Determination of selenium using atomically imprinted polymer (AIP) and hydride generation atomic absorption spectrometry.

This paper describes selenium determination based on Se(0) preconcentration in the imprinted polymer (synthesized with 2.25mmol SeO2, 4-vinylpyridine and 1-vinylimidazole) with subsequent detection on-line in HG-FAAS. During the synthesis, SeO2 is reduced to Se (0). Therefore, there are no MIP neither IIP in the present work, thus we denominated: AIP, i.e., atomically imprinted polymers. For the optimization of analytical parameters Doehlert design was used. The method presented limit of detection and limit of quantification of 53 and 177ngL(-1), respectively, and linear range from 0.17 up to 6µgL(-1) (r=0.9936). The preconcentration factor (PF), consumptive index (CI) and concentration efficiency (CE) were 232; 0.06mL and 58min(-1) respectively. The proposed method was successfully applied to determine Se in Brazil nuts (0.33±0.03mgkg(-1)), apricot (0.46±0.02mgkg(-1)), white bean (0.47±0.03mgkg(-1)), rice flour (0.47±0.02mgkg(-1)) and milk powder (0.22±0.01mgkg(-1)) samples. It was possible to do 12 analyzes per hour. Accuracy was checked and confirmed by analyzing certified reference material (DORM-2, dogfish muscle), and samples precision was satisfactory with RSD lower than 10%.

Solid-phase extraction system for Pb (II) ions enrichment based on multiwall carbon nanotubes coupled on-line to flame atomic absorption spectrometry.

The present paper proposes the application of multiwall carbon nanotubes (MWCNTs) as a solid sorbent for lead preconcentration using a flow system coupled to flame atomic absorption spectrometry. The method comprises the preconcentration of Pb (II) ions at a buffered solution (pH 4.7) onto 30mg of MWCNTs previously oxidized with concentrated HNO(3). The elution step is carried out with 1.0molL(-1) HNO(3). The effect of the experimental parameters, including sample pH, sampling flow rate, buffer and eluent concentrations were investigated by means of a 2(4) full factorial design, while for the final optimization a Doehlert design was employed. Under the best experimental conditions the preconcentration system provided detection and quantification limits of 2.6 and 8.6mugL(-1), respectively. A wide linear range varying from 8.6 up to 775mugL(-1) (r>0.999) and the respective precision (relative standard deviation) of 7.7 and 1.4% for the 15 and 200mugL(-1) levels were obtained. The characteristics obtained for the performance of the flow preconcentration system were a preconcentration factor of 44.2, preconcentration efficiency of 11min(-1), consumptive index of 0.45mL and sampling frequency estimated as 14h(-1). Preconcentration studies of Pb (II) ions in the presence of the majority foreign ions tested did not show interference, attesting the good performance of MWCNTs. The accuracy of the method was assessed from analysis of water samples (tap, mineral, physiological serum and synthetic seawater) and common medicinal herbs submitted to the acid decomposition (garlic and Ginkgo Biloba). The satisfactory recovery values obtained without using analyte addition method confirms the feasibility of this method for Pb (II) ions determination in different type of samples.