Solid Phase Extraction Of Trace Cadmium Using A Bean-coat Sorbent With Detection By Electrothermal Atomic Absorption Spectrometry

Natural biomaterials have been widely employed as green adsorbents to remove the pollution caused by various heavy metals with obvious advantages of biocompatibility and biodegradability. Most of the biomaterials are cost effective and have abundant functional groups on their surface, e.g., hydroxyl, carboxyl, amino, ester and thiol groups, providing abundant binding sites for the separation and enrichment of heavy metals. It also facilitates the elimination of matrix effect in the environmental and biological samples. As a heavy metal, cadmium can result in the pollution of atmosphere, water and soil, and cause carcinogenesis, teratogenesis and mutagenesis to human. However, the amount of cadmium in environmental and biological samples is actually very low. It is necessary to develop appropriate sample pretreatment methods in order to accurately detect and quantify cadmium in the real world samples.In this thesis, a novel green/biodegradable adsorbent, mungbean-coat, has been investigated for the adsorption of ultra-trace amounts of cadmium. Carboxylic groups on the bean-coat effectively retain the cadmium ions via coordinative interactions. This well facilitates the adsorption of cadmium ions which can readily be recovered by acid elution. In practice, based on the sequential injection system, bean-coat is used to pack a mini-column for on-line adsorption and preconcentration of cadmium from environmental samples with detection by electrothermal atomic absorption spectrometry for its unparalleled high sensitivity to the majority of metals with respect to the other atomic spectrometric techniques.By using a sample loading volume of1.4mL and an eluent volume of70μL, an enrichment factor of19.8along with a detection limit of1.4ng/L are achieved. A precision of2.4%RSD at the level of0.05μg/L (n=11) is derived. The present procedure has been applied for the determination of cadmium in certified reference materials (GBW08608Trace Elements in Water and CRM176Trace Elements in a City Waste Incineration Ash) and a snow water sample. Fair agreements are reached between the certified values and the experimental results, in addition to a satisfactory spiking recovery for the snow water sample.