bluuebunny/crossref_metadata_2025_split huggingface dataset:
Simultaneous liquid chromatographic determination of vanillylmandelic acid, homovanillic acid, and 5‐hydroxy‐3‐indoleacetic acid in urine, using isocratic elution and electrochemical detection
Authors: Richards D. A. , Titheradge A. C. 
Published: May 2005

AbstractA method for the simultaneous measurement of vanillylmandelic acid, homovanillic acid and 5‐hydroxyindoleacetic acid in urine is described. Based on reversed‐phase liquid chromatography with electrochemical detection, the procedure employs isocratic elution, thus making it suitable for use in the less well‐equipped clinical or research laboratory. A simple extraction of the acids from acidified urine into ethyl acetate, is followed by evaporating to dryness a portion of the organic layer, and redissolving the residue in chromatographic mobile phase. Up to 20 samples can be analysed in a single working day. The method is validated and the results obtained are compared with refereènce methods. The cause of contamination of the glassy carbon surface of the working electrode is investigated, and a simple electrochemical pretreatment is described that overcomes this problem. Finally, the extra clinical information that can be derived from multi‐metabolite assays is considered.
Studies on the chromatographic fractionation of metabolites of benzo[a]pyrene in faeces and urine from germfree and conventional rats
Authors: Egestad Börje , Pettersson Per , Sjövall Jan , Rafter Joseph , Hyvönen Kaija , Gustafsson Jan‐Åke 
Published: May 2005

AbstractRats, germfree and conventional, were dosed with 14C‐labelled benzo[a]pyrene. Faeces and urine were collected. Metabolites in faces were effectively extracted with a new method using a combination of solvents and solid sorbents. Metabolites in urine were extracted with octadecylsilane‐bonded silica. The metabolites were fractionated into groups by chromatography on a cation exchanger (SP‐LH‐20 or SP‐Sephadex C‐25) and an anion exchanger (TEAP‐LH‐20). Some of the groups were further purified by column chromatography and analysed by HPLC and TLC. The analyses show a complex pattern of metabolism. A large part of the metabolites (9–24% depending on animal type and route of excretion) had amphoteric properties, e.g. like glutathione and cysteine conjugates. The abundance of conjugates sensitive to β‐glucuronidase and sulphatase was low. The relative amount of acidic conjugates in faeces was much higher in the germfree than in the conventional rats indicating the influence of the intestinal flora on the metabolism. The results support the view that the mercapturic acid pathway is a quantitatively important metabolic route for benzo[a]pyrene in rats. The methods of extraction and group fractionation were designed to be generally applicable to the analysis of lipophilic xenobiotics and their metabolites.
Rapid and simple HPLC determination of 5,5‐dimethyl‐2,4‐oxazolidynedione in rabbit serum
Authors: Gaździk Wiesław R. , Filipek Marian , Kmiotek Witold 
Published: May 2005

AbstractA new method for the determination of 5,5‐dimethyl‐2,4‐oxazolidynedione (DMO) in rabbit serum by reversed phase‐HPLC with UV detection is described. The determination of DMO is performed without derivatisation. The internal standard is 5,5‐diethylbarbituric acid (barbital). The method is rapid and simple with sensitivity limit of 20 ng/mL, high recovery (above 92%) and is suitable for pharmacokinetic studies.
Study of doxorubicin photodegradation in plasma, urine and cell culture medium by HPLC
Authors: Le Bot M. A. , Riche C. , Guedes Y. , Kernaleguen D. , Simon S. , Begue J. M. , Berthou F. 
Published: May 2005

AbstractAn HPLC method was used to monitor the chemical stability of doxorubicin‐HCI (DXR) to light in plasma, urine and cell culture medium at room temperature. The results indicated that DXR was very unstable in cell culture medium and urine when exposed to light. It was more stable in plasma under the same conditions. In all the cases, the decrease in the amount of DXR is greatly dependent on light intensity (no noticeable degradation was observed after 8 h in the dark). These observations may be important for the correct interpretation of the effects and the toxicity of doxorubicin on cells incubated in cell medium, and for determination of urinary or plasma pharmacokinetic parameters.
Conditions for Quantitation of Dolichyl Phosphate, Dolichol, Ubiquinone and Cholesterol by HPLC
Authors: Elmberger P. Göran , Eggens Ivan , Dallner Gustav 
Published: May 2005

AbstractConditions for the isolation and quantitation of dolichyl phosphate, dolichol, cholesterol, and ubiquinone by reversed phase high performance liquid chromatography were investigated. A simple and fast sample preparation procedure using prepacked mini columns was employed. The UV spectra of the fractions obtained were examined and, in the case of dolichol compounds, the maximum absorbance around 205 nm was shown to be linearly dependent on the number of double bonds present in the isoprenolog. The analytical procedure described shows a very broad range of linearity (five orders of magnitude) and detects single dolichyl phosphate isoprenologs in amounts as small as 0.1 ng. The lowest overall recovery, that for dolichyl phosphate, is 77%. Use of isoprenolog 23 and ergosterol as internal standards reduced the variation in the method to 2.5, 4.0 and 5.5% for cholesterol, dolichyl phosphate and dolichol, respectively. The method described was employed to study the lipid composition of rat organs and biological variations in these compositions.
Separation of some antihistamines on impregnated TLC silica plates
Authors: Bhushan R. , Reena Chauhan  , Chauhan R. S. 
Published: May 2005

AbstractDifferent metal salts have been tried as impregnating reagents for developing TLC separation schemes for some antihistamines on silica gel ‘G’ plates, using a new solvent system benzene + dimethyl formamide + acetic acid (30:10:7). Spots were visualized by spraying with a solution of Dragendroff's reagent.
Reversed phase HPLC of different membrane‐bound variant surface glycoprotein preparations from Trypanosoma brucei brucei
Authors: Tetaert Daniel , Hublart Marylègne , Gomès Véronique , Boersma Arnold , Degand Pierre 
Published: May 2005

AbstractThe chromatographic behaviour of the membrane‐attached variant surface glycoprotein (mfVSG) of bloodstream forms of Trypanosoma brucei brucei AnTat 1.1 A preparations were studied by reversed phase high performance liquid chromatography (RP‐HPLC). Among the different preparation procedures used, only the trifluoroacetic acid extraction gave a mfVSG preparation which was eluted from the RP‐HPLC column. As well as for the soluble variant surface glycoprotein (sVSG) it was found that different mfVSG forms were eluted at different organic solvent concentrations from the RP‐HPLC column. In addition, in preliminary studies, we have attempted to characterize the factors responsible for the trypanosome surface coat assembly. Using chromatographic techniques (RP‐HPLC and thin layer chromatography), the results suggest a close relationship between the content of lipid‐containing species and the heterogeneity of mfVSG preparation.
Determination of halofuginone in bovine plasma by competing‐ion high performance liquid chromatography after solid phase extraction
Authors: Kinabo L. D. B. , McKellar Q. A. , Murray M. 
Published: May 2005

AbstractA high performance liquid chromatographic (HPLC) method for the determination of the anticoccidial and antitheilerial drug halofuginone in bovine plasma was developed. Samples were diluted with acetic acid (10%, v/v) and cleaned up on a Bond Elut C8 column. The analyte was eluted from the extraction column and chromatographed by reversed‐phase HPLC using decylamine as a competing‐ion reagent. Detection was by UV at 243 nm. Recovery from plasma was 75%, and within‐day and between‐day coefficients of variation were 5.23 and 6.35% respectively. The specificity and sensitivity of this method (limit of detection in plasma, 1 ng/mL) were sufficiently high to enable us to characterize the time course of the drug in plasma after oral administration of therapeutic doses to cattle.
High‐performance liquid chromatographic determination of β‐adrenoceptor blocking agents in body fluids
Authors: Šoltés Ladislav 
Published: May 2005

AbstractSeveral reports have been published reviewing high‐performance liquid chromatographic (HPLC) methods for the determination of β‐adrenoceptor blocking agents (β‐blockers) in biological materials (Flouvat et al., 1981; Mehta, 1983; Marko and Šoltés, 1984; Ahnoff et al., 1985; Tkaczyková and Šafařík, 1987). Of these, the paper by Mehta (1983) briefly summarizes the interrelationship between physicochemical properties of β‐blockers with prechromatographic treatment of biological samples, as well as with the HPLC methods used for the determination of 12 β‐adrenoceptor blocking drugs. The work by Ahnoff et al. (1985) concerning the monitoring of cardiovascular drugs also deals with HPLC assays of 18 β‐blockers in plasma.The Appendix to this report presents the great majority of HPLC methods for determining 30 β‐blockers in various body fluids. HPLC methods providing resolution and determination of individual β‐blocker enantiomers have not been included since this topic is being covered by Walle and Walle (1989). The Appendix is just a guide to the methods reviewed for the HPLC determination of parent β‐blockers as well as some of their metabolites co‐assayed in various body fluids. It does not include details such as the internal standard, recovery, setting of the detector, limit of determination, etc., given in the individual methods listed. The isolation technique of the drug(s) from the given body fluid represents the main step in the sample work‐up procedure. Along with this information, only the type of the HPLC column packing and the detection principle used by each method's developers are given.
High performance liquid chromatographic analysis of time‐dependent changes in urinary excretion of indoleamines following tryptophan administration
Authors: Tsuchiya Hironori , Ohtani Shigeru , Takagi Nobuhiko , Hayashi Tokishi 
Published: May 2005

AbstractAnalytical conditions of prepurification extraction and HPLC separation were optimized for determination of urinary serotonin and tryptamine. Under optimal conditions, serotonin, tryptamine and an internal standard were extracted with 15% v/v n‐propanol in diethyl ether from urine samples alkalized with a phosphate buffer (0.75 mol/L, pH 10.0), and then they were re‐extracted into an HCI solution (0.1 mol/L). Purified indoleamines were simultaneously separated by reversed‐phase ion‐pair HPLC with native fluorescence detection. Urinary serotonin and tryptamine were selectively determined within about 45 min per sample for the whole procedure. Analytical recovery, reproducibility and detection sensitivity were satisfactory for pursuing time‐dependent changes in indoleamine levels. Urinary excretion profiles of serotonin and tryptamine in subjects dosed with L‐tryptophan were successfully analyzed by our method.
Determination of total and free concentration of propranolol in human plasma by displacement electrophoresis in a two‐layer polyacrylamide gel using fluorimetric detection
Authors: Zelikman Ilya , Hjertén Stellan 
Published: May 2005

AbstractA new method based on displacement electrophoresis has been developed for the determination of the total and free concentration of propranolol, a β‐adrenergic blocker drug, in plasma. To determine the total concentration the drug is extracted from human plasma into a chloroform + heptane mixture in the presence of ammonia. After evaporation of the solvent mixture the residue is submitted to displacement electrophoresis in a glass tube containing a two‐layer polyacrylamide gel. When the propranolol electrophoretically leaves the gel column it is transferred by a buffer flow to the cuvette of a fluorimeter for continuous detection and quantification. The concentration of the free non‐protein bound drug can be determined by the same displacement electrophoresis technique following extraction of the plasma sample into the above organic solvent mixture in the absence of ammonia. Alternatively the extraction procedure can be exchanged for dialysis for 1 h. To decrease the risk that large size material might comigrate with propranolol two layers of polyacrylamide are used, one having small pores to retard such material. In addition, we use fluorimetric detection which means that many possible contaminants are not recorded and therefore do not affect a quantitative determination of propranolol.
‘In situ’ Edman degradation of protein(s) blotted to immobilon membranes suitable for unblocking reversible chemical modification and elimination of coomassie blue in sodium dodecyl sulfate‐polyacrylamide gel electrophoresis
Authors: Chirat Frédéric , Belaiche Denise , Malki Nouzha , Han Kia‐Ki 
Published: May 2005

AbstractConditions for unblocking reversible chemical modifications such as maleylation or citraconylation ‘in situ’ at the N‐terminus of proteins after transfer of proteins to immobilon membranes from SDS‐PAGE are described. Demaleylation or decitraconylation occurred at 55°C in 70% formic acid (pH 1.50) during 60 min. During the unblocking reaction, Coomassie blue dye was completely removed, resulting in superior high performance liquid chromatographic separation of phenylthiohydantoin‐amino acid (PTH‐AA) after Edman degradation (automatic gas phase sequencer). The protein fixed on the matrix after demaleylation and removal of Coomassie blue was not degraded. The possible cleavage at the aspartyl‐prolyl peptide bonds was considered, but no side reaction was observed. Furthermore, the incubation time in 70% formic acid at 55°C could be reduced to 10 min in the absence of maleylation of the starting material, and this was suitable for the removal of Coomassie blue and the quantification of phenylthiolhydantoin‐amino acids (PTH‐AAs) by HPLC. The yield from the starting protein through SDS‐PAGE, blotting, and Edman degradation to quantitative analysis of PTH‐aminoacid(s) by HLPC was established.
Capillary gas chromatographic determination of epomediol in human plasma and urine using a rapid solid‐phase extraction
Authors: Girometta Maria Angela , Loschi Loredana , Ventura Paolo , Canali Sergio , Giachetti Claudio , Zanolo Gianni 
Published: May 2005

AbstractA simple and precise method for the quantitation of epomediol in human plasma and urine is described. Each biological sample is added with the internal standard and applied directly to an Extrelut‐1 solid‐phase column. After absorption the column is eluted with chloroform and the eluate is evaporated to dryness. The residue, reconstituted in ethanol, is analysed by capillary gas chromatography. No interferences from possible metabolites or endogenous constituents can be noted. The method has been applied to human pharmacokinetic studies: the results of a subacute administration to volunteers are presented.
High performance liquid chromatography determination of cyanide in urine by pre‐column fluorescence derivatization
Authors: Sano Akira , Takezawa Masaaki , Takitani Shoji 
Published: May 2005

AbstractA method for the determination of cyanide in human urine has been developed. The method is based on the reaction of cyanide with 2,3‐naphthalenedialdehyde and taurine to give a fluorescent product for reversed‐phase HPLC separation and fluorometric detection. After centrifugation followed by dilution of urine samples, the specimens could be analysed directly by this method. The recovery of cyanide added to urine at concentration levels of 50 – 1000 pmol/mL was 85 – 96%. The detection limit of cyanide was 30 pmol/mL in urine. The method was successfully applied to the analysis of urine from smokers and nonsmokers. The mean concentrations of cyanide were found to be 215 pmol/mL for the former and 84 pmol/mL for the latter.
Reversed phase high performance liquid chromatography of glycopeptides
Authors: Wang Tsonghui , Chen Tsefang , Barofsky Douglas F. 
Published: May 2005

AbstractA practical procedure for isolating and purifying glycopeptides is described, viz. enzymatic hydrolysis—gel permeation chromatography—ion exchange chromatography—reversed phase HPLC. Using this procedure 28 glycopeptides from hen ovalbumin have been isolated some of which hitherto have not been identified. Water was a suitable mobile phase for preparing pure glycopeptides, and control of column temperature was important for good separations and reproducible retention times. Structural confirmation was by fast atom bombardment mass spectrometry.
Simultaneous analysis of furosemide and bumetanide in horse plasma using high performance liquid chromatography
Authors: Singh Ashok K. , McArdle Camille , Gordon Brad , Ashraf M. , Granley K. 
Published: May 2005

AbstractA high performance liquid chromatographic method is described for the simultaneous determination of furosemide and bumetanide in horse plasma. The C8 (3 μm) reversed phase column (4.8 × 150 mm) provided clear separation of furosemide and bumetanide with other components present in the horse plasma. The detection limit for both the drugs was 10 ng/mL. Both drugs were stable in plasma (at natural or acidic pH) for up to 24 h. The method is sufficiently sensitive to detect furosemide levels in plasma obtained from horses receiving a therapeutic dose of furosemide.
Rapid determination of the benzodiazepine antagonist flumazenil, Ro 15‐1788, by high performance liquid chromatography
Authors: Bun H. , Duplan V. , Crevat‐Pisano P. , Llurens M. , Durand A. 
Published: May 2005

AbstractA sensitive (2 ng/mL) and specific method for the determination of the benzodiazepine antagonist Ro 15‐1788 or flumazenil is described. Following a simple extraction, the compound is analyzed by reversed phase high performance liquid chromatography (HPLC) and detection at 245 nm. The method was applied to plasma specimens collected from patients receiving a single dose of this drug.
Purification of the membrane protein enzyme lipoamidase by affinity chromatography
Authors: Oizumi Jun , Hayakawa Kou 
Published: May 2005

AbstractLipoamidase, a membrane glycoprotein enzyme, was purified from brain membrane by means of various affinity columns. A column with immobilized Arg‐Phe‐NH2 was found to be the most effective. After loading the crude material of the membrane, and extensive washing of the column with sodium chloride (0.3 M) solution, the enzyme activity was eluted by a solution containing 1% of nonionic detergent (Nonidet P‐40). The fractions containing the lipoamidase activity were analyzed by SDS‐PAGE, and a single protein band detected in this fraction. On the other hand, lipoyl‐affinity columns with various resins were not effective in enzyme purification. Single step chromatography on the Arg‐Phe‐NH2 column enriched the membrane enzyme lipoamidase by 40‐fold. The mechanism by which this affinity resin effectively enriches the enzyme remains to be elucidated.
High performance ion exchange chromatography of human plasma lecithin: Cholesterol acyltransferase
Authors: Holmquist Leif 
Published: May 2005

AbstractHighly purified monomeric human plasma lecithin:cholesterol acyltransferase (LCAT), completely free of apolipoprotein D, has been chromatographed on a MonoQ HR 5/5 anion exchanger. LCAT eluted as symmetrical peaks after 12.8 min and 14.8 min at pH 5.0 and pH 6.0, respectively, using a linear NaCl gradient. The corresponding concentrations of NaCI effecting desorption of LCAT from the anion exchanger were 125 mM and 175 mM. At both pH values human serum albumin eluted earlier and was well separated from the enzyme. Rechromatography of LCAT in the eluates from these experiments at acid pH, on high performance gel filtration, demonstrated absence of aggregation. The nonspecific adsorption during anion exchange chromatography at pH 5.0 and pH 6.0 was negligible, as demonstrated by a linear relationship between injected amounts of LCAT and recorded peak areas for a 2–20 μg protein range. Zone immunoelectrophoresis assay indicated unaltered immunoreactivity of the eluted LCAT.
Determination of urinary tryptophan and its metabolites along the nicotinic acid pathway by high performance liquid chromatography with ultraviolet detection
Authors: Bizzarri Mariano , Catizone Angela , Pompei Marco , Chiappini Loretta , Curini Letizia , Lagana Aldo 
Published: May 2005

AbstractA fast and sensitive method is given for analysing urinary tryptophan and six of its metabolites on the nicotinic acid pathway. Kynurenine, tryptophan, 3‐hydroxykynurenine, anthranilic acid, 3‐hydroxyanthranilic acid, kynurenic acid and xanthurenic acid were isocratically eluted and completely resolved with a mobile phase of acetonitrile + sodium acetate buffer, pH 4.76 (4:96, v/v). The flow rate was 0.8 mL/min at the beginning and was then linearly increased to 1.2 after 6 min; after 14 min the flow was augmented from 1.2 to 2 mL/min. The effluent was monitored with a variable UV detector set at 254 nm for the first five peaks and at 280 and 325 nm for the penultimate peak and final peak. Analytical recoveries of the compounds after deproteinization varied between 64% and 98%. The reported method should enable one to examine easily, extensively, quantitatively and routinely urinary tryptophan and the most important metabolites of the nicotinic acid pathway.
Studies on the metabolism of lappaconitine in humans. Identification of the metabolites of lappaconitine in human urine by high performance liquid chromatography
Authors: Xie Fuming , Wang Hong‐Cheng , Li Jian‐Hua , Shu Hen‐Ling , Jiang Ji‐Rong , Chang Jen‐Pin , Hsieh Yu‐Yuan 
Published: May 2005

AbstractThe metabolités of lappaconitine in the urine of humans having been previously administered intramuscularly with lappaconitine hydrobromide were studied using high performance liquid chromatography with electrochemical and ultraviolet detection. The urine was extracted by means of liquid‐ and solid‐phase extractions. Each of the metabolites of lappaconitine was purified by high performance liquid chromatography on a reversed phase column and identified on the basis of the chromatographic behaviour and the detector response. It was proved that lappaconitine, N‐deacetyl‐16‐O‐demethyllappaconitine and N‐deacetyllappaconitine were excreted in urine from humans receiving lappaconitine.
A reversed phase high performance liquid chromatography approach in determining total red blood cell concentrations of 6‐thioguanine, 6‐mercaptopurine, methylthioguanine, and methylmercaptopurine in a patient receiving thiopurine therapy
Authors: Erdmann Gary R. , France Laura A. , Bostrom Bruce C. , Canafax Daniel M. 
Published: May 2005

AbstractA reversed phase high performance liquid chromatographic procedure was developed to quantify 6‐thioguanine, 6‐mercaptopurine, methylthioguanine, and methylmercaptopurine in red blood cells. The free base of each thiopurine was liberated from the respective nucleoside and nucleotide moiety by acid hydrolysis, which allowed for a determination of the total thiopurine present. 6‐Thioguanine and 6‐mercaptopurine were analyzed on an octadecyl‐ silane column using methanol + 20 mM sodium phosphate (15:85), pH 7.5, containing 0.07% tetrabutylammonium chloride. Detection was by potassium permanganate oxidation and fluorescence detection at 290 nm excitation and 400 nm emission. Methylmercaptopurine and methylthioguanine were analyzed on a cyanopropylsilane column using methanol + 40 mM sodium phosphate (18:82), pH 2.7, and then ultraviolet absorption at 314 nm and 290 nm, respectively. The method was used to quantify the four primary thiopurines present in red blood cells of an acute lymphoblastic leukemia patient. The procedure may be a therapeutic monitoring technique that quantifies the cytotoxic drug burden in patients receiving azathioprine or 6‐mercaptopurine therapy.