Pleurotus eryngii immobilized Amberlite XAD-16 as a solid-phase biosorbent for preconcentrations of Cd2+ and Co2+ and their determination by ICP-OES

This article reports a method that is used for the preconcentration and determination of Cd2+ and Co2+ in vegetables, using Pleurotus eryngii immobilized Amberlite XAD-16 as a solid-phase biosorbent. The concentrations of metals were determined by inductively coupled plasma-optical spectrometry (ICP-OES). Critical parameters, such as the pH of the solution, flow rate, the amount of biosorbent, type and volume of eluent, and the sample volume, that affect the solid-phase extraction (SPE) procedure were optimized. The optimum extraction conditions were determined as being a pH of 6.0 for Cd2+ and of 5.0 for Co2+; a sample flow rate of 2.0 mL min−1; 200.0 mg of biosorbent; and 5.0 mL of 1.0 mol L−1 HCl as eluent. The capacities of the biosorbent for metal uptake were found to be 11.3 and 9.8 mg g−1 for Cd2+ and Co2+ ions, respectively. Limit of quantitations (LOQs) were found to be 0.67 and 0.82 ng mL−1, respectively, for Cd2+ and Co2+. The linear working curves were observed to be in the linear range from 1.0 to 50.0 ng mL−1, and possessed high correlation coefficients. The use of the SPE method showed 50.7- and 35.7-fold improvements in the sensitivities of ICP-OES. The developed method was successfully applied to NCS ZC-73014 (a certified reference tea sample). Relative standard deviations (RSD) were lower than 5.0%. The Cd2+ and Co2+ concentrations in the different parts (leave, root, stem, and fruit) of purslane, onion, rocket, okra, and aubergine were determined after microwave digestion and solid-phase extraction by P. eryngii immobilized on Amberlite XAD-16.