Biomedical subjects

Rolf Karlícek

Publications and source records attributed to Rolf Karlícek.

7 recordsLinked to original sources

PubMed2005

Sequential injection extraction based on restricted access material for determination of furosemide in serum.

Restricted access material (RAM) column containing 25 microm C18 alkyl-diol support was integrated into the sequential injection analysis (SIA) manifold and the SIA-RAM system was tested for direct determination of furosemide in serum. LiChrospher ADS column based on restricted access material is proposed to direct injection of biofluids. The integration of RAM material into SIA enabled creation of a comprehensive on-line sample clean-up technique combined with fluorescence quantitation of analyte. Centrifuged and diluted serum sample was aspirated into the system and loaded onto the column using acetonitrile-water (2:98), pH 2.7. The analyte was retained on the column while proteins contained in the sample were removed to the waste without precipitation and clogging the column. Interfering substances complicating the detection were washed out by acetonitrile-water (15:85), pH 2.7 in the next step. The extracted analyte was eluted by means of acetonitrile-water (25:75), pH 2.3 to the fluorescence detector (emission filter 385 nm). The whole procedure comprising sample pre-treatment, analyte detection and column reconditioning took 20 min. The recoveries of furosemide from serum lay between 101.4 and 103.4% for three concentrations of analyte.

Adsorption↗

PubMed2005

Enantiomeric purity determination of tamsulosin by capillary electrophoresis using cyclodextrins and a polyacrylamide-coated capillary.

The chiral separation of racemic tamsulosin hydrochloride (TH) was carried out using cyclodextrin (CD)-mediated capillary electrophoresis (CE) with DAD at 200 nm. The best separation of enantiomers of the studied compound was achieved at 20 kV with 30 cm x 50 microm I.D. polyacrylamide (PAA)-coated fused-silica capillary (effective length 20 cm) and running buffer with sulfated-beta-CD (S-beta-CD) as chiral selector. Other selected native or derivatized CDs were also tested: beta-CD (5, 15 mmol l(-1)), carboxymethyl-beta-CD (5, 30 mmol l(-1)), dimethyl-beta-CD (15 mmol l(-1)) and hydroxypropyl-beta-CD (5, 30 mmol l(-1)). Several parameters such as capillary pretreatment, buffer type and concentration, pH of background electrolyte, methanol content, separation temperature and voltage, were optimized. The excellent baseline separation of chiral TH was successfully achieved within 12 min using 100 mmol l(-1) phosphate buffer with pH 2.5 containing 1.7 mmol l(-1) S-beta-CD. Rectilinear calibration range was 50.0-500.0 mumol l(-1) of each enantiomer (r = 0.9993-0.9996). The method was applied to the assay of R-TH in Omnic, capsules (nominal content 0.4 mg per capsule) with R.S.D. 2.75% (n = 6), recovery 99.3-101.7% and it was suitable for the chiral purity control of the active enantiomer in the pharmaceutical.

Acrylic Resins↗

PubMed2003

Reversed-phase porous silica rods, an alternative approach to high-performance liquid chromatographic separation using the sequential injection chromatography technique.

A commercially available porous silica rod column was used as a separation tool for the sequential injection analysis (SIA). A porous solid monolithic column showed high performance at a low pressure, allowing sequential injection analysis to be used for the first time for separation in HPLC fashion. In this contribution, we tried to demonstrate a new separation concept with SIA manifold for the simultaneous determination of four different compounds (methylparaben (MP), propylparaben (PP), triamcinolone acetonide (TCA) and internal standard ketoprofen (KP)) in a pharmaceutical triamcinolon cream 0.1% formulation. A Chromolith Flash RP-18e, 25 mm x 4.6 mm column with a 10 mm pre-column (Merck, Germany) and a FIAlab 3000 system (USA) with an 8-port selection valve and 10 ml syringe were used for sequential injection chromatographic separations in our study. The mobile phase used was acetonitrile-methanol-water (35:5:65, v/v/v) + 0.05% nonylamine, pH 2.5, flow rate 0.6 ml min(-1). The analysis time was <6 min. A novel sequential injection chromatography (SIC) technique with UV spectrophotometric detection was optimised and validated.

Chromatography, High Pressure Liquid↗

PubMed2003

Determination of salbutamol using on-line solid-phase extraction and sequential injection analysis. Comparison of chemiluminescence and fluorescence detection.

Determination of salbutamol using sequential injection analysis (SIA) with chemiluminescence and fluorescence detection has been devised. The chemiluminescence signal was emitted during the oxidation of salbutamol by potassium permanganate in sulfuric acid medium. Sodium polyphosphate was used as chemiluminescence enhancer. The fluorescence signal (excitation wavelength 230 nm) was also measured in sulfuric acid medium. Both detection techniques were compared with respect to the application of the methods to the determination of salbutamol in biological materials. The sample pre-treatment takes place directly in the SIA system, when salbutamol is adsorbed on the solid-phase (Baker-carboxylic acid) microcolumn integrated into the system. Sulfuric acid serves both as the reagent and the eluent. The lab-made SIA system consisted of a 2.5-mL Cavro syringe pump, ten-port Vici Valco selection valve and Spectra-Physics FS 970 fluorescence detector, which was lab-modified for chemiluminescence detection. The system was controlled by a PC using originally compiled LabVIEW-supported software. Concentrations, volumes of reagents and flow rates were optimised by a simplex method. Salbutamol was determined in the linear range 0.05-10 microg mL(-1) (RSD 1.53%), with the detection limit (3 sigma) 0.03 microg mL(-1) and sample throughput of 42 samples per hour with chemiluminescence detection in standard solutions. The fluorescence detection enabled the determination of salbutamol in standard solutions in the linear range 0.5-100 microg mL(-1) (RSD 2.69%), with the detection limit 0.2 microg mL(-1) and sample throughput of 24 h(-1). The proposed methods were applied to the determination of salbutamol in human serum and urine. However, serum is a very complicated matrix and the SIA-SPE analysis did not provide satisfactory results. It was possible to determine salbutamol in human urine using this technique. Better recovery was achieved with fluorescence detection.

Adrenergic beta-Agonists↗

PubMed2003

Determination of bopindolol by sequential injection technique with spectrophotometric detection.

In the proposed procedure, the determination of bopindolol using a sequential injection technique (SIA) with spectrophotometric detection at 560 nm is described. The new method of determination is based on the color reaction of the indole group in the molecule of bopindolol with 4-dimethylaminobenzaldehyde (Ehrlich's reagent) in acidic medium with production of a violet water-soluble complex. Due to the kinetic standpoint of reaction, the "stopped flow" technique with mixing coil between the valve and detector was tested and optimized. The proposed SIA system was used for the direct determination of bopindolol in tablets, negative effects of interfering substances (excipients of tablets) were not observed. The selectivity of the proposed method of determination was tested in the presence of seven interfering substances from the group of beta-blockers with good results. The interference effect was observed only in the presence of pindolol. The sample throughput with stopped flow technique was 40 samples per hour. Bopindolol was determined in the linear range from 1 to 10 microg ml(-1), RSD was less than 1% (n=10), with limit of detection (3sigma) 0.1 microg ml(-1) and limit of quantification 0.5 microg ml(-1). Obtained results were compared with conventional HPLC method, both analytical techniques were in good agreement.

Adrenergic beta-Antagonists↗

PubMed2003

On-line coupling of sequential injection extraction with restricted-access materials for sample clean-up and analysis of drugs in biological matrix.

In this contribution, the on-line coupling of solid phase extraction (SPE), based on a restricted-access material (RAM), with sequential injection technique (SIA) for the analysis of biological samples, is described. The SIA-RAM system was tested with a new potential antileucotrienic drug (VUFB-19363 (Quinlukast)) for serum analysis. The method is based on SPE with the novel internal-surface reversed-phase column packing material-alkyl-diol silica (ADS). The supports tolerate direct and repetitive injection of proteinaceous fluids (plasma, serum) and allow reversed-phase partitioning at the internal surface. A column packed with a 25 microm C18 alkyl-diol support was used for direct serum injection. Using a 6-port selection valve and the system of three mobile phases, the polar matrix compounds and metabolites are removed by sequentially aspirated mobile phases with lower content of the organic part (methanol-water (2:98) and following acetonitrile-water (20:80)) to the waste, and then, the analyte enriched on the column is eluted by a strong mobile phase (acetonitrile-methanol-water (40:20:40)) to the UV detector without transfer loss. With the fully automated SIA system, a total analysis time of less than 10 min was achieved. The only off-line sample pre-treatment step required to remove particulate matter was centrifugation. The studies showed a range of linearity (2-40 microg ml(-1)) and a high recovery (93.6-96.8%) of drug from the biological matrix with coefficients of variation (RSD) less than 5.0% (n = 6). This paper introduces a new, simple and robust analytical technique suitable for screening determination and direct analysis of drugs in biological materials.

Drug Contamination↗

PubMed2002

Automated simultaneous monitoring of nitrate and nitrite in surface water by sequential injection analysis.

A fully automated procedure based on Sequential Injection Analysis (SIA) methodology for simultaneous monitoring of nitrate and nitrite in surface water samples is described. Nitrite was determined directly using the Griess diazo-coupling reaction and the formed azo dye was measured at 540 nm in the flow cell of the fibre-optic spectrophotometer. Nitrate zone was passed through a reducing mini-column containing copperised-cadmium. After the reduction of nitrate into nitrite the sample was aspirated by flow reversal to the holding coil, treated with the reagent and finally passed through the flow cell. The calibration curve was linear over the range 0.05-1.00 mg N l(-1) of nitrite and 0.50-50.00 mg N l(-1) of nitrate; correlation coefficients were 0.9993 and 0.9988 for nitrite and nitrate, respectively. Detection limits were 0.015 and 0.10 mg N l(-1) for nitrite and nitrate, respectively. The relative standard deviation (RSD) values (n = 3) were 1.10% and 1.32% for nitrite and nitrate, respectively. The total time of one measuring cycle was 250 s, thus the sample throughput was about 14 h(-1). Nitrate and nitrite were determined in the real samples of surface water, and the results have been compared with those obtained by two other flow methods; flow injection analysis based on the same reactions and isotachophoretic determination used in a routine environmental control laboratory.

Automation↗