Spectrophotometric determination of trace mercury(II) in cereals with 2,4-bis(4-phenylazophenylaminodiazo)benzenesulfonic acid

A simple and low cost method for the determination of mercury has been developed. The method was based upon the highly sensitive color reaction of mercury(II) ions with 2,4-bis(4-phenylazophenylaminodiazo)benzenesulfonic acid ( BPPABSA ). We found that in the presence of 2.0% Triton X-100, the reagent reacts with mercury to form a stable red complex in a borax buffer solution at pH 10.22. The formed complex shows an absorption maximum at 530 nm. The apparent molar absorptivity is 2.18 × 10 5 L/mol cm. The content of mercury in the sample was low and some foreign ions might interfere with the determination of mercury(II), so we used sulfhydryl dextran gel ( SDG ) to separate and enrich trace mercury(II), which lead to a satisfactory result. Under the optimal conditions, Beer’s law is obeyed in the range of 0–15 μg/25 mL Hg 2+ , the detection limit and relative standard deviation are 0.86 ng/mL and 1.4–3.8%, respectively. The method has been applied to the determination of mercury in cereals with satisfactory results.