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Biomedical subjects

J Macek

Publications and source records attributed to J Macek.

At least 19 recordsLinked to original sources
PubMed2006

Rapid determination of valsartan in human plasma by protein precipitation and high-performance liquid chromatography.

A high-performance liquid chromatographic (HPLC) method for the determination of valsartan in human plasma is reported. The assay is based on protein precipitation with methanol and reversed-phase chromatography with fluorimetric detection. The preparation of a batch of 24 samples takes 20 min. The liquid chromatography was performed on an octadecylsilica column (50 mm x 4 mm, 5 microm particles), the mobile phase consisted of acetonitrile -15 mM dihydrogenpotassium phosphate, pH 2.0 (45:55, v/v). The run time was 2.8 min. The fluorimetric detector was operated at 234/374 nm (excitation/emission wavelength). The limit of quantitation was 98 ng/ml using 0.2 ml of plasma. Within-day and between-day precision expressed by relative standard deviation was less than 5% and inaccuracy did not exceed 8%. The assay was applied to the analysis of samples from a pharmacokinetic study.

Angiotensin Receptor Antagonists↗
PubMed2004

Rapid determination of tamsulosin in human plasma by high-performance liquid chromatography using extraction with butyl acetate.

A high-performance liquid chromatographic method with fluorescence detection for the determination of tamsulosin in human plasma is reported. The sample preparation involved liquid-liquid extraction of tamsulosin from alkalised plasma with butyl acetate and back-extraction of the drug to the phosphate buffer (pH 2). Butyl acetate is preferable to more commonly used ethyl acetate because of its much lower solubility in water. Liquid chromatography was performed on an octadecylsilica column (55 mm x 4 mm, 3 microm particles), the mobile phase consisted of acetonitrile-30 mM dihydrogenpotassium phosphate (25:75 v/v). The run time was 3.5 min. The fluorimetric detector was operated at 228/326 nm (excitation/emission wavelength). An analogue of tamsulosin, (R)-5-[2-[(3-(2-ethoxyphenoxy)propyl)amino]-2-methylethyl]-2-methoxybenzensulfonamide was used as the internal standard. The limit of quantitation was 0.4 ng/ml using 1 ml of plasma. Within-day and between-day precision expressed by relative standard deviation was less than 10% and inaccuracy did not exceed 5%. The assay was applied to the analysis of samples from several pharmacokinetic studies.

Adrenergic alpha-Antagonists↗
PubMed2003

Determination of mirtazapine in human plasma by liquid chromatography.

A rapid high-performance liquid chromatographic method for the quantitation of mirtazapine in human plasma is presented. The method is based on a liquid-liquid extraction and reversed-phase chromatography with fluorimetric detection. The separation was performed on a Luna microm C(18)(2) 50 x 4.6 mm I.D. column using an isocratic elution. Zolpidem hemitartrate was used as the internal standard. The between-day precision expressed by relative standard deviation was less than 5% and inaccuracy does not exceed 6%. A low limit of quantitation (1.5 ng/ml) and a short time of analysis (4 min) makes this assay suitable for pharmacokinetic studies.

Antidepressive Agents, Tricyclic↗
PubMed2003

Liquid chromatographic determination of carvedilol in human plasma.

A high-performance liquid chromatographic method for the quantitation of carvedilol in human plasma is presented. The method is based on protein precipitation with methanol, concentration of the supernatant by evaporation and reversed-phase chromatography with fluorimetric detection. The separation was performed on a Develosil 3 micro m ODS 100 x 4.6 mm I.D. column and the mobile phase consisted of acetonitrile-30 mM potassium dihydrogenphosphate buffer, pH 2 (30:70 v/v). With only 250 micro l of plasma used for sample preparation, the limit of quantitation 1.3 ng/ml was achieved. Dihydroergocristine mesylate was used as the internal standard. The between-day precision expressed by relative standard deviation was less than 6% and inaccuracy does not exceed 3%. The assay was used for pharmacokinetic studies.

Antihypertensive Agents↗
PubMed2002

Determination of alendronate in human urine as 9-fluorenylmethyl derivative by high-performance liquid chromatography.

A high-performance liquid chromatographic method for the quantitation of alendronate as the 9-fluorenylmethyl derivative (FMOC) in human urine is presented. The sample preparation involved coprecipitation with calcium phosphate, separation on diethylamine (DEA) solid-phase extraction (SPE) cartridge and derivatization with 9-fluorenylmethyl chloroformate in citrate buffer pH 11.9. Liquid chromatography was performed on an octadecylsilica column (150 x 4.6 mm, 3 microm particles); a gradient method with starting mobile phase acetonitrile-methanol-citrate/pyrophosphate buffer (20:15:65 v/v) was employed. The total run time was 21 min. The fluorimetric detector was operated at the following wavelengths: 260 nm (excitation) and 310 nm (emission). Pamdronate was used as the internal standard. The limit of quantitation was 3.5 ng/ml using 5 ml of urine. Within-day and between-day precision expressed by relative standard deviation was less than 8% and inaccuracy did not exceed 9%. The assay was applied to the analysis of samples from a pharmacokinetic study.

Alendronate↗
PubMed2002

Rapid determination of pseudoephedrine in human plasma by high-performance liquid chromatography.

A rapid high-performance liquid chromatographic method for the quantitation of pseudoephedrine in human plasma is presented. The sample preparation involved liquid-liquid extraction of pseudoephedrine from alkalised plasma with hexane-isoamylalcohol (9:1, v/v) and back-extraction of the drug to 0.02 M hydrochloric acid. Liquid chromatography was performed on an octadecylsilica column (50 x 4 mm, 5 microm particles); the mobile phase consisted of acetonitrile-phosphate buffer containing 0.1% of triethylamine, pH 2.4 (5:95, v/v). The run time was 4 min. The spectrophotometric detector was operated at 195 nm. Codeine was used as the internal standard. The limit of quantitation was 5.8 ng/ml using 0.5 ml of plasma. Within-day and between-day precision expressed by relative standard deviation was less than 7% and inaccuracy did not exceed 8%. The assay was applied to the analysis of samples from a pharmacokinetic study.

Calibration↗
PubMed2001

Separation of finasteride and analogues.

This review is focused on the different chromatographic strategies for determination of finasteride and its analogues in biological fluids. These compounds are used for the treatment of benign prostatic hyperplasia. Particular attention is paid to high-performance liquid chromatography with spectrophotometric and mass spectrometric detection, the clean-up procedures are also included. The relationships between pharmacokinetics of finasteride, dose administered and required limit of quantitation of the chromatographic assays are discussed. Tandem mass spectrometry is recommended as the detection method for measuring concentrations <1 ng/ml, while cheaper spectrophotometric detection may be selected for determination of higher concentrations.

Chromatography, Liquid↗
PubMed2001

Rapid and simple high-performance liquid chromatographic determination of nimesulide in human plasma.

A high-performance liquid chromatographic method for the quantitation of nimesulide in human plasma is presented. The method is based on protein precipitation with methanol and reversed-phase chromatography with spectrophotometric detection at 404 nm. The separation was performed on a Nucleosil 120-5 C18, 50 x 4-mm I.D. column and the mobile phase consisted of acetonitrile-methanol-15 mM potassium dihydrogenphosphate buffer, pH 7.3 (30:5:65, v/v). Only 250 microl of plasma are used for sample preparation and no internal standard is necessary. The limit of quantitation is 80 ng/ml and the calibration curve is linear up to 10,000 ng/ml. More than 20 samples can be analysed within 1 h. Within-day and between-day precision expressed by relative standard deviation is less than 5% and inaccuracy does not exceed 8%. The assay was used for pharmacokinetic studies.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2001

Rapid determination of citalopram in human plasma by high-performance liquid chromatography.

A rapid high-performance liquid chromatographic method for the quantitation of citalopram in human plasma is presented. The sample preparation involved liquid-liquid extraction of citalopram with hexane-isoamyl alcohol (98:2 v/v) and back-extraction of the drug to 0.02 M hydrochloric acid. Liquid chromatography was performed on a cyano column (45 x 4.6 mm, 5 microm particles), the mobile phase consisted of an acetonitrile-phosphate buffer, pH 6.0 (50:50, v/v). The run time was 2.6 min. The fluorimetric detector was set at an excitation wavelength of 236 nm and an emission wavelength of 306 nm. Verapamil was used as the internal standard. The limit of quantitation was 0.96 ng/ml using 1 ml of plasma. Within- and between-day precision expressed by relative standard deviation was less than 7% and inaccuracy did not exceed 6%. The assay was applied to the analysis of samples from a pharmacokinetic study.

Antidepressive Agents, Second-Generation↗
PubMed2000

Determination of finasteride in human plasma by liquid-liquid extraction and high-performance liquid chromatography.

A high-performance liquid chromatographic method for the quantitation of finasteride in human plasma is presented. The method is based on liquid-liquid extraction with hexane-isoamylalcohol (98:2, v/v) and reversed-phase chromatography with spectrophotometric detection at 210 nm. The mobile phase consists of acetonitrile-15 mM potassium dihydrogenphosphate (40:60, v/v). Clobazam is used as the internal standard. The limit of quantitation is 4 ng/ml and the calibration curve is linear up to 300 ng/ml. Within-day and between-day precision expressed by relative standard deviation is less than 5% and inaccuracy does not exceed 8%. The assay was used for pharmacokinetic studies.

Chromatography, High Pressure Liquid↗
PubMed1999

Determination of cetirizine in human plasma by high-performance liquid chromatography.

A high-performance liquid chromatographic method for the quantitation of cetirizine in human plasma is presented. The method is based on liquid-liquid extraction with dichloromethane and reversed-phase chromatography with spectrophotometric detection at 232 nm. Gradient elution was used to remove late eluting peaks. Diazepam was used as the internal standard. The limit of quantitation was 10 ng/ml using 0.5 ml of plasma. Within-day and between-day precision expressed by relative standard deviation was less than 10% and inaccuracy did not exceed 8%. The assay was applied to the analysis of samples from a pharmacokinetic study.

Cetirizine↗
PubMed1999

Determination of roxithromycin in human plasma by high-performance liquid chromatography with spectrophotometric detection.

A simple and reproducible method for the determination of roxithromycin in human plasma is presented. This method is based on liquid-liquid extraction with hexane-isoamylalcohol (98:2, v:v) and reversed-phase chromatography with spectrophotometric detection at 220 nm. The mobile phase consists of methanol-15 mM dihydrogen potassium phosphate (70:30, v:v), pH of the aqueous part of the mobile phase is 6.0. The column is operated at 60 degrees C. Clarithromycin is used as the internal standard. The limit of quantitation is 0.5 microg/ml and the calibration curve is linear up to 30 microg/ml. Within-day and between-day precision expressed by relative standard deviation is less than 5% and inaccuracy does not exceed 9%. The assay was used for pharmacokinetic studies.

Anti-Bacterial Agents↗
PubMed1997

Rapid and simple method for the determination of zolpidem in human plasma by high-performance liquid chromatography.

A simple and reproducible method for the determination of zolpidem in human plasma is presented. This method involves protein precipitation with methanol (2 ml of methanol are added to 0.5 ml of plasma) and reversed-phase chromatography with fluorescence detection (excitation wavelength 244 nm, emission wavelength 388 nm). The mobile phase consists of methanol-30 mM dihydrogen potassium phosphate-triethylamine (30:69:1). pH of the aqueous part of the mobile phase is 6.8. No internal standard is required. Limit of quantitation is 1.5 ng/ml and the calibration curve is linear up to 400 ng/ml. Within-day and between-day precision expressed by relative standard deviation is less than 5% and inaccuracy also does not exceed 9%. The assay is useful for pharmacokinetic studies.

Chromatography, High Pressure Liquid↗
PubMed1997

Determination of omeprazole in human plasma by high-performance liquid chromatography.

A new method for the determination of omeprazole in human plasma was developed. Omeprazole was extracted from plasma with toluene-isoamylalcohol (95:5, v/v), the organic phase was evaporated, dissolved in the mobile phase and injected into a reversed-phase C18 column. Flunitrazepam was used as an internal standard. The mobile phase consisted of 47% methanol and 53% of 0.1 M dipotassium hydrogenphosphate, pH 7.8. The spectrophotometric detection was performed at 302 nm. Limit of quantitation was 9.7 ng/ml and the calibration curve was linear up to 1240 ng/ml.

Chromatography, High Pressure Liquid↗
PubMed1996

Determination of furosemide in plasma and urine by gas chromatography/mass spectrometry.

A new method for the determination of furosemide (CAS 54-31-9) in plasma and urine by gas chromatography/mass spectrometry (GC/MS) has been developed. After acidification the samples were extracted by ethyl acetate and methylated by methyl iodide. The chromatography was carried out on a fused-silica capillary column with SE-54 stationary phase. Detection was performed by selected ion monitoring (ions 81 and 372 were monitored for furosemide and ions 363 and 406 for internal standard bumetanide). Limit of quantitation was 10 ng/ml for plasma and 40 ng/ml for urine and the calibration curves were linear up to 100,000 ng/ml.

Bumetanide↗
PubMed1995

Determination of ofloxacin in human plasma using high-performance liquid chromatography and fluorescence detection.

A new method for the determination of ofloxacin in human plasma was developed. Plasma proteins were precipitated with acetonitrile, the supernatant concentrated and injected into a reversed-phase C18 column. Enoxacin was used as an internal standard. The fluorimetric detection was performed at 282 nm for excitation and 450 nm for emission. Limit of quantitation was 20 ng/ml and the calibration curve was linear up to 6900 ng/ml.

Acetonitriles↗