HG-AFS Determination of Total Inorganic Arsenic in Urine with On-line Pre-reduction

A self-made on-line automatic reductor was designed and fabricated, for pre-reduction of inorganic arsenic(Ⅴ) to As(Ⅲ), which may possibly present in the urine sample. The pre-reduction was performed by mixing 4.8 mL of urine sample with 1.2 mL of the reductant (mixed solution of 100 g·L-1 thiourea-50 g ·L-1 ascorbic acid) and heated in a reactor at 70 ℃ for 2 min. An aliquot of the reduced As(Ⅲ) solution (1.5 mL) was reacted with 2.0 mL of 20 g·L-1 KBH4 (dissolved in 5 g·L-1 KOH solution) in the hydride generator, and the AsH3 formed was carried over to the atomizer by the carrier gas (Ar), and the AFS measurement was made. The proposed method has been applied to the analysis of children′s urine samples, and test for recovery was made on the base of these samples by standard addition method, giving values of recovery in the range of 90.2%-102.6%.