DEVELOPMENT AND VALIDATION OF A UV SPECTROPHOTOMETRIC METHOD FOR KOJIC ACID QUANTIFICATION BASED ON ITS ALUMINUM COMPLEXES

Kojic acid (KA) is a fungal metabolite that is widely used as a depigmenting agent in cosmetics. Although there are sophisticated techniques to quantify this substance, such as HPLC and LC-MS, cheaper and more accessible methods employing electronic spectroscopy are still needed. We have developed and validated an UV spectrophotometric method for KA quantification that is based on the analyte’s ability to form complexes with Al3+ ions. Superior selectivity is achieved with the presented method because KA-Al3+ complexes absorb at higher wavelengths than do noncomplexed KA. This approach has proven to be applicable for detection of KA in both raw materials and cosmetic creams. Detection is possible even in the presence of hydroquinone, which is frequently combined with KA in cosmetic preparations. Method validation results at 305 nm indicated appropriate selectivity and linearity in the range of 5 to 50 μg/mL (r= 0.9998). Sensitivity evaluation showed a DL= 0.15 μg/mL and QL= 0.46 μg/mL. Accuracy (recovery) was near 100% (99,53 – 101,24%). Method precision was determined through repeatability (RSD 0.402%, 1.284% and 1.192% for 10, 15 and 20 μg/ mL, respectively) and intermediate precision (RSD 2.171%, 0.976% and 0.440% for 10, 15 and 20 μg/ mL, respectively). Robustness was evaluated by varying the pH, temperature and reading time.