HG AFS DETERMINATION OF TRACE AMOUNTS OF ARSENIC AND MERCURY IN WATER

The hydride generation atomic fluorescence spectrometric method was adopted for the determination of arsenic and mercury in tap water. An appropriate amount of the water sample was taken and transferred to a 100ml volumetric flask. After pretreatment with thiourea and ascorbic acid solution (for determination of As) or with potassium dichromate solution (for determination of Hg), the sample solution was diluted to 100ml, the acidity of which was about 1.2mol·L -1 of HCl. An intermittent flow injection system was used for the generation of hydride of arsenic or mercury. The hydride generated was separated from the sample solution and led into the quartz atomizer of the AFS instrument. The analytical conditions used in the determination were shown in Tab 1. Calibration curves were prepared by using standard solutions of arsenic and mercury separately. The linear regression equations for determination of arsenic and mercury, together with their correlation coefficients and detection limits were shown below: for As: I f=49.1266 C -3.3686, r =0.9995, detection limit 0.0618μg·L -1 . for Hg: I f=912 2575 C -12.8634, r =0.9991, detection limit 0.0158μg·L -1 . RSD′s were found to be 0.66% ( n =11, ρ (As) =10.000μg·L -1 ) and 0.31% ( n =11, ρ (Hg)=1.000μg·L -1 ) for arsenic and mercury respectively. The method has been applied to the determination of tap water samples from four different water works, with RSD′s smaller than 3% ( n =9), and recoveries in the range of 97%～105%.