[Determination of cadmium in Chinese herbs by atomic absorption spectrometry using atom trapping technique].

A method has been proposed for the determination of cadmium by flame atomic absorption spectrometry (FAAS) using atom trapping technique. The experimental conditions including the flame condition, the trap position, the coolant water flow rate and the collection time, which affected on the absorbance of cadmium, were studied, and the optimum experimental conditions were the acetylene flow rate of 90 L.h-1, the distance of tube from the burner of 5 mm, the distance of tube from the light path of 2 mm and the coolant water flow rate of 1.5 L.min-1. The results showed that the absorbance was linearly dependent on the collection time in the range of 0-6 min for cadmium solution of 50 ng.mL-1. For 2 min collection time, the characteristic concentration and the detection limit for cadmium were 1.8 ng.mL-1 and 0.42 ng.mL-1, which were 16 and 5 times better than those of conventional flame atomic absorption spectrometry, respectively. The relative standard deviation(RSD) was 1.8% and the proposed method was successfully applied to the determination of cadmium in Chinese herbs with a recovery range of 89.5%-104%.