Accelerated stability testing of anti-aging cream: Formation of myristic acid and stearic acid as degradation products

Objective: This study aimed to determine the stability of anti-aging cream using the accelerated stability test and calculating the levels of myristic acid and stearic acid as degradation products. Methods: Optimum conditions and validation methods for the mixture of myristic acid and stearic acid were determined to obtain a valid method for determining the levels of degradation products in anti-aging cream. Derivatization was performed with the Lepage esterification method, which uses methanol-toluene 4:1 (v/v) and acetyl chloride catalysts. The analysis was performed using gas chromatography (GC) Shimadzu GC-17A system with an HP-1 column and flame ionization detection. Results: The column temperature was 120°C, with an increase of 10°C/min (up to 160°C) followed by an increase of 3°C/min (up to 220°C; maintained for 5 min) and an increase of 10°C/min (up to 260°C; maintained for 5 min). The injector and detector temperatures were 260°C and 280°C, respectively, with a flow rate of 1 mL/min. The retention times of myristic acid and stearic acid were 16.655 min and 28.169 min, respectively, with tailing factor values of 0.734 and 0.943, respectively. Validation results fulfilled our acceptance criteria, which obtained linearity for myristic acid at y=9.6483+190.78x, with a correlation coefficient (r) value of 0.9997, limit of detection (LOD)=0.0013 parts per million (ppm), and limit of quantification (LOQ)=0.0042 ppm. The linearity for stearic acid was determined at y=17.163+106.22x, with a correlation coefficient (r) value of 0.9998, LOD=0.0016 ppm, and LOQ=0.0053 ppm. Results of the anti-aging cream stability test indicated that the average remaining levels of isopropyl myristate from 0 to 3 months were 99.6283%, 99.1995%, 98.2571%, and 97.1511%, respectively. The average remaining levels of glyceryl monostearate were 99.6791%, 98.2881%, 96.2247%, and 93.7195% from 0 to 3 months, respectively. Conclusion: The expiration date of the anti-aging cream product was then calculated using zero-order kinetics and determined to be 10 months and 9 days.