Speciation of Ar senic in En vi ron men tal and Bi o log i cal Sam ples

bDe part ment of Chem is try, Uni ver sity of Rajasthan, Jaipur (Raj.)-302 004, In dia A novel arsine gen er a tor glass as sem bly is con structed and re ported for the spec tro pho to met ric de ter mi na tion and speciation of ar senic in real sam ples. In an arsine gen er a tor, so dium borohydride is added dropwise to the acidic sam ple so lu tion and arsine thus formed is re acted with sil ver diethyldithiocarbamate (Ag-DDTC) - Tritron-X (TX-100) so lu tion in pyridine to form a red col oured com plex. The com plex showed the ab sorp tion max i mum at max 540 nm. The mo lar ab sorp tivi ty of the method was found to be (1.55) 10 4 L mole -1 cm -1 at this wave length. The pres ence of non-ionic surfactant, i.e. TX-100 in the Ag-DDTC so lu tion, makes the method 3 times more sen si tive than the con ven tional Ag-DDTC method. Beer’s law is obeyed in the con cen tra tion range of 0.05-2.80 mg L -1 of ar senic. The de tec tion limit of the method was cal cu lated to be 20 g L -1 As. Speciation of arsenite from other forms of ar senic in sam ple so lu tions was car ried out by ex trac tion of arsenite with Pb-DDTC in chlo ro form, fol lowed by spec tro pho to met ric de ter mi na tion. Af t er arsenite sep a ra tion the sam ple is used for the ar se nate de ter mi na tion. To tal ar senic was de ter mined by acid de com po si tion of the same sam ple. The speciation data were found to be com pa ra ble ( 2%) with ICP-MS, with better pre ci sion (< 1%). The method has been suc cess fully ap plied for the speciation of ar senic in drink ing wa ter and dust sam ples of ar senic af fect ing the Rajnandgaon dis trict of Chhattisgarh, In dia, and urine and blood sam ples of pa tients with ar sen i cal dis eases. Con cen tra tion of to tal ar senic in tube-well wa ter of this area was 3-6 times more than the per mis si ble limit. Dust sam ples con tained less amounts of ar senic than the ground wa ter.