Background and aims: Cadmium is a common industrial and environmental contaminant causing adverse health effects on respiratory system and kidney. This has been classified as a human carcinogen. Biological monitoring of cadmium and its measurement in urine, hair, and nail samples can be considered as an evaluation of the internal dose. Because of trace concentration of analytes in biological samples and matrix interferences, the preparation of such complicated samples is necessary prior to analysis. This study deals with the optimization of parameters affecting solid phase extraction (SPE) procedure for the trace analysis of cadmium in workers’ hair and nail in city of Zanjan.

Methods: Solid phase extraction using XAD-4 resin was optimized with regard to effective factors. The optimized procedure was validated based on the “within-day” and “day-to-day” reproducibility experiments and suitable accuracy and precision were achieved. The optimized method was used for pre-treatment of hair and nail samples.

Results: Using the optimized method, the recoveries of the cadmium ion were more than 92%. A good reproducibility and repeatability was obtained for optimized method under the existing conditions. The concentrations of cadmium in hair and nail samples were 98.25 and 186.82 μg/g, respectively. Based on the results, the cadmium content of samples was more than recommended maximum level (10 μg/g). Conclusion: Solid phase extraction procedure using XAD-4 resin can be considered as a successful method to simplify the sample preparation for trace residue analysis. The findings indicated that, the developed method can be applicable for biological monitoring and for determination of analytes in different matrices like hair and nail to evaluate the occupational exposures.