Microsequential injection lab-on-valve system for the spectrophotometric bi-parametric determination of iron and copper in natural waters

The determination of iron and copper exploiting a microsequential injection lab-on-valve system with online spectrophotometric detection is described. A new, environmental friendly 3-hydroxy-4-pyridinone chelator, functionalized with a polyethylene glycol chain (MRB12) to improve water solubility, was used for iron determination. For copper determination, 1-(2-pyridylazo)-2-naphthol (PAN) was used. Different parameters affecting the formation of the complexes were studied, namely sample volume, reagent concentration, and buffer composition and concentration. The optimized conditions, 150 µL of sample volume and 250 mg L⁻¹ of MRB12 for iron determination, and 200 µL of sample and 120 mg L⁻¹ of PAN for copper determination, enabled an LOD of 15 and 18 µg L⁻¹ for iron and copper, respectively. The robustness of the developed procedure was assessed by the calculation of the relative standard deviation (RSD), 5% for iron determination and 2% for copper determination. The accuracy of the method was assessed comparing the results with two certified samples (RD<7.5%) and calculating recovery percentages with five river water samples (average<107%).