Determination of aluminum in food samples after preconcentration as aluminon complex on microcrystalline naphthalene by spectrophotometry

Abstract

Recebido em 17/4/10; aceito em 10/10/10; publicado na web em 26/1/11 A sensitive preconcentration procedure for spectrophotometeric determination of aluminum was developed. Aluminum as aluminon complex is adsorbed on microcrystalline naphthalene. The naphthalene containing the complex is dissolved in 3 mL of acetone and its absorbance is measured at 544 nm. The effect of various factors on the preconcentration of aluminum was investigated. The calibration graph was linear in the range of 1-60 µg L -1 . The limit of detection was 0.52 µg L -1 and relative standard deviation for the determination of 5 µg L -1 was 2.65%. The proposed solid phase extraction procedure was applied to determination of aluminum in food samples.Keywords: aluminum; preconcentration; food samples. INTRODUCTIONAluminum is a non essential element and toxic metal which is widespread throughout the environment. Some studies suggest that aluminum may be accumulated in the brain via different routes (drinking waters, food, and medicines) and interfere with the normal activities of nervous system. Aluminum causes problems for human health because this metal ion has been considered as a possible cause of renal osteodystrophy, Parkinson disease and Alzheimer's disease. 1 Therefore determination of trace levels of aluminum in food and environmental samples is of great importance.Various instrumental techniques have been used for the analysis of aluminum at trace levels. These include flame atomic absorption spectrometry, 2 inductively coupled plasma -mass spectrometry (ICP-MS), 3 inductively coupled plasma-atomic emission spectrometry (ICP-AES), 4,5 graphite furnace atomic absorption spectrometry 6 and spectrophotometery. 7-10 ICP-MS and ICP-AES are expensive instruments with high costs of operation. 11 Spectrophotometric methods are simple and low cost procedures that have been widely used for the determination of metal ions which could form a color complex with chromogenic reagents. 12,13 However, sometimes the sensitivity is not good enough for the determination of low concentrations of aluminum and a preconcentration step is often required. Several methods for the separation and preconcentration of aluminum with extraction procedures have been reported, e.g., liquidliquid extraction, 14 cloud point extraction 15 liquid-liquid microextraction 16 and solid phase extraction. [17][18][19] Solid phase extraction (SPE) has several advantages over other preconcentration procedure including simplicity, low consumption of reagents, rapidity and high preconcentration factor. 20 A variety of solid phase extractants such as Tiron modified resin, 17 nanometer-sized titanium dioxide 19 and naphthalene 21 have been used for preconcentration and determination of trace amounts of aluminum.In this paper a simple method with solid phase extraction is described for the determination of Al (III). Aluminon is used as a selective ligand for the formation of colored complex. This complex is retained on microcrystalline naphthalene in a mini column. The solid mass co...

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