Comparative Study on Three Pretreatment Methods for Atomic Absorptive Spectrophotometry Determination of Metal Elements in Lycium Barbarum.

A simple, fast and accurate method was explored to determine the mineralelements in Lycium barbaru.Three different pretreatment methods, including dry ashing method, HNO3-H2O2 and HNO3-HClO4 wet digestion, method were employed for digestion of the samples of Lycium barbaru. The concentrations of Na，K，Ca，Mg，Fe，Cu，Zn，Ni，Pb and Cd were determined by using atomic absorption spectrometry. The experimental results showed that the recovery rates of dry ashing method, HNO3-H2O2 and HNO3-HClO4 wet digestion method were in the ranges from 89.88% to 102.15%, 92.34% to 103.21% and 94.52% to 102.10% respectively; the relative standard deviation (RSD) of dry ashing method, HNO3-H2O2 and HNO3-HClO4 wet digestion method were lower than 3.037%, 2.751% and 2.496% separately. The RSD and recovery of three pretreatment methods were all satisfied with the analysis requirements. But compared with dry ashing method and HNO3-H2O2 wet digestion method, the recovery of HNO3-HClO4 wet digestion method was better, and the precision was higher. Besides, compared with three pretreatment methods, the average value of Na, K, Ca, Fe and Cd had statistical difference (p<0.05), and HNO3-HClO4 wet digestion method was significantly higher than others.In addition, HNO3-HClO4 wet digestion method taken a shorter time and less consumption of reagents. Therefore, HNO3-HClO4 wet digestion method can be used as the preferably pretreatment method for the determination of the contents of metal elements by atomic absorption spectrophotometry method.