Tannic acid as a chemosensor for colorimetric detection of Fe(II) and Au(III) ions in environmental water samples

A simple and efficient method to detect and quantify Fe(II) and Au(III) cations in environmental water samples was developed. The detection principle is based on the 1:1 mol-ratio complex formation between the probe molecule (tannic acid, TA) and Fe(II)/or Au(III), which yields visual color change and strong light absorbance at 518 nm and 534 nm, respectively. The association constant K-a for Fe(II) and Au(III) cations 4.01 x 10(4) and 4.13 x 10(4) M-1, respectively, was determined from Benesi-Hildebrand plot, indicating strong interactions between TA and target ions. This TA probe performed well in 50 mM phosphate buffer (PB, pH 9.0) solution and demonstrated an outstanding selectivity over 16 potential interfering metal ions and a good selectivity over Fe(III). The linear range in this study for Fe(II) and Au(III) cations was 0.25-100 mu M and 1.0-100 mu M, respectively. The detection limit of the TA probe for Fe(II) and Au(III) cations was found to be 0.080 and 0.50 mu M, respectively. The spike recovery for both metal ions in three environmental aqueous samples (spring water and pond water) was ranged 90.2%-117.2%. This study demonstrated that the TA probe is a simple and convenient detection method for analyzing water samples obtained from fresh water sources.

Automated summary

A simple and efficient method for detecting and quantifying Fe(II) and Au(III) cations in environmental water samples has been developed. The method is based on the 1:1 mol-ratio complex formation between the probe molecule and the target ions, and has demonstrated good selectivity and sensitivity.