Preconcentration, speciation of arsenic and selenium by the solid phase extraction and their determination by atomic absorption spectrometry

In this study, the preconcentration and speciation of inorganic arsenic and selenium by column solid phase extraction method using nano zirconium oxide ? boron oxide (ZrO2/B2O3) as solid phase have been carried out. As a detection method, hydride generation atomic absorption spectrometry (HGAAS) for arsenic and electrothermal atomic absorption spectrometry (ETAAS) for selenium have been used. The proposed preconcentration and speciation method for selenium depends on the retention of Se(IV) ions as its ammonium pyrrolidine dithiocarbamate (APDC) complex on the sorbent but not retention of Se(VI) under the optimum conditions. Similarly, while As(V) is retaining on the sorbent As(III) is not retaining. The contents of Se(VI) and As(III) have been calculated by using total Se and total As values, respectively. In order to determine the optimum preconcentration and speciation conditions, the effect of experimental parameters such as pH, flow rate of sample solution, volume of sample solution, type, concentration and volume of eluent have been investigated. For the preconcentration and speciation of selenium and arsenic, as the optimum pH values (recovery > 95%) 2 and 3 have been determined, respectively. The effects of other ions which may be interfere with the determination of analytes have also been investigated. Adsorption capacity of nano sorbent was found as 98.04 mg/g for As(V) and 95.23 mg/g for Se(IV) from studies of adsorption isotherm (Langmuir isotherm). Moreover, analytical performance criteria such as limit of detection, limit of quantitation, linear working range, precision and accuracy have also determined under optimum experimental parameters. Analytical limits of detection for As(V) and Se(IV) have been found 9.25 ng/L and 121 ng/L, respectively. The accuracy of the method has been checked by analyzing certified reference materials (SPS - WW1 Waste Water for As and NIST 1643e for Se) and spiked water samples, and it was shown that the determination could be performed with a relative error of about 5%. The precision of the method is also acceptable level for analytical purposes for trace analysis (relative standard deviation < 10%). Finally, the proposed preconcentration and speciation method has been applied for the determination of total As, total Se, As(III), As(V), Se(IV) and Se(VI) in various water samples including hot spring water.