Optimization of the preconcentration system of cadmium with 1(2-thiazolylazo)-p-cresol using a knotted reactor and flame atomic absorption spectrometric detection.

The present paper proposes an on-line preconcentration procedure for cadmium determination in drinking water samples. It is based on the precipitation of cadmium(II) ions on a knotted reactor (KR) using 1(2-thiazolylazo)-p-cresol (TAC) as complexing reagent. The optimization step was performed using a full factorial design involving the variables: pH, eluent concentration (nitric acid) and TAC concentration. The results of this experiment demonstrated that these variables at chosen levels are not statistically significant. Under optimized experimental established conditions, analytical parameters for the preconcentration method were: a detection limit of 40.0 ng/l, precision as relative standard deviation (RSD) of 1.2 and 1.0%, for cadmium concentration of 2.5 and 20.0 microg/l, respectively. The preconcentration factor considering the slopes of the analytical curves with and without preconcentration is 23 for a sample volume of 10 ml. This system shows a sampling frequency of 25 h(-1). In order to check the accuracy, the standard reference material, NIST SRM 1643d trace elements in water was analyzed. A comparison, using t-test demonstrates that there is not significant difference among the achieved results with proposed method and the certified values. The addition/recovery experiments in the samples analyzed demonstrated the accuracy and applicability of the system developed for cadmium determination in water samples.