Flow analysis by using solenoid valves for As(III) determination in natural waters by an on-line separation and pre-concentration system coupled to a tungsten coil atomizer

Abstract

Recebido em 11/2/04; aceito em 27/8/04; publicado na web em 28/1/05 A flow system coupled to a tungsten coil atomizer in an atomic absorption spectrometer (TCA-AAS) was developed for As(III) determination in waters, by extraction with sodium diethyldithiocarbamate (NaDDTC) as complexing agent, and by sorption of the As(III)-DDTC complex in a micro-column filled with 5 mg C18 reversed phase (10 µL dry sorbent), followed by elution with ethanol. A complete pre-concentration/elution cycle took 208 s, with 30 s sample load time (1.7 mL) and 4 s elution time (71 µL). The interface and software for the synchronous control of two peristaltic pumps (RUN/ STOP), an autosampler arm, seven solenoid valves, one injection valve, the electrothermal atomizer and the spectrometer Read function were constructed. The system was characterized and validated by analytical recovery studies performed both in synthetic solutions and in natural waters. Using a 30 s pre-concentration period, the working curve was linear between 0.25 and 6.0 µg L -1 (r = 0.9976), the retention efficiency was 94±1% (6.0 µg L -1 ), and the pre-concentration coefficient was 28.9. The characteristic mass was 58 pg, the mean repeatability (expressed as the variation coefficient) was 3.4% (n=5), the detection limit was 0.058 µg L -1 (4.1 pg in 71 µL of eluate injected into the coil), and the mean analytical recovery in natural waters was 92.6 ± 9.5 % (n=15). The procedure is simple, economic, less prone to sample loss and contamination and the useful lifetime of the micro-column was between 200-300 pre-concentration cycles.

Application of portable spectrometer for ultra trace metal analysis after ionic liquid based microextraction

“…3 For many years, research has been carried out on W-coils and they have been applied in the eld of AAS, including instrument development, 4 simultaneous determination of multiple-elements, 5 application of chemical modiers, 3 electrothermal vaporization (ETV) devices 6,7 and some couplings with preconcentration methods. [8][9][10][11][12][13][14] Recently, the rst batch of commercial instruments has been developed. In this research, ionic liquid based liquid phase microextraction (IL-LPME) was coupled with a portable W-coil ET-AAS instrument to expand its application and improve its analytical performance.…”