Microfluidic Paper-Based Analytical Device (Mu Pad) For Determining Hydroquinone In Facial Whitening Cream Using Phloroglucinol Reagent

A microfluidic paper-based analytical device (mu PAD) is developed in this work to analyze hydroquinone in facial whitening creams using phloroglucinol. The mu PAD features a hydrophobic barrier for detection and was fabricated using a wax printer with Whatman chromatographic paper. Detection was achieved by colorimetry based on the formation of an orange hydroquinone-phloroglucinol complex. The colored reaction product formed on the detection zone of the mu PAD was scanned, and the images obtained were processed with Image-J software to determine their color intensity (RGB value). Optimization of the process conditions was conducted to achieve sensitive measurements. The optimum conditions yielding maximum sensitivity included a reagent addition sequence of phloroglucinol. NaOH. sample (hydroquinone), 1 mu L of 0.5% phloroglucinol, 1 M NaOH, and 10-minute reaction. Under optimal conditions, the mu PAD produced two linear calibration curves for hydroquinone at concentrations of 10-100 mg/L (R-2 = 0.9979) and 250-1000 mg/L (R-2 = 0.9991). The method demonstrated very good selectivity for the target analyte in the presence of propylene glycol and resorcinol with satisfactory validity and average recovery close to 100%. The proposed mu PAD is a very simple and inexpensive technique for hydroquinone analysis and could be applied to cosmetics samples with satisfactory results.