ABSTRACT
In this study, a novel analytical method which consists of a combination of Fast Sequential Flame Atomic Absorption Spectrometry (FS-FAAS) and Continuous Flow Hydride Generation Atomic Absorption Spectrometry (CF-HGAAS) is proposed. The method developed was employed for the sequential determination of As and Sb at sub-µg L-1 levels in bottled mineral waters. A strong enhancement in the analytical throughput was obtained when compared with the traditional mono-element CF-HGAAS with a quartz tube atomizer (QTA). Variables which would affect the method performance such as Ar flow rate, HCl and NaBH4 concentrations as well as delay and integration time were optimized. A flame atomic absorption spectrometer working in fast sequential mode was used in all experiments. After just 20 s of read delay, As and Sb were sequentially determined in 6 s (3 s each element). A 26-2 fractional factorial design was employed for studies of potential interferents with transition metals that could be present in mineral water samples. Limits of detection obtained for As and Sb were 0.15 and 0.14 µg L-1, respectively. The accuracy of the proposed method was checked by the use of 2 certified reference materials: Trace elements in water (NIST 1643e) and Trace metals in drinking water (HPS TMDW). Good agreement between certified and found concentrations was observed. Finally, As and Sb were determined in commercial bottled mineral water samples. Adequate sensitivity, high throughput and minimization of reagents and sample consumption are the attractive features of this new method.
ABSTRACT
In this study, the combination of thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS) and fast sequential flame atomic absorption spectrometry (FS-FAAS) for the sequential determination of Cd, Cu, Pb and Zn is presented and a significant improvement in the analytical throughput of TS-FF-AAS is obtained. Ni tubes of different designs were evaluated observing the necessary read delay to obtain maximum absorbance and avoid memory effects. All experiments were performed in a flame atomic absorption spectrometer working in fast sequential mode fitted with a deuterium background corrector. The fast sequential TS-FF-AAS system has been optimized for Cd, Cu, Pb and Zn whereby it was found that a Ni tube with an internal diameter of 8 mm with 10 holes on the bottom side combined with a ceramic capillary of 0.5 mm internal diameter and a delay time of 60 seconds gave the best results (adequate absorbance values and no memory effects). After 60 seconds read delay, Cd, Cu, Pb and Zn could be determined in 12 seconds (3 seconds each element). Limits of detection obtained for Cd, Cu, Pb and Zn were 0.3, 7.5, 4.4 and 0.3 µg L-1, respectively.
ABSTRACT
Sediment samples from 25 sites in 17 rivers of the Pantanal (Brazil) were analyzed with the objective of evaluating pesticide contamination in sediments. Samples were extracted with an acetone, ethylacetate, and water mixture 2:2:1 (v/v/v). The extract was purified by flash chromatography with aluminum oxide and florisil. A multiresidue gas chromatography-mass spectrometry method was applied to monitor 23 pesticides of different chemical classes (organochlorine, organophosphorus, triazines, anilides and pyrethroids) with some of their degradation products. Compounds identified in sediment samples included lambda -cyhalothrin (1.0 to 5.0 micro g kg(- 1)), p,p'-DDT (3.6 micro g kg(- 1)), deltamethrin (20.0 micro g kg(- 1)) and permethrin (1.0 to 7.0 micro g kg(- 1)).
