Study On The Application Of Separation/pre-concentration Of Microporous Membrane Filter In Atomic Spectrometry Analysis

With the development of modern science and technology, element quantitative analytical technology has been maturing. But separation/pre-concentration technology still be a way for enhancing the sensitivity and selectivity of instrumental analytical method. Owing to many merits such as low costs, simple operation procedures and effective enrichment factor, separation/ pre-concentration technology of cellulose membrane filter had combined with spectrophotometry or atomic absorption spectrometry for the determination and analysis of trace heavy metal ions in environment, food, biologic samples successfully. This paper had studied on application of the commercial multi-channel membrane filtration device in the separation/pre-concentration technology of cellulose membrane filter and established the method of simultaneous determination of different heavy metal elements via separation/pre-concentration of cellulose membrane filter combined with inductively coupled plasma atomic emission spectrometry ( ICP–AES ). The method was applied to the determination of different trace heavy metal ions in real samples including water samples,food additives successfully. The detailed contents are described as follows:1. Based on collection of the chelates of metal(â…¡) with 2-(5-Bromo-2-pyridylazo)-5- diethyl-aminophenol (5-Br-PADAP) on microporous mixed cellulose ester membrane filter, a new method of simultaneous determination of trace cadmium(â…¡), copper(â…¡), lead(â…¡) and zinc (â…¡) in water samples by ICP–AES after separation/pre-concentration of microporous membrane filter had been established. The membrane with chelates was dissolved by small amount hot/concentrate nitric acid. The feasibility of multi-channel membrane filter device used for simultaneous filtration and pre-concentration had been studied. The influence of various experimental conditions such as pH, amounts of ligand and matrix effects were examined. Under the optimized experiment conditions, enrichment factors of 18, 19, 17, 19 and the detection limits (3σ, n=11) of 0.04, 0.15, 0.44 and 0.06μg/L were obtained for Cd(â…¡), Cu(â…¡), Pb(â…¡) and Zn(â…¡) in 100 mL water samples, respectively. The method had been applied to the determination of reference material( GBW 08517 ) and the results were satisfactory.2. Simultaneous determination of trace levels of Cd(â…¡), Cu(â…¡), Pb(â…¡) and Zn(â…¡) in food additives by microporous membrane filter combined with ICP–AES was developed. This method eliminates the severe interference of alkali metal and alkaline earth metal elements when ICP–AES was applied to determination of food additives through separation/ pre-concentration of analytes from the complex matrix. In addition, enrichment mechanism of cellulose membrane filter had been studied. Under the matrix of Na⁺, K⁺ and Mg²⁺, the limits of detection were 0.02– 0.03, 0.14 - 0.23, 0.31– 0.53, 0.10– 0.15μg/L for Cd(â…¡), Cu(â…¡), Pb(â…¡) and Zn(â…¡) respectively. The developed method was successfully applied to sodium benzoate, potassium sorbate and basic magnesium carbonate with spiked recoveries of 94%– 115% .Sample analysis results were checked by inductively coupled plasma mass spectrometry (ICP–MS) analysis directly.3. A new method for determination of trace nickel(â…¡) and silver(â… )in water samples by ICP–AES after separation/pre-concentration of microporous membrane filter was proposed. It is based on enrichment of nickel(â…¡) and silver(â… ) with ammonium pyrrolidinedithio- carbamate( APDC ) on microporous membrane filter at the potassium hydrogen phthalate buffer system of pH 5.0. Various factors which affect the collection of cellulose membrane filter and the process of determination of metal ions by ICP–AES were studied. The present method was successfully applied to the determination of nickel and silver in real samples such as mineral water, tap water, etc.