Spectrophotometric determination of iron(II) and iron(III) with pyrazine-2-carboxylic acid and interference elimination by computer assisted multicomponent analysis

The possibility to det. iron(II) and iron(III) in aq. soln. using pyrazine-2-carboxylic acid as a reducing and complexing reagent was tested. The absorption max. lies at 485 nm and the absorbance follows Beer's law over the range 0.2-20 mg/L of iron using 10.0 cm or 1.00 cm cells. Color is stable for several hours at room temp. over the pH range 5-7 (phosphate buffer) on addn. of a large excess of the reagent. Few ions interfere and, in this case, quite accurate results were obtained using software for spectrophotometric multicomponent anal. The possibility is suggested for the recovery of pyrazine-2-carboxylic acid which may be utilized for subsequent detns.