Evaluation of electrochemical hydride generation for spectrophotometric determination of As(III) by silver diethyldithiocarbamate

A batch electrochemical hydride generation system was developed for the spectrophotometric determination of inorganic As(III) by silver diethyldithiocarbamate. This method is based on electrochemical reduction of As to Arsine (AsH3) in acidic media and on the subsequent reaction of AsH3 with silver diethyldithiocarbamate to give an absorbing complex at 525 nm. The electrochemical generator consisted of a cathode cell separated from the anode cell by a porous glass frit and was operated with a constant direct current. A pre-activated graphite rod was used as cathode material for the production of AsH3. The parameters related to the electrochemical hydride generation were investigated. Under optimized conditions, only As(III) can be converted to AsH3 and a pre-reducing stage is required for total inorganic As analysis. The characteristic data of the electrochemical hydride generation and common hydride generation by NaBH4 were compared. Also, the effects of interferences and their elimination were investigated. An absolute detection limit of 0.5 mug (3s(b)) and a concentration detection limit of 0.05 mug/ml were obtained using a 10 ml sample volume. The relative standard deviation for five replicate analysis of 30 mug As(III) was 1.2%. The accuracy and recovery of the method were demonstrated by analysing spiked artificial sea water and tap water. (C) 2000 Elsevier Science B.V. All rights reserved.