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Abstract: A simple, sensitive and selective spectrophotometric method for the simultaneous determination of Co(II) and Pd(II) using partial least square (PLS) calibration and H-point standard addition method is described. The method is based on the complex formation of Co(II) and Pd(II) with 4-(2-pyridylazo) resorcinol (PAR) in acidic media and in the presence of sodium dodecyl sulfate (SDS) as a micellizing agent. Acidic media and the presence of a micellar system improve selectivity and sensitivity, respectively. By applying PLS calibration, Co(II) and Pd(II) can be determined in the range of 0.20–2.0 and 0.40–4.0μgml−1, respectively. The relative errors of prediction for the determination of Co(II) and Pd(II) in the 10 prediction samples were 1.69 and 1.72%, respectively. The results of applying H-point standard addition method show that Co(II) and Pd(II) can be determined simultaneously with concentration ratio of Co(II) to Pd(II) varying between 7:1 and 1:8 in the mixed samples. Both proposed methods (PLS and HPSAM) were applied to the determination of Co(II) and Pd(II) in several alloy solutions with satisfactory results. [Copyright &y& Elsevier]

Abstract: A simple, novel and sensitive spectrophotometric method was described for the simultaneous determination of cobalt, nickel and palladium. The method is based on the complex formation of Co, Ni and Pd with 1-(2-pyridylazo)-2-naphtol (PAN) in Tween-80 micellar media. All factors affecting on the sensitivity were optimized and the linear dynamic range for determination of Co, Ni and Pd was found. The experimental calibration matrix was designed by measuring the absorbance over the range of 520–700nm for 21 samples of 0.10–1.0, 0.050–0.50 and 0.050–4.0μgml−1 of Co, Ni and Pd, respectively. The partial least square (PLS) modeling based on singular value decomposition (SVD) was used for the multivariate calibration of the spectrophotometric data. The direct orthogonal signal correction was used for pre-processing of data matrices and the prediction results of model, with and without using direct orthogonal signal correction, were statistically compared. The effects of various anions and cations on selectivity of the method were investigated. The proposed method was successfully applied to the determination of Co, Ni and Pd in water and alloy samples. [Copyright &y& Elsevier]

• Determination of nitroaniline isomers in binary mixtures by four spectrophotometric methods. • Similar precision and accuracy of CC and RD methods compared to PLS and PCR methods. • Selection of best pair of wavelengths and divisor in proposed methods was studied. • No need to computer programs or sophisticated equipment in suggested methods. In the present work, four simple and economic spectrophotometric methods, namely constant center (CC), ratio difference (RD), H-point standard addition method (HPSAM), and ratio H-point standard addition method (RHPSAM) were employed for the simultaneous determination of meta and para -nitroaniline with severely overlapping spectra without unitizing the preliminary physical separation techniques. In each method, the parameters affecting the resolution of the spectra were optimized to determine the cited isomers in a binary mixture with a high accuracy. Under the optimized conditions, the results obtained showed that from cited methods used, the CC and RD methods have the least errors in determination of the concentration of highly spectral overlapping species. The mean percentage recovery values for the binary mixture of meta- and para -nitroaniline were found to be 95.98 and 98.78 using the RD method, and 101.85 and 100.23 using the CC method, respectively. For comparison of the powerful multivariate methods including the principal component regression (PCR) and partial least squares (PLS) were also applied. The mean percentage recovery values for the binary mixtures of the cited isomers were found to be 101.62 and 101.47 using the PCR method, and 101.00 and 101.36 using the PLS method, respectively. A statistical comparison of the methods demonstrated that there was no significant difference between the RD, CC, PCR, and PLS methods and the reported HPLC method regarding both accuracy and precision. The proposed methods have an admissible precision and accuracy for determination of the two isomers in their binary mixtures in tap water as a real sample. [ABSTRACT FROM AUTHOR]