Rapid Determination of 10 α-Hydroxy Acids

Significance of the Topic

Alpha-hydroxy acids (AHAs) are key ingredients in many cosmetic formulations, valued for their ability to accelerate cell renewal, improve skin texture, and reduce signs of aging. However, excessive or uncontrolled use can lead to skin irritation and heightened sensitivity to UV radiation. Regulatory agencies worldwide require reliable methods to quantify AHAs in cosmetics to ensure consumer safety and product compliance.

Objectives and Study Overview

This study aimed to develop a fast, high-resolution HPLC method for simultaneous determination of ten common AHAs in cosmetic products. Key goals included:

• Reducing total analysis time compared to existing protocols
• Achieving baseline separation of all target compounds and potential interferences
• Demonstrating method precision, accuracy, and suitability for real samples

Methodology and Instrumentation

A gradient HPLC method was implemented using methanol and 100 mmol/L diammonium hydrogen phosphate (pH 2.8) as mobile phases. Sample preparation involved hot water extraction, centrifugation, and membrane filtration following national guidelines. Calibration standards covered broad concentration ranges for each analyte to establish linearity.

Instrumentation Used

• Agilent 1260 Infinity II Prime flexible pump
• Agilent 1260 Infinity II vialsampler
• Agilent 1260 Infinity II multicolumn thermostat
• Agilent 1260 Infinity II DAD detector (214 nm, reference 360 nm)
• Agilent InfinityLab Poroshell 120 Aq-C18 column, 4.6 × 100 mm, 2.7 µm
• Agilent OpenLab CDS 2.6 software

Main Results and Discussion

The optimized method achieved complete separation of all ten AHAs within 12 minutes, with minimum resolution > 2.5. Precision tests (n=6) yielded retention time RSDs < 0.05% and peak area RSDs < 0.5%. Calibration curves for each compound exhibited excellent linearity (R² > 0.998). Recoveries in spiked moisturizer and cream samples ranged from 85% to 110%, confirming method accuracy and robustness even in complex matrices.

Benefits and Practical Applications of the Method

• Short analysis time increases laboratory throughput and efficiency
• High resolution ensures reliable quantification in diverse cosmetic matrices
• Wide linear ranges cover trace to major concentrations encountered in products
• Method aligns with regulatory requirements and supports quality control

Future Trends and Opportunities

Ongoing advancements in column technology and detector sensitivity may enable further reductions in analysis time and improved detection limits. Integration with automated sample handling and hyphenated techniques (e.g., LC-MS) could extend applications to novel AHAs, degradants, and related impurities. Data analytics and machine learning tools may also enhance method development and data interpretation in cosmetic analysis.

Conclusion

The developed Agilent 1260 Infinity II Prime HPLC method with the Poroshell 120 Aq-C18 column provides a rapid, precise, and accurate approach for quantifying ten α-hydroxy acids in cosmetics. With 12-minute run times, strong reproducibility, and broad applicability to real samples, the method supports routine quality control and regulatory compliance in the cosmetic industry.

References

• Zuo X; Han X; Liu C. A method of multiple evaluation in one test for determination of the content of 10 α-hydroxy acids in cosmetics. Hygiene Research. 2020;49(2):285–289,319.
• Li Y; Wu Z; Xiao S. Simultaneous determination of 10 α-hydroxy acids in cosmetics by high performance liquid chromatography. Chinese Journal of Health Laboratory Technology. 2017;27(19):2757–2760.
• U.S. Food and Drug Administration. Cosmetic ingredients: alpha-hydroxy acids. https://www.fda.gov/cosmetics/cosmetic-ingredients/alpha-hydroxy-acids#q5. Accessed June 2023.
• State Food and Drug Administration. Safety technical specifications for cosmetics (2015 edition). 2015.
• State Drug Administration. Notice on the inclusion of 9 inspection methods, including the detection method of free formaldehyde in cosmetics, into the safety and technical specifications for cosmetics (2015 edition), Circular No. 12 of 2019. 2019.