Separation and preconcentration of trace amount of zinc by modified alumina nano particles microcolumn and determination by FAAS

Despite continuous progress in instrumental methods for analysis, the direct determination of trace metals in many kinds of samples is still very often difficult due to insufficient sensitivity and selectivity of the methods used. Therefore, the pretreatment steps in analytical procedure, such as preconcentration of an analyte and/or its separation from the matrix components are frequently necessary. One of the most widely used techniques for preconcentration is solid phase extraction (SPE). Various substances have been proposed and applied as extractants in SPE, such as modified silica, alumina, active carbon, and so on [1-3]. In this work a simple and sensitive procedure based on solid phase extraction was developed for the preconcentration of trace amount of Zinc in water samples prior to flame atomic absorption spectrometric determinations. Zinc was complexed with ammonium pyrrolidine dithiocarbamate(APDC) and collected in a column packed with surfactant-coated nano meter sized alumina. The effects of various parameters such as pH, flow rate of sample and eluent, type and concentration of eluent, and APDC concentration have been studied. The adsorption capacity of modified nano-γ-alumina was found to be 67.66 mgg−1 at optimum pH. Under the optimum experimental conditions, the detection limit (3s) was 0.87 μgL-1 and The relative standard deviation for five replicate determinations of 50 μg L-1 Zn was 2.9 %. The proposed method has been applied to the determination of zinc at trace levels in certified reference material and real samples with satisfactory results.