Optimization of solid-phase extraction based on a new sol-gel material using a response surface methodology for the determination of copper in water samples by flame atomic absorption spectrometry

A simple method for solid-phase extraction and pre-concentration of trace amounts of copper prior to determination by flame atomic absorption spectrometry (FAAS) has been developed. The method is based on the adsorption of Cu(II) ions on a micro-column packed with a sol-gel material doped with 1-hexylpyridinium hexafluorophosphate [C6py+] [] ionic liquid and 8-hydroxyquinoline (oxine) as a novel solid-phase extractor. Different variables affecting the separation/pre-concentration conditions of analyte, including pH of the sample solution, buffer concentration, sample loading flow rate and elution conditions were investigated and optimized utilizing the central composite design (CCD). In the optimum conditions, the limit of detection (LOD), limit of quantification (LOQ) and enrichment factor were 0.5 µg L−1, 1.7 µg L−1 and 50, respectively. The relative standard deviation (RSD) for nine replicate determinations of 25 and 50 µg L−1 Cu were 1.8 and 1.3%, respectively. The calibration graph using the pre-concentration system was linear in the range of 2−120 µg L−1 with a correlation coefficient of 0.9989. A standard reference material (NIST SRM 1566b), was used for validation of the presented method. The optimized method was successfully applied to the determination of copper in several water samples.