Comparison of Partial Least Squares Regression and H-Point Standard Addition Method for Simultaneous Spectrophotometric Determination of Zinc, Cobalt and Nickel by 1-(2-Pyridylazo)2-Naphthol in Micellar Media

Abstract

Simultaneous spectrophotometric methods are described for the determination of Zn2+, Co2+ and Ni2+ by 1-(2-pyridylazo)2-naphthol (PAN) in micellar media, using absorbance correction-H-point standard addition method (HPSAM) and partial least squares (PLS) regression. The ligand and its metal complexes, i.e. Zn2+-PAN, Co2+-PAN and Ni2+-PAN, were made water-soluble by the neutral surfactant Triton X-100, and therefore extraction with organic solvents was no longer required. Formation of all of these complexes was complete within 10 min at pH 9.2. The linear range was 0.1–1.5 mg L−1 for Zn2+, 0.1–2.0 mg L−1 for Co2+ and 0.1–2.0 mg L−1 for Ni2+. The relative standard deviation (RSD) for the simultaneous determination of 0.50 mg L−1 each of Zn2+, Ni2+ and Co2+ by applying the H-point standard addition method was 2.55%, 2.04% and 3.70%, respectively. The total relative standard error for applying the PLS method to 9 synthetic samples in the linear ranges of these metals was 1.8%. Interference effects of common anions and cations were studied, and both methods were applied to the simultaneous determination of Zn2+, Co2+ and Ni2+ in alloy samples.