Evaluation of Arsine Generation in Arsenic Field Kit

Abstract

The recent outbreak of arsenic in groundwater of Bangladesh has prompted the widespread use of arsenic field kits. The kit involves the generation of arsine (AsH3) from inorganic arsenic species by reduction with Zn and HCl. The arsine then reacts with a test strip containing HgBr2 to produce a color that is compared with a color scale for quantitation. It is known that arsine gas is one of the most toxic substances known to man. The objective of this work is to measure the concentration of ambient arsine produced during the test and suggest a safe handling procedure. The analytical method is based on integrated AsH3 measurement by a single-point arsine monitor. The method can be used to measure 4−50 ppb arsenic in water with 10% in precision and accuracy. Experiments show that a typical test kit produces arsine with a 90% efficiency. The concentration of arsine produced even at low level can be more than 9 times above the 50 ppbv threshold limiting value (TLV). Actual kit experiments show that 50% of the arsine escapes the reaction cell during the test. We estimate that the maximum arsine concentration in the immediate vicinity of the kit can be more than 35 times TLV of arsine from a single experiment with 100 ppb total arsenic in solution. Particularly, field workers performing a large number of tests in highly affected areas are exposed to a much higher level of arsine. We suggest that the tests should be performed in well-ventilated places and that the worker should be provided with a gas mask to minimize arsine inhalation.