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PubMed1984

Determination of the herbicides paraquat and diquat in blood and urine by gas chromatography.

A gas chromatographic method is described for determining paraquat (I) and diquat (II) in human blood and urine. I or II was readily precipitated as its reineckate complex (III and IV) by addition of Reinecke reagent, although blood required deproteination with 3.4% perchloric acid or 10% trichloroacetic acid. The precipitation is completed in 1 h at room temperature. III and IV were easily reduced by treatment with a mixture of sodium borohydride and nickel(II) chloride to afford corresponding perhydrogenated products, 1,1'-dimethyl-4,4'-bipiperidine (V) from III and trans- and cis-perhydrodipyrido[1,2-a:2',1'-c] pyrazine (VI) from IV. The perhydrogenated products were determined by gas-liquid chromatography (GLC) without interference from the original components of the blood and urine. The GLC method (5% potassium hydroxide solution with 5% Apiezon L on Chromosorb W AW DMCS) is suitable for simultaneous determination with hydrogen flame-ionization detection in the range 1-70 micrograms/ml (0.7-50.7 micrograms/ml as I ion; 0.5-35.6 micrograms/ml as II ion) of I and II in blood and urine. The method could be applicable to the determination of the chemicals in postmortem tissue and as pollutants in soils.

Chemical Phenomena↗
PubMed1984

Determination of biogenic amines in meat by combined ion-exchange and capillary gas chromatography.

A procedure is described for the determination of putrescine, cadaverine and histamine in meat. Crude perchloric acid extracts were pre-separated on a weakly acidic cation exchanger and the amines quantified by capillary gas chromatography. The diamines were analysed as trifluoroacetyl derivatives and histamine was converted into N alpha-trifluoroacetyl-N tau-ethoxycarbonylhistamine. The accuracy of the determination of diamines was examined by a precipitation pre-separation method and by mass fragmentometric quantification. The proposed procedure allows the sensitive, sufficiently precise and highly specific determination of putrescine and cadaverine in meat.

Animals↗
PubMed2001

Value of high-performance liquid chromatographic analysis of anthocyanins in the differentiation of red grape cultivars and red wines made from them.

A HPLC method that allows the separation of several anthocyanins present in red grapes and red wines, using a linear gradient of acetonitrile in water at pH 1.3, using perchloric acid as an acid modifier, is described. Data clearly show that the anthocyanins profile of red grapes may be complex, but quite different for each cultivar studied. Thus, those molecules may be used as chemotaxonomic markers for classifying red grape cultivars. However, the anthocyanin profile of red wines clearly differs from that presented by grapes employed in making it, because red wine contains a higher relative amount of malvidin-3-O-glucoside than grapes, and the relative amount of other anthocyanins in wines is usually lower than in grapes. Therefore, the use of anthocyanins present in wines to determine the grape cultivar used for winemaking needs a careful evaluation of the influence of different technological procedures on the anthocyanins fingerprint.

Anthocyanins↗
PubMed1988

Measurement of the release of adenine nucleotides during platelet aggregation by small-bore-column isocratic high-performance liquid chromatography.

This paper describes a simple and sensitive method for measuring adenosine, adenosine monophosphate, adenosine diphosphate, and adenosine triphosphate in plasma and tissues. This method involves sample preparation by perchloric acid extraction, followed by high-performance liquid chromatography on a small-bore column with UV detection at 254 nm. The minimum detectable amounts were adenosine, 0.60 pmol; adenosine monophosphate, 0.90 pmol; adenosine diphosphate, 1.5 pmol; and adenosine triphosphate, 2.5 pmol. The interassay coefficient of variation for the measurement of these compounds was less than 4%. The influence of varying the pH and the concentration of phosphate, acetonitrile, and ion-pairing reagent are described. This method can be used to measure adenine nucleotide release during platelet aggregation.

Adenine Nucleotides↗
PubMed1987

Determination of thymosin beta 4 in human blood cells and serum.

A simple one-step procedure for the determination of thymosin beta 4 in whole blood, various blood corpuscles, plasma and serum by reversed-phase high-performance liquid chromatography (HPLC) is described. The blood cells were isolated by a Ficoll density gradient technique. The isolated cells were lysed and deproteinized with perchloric acid in the presence of an internal standard. The supernatant solution was neutralized by potassium hydroxide solution and thymosin beta 4 was measured by HPLC without further manipulations. The following amounts (fg per cell) were determined: polymorphonuclear leukocytes (409), mononuclear leukocytes (267) and platelets (22.3). Erythrocytes contained no thymosin beta 4. The average concentration of thymosin beta 4 in an extract of whole blood was 16.3 micrograms/ml. The concentration in plasma was less than 1% of that value. However, if serum was prepared and not immediately removed from the clotted blood, the concentration of the peptide increased from 0.04 to 2.1 micrograms/ml within 24 h. The biological significance of the findings is discussed.

Adult↗
PubMed1986

Reversed-phase high-performance liquid chromatographic assay for the determination of potency and impurities in tazadolene succinate bulk drug and capsules.

A reversed-phase assay based on high-performance liquid chromatography with a water-acetonitrile-tetrahydrofuran (THF)-triethylamine (TEA)-perchloric acid (pH 2.5) mobile phase and a Zorbax C8 column has been validated for the determination of the purity of tazadolene succinate (I) [E-(+/-)-1-(2-benzylidenecyclohexyl)azetidine succinate, U-53996H] bulk drug, the potency of tazadolene succinate hard-filled capsule formulations and impurity levels in bulk drug. The system resolves E- and Z-isomers and other structurally related molecules. Retention of these compounds is mainly dependent on the amount of acetonitrile and THF in the mobile phase. An amine must be present in the mobile phase to bring about elution of I. The potency assay utilizes testosterone as internal standard. Potency assays exhibited relative standard deviations (R.S.D.) of less than 1%. Quantitative recovery from hard-filled capsules (HFC) is obtained by using a simple extraction procedure. Potential process impurities, potential degradation products, and formulation excipients are resolved. The assay is linear for tazadolene succinate concentrations equivalent to 50-150% of the assay concentration. Impurities can be quantitated to levels equivalent to about 0.1% by weight with R.S.D. less than 5%. The estimated limit of detection for I is about 2 ng for a 20 microliters injection.

Analgesics↗
PubMed1991

Purine and pyrimidine compounds in murine peritoneal macrophages cultured in vitro.

Extracts of murine peritoneal macrophages were analysed by ion-pair reversed-phase high-performance liquid chromatography during incubation at 37 degrees C in vitro. Four-step gradient elution was applied to an ODS column (250 x 4.6 mm I.D.) at a flow-rate of 1.3 ml/min, allowing the separation of hypoxanthine, inosine, guanosine, adenosine, IMP, CDP, AMP, GDP, UDP, ADP, CTP, GTP, UTP and ATP within 50 min. Samples of 0.4 . 10(6)-0.5 . 10(6) cells were washed twice with RPMI 1640 medium and extracted with perchloric acid. Nucleotide concentrations of murine peritoneal macrophages did not change during incubation for 4 days in vitro.

Animals↗
PubMed1990

Direct stereochemical resolution of aspartame stereoisomers and their degradation products by high-performance liquid chromatography on a chiral crown ether based stationary phase.

The direct stereochemical resolution of the four stereoisomers of aspartame (N-DL-alpha-aspartyl-DL-phenylalanine methyl ester) and their degradation products was achieved on a high-performance liquid chromatography chiral stationary phase based upon a chiral crown ether. The chromatographic conditions included a mobile phase composed of aqueous perchloric acid adjusted to a pH of 2.8 and modified with 1.5% of 2-propanol and a temperature gradient. The active L,L-isomer (sold under the brand name NutraSweet) was measured in a diet cola and coffee sweetened with NutraSweet. Degradation products of NutraSweet were also detected but no racemization of stereochemical contamination was observed.

1-Propanol↗
PubMed1990

Simultaneous measurement of L-dopa, its metabolites and carbidopa in plasma of parkinsonian patients by improved sample pretreatment and high-performance liquid chromatographic determination.

A procedure is described for the determination of L-3,4-dihydroxyphenylalanine (L-DOPA), its metabolites and carbidopa (CD) in plasma of Parkinsonian patients by high-performance liquid chromatography with dual working-electrode coulometric electrochemical detection. An efficient sample preparation scheme is presented for the isolation of L-DOPA, its metabolites and the catecholamines from the same plasma aliquot. After a simple deproteinization with methanol containing 2% of 0.5 M perchloric acid and evaporation of the solvent, L-DOPA, its metabolites and CD were separated with a 5-micron Nucleosil C18 column. Catecholamines were extracted from the supernatant of the deproteinized plasma by ion exchange on small columns and adsorption on alumina. Recoveries were close to 100% for L-DOPA, its metabolites and CD and 70% for catecholamines. The use of the same mobile phase for the concurrent assay of L-DOPA, its metabolites and catecholamines considerably increased the throughput of samples in the chromatographic system. The dual-electrode coulometric detector afforded peak identification by comparing current ratios. Monitoring of data from patients under L-DOPA therapy is reported.

Carbidopa↗
PubMed1987

Sensitive method for the measurement of amiodarone and desethylamiodarone in serum and tissue and its application to disposition studies.

A high-performance liquid chromatographic (HPLC) method for the measurement of amiodarone (AM) and its metabolite(s) in serum and tissues was developed. The method uses a 5-micron silica column, methanol containing 0.02% perchloric acid at pH 4 as the mobile phase, and ultraviolet detection at 240 nm. The standard curves for AM and desethylamiodarone (DAM) were linear for serum (range 0.025-6.0 microgram/ml) and tissues (range 0.1-0.5 micrograms for 10-25 mg wet weight). There was a significant decrease as a function of time in AM and DAM concentrations in patients' sera left at ambient temperature in the presence of light. This HPLC method was applied to studies on serum AM elimination kinetics in patients and on tissue uptake during chronic AM administration to rabbits. The elimination half-life (5.8 h) of AM after a 5 mg/kg intravenous dose to a patient was similar to that after acute oral doses. AM, being lipophilic, accumulated maximally in the fat tissue (56 micrograms/g wet weight), followed by lung and liver in rabbits injected with AM for six weeks. The latter two tissues also contained nearly equal quantities of DAM. The high concentrations of AM and DAM in the liver and lungs may be related to the hepatic toxicity and pulmonary fibrosis associated with chronic AM therapy. Two new metabolites were found in the lung and bile of AM-treated rabbits, but these have not yet been identified.

Amiodarone↗
PubMed1987

Determination of N-acetylcysteine, intact and oxidized, in plasma by column liquid chromatography and post-column derivatization.

N-Acetylcysteine in plasma may exist as intact N-acetylcysteine (NAC) or be oxidized to disulphides, either as a dimer or mixed with other thiol-containing compounds. To prevent oxidation of NAC, whole blood was immediately centrifuged after collection and the plasma proteins were precipitated with perchloric acid. NAC was measured by direct injection of the supernatant into the chromatographic system and the oxidized forms, coupled to small sulphides (ONACS), were determined after reductive cleavage of all NAC disulphides in the supernatant with dithiothreitol before injection. The total plasma concentration of the compound, i.e., including the fraction coupled to proteins (ONACP), was assayed after an initial reduction of the disulphide linkages in plasma. After subsequent precipitation of proteins, the supernatant was directly injected. The chromatographic system was a reversed-phase column (C18) with an acidic mobile phase. After a fast (less than 6 s) post-column reaction with pyrenemaleimide, NAC was detected by fluorimetry. The contribution to the band broadening by the reactor was about 10%. The limit of quantification of NAC in plasma was 240 nM, with an intra-assay precision of 14%.

Acetylcysteine↗
PubMed1986

Mild interaction of proteins with butyl and hydroxyl groups on the surface of polymer gels TSK HW-65 and butyl toyopearl 650-M.

Interaction of bovine serum albumin (BSA) with butyl and hydroxyl groups on adsorbent gel surfaces was investigated by using TSK HW-65 and Butyl Toyopearl 650-M gels. It was found that BSA was adsorbed on the gel not only from highly concentrated ammonium sulphate but also from dilute perchloric acid, trichloroacetic acid, etc. Some eluent modifiers, such as organic solvents (30% aqueous methanol or acetonitrile), salt solutions (0.18-0.2 M phosphate) and hydrogen-bond breaking reagents (3-7 M urea, 10 M ethylene glycol, 0.1% triethylamine) were found to be effective in facilitating the elution of trapped BSA from the gel. The conformational change of BSA in these solutions was slight except for urea, and it was reversibly recovered after removal of the modifier from the aqueous solutions, except for the hydrogen-bond breaking reagents.

Adsorption↗
PubMed1991

High-performance liquid chromatographic determination of L-3-(3,4-dihydroxyphenyl)-2-methylalanine (alpha-methyldopa) in human urine and plasma.

A procedure is described for the determination of alpha-methyldopa (MD) [L-3-(3,4-dihydroxyphenyl)-2-methylalanine], its metabolite and catecholamines in the urine and plasma of patients undergoing MD therapy, by high-performance liquid chromatography with dual working electrode coulometric detection. An efficient sample preparation procedure is presented for the isolation of endogenous MD, its metabolite and catecholamines from plasma or urine. After deproteinization of a plasma sample with methanol containing 2% of 0.5 M perchloric acid and dilution of a urine sample (1:200), MD, dihydroxyphenylacetic acid (DOPAC), 3-O-methylmethyldopa (3-OMMD) and homovanillic acid (HVA) were separated with a Supelcosil LC-18 column. Catecholamines were extracted from the supernatant of deproteinized plasma or from urine by ion exchange on a Sephadex CM-25 column and subsequent adsorption on alumina. The use of the same mobile phase for the concurrent assay of MD, its metabolite and catecholamines increased considerably the efficiency of sample separation. Recoveries were close to 100% for MD, DOPAC, 3-OMMD and HVA and 70% for catecholamines. The effects of various experimental parameters related to mobile phase composition on chromatographic performance are reported. The purity of the eluted compounds was tested by recording both the first detector response (oxidation current) and the second detector response (reduction current). The ratio of the detector responses yielded a chemical reversibility ratio for the detected compound. A number of applications such as monitoring data from patients under MD therapy are presented.

Chromatography, High Pressure Liquid↗
PubMed1997

Simple high-performance liquid chromatographic method for the determination of all seven vitamin B6-related compounds.

A simple, sensitive, isocratic high-performance liquid chromatographic method has been developed for the separation of all seven vitamin B6-related compounds. The separation is accomplished using an ODS column and a mobile phase of 0.15 M sodium dihydrogenphosphate, adjusted to pH 2.5 with perchloric acid. The concentration of the compounds is determined with a fluorescence detector (excitation, 290 nm; emission, 389 nm). Isopyridoxal is used as an internal standard. The fluorescence intensity of pyridoxal-5'-phosphate is enhanced by post-column derivatization with sodium bisulfite. All seven compounds are separated in less than 20 min at a flow-rate of 1 ml/min. Applications of this method to yeast cell-free culture media, baker's yeast extract, egg and milk are presented.

Chromatography, High Pressure Liquid↗
PubMed1997

High-performance liquid chromatographic determination of polyamines in milk as their 9-fluorenylmethoxycarbonyl derivatives using a column-switching technique.

A high-performance liquid chromatographic method for the determination of polyamines in milk is milk is described. Polyamines were extracted in perchloric acid and derivatized with 9-fluorenylmethoxycarbonyl chloride (FMOC-Cl). The excess of reagent was reacted with aspartic acid before the analysis on a column-switching system. Linearity of derivatization was calculated for each amine and the coefficient of regression ranged from 0.994 to 0.999. Chromatographic separation of FMOC-polyamines was achieved with a gradient elution programme of water-acetonitrile. The correlation coefficients of the standard curves in the concentration range from 0.5 to 5 nmol ml-1 were higher than 0.991. The repeatability of the method, expressed as R.S.D. for each polyamines ranged from 3.0 to 8.6%. The percent mean recoveries at 1 nmol ml-1 spiking level were 49 +/- 3, 58 +/- 5, 61 +/- 5 and 48 +/- 4 for putrescine, cadaverine, spermidine and spermine, respectively. The limit of detection, calculated on the basis of three times signal-to-noise ratio, was 50 pmol ml-1 for each polyamine.

Animals↗
PubMed1998

Determination of amoxicillin in human serum and plasma by high-performance liquid chromatography and on-line postcolumn derivatisation.

A high selective, sensitive and fast HPLC method developed for the determination in human serum and plasma. After protein precipitation with perchloric acid, an aliquot of the supernatant was neutralized by mixing it with sodium acetate solution and injected into a C18 HPLC column. Detection was done by a fluorescence detector after on-line postcolumn derivatisation with fluorescamine. The practical limit of quantification was 0.1 microgram/ml using 0.3 ml of plasma. Linearity was given in the tested range of 0.1 to 15 micrograms/ml plasma. Inter-day precision (relative standard deviation) over 7 days for 0.42 micrograms/ml was +/- 7.27%; for 4.54 micrograms/ml, +/- 5.24% and for 13.18 micrograms/ml, +/- 5.25%. Stability over 50 days in serum and plasma occurs at -70 degrees C but not at -20 degrees C (-25 to -35% reduction). This method was used for thousands of human serum and plasma samples.

Amoxicillin↗
PubMed1998

Estimation of chlorzoxazone hydroxylase activity in liver microsomes and of the plasma pharmacokinetics of chlorzoxazone by the same high-performance liquid chromatographic method.

We have developed a HPLC method which allows the determination of chlorzoxazone and its hydroxy metabolite in rat liver microsomes and in human plasma. We found that dehalogenated chlorzoxazone or 2-benzoxazolinone was a convenient and stable internal standard. Proteins were precipitated with diluted perchloric acid and the supernatant was extracted with ethyl acetate. Complete resolution of the peaks was achieved within 20 min with a Spherisorb ODS-1 column. The inter-day R.S.D.s were 6.5% at 0.5 microgram/ml of hydroxychlorzoxazone and 5.8% at 1 microgram/ml of chlorzoxazone in human plasma. The reproducibility of the method has been demonstrated for a large number of samples over a long period.

Animals↗
PubMed1999

Determination of trovafloxacin in human body fluids by high-performance liquid chromatography.

For the quantitative determination of trovafloxacin (a new naphthyridinone antibacterial agent) in serum and urine a simple isocratic HPLC method with fluorimetric detection is described. Serum was deproteinised with a mixture of acetonitrile and perchloric acid. The protein-free extract was separated on a reversed-phase column (Nucleosil 100-5 C18) and quantified by means of fluorescence (excitation 275 nm, emission 405 nm). The mobile phase consisted of a mixture of 250 ml acetonitrile and 750 ml distilled water containing 10 mmol/l tetrabutylammonium phosphate. Urine was diluted with 0.25 mol/l phosphoric acid 1:20 (v/v) which was adjusted to pH 3.6 with sodium hydroxide solution. Diluted urine samples were separated on a cation-exchange column (Nucleosil 100-5 SA) and also detected by means of fluorescence. Trovafloxacin was sufficiently separated from endogenous compounds. Results of validation are given. The method was applied successfully to a study of healthy volunteers.

Anti-Infective Agents↗