Determination of cocaine and methadone in urine samples by thin-film solid-phase microextraction and direct analysis in real time (DART) coupled with tandem mass spectrometry.

The use of thin-film solid-phase microextraction (SPME) as the sampling preparation step before direct analysis in real time (DART) was evaluated for the determination of two prohibited doping substances, cocaine and methadone, in urine samples. Results showed that thin-film SPME improves the detectability of these compounds: signal-to-blank ratios of 5 (cocaine) and 13 (methadone) were obtained in the analysis of 0.5 ng/ml in human urine. Thin-film SPME also provides efficient sample cleanup, avoiding contamination of the ion source by salt residues from the urine samples. Extraction time was established in 10 min, thus providing relatively short analysis time and high throughput when combined with a 96-well shaker and coupled with DART technique.

ssDNA aptamer-based column for simultaneous removal of nanogram per liter level of illicit and analgesic pharmaceuticals in drinking water.

Aptamers are a new class of single-stranded DNA/RNA molecules selected from synthetic nucleic acid libraries for molecular recognition. Our group reports a novel aptamer column for the removal of trace (ng/L) pharmaceuticals in drinking water. In this study, cocaine and diclofenac were chosen as model molecules to test the aptamer column which presented high removal capacity, selectivity, and stability. The removal of pharmaceuticals was as high as 88-95%. The data of adsorption were fitted with Langmuir isotherm and a pseudo-second-order kinetic model. A thermodynamic experiment proved the adsorption processes were exothermic in spontaneity. The kinetics of aptamer was composed of three steps: activation, binding, and hybridization. The first step was the rate-controlling step. The adsorption system was divided into three parts: kinetic, mixed, and thermodynamic zones from 0% to 100% binding fraction of aptamer. Furthermore, the aptamer column was reusable and achieved strong removal efficiency from 4 to 30 °C at normal cation ion concentration (5-100 mg/L) for multipollutants without cross effects and secondary pollution. This work indicates that aptamer, as a new sorbent, can be used in the removal of persistent organic pollutants, biological toxins, and pathogenic bacteria from surface, drinking, and ground water.

NMR regulatory analysis: enantiomeric purity determination for (R)-(-)-desoxyephedrine and antipode methamphetamine.

Regulatory enantiomeric purity direct determination for (S)-(+)-methamphetamine, the widely abused DEA schedule II controlled substance, and (R)-(-)-desoxyephedrine, over-the-counter nasal inhaler decongestant were developed using 400 MHz 1H NMR spectroscopy. The efficient enantiomeric differentiation was obtained using a diamagnetic chiral solvating agent to dissimilarly perturb the NMR spectra of the enantiomeric solutes. Nonequivalence behavior was studied in terms of all variables that affect population and intrinsic spectra of the fast diastereomeric solvates. Assignment of enantiomer configuration was based on the relative field position of the resolved enantiomeric signals. Optimization of experimental conditions provided significant resolved enantiomeric signals suitable for quantification. Utilizing the relative intensities of the corresponding enantiomeric signals of the N-CH3 assigned to (S)-(+)-methamphetamine and (R)-(-)-desoxyephedrine, the analysis of synthetic enantiomeric mixtures by the proposed methods demonstrated excellent agreements with the known values of the enantiomers present. The mean +/- SD recovery values for the (R)-(-)-enantiomer was 99.9 +/- 0.4% of added antipode (n = 7). The optically pure enantiomer was used to establish the minimum amount detected by the proposed NMR spectroscopic method.