Determination of low levels of Cd(ii) in cosmetic products by spectrophotometry after separation/preconcentration with cloud point extraction

Abstract

In the present study, a simple, low-cost and efficient method was developed for the extraction and preconcentration of Cd(II) from cosmetic products by using cloud point extraction (CPE) prior to spectrophotometric detection. The method is based on the ternary complex formation of Cd(II) ions with 2′,7′-dichlorofluorescein (DClF) in the presence of 2,2′-bipyridine (Bipyr) and NaCl as chelating and salting-out agents at pH 7.0 respectively, and then their extraction into the micellar phase of polyethylene glycol tert-octylphenyl ether (Triton X-114). The effects of various variables affecting complex formation and CPE efficiency were investigated and optimized. The calibration graph was highly linear in the range of 8–120 μg L⁻¹ with a good regression coefficient, in which the absorbance decreased with increase in the concentration of Cd(II) at 502 nm. The limits of detection and quantification were 2.5 and 8.3 μg L⁻¹ with a sensitivity enhancement factor of 31.4, respectively. The relative standard deviations (RSDs) were in the range of 2.5–5.1% (for 15, 30 and 60 μg L⁻¹, n: 5). The recovery rates of spiked samples were in the range of 97.2–103% (15, 30 and 60 μg L⁻¹, n: 5). The accuracy of the method was determined by the analysis of a certified reference material (CRM 1548a typical diet). It has been observed that the result for Cd(II) is statistically within 95% confidence limit for the certified value. The results show that the proposed method can be applied satisfactorily to determine Cd(II) in cosmetic products.