288 JOURNAL OF COSMETIC SCIENCE
(22) Bonfilio R, Cazedey ECL, de Araújo MB, Nunes Salgado HRN. Analytical validation of quantitative
high-performance liquid chromatographic methods in pharmaceutical analysis: A practical approach.
Crit Rev Anal Chem. 2012 42(1):87–100. doi:10.1080/10408347.2012.630926
(23) The United States Pharmacopeia. USP 32 The National formulary. NF. WorldCat.org.AccessedDecember13,
2022. https://www.worldcat.org/title/united-states-pharmacopeia-usp-32-the-national-formulary-nf-27/
oclc/638237085 27
(24) Center for Drug Evaluation and Research (CDER) Reviewer Guidance’ Validation of Chromatographic
Methods. Published Online 1994.
(25) Lee YS, Choi KM, Choi MH, et al. Simultaneous HPLC analysis of ceramide and dihydroceramide in
human hairs. Arch Pharm Res. 2009 32(12):1795–1801. doi:10.1007/S12272-009-2219-5
(26) Kolarič L, Šimko P. Determination of cholesterol content in butter by HPLC: up-to-date optimization,
and in-house validation using reference materials. Foods. 2020 9(10):1378. doi:10.3390/FOODS9101378
(27) Green JM. Peer Reviewed: A Practical Guide to Analytical Method Validation. Anal Chem.
1996 68(9):305A–309A. doi:10.1021/AC961912F

289
J. Cosmet. Sci., 74.5, 289–300 (September/October 2023)
*Address all correspondence to Georgia E. Tsotsou, gtsotsou@uniwa.gr
Extraction-Free, In Situ Analysis of Glucose in Cosmetic
Formulations Based on Digital Image Colorimetry by
Smartphone
GEORGIA ELENI TSOTSOU AND ANASTASIA KYRIAKI TSARA
Department of Biomedical Sciences, University of West Attica, Egaleo, Greece (G.E.T., A.K.T.)
Cosmetic S.A., Karellas, Koropi, Greece (G.E.T)
Accepted for publication September 26, 2023.
Synopsis
We are proposing an extraction-free methodology for in situ quantifying glucose in cosmetic formulations
including oil-in-water (O/W) emulsions, shampoos, or gels. Quantification is based on the known glucose
oxidase/peroxidase reaction which is employed directly into the cosmetic formulation to generate a colored
product. Digital image colorimetry is then used to capture, calibrate, and quantify responses by the image-
processing software ImageJ. We have demonstrated a linear relationship between smartphone camera-
captured color intensity of the treated formulation and glucose concentration in all studied formulations.
Upon methodology validation, favorable technical characteristics were obtained for glucose analysis in an
O/W emulsion: the linearity range under the conditions employed was between 0 and 6.4*10−3% weight
per weight concentration of glucose in the formulation. Additionally, analysis of two quality control samples
yielded a coefficient of variation ≤11.6%, while bias was not higher than ±11.1%. Last, we successfully applied
the proposed analysis setup in combination with a standard addition procedure to quantify spiked glucose in
O/W emulsions, including colored emulsions, where bias was found between ±3.2% and ±15.9%. The above
results indicate acceptable reproducibility and accuracy for the proposed methodology and accountable matrix
effect. This study may open the route for routine glucose quantification in cosmetic or food emulsions and
galenic ointments.
INTRODUCTION
Glucose is a hygroscopic molecule, component of the natural moisturizing factor (NMF)
and is often used for its humectant/skin conditioning properties in skin care applications
either added directly to the formulation or indirectly, as component of natural extracts. In
addition, it has a role in certain formulations as a flavoring agent. Glucose is commonly
present in bath products, cleansing products, skin care products, makeup, and hair care
products. Moreover, it is also used in skin whitening products thanks to its indirect anti-
melanogenic effect at 2% weight per weight concentration (w/w).1 Glucose concentration in
cosmetic products ranges widely, from 10−4% to 91% in leave-on products and from 10−4%
to 84% in products intended for dermal contact.2