Biomedical subjects

Josef Havel

Publications and source records attributed to Josef Havel.

27 records · Page 2Linked to original sources

PubMed2002

Electrophoretic behavior of adamantane derivatives possessing antiviral activity and their determination by capillary zone electrophoresis with indirect detection.

Separation and determination of adamantane derivatives with antiviral activity, namely amantadine (1-adamantan amine), memantine (1-amino-3,5-dimethyl adamantane) and rimantadine (alpha-methyl-1-adamantane methylamine), were examined by capillary zone electrophoresis. After optimization, an indirect detection method using 5 mM 4-methylbenzylamine in ethanol/water solution (1:4) as simultaneously absorbing and buffering background electrolyte with detection at 210 nm was found suitable for determination of the individual compounds (limit of detection was 0.35 mg L(-1) for memantine hydrochloride, S/N = 3). Baseline separation of all the three compounds was reached by addition of alpha- or beta-cyclodextrins to the electrolyte in concentrations of 20 and 2 mM, respectively.

Amantadine↗

PubMed2002

Simultaneous determination of trans-resveratrol and sorbic acid in wine by capillary zone electrophoresis.

A method for separation and determination of sorbic acid, a food and beverage preservative, and trans-resveratrol, a biomedically active substance, in wine by capillary zone electrophoresis is described. A solid-phase extraction step on C18-column prior to the electrophoretic separation providing lower detection limits was used for trans-resveratrol determination. For determination of sorbic acid direct analysis of wine (without a preconcentration step) was used. The method is rapid and sensitive and was applied to the analysis of wines from Alsace, France.

Electrophoresis, Capillary↗

PubMed2002

Capillary zone electrophoresis of humic acids from the American continent.

A multicomponent background electrolyte (BGE) was developed and its composition optimized using artificial neural networks (ANN). The optimal BGE composition was found to be 90 mM boric acid, 115 mM Tris, and 0.75 mM EDTA (pH 8.4). A separation voltage of 20 kV, 20 degrees C and detection at 210 nm were used. The method was applied to characterize several humic acids originating from various countries of the American continent: soil (Argentina), peat (Brazil), leonardite (Guatemala and Mexico) and coal (United States). Comparison with humic acids of International Humic Substances Society (IHSS) standard samples was also done. Well reproducible electropherograms showing a relatively high number of peaks were obtained. Characterization of the samples by elemental analysis and UV spectrophotometry was also done. In spite of the very different origins, the similarities between humic acids are high and by matrix assisted desorption/ionization-time of flight (MALDI-TOF)-mass spectrometry it was shown that most of the m/z patterns are the same in all humic acids. This means that humic acids of different origin have the same structural units or that they contain the same components.

Americas↗

PubMed2002

Capillary electrophoretic study of interactions of metal ions with crown ethers, a sulfated beta-cyclodextrin, and zwitterionic buffers present as additives in the background electrolyte.

Stability constants of K, Na, Ca, and Ba with 18-crown-6, K, Na, Li with sulfated beta-cyclodextrin and K, Li, Ca, Mg, Sr, and Ba ions with ([2-hydroxy-1,1-bis(hydroxymethyl) ethyl]-amino)-1-propanesulfonic acid (TAPS) were determined by capillary electrophoresis and computed using a general least squares minimizing program CELET. The results for 18-crown-6 agreed well with those evaluated by graphical methods or reported in the literature. Previously unknown stability constants of sulfated beta-cyclodextrins and TAPS determined for alkali and alkaline earth metals show that sulfated beta-cyclodextrin interacts with monovalent metals allowing to manipulate their effective mobility. It interacts stronger with divalent metal cations. TAPS, as zwitterionic buffer widely used in various analytical, biochemical and other applications, forms complexes with alkali and alkaline earth cations, and although the stability constants are rather low, the equilibria should be taken into account when TAPS is used and metal cations are present in solution at the same time.

Buffers↗

PubMed2002

Artificial neural networks for modeling electrophoretic mobilities of inorganic cations and organic cationic oximes used as antidote contra nerve paralytic chemical weapons.

Electrophoretic mobility of various analytes can be modeled and thus also predicted using artificial neural networks (ANNs) evaluating experiments done according to a suitable experimental design. In contrast to response surfaces modeling which can be used to predict optimal separation conditions, ANNs combined with experimental design were shown to be efficient for modeling and prediction of optimal separation conditions, while no explicit model and any knowledge of the physicochemical constants is needed. Methodology has been developed and demonstrated on separation of inorganic cations and organic oximes while various additives (methanol, complexation agent), pH or buffer concentration were followed. In our approach proposed the number of experiments necessary to find optimal separation conditions can be reduced significantly.

Antidotes↗

PubMed2002

Quantitative analysis of chiral compounds from unresolved peaks in capillary electrophoresis using multivariate calibration with experimental design and artificial neural networks.

Quantitation of optical isomers can be achieved even from incompletely resolved peaks with a multivariate calibration applying a combination of experimental design and artificial neural networks (ANN). Using the proposed approach, method development can be more efficient and analysis time shortened while quantitation of optical isomers with acceptable precision (+/-1-3%) can be achieved.

Journal Article↗

PubMed2002

Capillary electrophoresis determination of two reactive dyes: monitoring of activation and hydrolysis in different alkali media.

HPLC often meets with difficulty in analyzing reactive dyes, their activation, and posterior hydrolysis. In this work, capillary electrophoresis methodology for two reactive dyes, C.I. Reactive Black 5 and C.I. Reactive Red 198, was studied. The methods developed permit the separation and detection of these reactive dyes and their major hydrolytic products. These methods can be used successfully for the optimization of these dye syntheses, purification process, formulation, and also to monitor effluents and dye-bath mixtures and extrapolation to similar compounds. Simple background electrolyte systems, such as 10 mM phosphate or 0.65% hydroxypropylmethylcellulose in 40 mM acetate, were used to follow the hydrolysis mechanism and process in the two different alkali media studied.

Chromatography, High Pressure Liquid↗

PubMedDate not supplied

Use of germanate as a background electrolyte for capillary zone electrophoresis.

The possibilities of using germanate as a background electrolyte (BGE) in capillary zone electrophoresis (CZE) were investigated. Germanate can be obtained with spectral purity and, due to its two pKa values, possesses higher buffer capacity and can be used in a wider pH range than borate. The advantages and disadvantages of germanate among other polyanions for use as a background electrolyte for CE analysis are discussed.

Electrolytes↗

PubMedDate not supplied

Determination of physostigmine and pyridostigmine in pharmaceutical formulations by capillary electrophoresis.

Physostigmine (PHY) and pyridostigmine (PYR) are two important anticholinesterase compounds with several clinical uses. Recently, PHY has been investigated for the treatment of senile dementia in Alzheimer's disease. However, both PHY and PYR have gained importance as antidotes for anticholinergic drugs. In military medicine, PYR is used as a prophylactic against nerve gas poisoning and was used in Saudi Arabia during the Gulf War in 1991. A new capillary zone electrophoresis (CZE) method for the rapid determination of PHY and PYR in pharmaceutical preparations has been developed. An untreated fused-silica capillary tube (75 microm i.d., 44 cm total length, 36.5 cm length to the detector) was employed with detection at 200 and 270 nm for PHY and PYR, respectively. The optimal separation conditions for PHY were: 50 mM boric acid-HCl buffer (pH 3.25) with 30 mM NaClO4, electrokinetic injection for 5 sec at -5 kV, temperature 25 degrees C, and separation voltage 15 kV. The optimal separation conditions for PYR were: 20 mM phosphate buffer (pH 7), electrokinetic injection for 20 sec at -10 kV, temperature 25 degrees C, and separation voltage 15 kV. The limits of detection (LOD, S/N = 3) were 70 and 60 ppb for PHY and PYR, respectively. The method can be used for the monitoring of possible main degradation products in tablets of military antidote formulations.

Chemistry, Pharmaceutical↗