NCJ Number
191458
Journal
Journal of Forensic Sciences Volume: 46 Issue: 4 Dated: July 2001 Pages: 822-829
Editor(s)
Michael A. Peat Ph.D.
Date Published
July 2001
Length
8 pages
Annotation
This article examined the comparison of the infrared transmission spectrum of cocaine hydrochloride (HCI) to its attenuated total reflection (ATR).
Abstract
Transmission and internal reflection are two of the most common methods in collecting infrared spectra. Transmission has been the traditional method in recording infrared absorption spectra. However, today attenuated total reflection (ATR) spectra collected using the internal reflection method are displacing the older technique. This article compared transmission and internal reflection infrared spectra of cocaine. Cocaine (base) and cocaine hydrochloride were selected to illustrate the comparisons between transmission and ATR spectra. The differences found were small. However, they could cause confusion when directly comparing ATR to transmission spectra. The carbonyl absorption bands found between 1800 and 1650 cm were notable for their differences in intensities and peak shifts. They were a direct result of differences between the reflection and transmission processes. Either the transmission or internal reflection method can be used to evaluate forensic evidence. Transmission and internal reflection are two different methods for infrared analysis. While similar, each produced unique infrared data. Transmission produced absorption spectra and internal reflection produced ATR spectra. Graphs