On the perspectives of capillary electrophoresis modes for the determination of morphine in human plasma without sample pretreatment

Screening and confirmation of drugs of abuse in body fluids are important for the medicinal treatment and form the legal basis of court judgments. A fast and precise identification of toxic substances is necessary. Morphine was determined in human plasma by capillary zone electrophoresis (CZE) and micellar electrokinetic capillary chromatography (MECC) using sample stacking mode. The electrophoretic separation was performed in an uncoated fused-silica capillary, 70 cm long to the detector, with an additional 10 cm to the cathode (75 microm i.d. and 360 microm o.d.). The UV absorbance detection was set at 190 nm. The electrophoretic buffers were prepared from 60 to 300 mm disodium tetraborate decahydrate, pH 10.5. Sodium dodecyl sulfate was added to the final solution in a concentration of 60 mm for MECC. All electrophoretic separations were carried out at 10 kV and the capillary temperature was ambient (25 degrees C). A linear calibration graph was obtained in the concentration range studied (50-5000 ng/mL). Several samples of drug-free plasma were checked for potential endogenous interference and the results showed no interference from the endogenous components, which co-migrated with morphine. As little as 50 ng/mL of morphine could be successfully analyzed by MECC in the concentration mode with acceptable precision. It is possible to determine morphine directly in plasma at therapeutic concentrations.     

Kinetics and mechanism of the copper(II) catalyzed oxidation of N-substituted p-phenylenediamines by 2,3,9,10-tetramethyl-1,4,5,7,8,11,12,14-octaazacyclotetradeca-1,3,8,10-tetraenecopper(II)

The kinetics of oxidation of N,N-dimethyl- and N,N,N,N-tetramethyl-p-phenylenediamines, to the corresponding semiquinonediimine radical and the quinonediimine, with a macrocyclic copper(II)-complex were studied at pH7. Under pseudo-first order conditions, the reaction rate for the N,N,N,N-tetramethyl derivative was much faster than for N,N-dimethyl-p-phenylenediamine, due to the increased probability of electron transfer. The reaction rate decreases with increasing acidity of the medium as a result of protonation of the amine nitrogen atoms. The rate constants and activation parameters were evaluated and the reaction was found to be enthalpy controlled. Furthermore, kinetic measurements revealed a remarkable superadditive effect when CuCl₂ solution was added, even at concentrations lower than that of the copper complex. This observation was used for the kinetic determination of copper ions at concentrations <10^–5M.     

A MEMS Tunable Optical Ring Resonator Filter

In this work, a new architecture for a ring resonator tunable optical filter is proposed. In this architecture, two rings are connected to each other by a directional coupler and tuning is achieved through the control of the separation between the coupler two parallel guides using a micro-electro-mechanical systems (MEMS) actuator. The optical performance of the filter is tested using the FDTD and an analytical model is developed to predict its performances. A good agreement between the analytical and numerical results is obtained. The MEMS design is also presented and verified using an finite element method (FEM) analysis.     

A liquid chromatography tandem mass spectrometry method for the simultaneous quantification of 20 drugs of abuse and metabolites in human meconium

A method for the simultaneous quantification of 20 cocaine, amphetamine, opiate, and nicotine analytes in meconium, the first neonatal feces, by liquid chromatography tandem mass spectrometry was developed and validated. Specimen preparation included methanol homogenization and solid phase extraction. Two injections were required to achieve sufficient sensitivity and linear dynamic range. Linearity ranged from 0.5–25 up to 500 ng/g (250 ng/g p-hydroxymethamphetamine), and correlation coefficients were >0.996. Imprecision was <10.0% CV, analytical recovery 85.5–123.1%, and extraction efficiencies >46.7% at three concentrations across the linear range. Despite significant matrix effects of −305.7–40.7%, effects were similar for native and deuterated analytes. No carryover, endogenous or exogenous interferences were observed, with analyte stability at room temperature, 4 °C, and −20 °C and on the autosampler >70%, except for 6-acetylmorphine, hydrocodone, oxycodone, and morphine. Method applicability was demonstrated by analyzing meconium from drug-exposed neonates.