并且能够方便地用于在高度污染的大面积地理区域快速监测砷。
