Application of micellar electrokinetic capillary chromatography to the discrimination of red lipstick samples

Marta Gładysz; Małgorzata Król; Karolina Mystek; Paweł Kościelniak

doi:10.1016/j.forsciint.2019.03.021

Application of micellar electrokinetic capillary chromatography to the discrimination of red lipstick samples

Forensic Sci Int. 2019 Jun:299:49-58. doi: 10.1016/j.forsciint.2019.03.021. Epub 2019 Mar 23.

Authors

Marta Gładysz¹, Małgorzata Król², Karolina Mystek¹, Paweł Kościelniak¹

Affiliations

¹ Laboratory for Forensic Chemistry, Department of Analytical Chemistry, Faculty of Chemistry, Jagiellonian University in Kraków, Gronostajowa 2, 30-387 Kraków, Poland.
² Laboratory for Forensic Chemistry, Department of Analytical Chemistry, Faculty of Chemistry, Jagiellonian University in Kraków, Gronostajowa 2, 30-387 Kraków, Poland. Electronic address: krolm@chemia.uj.edu.pl.

PMID: 30954628
DOI: 10.1016/j.forsciint.2019.03.021

Abstract

The main aim of this study was to apply capillary electrophoresis (CE) to the discrimination of red lipsticks - the first step towards developing the methodology for forensic purposes. The separation method was optimized using a mixture of eight dyes and micellar electrokinetic capillary chromatography (MEKC). The influence of the buffer pH and the concentration of SDS on the separation of dye mixtures was investigated. The best separation (highly efficient with the large resolution capacity in relatively short time) was accomplished using a buffer at pH 9 enriched with 80 mM SDS. The developed separation method was evaluated, determining the stability of sample (5 h) and buffer (10 h), the limit of detection of dyes (LOD < 1 μg·mL^-1), the repeatability of migration times in one day (RSD < 1.2%), and over three days (RSD < 2.4%), as well as the reproducibility using different capillaries and CE instruments. In order to develop a versatile extraction method for compounds from red lipsticks, various types of solvents, temperatures and durations of ultrasound assisted extraction (UAE) were tested. The use of a specially designed and constructed device for repetitive sampling without contamination was suggested. The extraction method was characterized in terms of precision, obtaining very good results for the qualitative (RSD of migration time < 2.0%) and quantitative (RSD of peak height < 10.0%) methods. The proposed UAE/MEKC-DAD method was successfully applied to distinguish red lipstick samples with a very similar hue, achieving a high value of discrimination power (DP = 0.998). It was found that it has great potential in forensic investigations.

Keywords: Cluster analysis; Discrimination; Extraction; MEKC; Optimization; Red lipsticks.