Comparison of Two Preconcentration Methods for the Determination of Nickel Using a Ni–2-(2-thiazolylazo)-p-Cresol Complex: Extraction and Sorption onto Ion Exchange Resin

2-(2-Thiazolylazo)- p -cresol ( TAC ) reacts with Ni(II) at pH 6–10 and forms a 1 : 2 blue complex. The stability constant of this complex is 5.0 ± 0.3. The complex has maximum absorption at 600 nm with the molar absorptivity of 27063 L/mol cm. Two preconcentration methods for the determination of Ni (an extraction method and sorption onto an ion exchange resin) at ppm levels using a Ni−TAC complex in EtOH−H 2 O (1 : 1, v/v) are described. For the extraction method, the linear regression was y = 0.0375 x – 0.0007, and the coefficient of determination ( r 2 ) was 0.9995. The limit of detection ( LOD ) was 9 µg/L, and the limit of quantification ( LOQ ) was 28 µg/L. The assay recovery was 83 ± 6%, and the intermediate precision (relative standard deviation ( RSD ), %) was 2.3%. For the method including sorption onto an ion exchange resin, the linear regression was y = 0.0391 x – 0.0001, and the coefficient of determination ( r 2 ) was 0.9995. The LOD and LOQ were 7 and 25 µg/L, respectively. The assay recovery was 99 ± 6%, and the intermediate precision (RSD) was 2.2%. Sorption onto an ion exchange resin is simple and precise and offers higher recovery compared to the extraction method for Ni quantification. Based on the findings in the present study, the preconcentration method including sorption onto an ion exchange resin could be applied to the determination of Ni in wastewater.