Differential spectroscopy of cocaine and its structural analogues in sample characterization

In forensic science, the need to adequately identify cocaine and differentiate it from closely related compounds within a short time is desirable. Application of ultraviolet (UV) spectroscopy in this respect is limited because of the broadness of UV peaks. Derivative transformation of UV spectra, a relatively new technique, is shown in this work to enhance characteristic information from UV spectra to aid identification of cocaine. Cocaine is characterized with a triplet peak at around 230 nm in the second order derivative. Ratio of peak amplitude was also used to characterize cocaine. The ratio of the negative to positive peak amplitude around 230 nm differentiates cocaine from other compounds tested. In addition, the ratio of a pair of peak amplitudes around 275 nm in the second order derivative gave characteristic properties which are statistically significant in the differentiation of cocaine from benzoic acid and benzocaine. Application of derivative spectroscopy for identification purposes is a promising area for more extensive exploitation in forensic science.