Jean-Pierre Dubost

Separation of new antidepressants and their metabolites by micellar electrokinetic capillary chromatography

Selective serotonin reuptake inhibitors (SSRIs), serotonin noradrenergic reuptake inhibitors (SNaRIs) and noradrenergic and specific serotoninergic antidepressant (NaSSA) are widely used in the treatment of depression. An increase in antidepressant intoxications led to the development of reliable analytical methods for their analysis. A new determination procedure for these compounds (milnacipran, venlafaxine, desmethylvenlafaxine, mirtazapine, desmethylmirtazapine, citalopram, desmethylcitalopram, fluvoxamine, paroxetine, sertraline and fluoxetine) was developed by micellar electrokinetic capillary chromatography (MEKC) with diode array detection (DAD). Separation and determination were optimised on an uncoated fused-silica capillary (600 mm, 75 microm I.D.). The migration buffer consisted of 20 mM sodium borate, pH 8.55, with 20 mM SDS and 15% isopropanol, at an operating voltage of 25 kV. The column temperature was maintained at 40 degrees C. Injection in the capillary was performed in the hydrodynamic mode (0.5 p.s.i., 15 s). In these conditions, the migration time of the antidepressants was less than 11 min. In most cases, calibration curves were established for 30 - 2000 ng/ml (r > 0.995). The limit of detection and the limit of quantification were ranged between 10 and 20 and between 20 and 30 ng/ml, respectively, for all the molecules. This method allowed the determination of some of these compounds in biological fluids (blood, urine) in post-mortem cases. Samples (1 ml) were extracted with diethyl ether (5 ml) at pH 9.6 and reconstituted in diluted migration buffer. Similar results were obtained by a HPLC-DAD determination, performed as a reference method. These results suggest that this MEKC method can be useful for the determination of new antidepressants in post-mortem cases.

Comparison of high-performance liquid chromatography and capillary zone electrophoresis for the determination of parabens in a cosmetic product.

A high-performance liquid chromatographic method (HPLC) and a capillary zone electrophoresis method (CZE) have been developed for the analysis of methylparaben, ethylparaben, propylparaben and butylparaben in a commercial cosmetic product. A very simple extraction procedure with acidified diethylether was developed. The HPLC method involved a C18 reversed-phase column and a gradient of methanol and water-acetic acid (1%). Electrophoretic separation was performed on a fused-silica capillary with a mixed 15 mM tetraborate buffer (pH 9.2) and methanol (85:15, v/v). The calibration curves were linear from 1 to 40 microg/ml in HPLC and from 5 to 200 microg/ml in CZE. The limit of detection in CZE (0.21 microg/ml) was higher than in HPLC (0.05 microg/ml). Repeatability and intermediate precision were satisfactory for both methods (RSD values < 3.23% in HPLC and < 3.26%, in CZE). Only HPLC allowed the separation of butylparaben isomeric forms when CZE analysis was less time and reagents consuming. These results suggest that HPLC and CZE coupled with a simple extraction process are both suitable for parabens determination in cosmetic products.

Determination of pKa values of 2-amino-2-oxazolines by capillary electrophoresis.

The dissociation constants of new 2-amino-2-oxazolines were determined by capillary electrophoresis (CE) as a new technique. A method based on a linear model has been used in the CE determination. A series of eight 2-amino-2-oxazolines are investigated to determine their ionization constant. Among them, three new oxazolines synthesized are presented. The Ka values were obtained from the plots of reciprocal effective mobility against inverse concentrations of protons. The potentiometric method (PM) was performed as a comparative method. No significant differences were observed between the determined dissociation constants using both methods. Thus, the pKa values have been found to vary between 8.55 and 8.68.

Development and validation of a rapid capillary electrophoresis method for the determination of oseltamivir phosphate in Tamiflu ® and generic versions

A rapid and reliable capillary zone electrophoresis method was developed and validated for the assay of oseltamivir phosphate in capsules. Separation was carried out in fused silica capillary (60.2 cm total length and 10.0 cm effective length, 75 microm i.d.) by applying a potential of -15 kV at 25 degrees C. The selected electrophoretic buffer consisted of 50 mM sodium phosphate, pH 6.3 (direct UV detection, 226 nm). A short electrophoretic analysis time (less than 1.5 min) was obtained using the short end injection mode. The method was validated in terms of specificity, linearity, precision and accuracy. The RSD values were 0.94 and 0.98% for repeatability and intermediate precision, respectively. Recovery determinations allowed the calculation of a confidence interval from 98.64 to 100.26% with a relative standard deviation value of 0.38%. LOD and LOQ were estimated at 0.97 and 3.24 microg/mL, respectively. The validated method was successfully applied to the determination of oseltamivir in three commercially available capsules (Tamiflu, Saiflu and Flufy). The results were in good agreement with those obtained by a HPLC method previously developed in our laboratory. This method presents advantages including short run time, simple and rapid sample preparation and no use of non-aqueous solvent throughout the analysis.

Simultaneous Determination of Irbesartan and Hydrochlorothiazide in Tablets by Derivative Spectrophotometry

Abstract A second-derivative spectrophotometric method for the simultaneous determination of irbesartan (IRB) and hydrochlorothiazide (HCT) in tablets is described. Measurements were made at the zero-crossing wavelengths at 230.1 nm for IRB and 232.7 nm for HCT. The calibration graphs were linear in the range of 14.4–33.6 mg L−1 for IRB and 1.2–2.8 mg L−1 for HCT. The limits of quantitation were 5.0 and 1.1 mg L−1. The proposed method was successfully applied to the simultaneous determination of IRB and HCT in commercial tablets with a high percentage of recovery, good accuracy, and precision.

Spectrophotometric, spectrofluorimetric, HPLC and CZE determination of mirtazapine in pharmaceutical tablets.

Four analytical methods have been developed for the quality control of tablets containing mirtazapine: spectrophotometry, spectrofluorimetry, high performance liquid chromatography (HPLC) and capillary zone electrophoresis (CZE). All the methods only require a simple extraction procedure of mirtazapine from the tablets before analysis. The concentration of mirtazapine in solutions was determined in the linearity range of 5-25 microg/ml at lambda=315 nm for spectrophotometry and at lambda=220 nm for HPLC and CZE. Spectrofluorimetric determinations were achieved at lambda(excitation)=328 nm and lambda(emission)=415 nm in the linearity range of 2-25 ng/ml. All the methods gave similar results and were validated for selectivity, linearity, precision and sensitivity. Spectrometric methods gave slightly higher RSD values (up to 2.54%). The four methods were directly and easily applied to the pharmaceutical preparation with accuracy, resulting from recovery experiments between 99.72% in HPLC and 101.47% in spectrofluorimetry.

Investigation of porous graphitic carbon at high-temperature liquid chromatography with evaporative light scattering detection for the analysis of the drug combination artesunate—Azithromycin for the treatment of severe malaria

Artesunate combined therapies represent the best option for the treatment of malaria and require the development of new methods of analysis. Retention, selectivity and detection with high-temperature liquid chromatography-porous graphitic carbon-evaporative light scattering detection was studied for artesunate and azithromycin separation. Organic solvent, concentration of organic modifiers, temperature and flow rate were all relevant parameters to optimize this separation. The behaviour of artesunate in the tested conditions appeared close to a neutral compound. In CH(3)OH, only azithromycin retention was dramatically altered depending on the [triethylamine]/[formic acid] ratio and on the temperature, whereas in CH(3)CN, azithromycin, artesunate, artemisinin and dihydroartemisinin retentions decreased with the temperature increase whatever the organic modifier ratio. The best efficiency was obtained with CH(3)CN. 25% variation of the concentration values of the organic modifiers did not significantly influenced the retention. The sensitivity of ELSD increased with the flow rate decrease. Peak area and S/N ratio dramatically decreased with the flow rate increase by 10- and 5-fold for artesunate and azithromycin, respectively. Non-linear calibration curves were obtained for both artesunate and azithromycin.

Simultaneous determination of rutin and benzocaine in suppositories by reversed-phase high-performance liquid chromatography

A simple and precise reversed-phase HPLC procedure for the simultaneous determination of rutin and benzocaine in suppositories is proposed. The chromatographic conditions were: Apex ODS column; methanol-10 mM triethylamine aqueous solution pH 3.0 (57 : 43, v/v) as the mobile phase; detection wavelength, 270 nm. Calibration curves were linear at concentration ranges 6.0 μg ml−1–14.0 μg ml−1 and 1.5 μg ml−1– 3.5 μg ml−1 for rutin and benzocaine, respectively. The reproductibility was 1.05% and 0.95% for rutin and benzocaine, respectively.

Determination of artesunate using reversed-phase HPLC at increased temperature and ELSD detection.

Artesunate (ART) determination can be performed by evaporative light scattering detection with mobile phase composed of CH(3)CN/HCOOH 0.01 M (40:60 v/v; pH 2.85). Evaporative light scattering detection instead of UV detection allowed to improve the sensitivity and the LOD. However, the evaporative light scattering detection response of dihydro-artemisinin appears weaker than for ART, whereas with UV detection the response of ART and dihydroartemisinin seemed similar. Constant analysis time was obtained on using the mobile phase with a flow rate of 0.5 mL/min and column temperature at 60 degrees C instead of 0.7 mL/min at room temperature. This led to less solvent consumption. Moreover, decrease in the flow rate and increase in the column temperature were advantageous for higher sensitivity with both evaporative light scattering detection and UV detection. ART determination in rectal gel and suppositories were compared with these different detection modes and similar results were obtained.

Simultaneous Determination of Two Synthetic Dyes Erytrosine and Sunset Yellow in a Pharmaceutical Syrup By First Derivative Visible Spectrophotometry

ABSTRACT. A rapid first derivative spectrophotometric method for simultaneous determination of two synthetic dyes, erytrosine (E 127) and sunset yellow (E 110), in a mixture is proposed. The procedure does not require any separation step. The method was applied for determining the two compounds in a pharmaceutical syrup. Good linearity, accuracy, precision and selectivity were found, and the method is proposed for routine quality control purposes.