Study On Determination Of Trace Cadmium In Food With Solid-phase Spectrophotometry

Cadmium is a heavy metal element with accumulation toxicity.Varied methods have been developed for determination of cadmium(â…¡) such as AAS,AFS,ICP-MS, et cetera.The solid-phase spectrophotometry(SPS) is a technique which can provide various important advantages:high sensitivity,selectivity as well as simplicity and speed,make the method indispensable in analysis of cadmium(â…¡) in food samples.A highly sensitive and selective solid-phase spectrophotometric method for the determination of trace amounts of cadmium(â…¡) is described.Cadmium(â…¡) was sorbed on a crosslinked-styrene-type macroporous adsorption resin D4020 as a Cd(â…¡)-o-hydroxybenzenediazoaminoazobenzene(o-HDAA) complex.In pH 10.5 borax buffer,resin phase absorbances at 557 and 800 nm were measured directly with an apparent molar absorptivity of 1.66×10⁷ L/mol·cm(82-fold of it in solution). The linear range of the determination was 3.0-100μg/L in aqueous solution.The detection limit and the quantification limit were found to be 0.9 and 2.9μg/L, respectively.The relative standard deviation of 16 replicate determinations of 1.0μg cadmium(â…¡) in 100 mL samples was of 3.6%and 5.0μg cadmium(â…¡) in 100 mL samples was of 2.8%.The tolerance limit of coexistent ions was also investigated.Most of them are in tolerable amount.For practical analyses,2 mL mixed masking reagent which contains acetylacetone,dimethylglyoxime,Na₄P₂O₇ and KSCN used can eliminate the interferences caused by Cu,Fe,Co,Ni and Hg.The procedure was validated by AAS with the results in agreement with the true values.The method was applied to the determination of cadmium(â…¡) in food and water samples with satisfactory results.Solid-phase diffuse-reflection spectrophotometry(RF-SPS) method was also developed and was compared with the proposed method(Transmission-SPS).It showed that RF-SPS has better reproducibility than the Transmission-SPS,as well as Transmission-SPS has better sensitivity than RF-SPS.