Determination of Trace Amounts of Aluminum by Light-Absorption Ratio Variation Combined with Continuous Flow Analysis
WANG Hong-yan, GAO Hong-wen2
1. Anhui Key Laboratory of Spin Electron and Nanomaterials (Cultivating Base), Department of Chemistry & Biology, Suzhou University, Suzhou 234000, China 2. State Key Laboratory of Pollution and Resource Reuse College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China
Abstract：In a pH 5.66 acetate-acetic acid medium, the complex reaction of Al(Ⅲ) with chlorophosphonazo-mS (MSCPA) is very sensitive. In order to react with Al(Ⅲ) completely, MSCPA must be added excessively enough. Without doubt, the excess MSCPA in the reaction solution affected the measurement of light-absorption of the Al-MSCPA complex. Thus, ordinary spectrophotmetry is unfit for the measurement of such a complex. To eliminate such an interference, both A537 nm and A618 nm were selected as the work wavelengths and the spectral correction technique was applied to the characterization of the above complex. The result showed that the composition ratio of Al(Ⅲ) to MSCPA is 1∶1. Using the complexation, a new dual-wavelength approach named the light-absorption ratio variation approach (LARVA) was applied to the determination of trace amounts of Al(Ⅲ), which often increases the sensitivity up to 10 times better than ordinary spectrophotometry. From the LARVA, the less the MSCPA added, the higher the sensitivity obtained. However, a too low amount of MSCPA caused an obvious error in the measurement because of the noise of instrument background. In the present work, 2.80 μmol·L-1 MSCPA was added into the Al(Ⅲ) solution. The absorbance ratio difference (ΔAr) of the Al-MSCPA solution is proportional to the Al(Ⅲ) concentration in the range of 0 and 0.150 mg·mL-1. The LOD of Al(Ⅲ) is only 2 mg·L-1. The result indicated that many kinds of metal ions did not affect the direct determination of Al(Ⅲ). Besides, the addition of thiourea solution may mask Fe(Ⅲ) and Cr(Ⅲ) effectively. The complexation between Al(Ⅲ) and MSCPA was completed in 2 min, and the color absorption of solution remained almost constant for more than 1 h. Therefore, a set of continuous flow analysis (CFA) device was designed for the online rapid analysis of Al(Ⅲ) and coupled with LARVA to increase greatly the analytical efficiency. The results showed that the LOD of Al(Ⅲ) is 6.5 mg·L-1 and the analytical rate is about 30 samples per hour. This method has been applied satisfactorily to the determination of trace amounts of aluminum in two chemical reagents, giving recoveries in the range of 97.6%-103.5%.
Key words：Light-absorption ratio variation approach;Continuous flow analysis;Determination of aluminum;Chlorophosphonazo-mS
王红艳1,2,郜洪文2. 光吸收比差-连续流动分析组合技术测定痕量铝[J]. 光谱学与光谱分析, 2008, 28(12): 2961-2965.
WANG Hong-yan, GAO Hong-wen2. Determination of Trace Amounts of Aluminum by Light-Absorption Ratio Variation Combined with Continuous Flow Analysis. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2008, 28(12): 2961-2965.
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