Comparison & analysis of different hues of shoe polish stains using Thin Layer Chromatography (TLC)

Abstract

Shoe polish is considered as an important trace evidence found in cases related to physical and sexual assault, theft, counterfeit and murder. This study focuses on comparison and discrimination of different shades of Shoe polish stains using Thin Layer Chromatography (TLC). 14 shoe polish samples of eight different brands with different shades were collected and analysed. Five different solvent systems were analysed among them only 2 solvent systems namely Ethyl Acetate: Methanol: Water (7:2:1 v/v/v) and Ethyl Acetate: Benzene: Water (5:3:2 v/v/v) were selected for TLC. All the pigmented samples gave comparatively similar results with solvent 1 (Ethyl Acetate: Methanol: Water) and solvent 3 (Chloroform: Methanol: Water). Moreover both solvent 1 and solvent 2 gave results (extraction solvent being different) with sample 13 that solvent 3 was unable while solvent 2 also gave results with sample 3 which solvent 1 and 3 both were unable. Hence, we can say that solvent system 1 i.e., (Ethyl Acetate: Methanol: Water- 7:2:1 v/v/v) is the best solvent as it gave good results for most of the pigmented samples of different brands on the other hand methanol is the good extraction solvent compared to ethyl acetate and tetrahydrofuran as it separated the pigments from the waxes very prominently. The new solvent system proposed in the study after experimentation can be used for analysis of shoe polish stain. For quantification and distinction of each shoe polish samples in a detailed manner further instrumental analysis is recommended. The data obtained from this study can be helpful in the preliminary stage of identifying different trace evidences which may look like shoe polish in physical appearance.