One-shot flow injection spectrophotometric simultaneous determination of copper, iron and zinc in patients’ sera with newly developed multi-compartment flow cell

We propose here an affordable flow injection method for simultaneous spectrophotometric determination of copper, iron and zinc in patients’ sera. The use of a newly designed multi-compartment flow cell allowed the simultaneous determination of the three metals with a single injection (‘one-shot’) and a double beam spectrophotometer. The chemistry relied on the reactions of these metals with 2-(5-nitro-2-pyridylazo)-5-[N-propyl-N-(3-sulfopropyl)amino]phenol (nitro-PAPS) to form corresponding colored complexes. At pH 3.8, only copper–nitro-PAPS complex was formed in the presence of pyrophosphate as a masking agent for iron, and then the copper and iron(II) complexes were formed in the presence of reductant (ascorbic acid) at the same pH, and finally all three metals reacted with nitro-PAPS at pH 8.6. The characteristics were introduced into the flow system to determine each metal selectively and sensitively. Under the optimum conditions, linear calibration curves for the three metals were obtained in the range of 0.01–1 mg L−1 with a sample throughput rate of 20 h−1. The limits of detection (3σ) were 3.9 μg L−1 for copper, 4.1 μg L−1 for iron and 4.0 μg L−1 for zinc. The proposed method was applied to analysis of some patients’ sera.