Ultraviolet resonance Raman spectroscopy for the detection of cocaine in oral fluid.

Detecting and quantifying cocaine in oral fluid is of significant importance for practical forensics. Up to date, mainly destructive methods or biochemical tests have been used, while spectroscopic methods were only applied to pretreated samples. In this work, the possibility of using resonance Raman spectroscopy to detect cocaine in oral fluid without pretreating samples was tested. It was found that ultraviolet resonance Raman spectroscopy with 239-nm excitation allows for the detection of cocaine in oral fluid at 10µg/mL level. Further method development will be needed for reaching the practically useful levels of cocaine detection.

Analysis of street cocaine samples in nasal fluid by Raman spectroscopy.

The principal objective of this work was to demonstrate the capability of Raman spectroscopy to detect small amounts of cocaine in nasal fluid, and to identify the main drug and the most widely used cutting agents. Initially, standard samples were analysed and sampling conditions were studied by comparing different swabs used for the sample collection. Once the most appropriate swab was selected, which permitted a relatively simple detection of the standard cocaine hydrochloride, qualitative analyses of real samples were carried out. Three street cocaine samples were analysed, and the presence of cutting substances was highlighted by the appearance of different bands not corresponding to the ones of the standard cocaine. To identify the substances present in each sample, the spectra of the street cocaine samples were collected and compared with a digital library created on purpose with the spectra of the most common cutting agents. In this case, correlation coefficients permitted to recognize the most important substances presumably present in the samples, and gave an estimation of the purity of the cocaine. However, when nasal fluid was present, its strong signal could overlap or interfere with the smaller signal of the cutting substances, hindering their identification.

Portable capillary electrophoresis instrument with automated injector and contactless conductivity detection.

A portable capillary electrophoresis instrument featuring an automated, robust, valve-based injection system was developed. This significantly facilitates operation in the field compared to previous injection approaches. These generally required delicate manual operations which are difficult to perform outside the laboratory environment. The novel system relies on pressurized air for solution delivery and a micromembrane pump for sample aspiration. Contactless conductivity detection was employed for its versatility and low power requirement. The instrument has a compact design, with all components arranged in a briefcase with dimensions of 45 × 35 × 15 cm (w × d × h) and a weight of about 8 kg. It can operate continuously for 9 h in the battery-powered mode. Depending on the task at hand, the injection system allows easy optimization for high separation efficiency, for fast separations, or for low limits of detection. To illustrate these features, the separation of four anions within 16 s is demonstrated as well as the determination of nitrite below 1 µM. The determination of phosphate at a sewage treatment plant was carried out to demonstrate a field application.