The use of concentrated multiple reflection ATR spectroscopy in the analysis of nail polish as forensic evidence

Multiple reflection ATR spectroscopy is a technique used in cases where additional sensitivity is required over that provided by single reflection. Normally, multiple reflection equipment requires significantly more sample in order to adequately cover a larger sampling area. These larger sample amounts may not be available in forensic investigations. In this work, the capabilities of a concentrated multiple reflection ATR (CMRATR) accessory, in which all reflections are confined to a very small area, are demonstrated. Liquid solution sample sizes of only 5 to 15 μl are required. The accessory is used with an evaporative technique which further enhances sensitivity by concentrating the solute in close contact onto the ATR sampling surface. The technique along with a multivariate statistical analysis is used to discriminate visually similar nail polish samples made by different manufacturers.