Study of the solid phase extraction and spectrophotometric determination of nickel using 5-(4 - chlorophenylazo)-6-hydroxypyrimidine-2,4-dione in environmental samples

A rapid, sensitive and selective method for the determination of nickel based on the rapid reaction of nickel(II) with 5-(4 -chlorophenylazo)-6-hydroxypyrimidine-2,4-dione (CPAHPD) and the solid phase extraction of the Ni(II)–CPAHPD complex with C18 membrane disks has been developed. In the presence of pH 6.8 buffer solution and cetylpyridinium bromide (CPB) medium, CPAHPD reacts with nickel to form a red complex of a molar ratio of 1:1 (nickel to CPAHPD). This complex was enriched by solid phase extraction (SPE) with C18 membrane disks. An enrichment factor of 100 was obtained by elution of the complex from the disks with the minimal amount of isopentyl alcohol. The molar absorptivity and Sandell sensitivity of the complex was 3.11 · 105 L mol^-1 cm^-1 and 0.0189 ng cm^-2, respectively at 549 nm in the measured solution. Beer’s law was obeyed in the range of 0.01–0.37 μg mL^-1, while that obtained by Ringbom plot was in the range of 0.025–0.35 μg mL^-1. The detection and quantification limits were calculated and found to be 0.003 and 0.01 μg mL^-1. The proposed method was applied to the determination of nickel in water, food, biological and soil samples with good results.