Simultaneous determination of tramadol and lidocaine in urine by end-column capillary electrophoresis with electrochemiluminescence detection

Tramadol and lidocaine, used as analgesic and local anesthetic in surgery, are partly excreted by kidney. For the first time, we developed a simple and sensitive method, based on capillary electrophoresis with electrochemiluminescence (ECL) detection by end column mode without joint to monitor tramadol and lidocaine in urine. To eliminate the influence of ionic strength of urine sample, analytes were extracted by ether. Tripropylamine (TPA) was used as internal standard. ne recoveries of tramadol and lidocaine were between 94% and 97% at different levels. The method exhibited the linear range for the tramadol and lidocaine from 1.0 X 10(-7) to 1.0 X 10(-4) mol/L with correlation efficient of 0.998. The relative standard deviation (RSD) was 2.9% and 2.7% (n = 8) for tramadol and lidocaine, respectively. The limit of detection (LOD) was 6.0 x 10(-8) mol/L and 4.5 x 10(-8), mol/L (S/N = 3) for tramadol and lidocaine, respectively. The application for detecting tramadol and lidocaine in urine of patients showed that the method was valuable in clinical and biochemical laboratories for detecting tramadol, lidocaine and other tertiary amine pharmaceuticals for various purpose, such as metabolism investigation.

Electrochemiluminescent determination of L-cysteine with a flow-injection analysis system

A flow-injection electrochemiluminescent method for L-cysteine determination has been developed based on its enhancement of the electrochemiluminecence of luminol at a glassy carbon electrode. This method is simple and sensitive for cysteine determination. Under the selected experimental parameters, the linear range for cysteine concentration was 1.0 x 10(-6) - 5.0 x 10(-5) mol/l, and the detection limit was 0.67 mumol/l (SIN = 3). The relative standard deviation for 11 measurements of 1.0 x 10(-5) mol/l cysteine was 4.5%. The proposed method has been applied to. the detection of cysteine in pharmaceutical injections with satisfactory results.

Flow injection determination of dopamine based on inhibited electrochemiluminescence of luminol

A flow injection method has been developed for the determination of dopamine based on its inhibition of the electrochemiluminescence of luminol. This method is simple and sensitive for dopamine detection. Under the selected experimental conditions, the decreased electrochemiluminescent intensity is linear with dopamine concentration in the range of 5.0 x 10(-8)-1.0 x 10(-5) mol/L with a detection limit of 30 nmol/L. The relative standard deviation of eleven determinations is 1.9% for 1.0 x 10(-6) mol/L dopamine. The proposed method has been applied to the detection of dopamine in pharmaceutical injections with satisfactory results.

New technique for capillary electrophoresis directly coupled with end-column electrochemiluminescence detection

capillary electrophoresis (CE) is characterized. A 300 mum diameter Pt working electrode was used to directly couple with a 75 mum inner diameter separation capillary without an electric field decoupler. The hydrodynamic cyclic voltammogram (CV) of Ru(bpy)(3)(2+) showed that electrophoretic current did not affect the ECL reaction. The presence of high-voltage (HV) field only resulted in the shift of the ECL detection potential. The distance of capillary to electrode was an important parameter for optimizing detection performance as it determined the characteristics of mass transport toward the electrode and the actual concentration of Ru(bpy)(3)(2+) in the detection region. The optimum distance of capillary to electrode was decided by the inner diameter of the capillary, too. For a 75 mum capillary, the working electrode should be placed away from the capillary outlet at a distance within the range of 20-260 mum. The effects of pH value of ECL solution and molecular structure of analytes on peak height and theoretical plate numbers were discussed. Using the 75 mum capillary, under the optimum conditions, the method provided a linear range for tripropylamine (TPA) between 1 x 10(-10) and 1 X 10(-5) mol/L with correlation coefficient of 0.998. The detection limit (signal-to-noise ratio S/N = 3) was 5.0 x 10(-11) mol/L. The relative standard deviation in peak height for eight consecutive injections was 5.6%. By this new technique lidocaine spiked in a urine sample was determined. The method exhibited the linear range for lidocaine from 5.0 x 10(-8) to 1.0 X 10(-5) mol/L with correlation efficient of 0.998. The limit of detection (S/N = 3) was 2.0 x 10(-1) mol/L.

Flow injection analysis of histidine with enhanced electrogenerated chemiluminescence of luminol

A simple and sensitive flow injection method is presented for the determination of histidine based on its enhancement of electrogenerated chemiluminescence (ECL) of luminol. After optimization of the experimental parameters, the working range for histidine was in 1.0 x 10(-6) to 1.0 x 10(-3) mol/L with a detection limit (S/N = 3) of 0.56 mumol/L. The relative standard deviation was 1.6% for 11 measurements of 5 x 10(-5) mol/L histidine solution. The proposed method has been successfully applied to the determination of histidine in real pharmaceutical preparation.

A novel flow through optical fiber biosensor for glucose based on luminol electrochemiluminescence

A novel flow injection optical fiber biosensor for glucose based on luminol electrochemiluminescence (ECL) is presented. The sol-gel method is introduced to immobilize glucose oxidase (GOD) on the surface of a glassy carbon electrode. After optimization of the working conditions, glucose could be quantitated in the concentration ranges between 50 muM and 10 mM with a detection limit of around 26 muM. Signal reproducibility was about 3.62% relative standard deviation for 11 replicated measurements of 0.1 mM glucose. The ECL biosensor also showed good selectivity and operational stability. The proposed method can be applied to determination of glucose in soft drink samples.

Chemiluminescence determination of trace ascorbic acid with chromium (VI)-H2O2-luminol system

A new chemiluminescence(CL) system for the determination of ascorbic acid has been established. By the fast reduction reaction between chromium(VI) and ascorbic acid, chromium(M was generated to react with luminol and hydrogen peroxide in alkaline aqueous solution and hydrogen peroxide to produce CL. The CL emission intensity was correlated with ascorbic acid concentration in the range 8.0 x 10(-9) to 1.6 x 10(-4) mol/L, and the detection limit was 8.0 x 10(-9) mol/L ascorbic acid. The relative standard deviation (n = 11) for 1.0 x 10(-6) mol/L ascorbic acid is 0.9%. The method has been applied to the determination of ascorbic acid in vitamin C tablets with satisfactory results.

A chemiluminescence optical fiber glucose biosensor based on co-immobilizing glucose oxidase and horseradish peroxidase in a sol-gel film

An optical fiber bienzyme sensor based on the luminol chemiluminescent reaction was developed and demonstrated to be sensitive to glucose. Glucose oxidase (GOD) and horseradish peroxidase (HRP) were co-immobilized by microencapsulation in a sol-gel film derived from tetraethyl orthosilicate(TEOS). The calibration plots for glucose were established by the optical fiber glucose sensor fabricated by attaching the bienzyme silica gel onto the glass window of the fiber bundle. The linear range was 0.2-2 mmol/L and the detection limit was approximately 0.12 mmol/L. The relative standard deviation was 5.3% (n = 6). The proposed biosensor was applied to glucose assay in ofloxacin injection successfully.

Anodic voltammetric behavior of ethacridine at a glassy carbon electrode

The anodic voltammetric behavior of ethacridine (EAD) in the presence of various electrolytes was studied by using linear potential sweep voltammetry, differential-pulse voltammetry and cyclic voltammetry at a glassy carbon electrode. In the medium of 0.1 mol/L NaOH solution, an oxidative peak of ethaeridine was obtained. The peak potential is at about 0.40 V (vs. Ag/AgCl). The peak current is linearly increased with the concentration of ethaeridine over the range of 0.05 similar to 80 mg/L. The method has been used for the direct determination of ethacridine in injection. The relative standard deviation (n = 10) is 1.4% similar to 2.7%. The recoveries of ethacridine in urine samples are 89% similar to 95%. The mechanism of the electrode reaction was also discussed.

Determination of ascorbic acid by flow injection chemiluminescence suppression method

chemiluminescence suppression method for the determination of ascorbic acid based on Luminol-KIO4-H2O2-ascorbic acid system was established. The linear range for ascorbic acid is 1.0 x 10(-7) similar to 1.0 x 10(-5) mol/L and the detection limit is 6.0 x 10(-8) mol/L. The relative standard deviation (n = 11) is 1.0% for 8.0 x 10(-7) mol/L ascorbic acid. The method has been used to determine the content of ascorbic acid in tablets and injections with satisfactory results.

Sol-gel-derived, polishable, 1 : 12-phosphomolybdic acid-modified ceramic-carbon electrode and its electrocatalytic oxidation of ascorbic acid

Novel ceramic-carbon electrodes (CCEs) containing 1:12-phosphomolybdic acid (PMo12) were constructed by homogeneously dispersing PMo12 and graphite powder into methyltrimethoxysilane-derived gel. Peak currents for the PMo12-doped CCE were surface-controlled at lower scan rates but diffusion-controlled at higher scan rates and peak potentials shifted to the negative potential direction with increasing pH. In addition, the electrode exhibited electrocatalytic activity toward the oxidation of ascorbic acid. The PMo12-modified CCE presented good chemical and mechanical stability and good surface renewability (ten successive polishing resulted in less than 5% relative standard deviation). (C) 2000 Elsevier Science B.V. All rights reserved.

Three-dimensional quantitative structure-activity relationship of the opioid antagonist with potent anorectant activity of 3,4-dimethyl-4-(3-hydroxyphenyl) piperidine

A series of 3,4-dimethyl-4-(3-hydroxyphenyl) piperidine opioid antagonists with varying substituents on the nitrogen were evaluated for their effect on food consumption in obese Zucker rats. In developing three-dimensional quantitative structure-activity relationship (3D-QSAR) studies for this series of opioid antagonists, different structure alignments have been tested to predict the anorectant activities. The interaction energies between molecules and the probe atom were then correlated with anorectant activity using partial least squares (PLS) method. The steric and electrostatic features of the 3D-QSAR were presented in the form of standard deviation coefficient contour maps of steric and electrostatic fields. The results showed that 3D-QSAR results are much better than the results obtained by 2D-QSAR.

Anodic voltammetric behavior of medecamycin at a glassy carbon electrode

The anodic voltammetric behavior of medecamycin (MD) in the presence of various electrolytes was studied by linearsweep voltammetry, differential-pulse voltammetry and cyclic voltammetry at a glassy carbon electrode. In phosphate buffer solutions (pH = 9.4), MD is oxidized irreversibly. The peak potential is at about +0.75 V (vs.Ag/AgCl). The height of the peak is linearly increased with the concentration of MD over the range of 5 x 10(-5) similar to 1 x 10(-1) g/L. The method has been used for the direct determination of MD in tablets. The relative standard deviation (n = 10) is 1.8%. The recoveries of MD in urine samples are in the range of 95% similar to 115%.