New, Fast, and Sustainable Method by HPLC for Simultaneous Determination of Ascorbic Acid and Nicotinamide in the Study of Cosmetic Emulsions

Aims: This study aimed to develop a new, fast and sustainable method by highperformance liquid chromatography (HPLC) for simultaneous determination of ascorbic acid and nicotinamide in the cosmetic emulsion. Background: Nicotinamide (NIC) and ascorbic acid (AA) are powerful antioxidants. AA presents excellent reducing power and protects the cell from oxidation. NIC is a precursor of NADPH and NADH, substances that present a strong reduction power, resulting in a huge antioxidant capacity. Objective: A new, fast and sustainable method using HPLC was developed and validated for simultaneous quantification of AA and NIC in the cosmetic emulsion. Methods: For this purpose, purified water with 0.01 % of trifluoracetic acid and ethanol (95:5, v/v), Symmetry Shield column (4.6 x 250 mm, 5 μm), 20 μL, 1.7 mL min^-1 at 254 nm were used. The method was validated according to the ICH, AOAC, and ANVISA, following parameters of linearity, detection and quantification limits, selectivity, accuracy, precision, and robustness. Results: The method was fast (2.7 min for AA and 3.2 min for NIC), linear between 20 and 80 μg mL^-1 (r = 0.9991 for AA and r = 0.9999 for NIC), precise (RSD < 5 % for AA and NIC), accurate (RSD 0.53 % for AA and 1.02 % for NIC), and selective for the emulsion base, and also robust to small changes in flow rate, injection volume, and purified water source. Conclusion: This work shows an ecologically alternative for the quantification of AA and NIC in the study of cosmetic emulsion by HPLC, which contemplates the requirements of the current green and sustainable analytical chemistry.