Increasing numbers of accidents caused by drivers under the influence of drugs, raise drug tests to worldwide interest. We developed a one-step extraction technique for cocaine in saliva and analyzed reference samples with laser spectroscopy employing two different schemes. The first is based on attenuated total reflection (ATR), which is applied to dried samples. The second scheme uses transmission measurements for the analysis of liquid samples. ATR spectroscopy achieved a limit of detection (LOD) of 3μg/ml. The LOD for the transmission approach in liquid samples is < 10 μg/ml. These LODs are realistic as such concentration ranges are encountered in the saliva of drug users after the administration of a single dose of cocaine. An improved stabilization of the set-up should lower the limit of detection significantly.
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.