Highly Selective Spot Test of Aluminum (III) at ppb Level by Reverse Phase TLC with Sample Drop Loading

Kudo Yuki, Takahashi Naoshi, Nukaga Koji, Mizuguchi Hitoshi, Endo Masatoshi, Shida Junichi

doi:10.2116/bunsekikagaku.57.273

A highly selective, sensitive, and practically useful spot test of aluminum(III) has been developed. In this method, a 5 μL of ethanol-aqueous (1 + 1) sample solution containing metal chelates with 2,2'-dihydroxyazobenzene (DHAB) is loaded on a hydrophobic surface of an octadecylsilanized (ODS) silica plate, and thin-layer chromatography (TLC) is directly performed without drying the sample drop. The fluorescent aluminum(III) chelate remains selectively at the loading position, whereas the excess reagent, DHAB, and the chelates of the other metal ions are eluted. The fluorescent spot, which is observed only at the loading position, retains the circular shape of the initial interface between the sample drop and the plate. Immediately performing chromatographic separation after sample loading is effective for avoiding aluminum(III) contamination, which is caused by elution from the ODS-silica, because of the slow rate of formation of the aluminum(III)-DHAB complex. Furthermore, the matrix tolerance of the proposed method is superior to that of the previous method, in which chromatographic separation is performed after drying the sample drop. The visual detection limit is 1.0 μg/L. The calibration curve assessed with the densitometric responses with an excitation beam (505 nm) is linear over the concentration range up to 27 μg/L. The detection limit, which is calculated with 3.3σ at a concentration of 1.4 μg/L, is 0.2 μg/L (n = 5). The proposed method has been applied to the determination of parts per billion levels of aluminum(III) ion in river-water samples.

Highly Selective Spot Test of Aluminum (III) at ppb Level by Reverse Phase TLC with Sample Drop Loading

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