bluuebunny/crossref_metadata_2025_split huggingface dataset:
Specific high performance liquid chromatographic determination of the molecular weight and concentration of hyaluronic acid in complex mixtures by labelled hyaluronate binding proteins
Authors: Orviský E. , Kéry V. , Stančiková M. 
Published: May 2005

AbstractA simple High perfomance liquid chromatographic (HPLC) method for the specific determination of the molecular weight and concentration of hyaluronic acid (HA) in complex mixtures has been developed. Hyaluronate‐binding proteins isolated from bovine cartilage labelled by 125I or fluoresceinisothiocyanate were used as specific markers. The specific binding affinities of the markers were compared and were found to have association constants of 1.6 × 107 M−1 and 1.2 × 107 M−1 respectively. The HA levels and molecular weight distributions can be easily determined in the range 10‐500 ng/mL in complex mixtures by the use of markers, molecular sieving HPLC columns and appropriate detectors. It has been demonstrated clearly that the method is useful for the highly specific determination of the parameters in complex biological samples such as serum and synovial fluids and is recommended for clinical applications.
High performance liquid chromatographic analysis of tetroxoprim and sulphadiazine in serum and urine
Authors: Alkaysi Hanan N. , Salem Mutaz Sheikh , Badwan Adnan A. 
Published: May 2005

AbstractQuantitative determination of tetroxoprim and sulphadiazine in serum and urine was performed using reversed phase high performance liquid chromatography. Protein precipitation using 10% perchloric acid was utilized for purification of serum samples while urine samples were diluted prior to analysis. The mobile phase consisted of triethylammonium acetate buffer (85%), acetonitrile (12%) and methanol (3%), with a final pH of 4.2. The eluent was monitored at 280 nm. Benzoic acid was used as an internal standard. Standardization, validation and application of the method is described.
Preparation of glycine‐conjugated bile acids and their gas/liquid chromatographic analysis on an aluminum‐clad flexible fused silica capillary column
Authors: Iida Takashi , Tamaru Tamaaki , Chang Frederic C. , Goto Junichi , Nambara Toshio 
Published: May 2005

AbstractThis paper describes a method for the direct gas/liquid chromatographic (GC) analysis of 46 glycine‐conjugated bile acids, which differ from one another in the number, position and configuration of the hydroxyl groups at positions C‐2, C‐3, C‐4, C‐6, C‐7 and/or C‐12. Free bile acids were converted quantitatively on a micro scale to ethyl ester‐trimethylsilyl (Et‐TMS) and methyl ester‐dimethylethylsilyl (Me‐DMES) ether derivatives of the corresponding glycine conjugates. The Et‐TMS and Me‐DMES ethers of the glycine conjugates were chromatographed on an aluminum‐clad flexible fused‐silica capillary column coated with a thin film (0.1 μm) of chemically bonded and cross‐linked methylpolysiloxane. Relative retention time (RRT) and methylene unit (MU) values were determined for the 46 compounds and their GC behaviour was discussed. The derivatization procedure and the retention data would be useful for the direct GC identification of unknown glycine‐conjugated bile acid mixtures extracted from biological samples.
A sensitive and specific high performance liquid chromatographic assay for imidazole dipeptides and 3‐methylhistidine in human muscle biopsies, serum and urine
Authors: Teahon K. , Rideout J. M. 
Published: May 2005

AbstractA sensitive and specific high performance liquid chromatographic method is described for measuring imidazole dipeptides and 3‐methylhistidine in human muscle biopsies, serum and urine. Muscle extract, serum or urine was reacted with o‐phthaldialdehyde and the derivatives were separated by reversed phase chromatography with column swithing and fluorescence detection.
Quantitative determination of valproic acid and 14 metabolities in serum and urine by gas chromatography/mass spectrometry
Authors: Fisher E. , Wittfoht W. , Nau H. 
Published: May 2005

AbstractA method for the determination of the antiepileptic drug valproic acid and 14 of its metabolites in serum and urine by gas chromatography/mass spectrometry with selected ion monitoring of the trimethylsilylated derivatives has been developed. Sample preparation, including hydrolysis of VPA‐conjugates and removal of urea in urine is carried out at pH 5.0 and is rapid and simple. The samples are extracted with ethyl acetate and the concentrated extracts are trimethylsilylated. Analysis with adequate separation of metabolites is achieved with a DB 1701 fused silica (Megabore) capillary column. The method exhibits high recovery and reproducibility and is sufficiently sensitive and selective for analysis of small sample volumes. Application of the method for screening patient serum and urine samples for unusual metabolite patterns, with possible predictive value for early detection of liver injury, is presented.
Enhanced selectivity of the isolation of basic drugs from body fluids by means of extraction minicolumns and sophisticated elution schemes
Authors: Šcoltés Ladislav 
Published: May 2005

AbstractThe paper presents results and experience obtained in the isolation of a number of basic polar/non‐polar solutes (drugs, their metabolites and structural derivatives) from biological samples by using the separation minicolumns SeparcolR SI and SeparcolR SI C18 L/T. The aim was to provide insight into some simple procedures yielding optimal selectivity/specificity of the isolation of the studied solutes either by proper selection of the sorbent or by applying sophisticated elution schemes which use to advantage different properties of the eluents/solvents.
Isolation of clobazam–orosomucoid complexes from Patients' sera
Authors: Treuheit Michael , Halsall H. Brian 
Published: May 2005

AbstractOrosomucoid, a member of the lipocalin family, may function in the in vivo transport of lipophilic compounds such as basic and neutral drugs. We describe the identification of 7‐chloro‐1‐methyl‐1,5‐benzodiazepine‐2,4‐dione (clobazam) bound to the serum orosomucoid from individuals actively taking this tranquillizer. This suggests not only that other endogenous factors limit access to the benzodiazepine binding site on human serum albumin, but also that the differential binding of benzodiazepines and their metabolites by orosomucoid should be considered in determining therapeutic doses, particularly in the acute phase response.
Determination of urinary free cortisol by high performance liquid chromatography with sulphuric acid–ethanol derivatization and column switching
Authors: Nozaki Osamu , Ohata Tsuneko , Ohba Yasuhiro , Moriyama Hiroyuki , Kato Yoshio 
Published: May 2005

AbstractA rapid and highly sensitive determination method for urinary free cortisol has been developed using reversed phase high performance liquid chromatography (HPLC) with a precolumn for sulphuric acid‐ethanol fluorescence derivatization and column switching. Urinary cortisol, eluted from the octadecylsilane‐bonded silica (ODS) minicolumn with 90% aqueous ethanol, was derivatized with the addition of sulphuric acid only at ambient temperature. Cortisol derivatives injected directly onto the ODS precolumn were purified on‐line. After switching the columns, the cortisol derivative was separated on an ODS analytical column with a retention time of 15.3 min and monitored at an emission wavelength of 520 nm (exitation wavelength of 365 nm) to decrease the detection limit to 0.26 μg/dL (signal‐to‐noise ratio = 3). The automated HPLC operation resulted in good reproducibility and recovery of the stable cortisol derivative at 5°C.
Simple and highly sensitive determination of free fatty acids in human serum by high performance liquid chromatography with fluorescence detection
Authors: Iwata Tetsuharu , Inoue Kouji , Nakamura Masaru , Yamaguchi Masatoshi 
Published: May 2005

AbstractA highly sensitive and simple reversed phase high performance liquid chromatographic (HPLC) method for the quantitative determination of free fatty acids in human serum is presented. The method is based on the direct derivatization of serum fatty acids with 6,7‐dimethoxy‐1‐methyl‐2(1H)‐quinoxalinone‐3‐propionylcarboxylic acid hydrazide. The derivatization reaction proceeds in aqueous solution in the presence of pyridine and 1‐ethyl‐3‐(3‐dimethylaminopropyl)carbodiimide at 37°C. The resulting derivatives are separated within 75 min on a reversed phase column (YMC Pack C8) with a gradient elution of aqueous acetonitrile and detected fluorimetrically. The detection limits are 2.5–5 fmol in a 10 μL injection volume. The sensitivity permits precise determination of free fatty acids in 5 μL serum. The method is simple and is without the conventional liquid–liquid extraction steps of serum fatty acids.
A sensitive determination method for mexiletine derivatized with dansyl chloride in rat plasma utilizing a HPLC peroxyoxalate chemiluminescence detection system
Authors: Nishitani Atsuhiko , Kanda Susumu , Imai Kazuhiro 
Published: May 2005

AbstractA sensitive determination method for a non‐fluorescent anti‐arrhythmic drug, mexiletine, in rat plasma is presented utilizing a HPLC peroxyoxalate chemiluminescence (PO‐CL) detection system. After an internal standard (4‐methylmexiletine, 4.35 pmol) and 0.1 N sodium hydroxide solution were added to 5 μL rat plasma, the solution was poured onto an Extrelut 1 column. Both mexiletine and the internal standard were eluted with diethy ether and then the eluate was evaporated to dryness. The residue was dissolved in 0.2 M borate buffer (pH 8.5) and mixed with dansyl chloride (75 nmol) in acetronitrile. After standing of 90 min at room temperature, 0.5 N HCI was added to the reaction mixture to stop the reaction and a 2/45 aliquot of the mixture was subjected to a HPLC PO‐CL detection system using bis(4‐nitro‐2(3,6,9‐trioxadecyloxycarbonyl)phenyl)oxalate (TDPO) and hydrogen peroxide. The calibration curve for mexiletine in rat plasma was linear over the range 20–100 ng/mL plasma (20.6–103 fmol/injection). The detection limit (S/N = 2) was 1.0 fmol over the whole procedure. The method was applied to the measurement of the time courses of plasma mexiletine concentration after oral administration of the drug [25 mg (115.9 μmol)/kg] to rats.
The influence of synthetic conditions on the stability of methotrexate‐monoclonal antibody conjugates determined by reversed phase high performance liquid chromatography
Authors: Hudecz F. , Garnett M. C. , Khan T. , Baldwin R. W. 
Published: May 2005

AbstractMethotrexate (MTX) has been convalently attached to an IgG‐type monoclonal antibody (791T/36) directed to tumour‐associated antigen gp72. Conjugates were synthesized by the active ester method using MTX N‐succinimidyl ester at various pH values (7.5–10.5). Following purification by gel filtration, high performance liquid chromatography was used to assess the free drug or its derivatives in samples of MTX–791T/36 conjugates previously treated (or not) with hydroxylamine. Quantitative analysis, performed on a reversed phase column (pore size 300 Å) with isocratic acetonitrile–sodium acetate buffer (pH 4.8) as mobile phase, indicated no detectable amount of free methotrexate in hydroxylamine‐treated conjugates even six months after their preparation. Similar observations were made with conjugates, whose synthesis were performed at pH ⩾ 10. In contrast, the presence of increasing amounts of drug/metabolite could be demonstrated in samples produced at lower pH values. Based on these findings, the pH‐dependent kinetics of MTX release has been determined and used to design conditions under which stable MTX–791T/36 conjugates could be prepared without hydroxylamine reaction.
Measurement of N‐acetylneuraminic acid in human serum and urine by high performance liquid chromatography with chemiluminescence detection
Authors: Ishida Junichi , Nakahara Toshihiro , Yamaguchi Masatoshi 
Published: May 2005

AbstractA highly sensitive method for the determination of N‐acetylneuraminic acid in human serum and urine is investigated. This method employs high performance liquid chromatography with chemiluminescence detection. N‐Acetylneuraminic acid, released by hydrochloric acid hydrolysis of serum and urine, and N‐glycolylneuraminic acid (internal standard) are converted into chemiluminescent derivatives with 4,5‐diaminophthalhydrazide dihydrochloride, a chemiluminescence derivatization reagent for α‐keto acids. The derivatives are separated within 35 min on a reversed phase column, TSKgel ODS‐120T, with isocratic elution, followed by chemiluminescence detection; the chemiluminescence is produced by the reaction of the derivatives with hydrogen peroxide in the presence of potassium hexacyanoferrate(III) in alkaline solution. The detection limit for N‐acetylneuraminic acid is 9 fmol (signal‐to‐noise ratio = 3). This sensitivity permits precise determination of N‐acetylneuraminic acid in 10 nL of serum or 50 nL of urine. The method is applied to the determination of the N‐acetylneuraminic acid in human sera from normal subjects and cancer patients and in normal urine.
An improved method for preparation of perbenzoylated ganglioside‐derived sialic acids and nanogram detection of N‐acetyl‐ and N‐glycolylneuraminic acid by high performance liquid chromatography
Authors: Unland Frank , Müthing Johannes 
Published: May 2005

AbstractAn improved method for the preparation of perbenzoylated ganglioside‐derived sialic acids is described. After mild acid hydrolysis, isolation of sialic acids can be achieved by Folch partition (Method A) or by anion exchange chromatography (Method B). Perbenzoylated sialic acids were freed from benzoylation reagents by a second Folch partition. Total recoveries of both methods were found to be ⩾90%, calculated from metabolically labelled gangliosides. Derivatized N‐acetylneuraminic and N‐glycolylneuraminic acids were separated and quantified by isocratic high performance liquid chromatography using a RP18 column as the stationary phase and methanol: water (8:2) as the mobile phase. Both sialic acids were completely separated and eluted as single peaks within 15 min, monitored by UV detection. As little as 20 ng of neuraminic acid could be detected, the detector being linear up to 5 μg tested.
Multimodal liquid chromatographic separation methods in the study of ethimizol metabolism in man
Authors: Šoltés Ladislav 
Published: May 2005

AbstractThe metabolism of ethimizol in the human body has been investigated. Focus was on the detection and demonstration of the regioselective pathway of metabolic demethylation of ethimizol by determining the presence of the corresponding metabolites in blood, saliva and urine. Isolation, purification and identification of the metabolites present in the biological samples was achieved by applying a combination of the following methods: solid phase extraction, high performance liquid chromatography, high performance thin layer chromatography, nuclear magnetic resonance and mass spectrometry. The suggested chemical structures were definitely established by comparing the physicochemical characteristics of the ethimizol metabolites obtained from the individual biological fluids with the characteristics of synthetized authentic derivatives.
Non‐labelled benzodiazepines partitioned into synaptosomal membranes: their extraction and quantification by high performance liquid chromatography
Authors: Perillo Maria A. , Garcia Daniel A. 
Published: May 2005

AbstractA method for the extraction and quantification by high performance liquid chromatography (HPLC) of non‐labelled benzodiazepines partitioned into biological membranes has been developed. The benzodiazepine (BZD) was partitioned in a synaptosomal membrane–buffer system. The membranous pellet was separated by centrifugation and from this pellet, previously submitted or not to a proteolytic treatment and resuspended in the same buffer, the BZD was extracted by the addition of the proper volume of ethyl acetate, i.e. that capable of extracting at least 99.5% of the total drug in the aqueous phase. Optimal conditions for maximum proteolysis were: incubation of membranes at a final concentration of 1 mg protein/mL in the presence of 0.08 mg of Protease type I per mL for 90 min. at 45°C. Although the efficiency of the proteolysis was demonstrated not only by kinetic but also by electrophoretic evidence, recovery of BZD in the organic solvent was not increased by the enzymatic treatment at a mass BZD/protein ratio in the range 4–4.6 10−5 μg BZD/mg protein. For the HPLC quantification a reversed phase ODS column was used with methanol: water (1:1) plus 3.5% acetic acid as the mobile phase at a constant pressure and 1 mL/min flow rate. The UV detector was calibrated at 265 nm. Calibration curves were constructed by plotting peak height or peak area vs. nmoles BZD and adjusted to straight lines by a regression analysis by the least squares method. The peak height was selected as the detection method. Intra‐ and inter‐assay precision did not exceed 10% and the total recovery was 100%.
Simultaneous determination of pseudouridine and creatinine in urine of normal children and patients with leukaemia by high performance liquid chromatography
Authors: Li Yongtian , Wang Shaoshen , Zhong Ning 
Published: May 2005

AbstractA reversed phase high performance liquid chromatographic method for the simultaneous determination of pseudouridine (PU) and creatinine (Cr) in urine is described. The mobile phase was 0.01 mol phosphate buffer (pH 6.1) containing 2.5 mmol octanesulphonic acid as the ion pairing agent. UV detection was set at 250 nm. Variation in pH value affected the retention time of PU and Cr significantly; Their separation from interfering peaks was also affected. The recoveries of PU and Cr were 89.93% and 90.35%, respectively. The standard deviation of the method for PU was 48.69 ± 0.063 (nmol/μmol Cr, mean ± SD, n = 5). The urine samples from 233 normal children of different ages and 119 patients with leukaemia were analysed by this method. The normal reference value was appraised by comparison with the percentage of immature cells in the bone marrow. The results showed that the sensitivity of the method was 94.12%, the specificity was 95.86%, the accuuracy was 95.50%, the positive predictive value was 82.05% and the negative predictive value was 98.78%. The method can be used to evaluate the state of the leukaemia, and to monitor the effect of treatment.
One‐step preparation of Hageman factor fragment concentrate
Authors: Simonianová E. 
Published: May 2005

AbstractThe Hageman factor fragment (HFf) concentrate was prepared from acetone and dextran sulphate activated human plasma by chromatography on a CM‐Sephadex column. The preparation was free of the main kallikrein inhibitors—Cl‐inactivator, α2‐macroglobulin, antithrombin III and α1‐antitrypsin. The HFf concentrate can serve as an activator of prekallikrein in patient plasma.
Quantitative determination of a new anticonvulsant (CGS 18416A) in human plasma using capillary gas chromatography/mass spectrometry
Authors: Hayes M. J. , Khemani L. , Leal M. , Powell M. L. 
Published: May 2005

AbstractAn analytical method has been developed for the determination of a new antiepileptic drug, CGS 18416A, in human plasma. CGS 18416A is a new anticonvulsant representative of a novel class of water‐soluble agents being developed for the treatment of epilepsy. Preclinical trials indicate sustained efficacy at relatively low oral doses, indicating a need for a sensitive assay. The method is based on capillary gas chromatography/mass spectrometry and utilizes stable isotope‐labelled CGS 18416A as the internal standard. Samples (1 mL) are acidified, then washed with pentane/ethyl acetate, followed by liquid/liquid extraction at pH 11 with pentane/ethyl acetate. Extracts are then concentrated and analysed directly by gas chromatography/mass spectrometry. Separation is accomplished on a thick film methylsilicone capillary column. Mass spectrometry was carried out under positive ion ammonia Cl conditions with selected ion monitoring of the protonated molecular ions (m/z = 248 and 252) for CGS 18416A and the 13CD3‐CGS 18416A, respectively. Specificity was demonstrated by the lack of interfering peaks at the retention time of CGS 18416A and the internal standard. Recovery and reproducibility assessments indicate good accuracy and precision over the validated concentration range of 0.2–51 ng/mL. The limit of quantification is 0.2 ng/mL and the method has sufficient sensitivity to support clinical trials. This is illustrated with an example of quantification in a normal volunteer following oral dosing.
Determination of naphazoline in rat plasma using column liquid chromatography with ultraviolet detection
Authors: Chabenat Christiane , Boucly Patrick 
Published: May 2005

AbstractA sensitive (1 ng/mL) and rapid method for the determination of naphazoline in rat plasma is described. Following extraction, the compound is analysed by reversed phase high performance liquid chromatography and ultraviolet detection at 214 nm.
A new method for the purification of cytochrome‐P450 from human liver microsomes
Authors: Isa Majed , Cumps Jean , Fossoul Claudine , Atassi Ghanem 
Published: May 2005

AbstractA procedure for the solubilization and purification of cytochrome‐P450 (cyt‐P450) from human liver microsomes is described. Successive treatment of microsomes with protease XXVII and 3‐(3‐cholamidopropyl)dimethylammoniopropanesulphonic acid gave a solubilized cyt‐P450 in more than 80% yield and with a three‐fold increae in specific activity. With this treatment it was possible to eliminate 80% of cytochrome‐b5 and 75% of NADPH cyt‐P450 reductase. The solubilized cyt‐P450 was filtered on a Sephacryl‐200 column and then subjected to high performance liquid chromatography with a Mono‐P column (chromatofocussing). The recovery of separated cyt‐P450 was about 50% with a specific activity of 11.5 nmol cyt‐P450/mg protein. Also with this technique it was possible to determinate the isoelectric points of cyt‐P450. These results allowed us to confirm the usefulness of our method, for the study the cyt‐P450 from surgical biopsies.
Determination of low molecular weight aliphatic primary amines in urine as their benzenesulphonyl derivatives by gas chromatography with flame photometric detection
Authors: Kataoka Hiroyuki , Ohrui Satoshi , Miyamoto Yoshiaki , Makita Masami 
Published: May 2005

AbstractA selective and sensitive method for the determination of low molecular weight aliphatic primary amines in urine is described. These amines were converted into their benzenesulphonyl derivatives by a modified Hinsberg procedure, and measured by gas chromatography with flame photometric detection (FPD–GC) using a DB‐1 capillary column. The derivatives were very stable and provided excellent FPD responses. By FPD‐GC, linear calibration curves were obtained in the range 10–200 ng of methylamine, ethylamine, n‐propylamine, isobutylamine and n‐butylamine using tert‐butylamine as an internal standard, and the detection limits of these amines were ca. 6–25 pg as the injection amount. Benzenesulphonamide derived from ammonia was converted into its N‐dimethylaminomethylene derivative which has a longer retention time, and separated from benzenesulphonyl derivatives of low molecular weight primary amines on the chromatogram. The recoveries of aliphatic primary amines added to urine samples were 91–107% and the relative standard deviations were 0.2–4.5%. Analytical results of aliphatic primary amine contents in urine samples of normal subjects are presented.