Infrared attenuated total reflection (IR‐ATR) spectroscopy for detecting drugs in human saliva

Abstract

The consumption of drugs is of great concern worldwide. Various drug tests for humans have been developed but there is no compact and easy-to-use test device available yet for direct semi-quantitative drug testing in the field. We suggest using attenuated total reflection (ATR) infrared spectroscopy as a sensing method to analyze human saliva samples with respect to drugs. In this paper, we present ATR spectra in the infrared range between 2300 and 900 cm(-1) as a first step towards such a device. We emphasize the common drug cocaine and its metabolites and investigate the problems of spectral interferences of selected diluents, masking agents, common medication, and soft drinks. Furthermore, spectra of saliva samples are recorded and a time-dependent change of the spectral signatures after alcohol consumption is presented. To the best of our knowledge, it is the first time that not only spectra of the drug of interest (cocaine) dissolved in water and in saliva but also spectra of interfering compounds possibly present in the saliva sample of a tested subject are discussed. This paper presents the most appropriate spectral range for strong cocaine absorption (including its metabolites) and minimum interference by the investigated substances. This spectral window is found to be between 1800 and 1710 cm(-1). In addition, we demonstrate the feasibility to identify cocaine in saliva at a concentration of 0.020 mg/ml with IR-ATR-spectroscopy without any separation or extraction procedures. For example, this technique could also be applied for drug detection in waste water.

Cocaine detection in liquid using a fibered platform and a mid-infrared quantum cascade laser

“…The carboxyl-group resonance of cocaine around 5.8 µm (1720 cm -1 ) provides a small cross-talk with other potentially interfering species [4]. The carboxyl-group resonance of cocaine around 5.8 µm (1720 cm -1 ) provides a small cross-talk with other potentially interfering species [4].…”

Spectroscopic Trends for the Determination of Illicit Drugs in Oral Fluid

“…The new spectra obtained showed some differences, but the studied substances did not impede the detection of cocaine. Additionally, alcohol concentration and its temporal evolution were easily detected in oral fluid [30].…”

“…20 In a first study, Hans et al [30] presented infrared spectra of cocaine in water and human oral fluid exploring, in addition, the possible spectral interferences of diluents, masking substances or common medicine. They evaluated the most appropriate absorbance range with the final goal to develop a compact and easy-to-use device for direct semi-quantitative drug testing.…”

“…In their previous work [30] they introduced the FTIR-ATR spectroscopy without sample preparation to study spectral interferences and to explore the LOD of cocaine in oral fluid. A high influence of the IR absorbance of water throughout the region of interest for cocaine detection, in particular between 1800 and 1200 cm -1 , was observed.…”

Computational Design and Fabrication of Optical Fibre Fluorescent Chemical Probes for the Detection of Cocaine

“…Evaluation of the composition of street Cocaine seized in two regions of Brazil has also been recently reported. [26] In addition, attenuated total reflection infrared spectra of saliva samples have been recorded [27] with a particular interest in detecting Cocaine and measuring spectral interferences of selected diluents, masking agents, common medication, and soft drinks.…”