Sensing cocaine in saliva with attenuated total reflection infrared (ATR-IR) spectroscopy combined with a one-step extraction method

Abstract

On-site drug tests have gained importance, e.g., for protecting the society from impaired drivers. Since today's drug tests are majorly only positive/negative, there is a great need for a reliable, portable and preferentially quantitative drug test. In the project IrSens we aim to bridge this gap with the development of an optical sensor platform based on infrared spectroscopy and focus on cocaine detection in saliva. We combine a one-step extraction method, a sample drying technique and infrared attenuated total reflection (ATR) spectroscopy. As a first step we have developed an extraction technique that allows us to extract cocaine from saliva to an almost infrared-transparent solvent and to record ATR spectra with a commercially available Fourier Transform-infrared spectrometer. To the best of our knowledge this is the first time that such a simple and easy-to-use one-step extraction method is used to transfer cocaine from saliva into an organic solvent and detect it quantitatively. With this new method we are able to reach a current limit of detection around 10 μg/ml. This new extraction method could also be applied to waste water monitoring and controlling caffeine content in beverages.

Spectroscopic Trends for the Determination of Illicit Drugs in Oral Fluid

“…If the oral fluid sample was extracted right after the collection and preparation of the sample, a good reproducibility could be observed. It was concluded that this method not only allowed to reach a LOD of 10 mg/L or lower after extraction in PCE (see table 2), but also allowed to overcame the problem of concentration changes due to the small variations in the dried sample pattern [31].…”

“…Hence, the employment of bidimensional NMR appears a promising tool to improve the technique and then to be able to determine the presence of illicit drugs in oral fluid. 31 Spectroscopic methods appear to be an excellent combination of fast and non-destructive tools, although until now they have been scarcely used for drugs detection in oral fluid. Actually, they still need improvements to be applied for the determination of a wide range of drugs in real samples and to be of real interest for clinical and forensic applications.…”

“…A commercially available FTIR spectrometer with an ATR crystal, operating between 2300 and 900 cm -1 , was used [31]. Initially, a cocaine-doped oral fluid sample was spread on the crystal surface of the ATR unit and two spectra were recorded, before and after the sample dried up.…”