Biomedical subjects

Christian Fernandes

Publications and source records attributed to Christian Fernandes.

4 recordsLinked to original sources

PubMed2006

Dissolution test for lamivudine tablets: optimization and statistical analysis.

A comparison of different methods for dissolution test used by five different manufacturer laboratories of lamivudine tablets is made, evaluated, and discussed. Dissolution medium (water and hydrochloric acid pH 1.2), apparatus (paddles and baskets) and time (30 and 60 min) were analyzed. The determination was accomplished by spectrophotometry at 270 nm. Analysis of variance (ANOVA) factorial design 5 x 2 x 2 x 2 with six repetitions, with post hoc multiple comparisons between means conducted by Duncan test at 0.05 significance level was used. After the comparative analysis of the results, optimal dissolution conditions were determined as follows: water as dissolution medium, paddles at the stirring speed of 50 rpm as apparatus and time of 30 min. The method was applied to the dissolution test of samples from eleven batches of tablets, produced by five different laboratories.

Analysis of Variance↗

PubMed2006

Optimization of the SPME parameters and its online coupling with HPLC for the analysis of tricyclic antidepressants in plasma samples.

Solid-phase microextraction (SPME)-liquid chromatography (LC) is used to analyze tricyclic antidepressant drugs desipramine, imipramine, nortriptyline, amitriptyline, and clomipramine (internal standard) in plasma samples. Extraction conditions are optimized using a 2(3) factorial design plus a central point to evaluate the influence of the time, temperature, and matrix pH. A Polydimethylsiloxane-divinylbenzene (60-mum film thickness) fiber is selected after the assessment of different types of coating. The chromatographic separation is realized using a C(18) column (150 x 4.6 mm, 5-microm particles), ammonium acetate buffer (0.05 mol/L, pH 5.50)-acetonitrile (55:45 v/v) with 0.1% of triethylamine as mobile phase and UV-vis detection at 214 nm. Among the factorial design conditions evaluated, the best results are obtained at a pH 11.0, temperature of 30 degrees C, and extraction time of 45 min. The proposed method, using a lab-made SPME-LC interface, allowed the determination of tricyclic antidepressants in in plasma at therapeutic concentration levels.

Antidepressive Agents, Tricyclic↗

PubMed2005

Automated microcolumn-switching system for drug analysis by direct injection of human plasma.

This study presents the application of a system that joins the known advantages of capillary liquid chromatography (e.g., higher concentration of the analytes and lower consumption of mobile phase) with those of column-switching using restricted access material (RAM) (sample clean up and extraction) to the analysis of fluoxetine in plasma samples. Automatically, the system loads the biological sample, while a RAM-BSA-C18 column (50 mm x 520 microm) excludes the macromolecules and focuses the analytes; afterwards, a second mobile phase elutes the analytes, in backflush mode, and provides the separation in a C18 analytical column (100 mm x 520 microm). We optimized the procedure for a total analysis time of 25 min. Using this approach the calibration curve shows r=0.998 with a linearity range from 20 to 500 ng ml(-1). Precision, calculated as relative standard deviation (RSD), was<20%. The developed miniaturized system showed to be adequate and attractive, demonstrating a large potential for sample preparation.

Automation↗

PubMed2005

Development of an improved heated interface for coupling solid-phase microextraction to high-performance liquid chromatography.

The aim of the study described in this report has been the development and the evaluation of a new improved interface to be operated under continuous heating, for on-line coupling solid-phase microextraction (SPME) to high-performance liquid chromatography (HPLC). Heating is desirable to increase desorption rate and decrease carryover. The results obtained have been compared with that obtained by off-line desorption and online desorption without heating. The SPME-HPLC interface described here has an inner volume of 60 microL, fixation for infinite points and a novel leak less sealing system. When the heating system was used, the area values were almost 10-fold higher than that obtained using the off-line mode. The obtained chromatograms showed an increasing of the area and height of chromatographic peaks and proved the excellent performance and reproducibility of the interface developed in this work.

Chemical Fractionation↗