Cloud Point Extraction Coupled with Complexation Colorimetry for the Determination of Trace Amount of Pentavalent Antimony in Water

Abstract

The traditional 5-Br-PADAP (2-(5-bromo-2-pyridylazo)-5-(diethylamino)phenol) spectrophotometric method for determining antimony in water involves the use of highly toxic Sb(III) standards, requires large volumes of chemical reagents, and exhibits low sensitivity. To overcome these drawbacks, this paper couples cloud point extraction (CPE) with complexation colorimetry for the determination of trace antimony in water. This approach enables simultaneous enrichment and high-precision determination of trace pentavalent antimony [Sb(V)]. The effects of various parameters on CPE efficiency were systematically investigated, and the method performance was evaluated in the concentration range of 1–25 μg/L. The results show that under the optimized conditions (4.0 mol/L HCl; 2 mL of 2% Triton X-114; 0.2 mL of 200 mg/L Rhodamine B; extraction temperature 45°C; equilibration time 15 min), the proposed method exhibits good linearity (R² = 0.9978), high precision (relative standard deviation 3.33%), good accuracy (relative error 1.73%), and a low method detection limit (MDL = 0.554 μg/L). When combined with ozone-assisted oxidation pretreatment, this approach can be widely used to determine both total antimony and the distribution of antimony valence states.