DETERMINATION OF IRON(III) IN PHARMACEUTICAL SAMPLES USING DIALYSIS IN A SEQUENTIAL INJECTION-ANALYSIS SYSTEM

The use of membranes for on-line separations in flow-through dialysers as part of flow systems is extremely useful for automated sample prep aration. Iron(III) was separated from a sample matrix by dialysis in a sequential injection system. The dialysed iron was complexed with tir on and the resulting complex was monitored spectrophotometrically at 6 67 nm. The influence of various parameters, including pump speed for b oth the donor and recipient streams, sample volume, reagent volume, di alysis time and the effect of multiple how reversals, on dialysis effi ciency was studied. The system proved to be feasible for the determina tion of iron in pharmaceutical samples which are usually turbid and co ntain undissolved organic particles. The system is fully computerised and is able to monitor iron(III) in samples at a frequency of 8 sample s per hour with a relative standard deviation (RSD) of <1.50% in the l inear calibration range (100-1000 mg l(-1)). The 3 sigma detection lim it is 45.0 mg l(-1). Although the sample frequency of the proposed seq uential injection system is much lower than that of conventional flow injection systems, the volume of sample used is much smaller and the c onsumption of reagents is much lower, which is more cost effective. Us ing the feature of multiple flow reversals, the percentage dialysis ca n be improved to up to 4.5%, which compares well with the 4% obtained with conventional how injection analysis. (C) 1997 Elsevier Science B. V.