Simultaneous detection of hazardous skin whitening agents in Indian cosmetic products using a green chromatographic technique

Abstract

The present work mainly highlights the simultaneous detection of four skin whitening agents i.e. hydroquinone (HQ), resorcinol (RS), catechol (CC) and 3,3′-dichlorobenzidine (DCB) in facial creams and body lotion. Among these, the first three are positional isomers of dihydroxybenzene so simultaneous separation is difficult with the conventional reverse-phase high-performance liquid chromatographic technique (RP-HPLC). The selected skin whitening agents were detected in facial cream and body lotion using micellar liquid chromatography coupled to a photodiode array detector (MLC-PDA). In the present study, optimization of the method was accomplished using response surface methodology (RSM) with central composite design (CCD). The second-order polynomial model for predicting the optimal chromatographic run time was evaluated by the analysis of variance (ANOVA) and 3D response surface plots for the interactions between three variables were constructed. Three experimental parameters which were chosen as independent variables were; surfactant concentration (SDS), the volume percentage of organic modifier (OM) and pH of the mobile phase. The second-order polynomial model for predicting the optimal chromatographic run time was evaluated by the analysis of variance (ANOVA) and 3D response surface plots for the interactions between three variables were constructed. Three experimental parameters which were chosen as independent variables were; surfactant concentration (SDS), percentage of organic modifier (OM) and pH of the mobile phase. The second-order polynomial model for predicting the optimal chromatographic run time was evaluated by the analysis of variance (ANOVA) and 3D response surface plots for the interactions between three variables were constructed. Three experimental parameters which were chosen as independent variables were; surfactant concentration (SDS), percentage of organic modifier (OM) and pH of the mobile phase. The optimized mobile phase was 0.15 M SDS and 7% 1-butanol, buffered at pH 7 with 0.01 M NaH2PO4. The chromatographic run time for simultaneous determination of selected analytes was 7.5 min. The correlation coefficient (r2) values were satisfactory between 0.998–0.999 over the linear concentration range. Limits of detection (LODs) and the limits of quantification (LOQs) for the four skin whitening agents were in the range of 0.05–0.07 μg/mg and 0.11–0.14 μg/mg, respectively. Trueness (98.4–102.7%) and precision (< 4.3%) were acceptable. The developed method was fast, cost-effective, and green which could easily analyze complex matrices (facial creams, body lotion) without any pretreatment other than filtration. The results indicated that the MLC-PDA method proved to be more suitable for the simultaneous separation of selected positional isomers.