Determination of metformin hydrochloride using precolumn derivatization with acetaldehyde and capillary electrophoresis coupled with electrochemiluminescence.

A novel method was developed using capillary electrophoresis (CE) coupled with tris(2,2'-bipyridyl)ruthenium(II) electrogenerated chemiluminescence (ECL) for highly sensitive detection of metformin hydrochloride (MH) derivatizatized with acetaldehyde. The precolumn derivatization of MH with acetaldehyde was performed in phosphate buffer solution (0.3 mol/L, pH 7.5) at room temperature for 120 min. The effects of acetaldehyde concentration, buffer pH, electrokinetic voltage and injection time were investigated. Under optimized detection conditions, the MH ECL detection sensitivity was more than 120 times that without derivatization. The linear concentration range for MH was 0.001-15.00 µg/mL (with a correlation coefficient of 0.9992). The detection limit was 0.31 ng/mL with a signal:noise ratio of 3. The recoveries of MH in human urine were in the range 98.50-99.72%. Copyright © 2011 John Wiley & Sons, Ltd.

Determination of the number of binding sites and binding constant between diltiazem hydrochloride and human serum albumin by ultrasonic microdialysis coupled with online capillary electrophoresis electrochemiluminescence.

A simple, sensitive and selective determination of diltiazem hydrochloride (DLT) is described using capillary electrophoresis electrochemiluminescence (CE-ECL). The CE-ECL parameters that affect separation and detection were optimized. Under the optimized conditions, the linear range of DLT was from 0.02 to 100 µmol/L (r(2) = 0.9983), with the detection limit of 5.1 nmol/L (3σ). The relative standard deviations of ECL intensity and the migration time were <2% for 0.1 µmol/L and 22 µmol/L DLT (n = 11). A new technique for determining of the number of binding sites and binding constant between DLT and HSA was developed using ultrasonic microdialysis coupled with CE-ECL. The number of binding sites and binding constant were 5.9 and 6.3 × 10(4) L/mol, respectively. The time required for ultrasonic microdialysis was 10 times less than that for traditional dialysis. Compared with traditional dialysis, ultrasonic microdialysis is simple, rapid, and should be applicable to a wide range of interactions of drugs and biomacromolecules.

Determination of galanthamine in Bulbus Lycoridis Radiatae by coupling capillary electrophoresis with end-column electrochemiluminescence detection.

A novel method for the determination of galanthamine (GAL) in Bulbus Lycoridis Radiatae has been developed based on coupling CE with an end-column tris(2,2'-bipyridyl)ruthenium(II) electrochemiluminescence (ECL). Parameters affecting CE separation and ECL detection were investigated and optimized. Baseline separation of GAL from other components in the Bulbus Lycoridis Radiatae sample was achieved with an 18 mmol/L phosphate running buffer at pH 9.0. Under the optimized conditions: 12 kV CE-separation voltage, ECL detection potential at 1.25 V with 5 mmol/L Ru(bpy)(3)(2+) and 50 mmol/L phosphate buffer at pH 7.5 in the detection reservoir, the linear range of GAL concentration was from 0.8 ng/mL to 2 microg/mL, whereas the detection limit was 0.25 ng/mL (S/N=3). The proposed method was successfully demonstrated for the determination of GAL in Bulbus Lycoridis Radiatae.

Pharmacokinetics of pefloxacin mesylate in human urine using capillary electrophoresis electrochemiluminescence detection.

A novel and simple method to determine pharmacokinetics of pefloxacin mesylate (PM) in urine of seven healthy adults was developed. The proposed methodology was based on the electrochemiluminescence (ECL) of tris(2,2'-bipyridine)ruthenium (II) at a platinum electrode. The ECL intensity was found greatly enhanced in the presence of PM, which could directly participate in the light-emitting reaction as the reductant (in former/unchanged form). Under optimised conditions, the calibration curve was linear from 0.02 to 12 mg/L with a detection limit of 0.004 mg/L (sigma=3). The RSD of the peak height was less than 2.4% (n=6). The recoveries in human urine were 96.2% to 98.3%. The highest excretion rate in urine was observed during the period 1.5-2 h after oral administration. The urinary excretion ratio of PM was 13.6% within 48 h.

Pharmacokinetics of amoxicillin in human urine using online coupled capillary electrophoresis with electrogenerated chemiluminescence detection.

A novel and sensitive method for the determination of amoxicillin (AM) in human urine has been established using capillary electrophoresis (CE) coupled with electrochemiluminescence (ECL) detection, based on the ECL enhancement of Tris(2,2'-bipyridyl) ruthenium(II) with AM. The effects of several factors such as the detection potential, the concentration and the pH of phosphate buffer, the electrokinetic voltage and the injection time were investigated. Under the optimal conditions, the linear concentration of AM ranged from 1.0 ng/ml to 8.0 microg/ml (with a correlation coefficient of 0.9999). The limit of detection was 0.31 ng/ml. The mean recovery was 95.77% with relative standard deviations of no larger than 2.2%. This method is quick (the total run time within 6 min). This method has been successfully applied to a pharmacokinetic study in human urine after oral administration of AM.