FLOW-INJECTION STANDARD SUBTRACTION METHOD FOR THE DETERMINATION OF IRON(III) BASED ON ITS CATALYTIC EFFECT AND INHIBITION OF EDTA/

A new approach for the how-injection catalytic determination of 10(-6) M levels of iron(III) is proposed. This method is based on the cataly tic effect of iron(III) on the oxidative coupling of p-anisidine with N,N-dimethylaniline to form a blue compound (lambda(max)=735 nm) in th e presence of hydrogen peroxide and 1,10-phenanthroline as an activato r, and the inhibitory effect of EDTA on the iron(III)-catalyzed reacti on. The concentration of iron(III) can be determined from only two flo w signals which are obtained by injecting the iron(III) and iron(III) plus EDTA solutions into the flow lines without a calibration graph fo r iron(III); this procedure may be called standard subtraction. The pr oposed method permits the analysis of 12 samples per hour (24 peaks pe r hour) and was successfully applied to the determination of iron in s tandard iron ore samples. (C) 1998 Elsevier Science B.V. All rights re served.