Dear Sayan,

You can use the following procedure taken from the attached manuscript:

Aliquots of standard solution containing not more than 6µg of As(V) is taken in a series of 25mL standard flask. To this solution added 1mL of 1% acidified molybdate, 1mL of 0.01% ammonium vanadate followed by 2mL each of 0.02% Rhodamine B and 0.1% polyvinyl alcohol. The solution was diluted to the mark with distilled water and the absorbance was measured at 590 nm in 10 mm cells against reagent blank.

The concentration of As (V) was determined from the calibration graph.

Dear Sayan,

You can use the following procedure taken from the attached manuscript:

Aliquots of standard solution containing not more than 6µg of As(V) is taken in a series of 25mL standard flask. To this solution added 1mL of 1% acidified molybdate, 1mL of 0.01% ammonium vanadate followed by 2mL each of 0.02% Rhodamine B and 0.1% polyvinyl alcohol. The solution was diluted to the mark with distilled water and the absorbance was measured at 590 nm in 10 mm cells against reagent blank.

The concentration of As (V) was determined from the calibration graph.

Dear Sir. Concerning your issue about the determination of arsenate ions in water by UV/VIS spectrophotometer. Arsenic can be determined spectrophotometrically by using variamine blue as a chromogenic reagent. The method is based on the reaction of arsenic(III) with potassium iodate in acid medium to liberate iodine, which oxidizes variamine blue to form a violet coloured species having an absorption maximum at 556 nm. Beer’s law is obeyed in the range 0.2-14 μg mL-1 of As(III). The molar absorptivity, Sandell’s sensitivity, detection limit and quantitation limit were found to be 1.43×104 L mol-1cm-1, 5.26×10-2 μg cm-2, 0.022 and 0.072 μg mL-1, respectively. The optimum reaction conditions and other analytical parameters were evaluated. The proposed method has been successfully applied for the determination of arsenic in various environmental and biological samples. Also vanillin-2- amino nicotinic acid (VANA) has been proposed as new analytical reagent for the direct non-extractive spectrophotometric determination of Arsenic. I think the following below links and the attached files may help you in your analysis:

http://www.scholarsresearchlibrary.com/articles/a-simple-spectrophotometric-method-for-the-determination-ofarsenic-in-industrial-and-environmental-samples-using-vanilli.pdf

http://sphinxsai.com/2015/ch_vol7_no5/3/(2333-2340)V7N5.pdf

Thanks