[Determination of total arsenic in food by borohydride reduction colorimetric method]

A method for determination of total arsenic in food by borohydride reduction colorimetry is presented. After samples' digestion, the arsenic is converted into trivalent arsenic by KI-thiourea under heating when the solution's acidity is more than 1.0mol/L. Trivalent arsenic is then reduced by sodium borohydride to arsine gas which can react with AgNO3 in absorbing solution to form a yellow substance whose maximum absorption wavelength is 400nm. The method was applied to the determination of total arsenic in grape wine, carp, dried shrimp, rice powder and lettuce, and the variation coefficients were 13.3%, 12.8%, 8.2%, 12.2% and 7.2%, respectively. The recoveries from dried shrimp, carp and rice powder were 98.0%-112.0%, 82.0%-98.8%, and 84.2%-115.0%, respectively. The method was also applied to the determination of arsenic in reference material rice powder NBS 1568 and the result, 0.37-0.43mg/kg, coincided with the given value 0.41 +/- 0.05mg/kg.