Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “CHROMATOGRAPHY”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 361 records · Page 20Linked to original sources
PubMed1986

Determination of denzimol, a new anticonvulsant agent, and its main metabolite in biological material by gas chromatography and high-performance liquid chromatography.

Two methods, using gas chromatography (GC) and high-performance liquid chromatography (HPLC), were developed in order to investigate the pharmacokinetics of denzimol hydrochloride, N-[beta-[4-(beta-phenylethyl)phenyl]-beta-hydroxyethyl] imidazole hydrochloride, which is a new anticonvulsant drug, and of its main metabolite, N-[beta-[4-(beta-phenyl-beta(alpha)-hydroxyethyl)phenyl] -beta-hydroxyethyl]-imidazole (referred to as M2), in humans. Both methods involve the use of a homologue of denzimol as an internal standard. The GC method is more sensitive (sensitivity limit 2.5 ng/ml for denzimol and 15 ng/ml for M2) and was utilized for the determination of denzimol and M2 in plasma. The GC method is specific, precise (relative standard deviations are 3.26, 2.12 and 1.72% at 10, 100 and 1000 ng/ml for denzimol and 6.45, 4.17 and 3.38% at 50, 500 and 1000 ng/ml for M2) and accurate (mean recovery +/- S.D. is 102.58 +/- 4.10% for denzimol and 99.72 +/- 7.75% for M2). The HPLC method is very simple and quick to perform. This method has a sensitivity limit of 0.5 micrograms/ml for denzimol and 1 microgram/ml for M2, and allows the determination of both compounds in urine with high selectivity, reproducibility (relative standard deviations are 2.05, 3.50 and 1.02% for denzimol and 2.78, 2.80 and 1.73% for M2, at concentrations of 15, 35 and 70 micrograms/ml) and accuracy (mean recovery +/- S.D. is 103.57 +/- 2.97% for denzimol and 95.91 +/- 1.59% for M2). The common anticonvulsants, when present in plasma, do not interfere with the monitoring of denzimol levels.

Anticonvulsants↗
PubMed1990

Amino acid analysis of physiological fluids by high-performance liquid chromatography with phenylisothiocyanate derivatization and comparison with ion-exchange chromatography.

The suitability of pre-column derivatization with phenylisothiocyanate followed by high-performance liquid chromatography was investigated as a means of analyzing free amino acids in plasma and other physiological fluids. A comparison was made between this method and a conventional ion-exchange method. The correlation coefficient for all the amino acids tested was greater than 0.9, except for proline and tryptophan. Various forms of sample preparation were tried for plasma and amniotic fluid; it was finally decided that protein precipitation with acetonitrile was most suitable. Ultrafiltration was used for cerebrospinal fluid preparation while urine was treated the same as a standard mixture. The retention times relative to the internal standard (nor-leucine) are given for over 90 compounds. Some of these were chromatographed underivatized because they are known to be present in some physiological fluids and absorb at 254 nm because of their aromaticity. The imprecision for this method compared favourably with the standard ion-exchange method although each had specific amino acids for which the imprecision was poor. The technique is suitable for the same routine clinical analysis purposes as high-resolution ion-exchange chromatography. It also offers the advantages of speed of analysis, sensitivity and equipment versatility over the conventional ion-exchange methods.

Amino Acids↗
PubMed1989

Simultaneous determination of the primary prostanoids prostaglandin E2, prostaglandin F2 alpha and 6-oxoprostaglandin F1 alpha by immunoaffinity chromatography in combination with negative ion chemical ionization gas chromatography-tandem mass spectrometry.

The simultaneous determination of prostaglandin E2 (PGE2), prostaglandin F2 alpha (PGF2 alpha) and 6-oxoprostaglandin F1 alpha (6-oxo-PGF1 alpha) in urine using immunoaffinity chromatography in combination with negative ion chemical ionization gas chromatography-tandem mass spectrometry (NICI-GC-MS-MS) is described. Monoclonal antibodies against PGE2 (100% cross-reactivity with 6-oxo-PGF1 alpha) and PGF2 alpha were both coupled to a derivatized agarose matrix. After extraction with a C18 cartridge the sample was applied to the immunoaffinity column. The prostaglandins with eluted with acetone-water and the methoxime-pentafluorobenzyl-trimethylsilyl (MO-PFB-TMS) derivatives (PGE2 and 6-oxo-PGF1 alpha) and the PFB-TMS derivative (PGF2 alpha) were quantified by GC-MS-MS. For reproducibility experiments, spiked urine samples were analysed several times. The correlation coefficients were 0.997 (6-oxo-PGF1 alpha) and 0.999 (PGE2 and PGF2 alpha) and the slopes were 0.99 and 1.03, respectively. The inter-assay coefficient of variation ranged from 8.6 to 9.5% for the unspiked urine samples and from 2.0 to 5.2% for the spiked samples. This method offers several advantages, e.g., high specificity and sensitivity, good reproducibility and an increase in sample throughput.

6-Ketoprostaglandin F1 alpha↗
PubMed1989

Determination of the lipid peroxidation product trans-4-hydroxy-2-nonenal in biological samples by high-performance liquid chromatography and combined capillary column gas chromatography-negative-ion chemical ionisation mass spectrometry.

trans-4-Hydroxy-2-nonenal (HNE) is an aldehyde end-product of lipid peroxidation in biological systems which is capable of producing a range of powerful biological effects. We wish to describe a sensitive and selective strategy for the determination of HNE in biological samples. The method is based on the formation of the O-pentafluorobenzyl (O-PFB) oxime derivatives of HNE and its deuterated internal standard which, after sample clean-up by solid-phase extraction and purification by high-performance liquid chromatography (HPLC), were derivatised further to trimethylsilyl ethers. Subsequent capillary column gas chromatography-negative-ion chemical ionisation mass spectrometry (GC-NICIMS) using selected-ion monitoring allowed quantitation in the low ng/ml range. The use of an internal standard and the O-PFB oxime derivatives circumvented the problems encountered previously by other workers because of the volatility and instability of HNE. The syn-isomer of HNE O-PFB oxime followed the anti-isomer on the HPLC and GC columns used, giving a distinctive pair of peaks of characteristic relative proportion. Moreover, the NICI mass spectra of the geometrical isomers were significantly different, providing further evidence to validate the identity of any endogenous HNE recovered. The method was used to identify and quantify HNE in platelets, monocytes, plasma and oxidised low-density lipoprotein.

Aldehydes↗
PubMed1990

Determination of metrifonate and dichlorvos in whole blood using gas chromatography and gas chromatography-mass spectrometry.

Analytical methods for determining metrifonate and dichlorvos in whole blood and a sampling procedure suitable for pharmacokinetic studies in man are described. Metrifonate concentrations were determined after chloroform extraction using gas chromatography-nitrogen-phosphorus detection. The within-assay coefficients of variation were 4 and 9% at 19.4 and 0.8 mumol/l (limits of determination), respectively. Dichlorvos was determined using gas chromatography-mass spectrometry of toluene extracts. The within-assay coefficients of variation were 2 and 5% at 225 and 50 nmol/l (limits of determination), respectively. Since both substances are chemically unstable, the blood was collected by dripping it directly from the vein into 0.74 M phosphoric acid.

Chromatography, Gas↗
PubMed1985

Determination of circulating ethyl loflazepate metabolites in the baboon by radio-high-performance liquid chromatography with injection of crude plasma samples: comparison with solvent extraction and thin-layer chromatography.

Circulating ethyl loflazepate metabolites in the baboon were determined, following a single oral administration of the 14C-labelled drug, by radio-high-performance liquid chromatography with injection of crude plasma samples and by selective extraction with thin-layer chromatographic analysis of the radioactive components. Metabolites identified by comparing their chromatographic behaviour with synthetic standards were loflazepate, descarboxyloflazepate and 3-hydroxydescarboxyloflazepate. Loflazepate represented about 70% of the circulating radioactivity; the two other metabolites were present in amounts too small to allow accurate quantification. The parent drug was not present in the blood. Comparison of high-performance liquid chromatography with solvent extraction demonstrated the inaccuracy of the latter to be caused by the conversion of loflazepate to descarboxyloflazepate.

Animals↗
PubMed1985

Determination of promethazine in human plasma by automated high-performance liquid chromatography with electrochemical detection and by gas chromatography-mass spectrometry.

A highly specific and sensitive method using automated high-performance liquid chromatography with electrochemical detection (HPLC-ED) and a method using gas chromatography-mass spectrometry (GC-MS) have been developed for the quantitative determination of promethazine in plasma. The lowest detectable concentration by HPLC-ED is 0.1 ng/ml of plasma and by GC-MS 0.5 ng/ml of plasma. The HPLC-ED method incorporates a valve switching unit to prevent all of the electroactive impurities from entering the electrode compartment, thus maintaining the sensitivity of the detector for the analyses of large numbers of samples. The GC-MS method incorporates the highly specific selected-ion monitoring technique. Plasmas derived from healthy subjects each given a single 50-mg oral dose of promethazine were analyzed by both HPLC-ED and GC-MS. The two methods compare favorably with a correlation coefficient of 0.92 and a slope of 1.059. While both methods are suitable for studying single-dose pharmacokinetics of promethazine, the automated HPLC-ED method has a decided advantage in being more sensitive and suitable for unattended overnight analyses of the large number of samples encountered in pharmacokinetic studies. The specificity of the HPLC-ED method is demonstrated by comparison to the GC-MS analysis of biological samples.

Chromatography, High Pressure Liquid↗
PubMed1983

Determination of quinidine in serum by spectrofluorometry, liquid chromatography and fluorescence scanning thin-layer chromatography.

Quinidine is determined in serum by direct and extraction spectrofluorometry, by reflectance fluorescence scanning thin-layer chromatography (TLC), and by high-performance liquid chromatography (HPLC). Least-squares analyses of patients' sera (n = 62) analyzed first by direct fluorometry (x) and then HPLC (y) gave a slope of 0.52, an y-intercept of -0.40, a standard error of estimate of 0.65, and a correlation coefficient of 0.83. Comparison of patients' sera (n = 59) determined by extraction fluorometry (x) and then HPLC (y) gave a slope of 0.998, an y-intercept of -0.175, a standard error of estimate of 0.30, and a correlation coefficient of 0.96. Comparison of patients' sera (n = 36) by HPLC (x) and then reflectance fluorescence scanning TLC (y) gave a slope of 0.837, an y-intercept of 0.152, and a correlation coefficient of 0.94. Methaqualone and oxazepam interfere with HPLC. Within-run precision is 1.6, 1.0, 5.2 and 3.0% by direct fluorometry, extraction fluorometry, TLC and HPLC while between-run precision is 5, 3.5, 9 and 6.0%, respectively.

Chromatography, High Pressure Liquid↗
PubMed1984

Comparison of high-performance liquid chromatography with electrochemical detection and gas chromatography-mass fragmentography for the assay of salsolinol, dopamine and dopamine metabolites in food and beverage samples.

High-performance liquid chromatography with electrochemical detection (HPLC-ED) and combined gas chromatography--mass spectrometry in the single-ion monitoring mode (GC--MS-SIM) have been used for the determination of salsolinol, dopamine, 3,4-dihydroxyphenylacetic acid, 3,4-dihydroxyphenylethanol and norepinephrine in a selection of food and beverage samples. The unique specificity of the SIM mode allows a simple one-step extraction to be used even for complex sample matrices. We have been able to demonstrate the quantitative and qualitative advantages offered by GC--MS over HPLC--ED by direct comparison of the chromatographic data obtained. We demonstrate that the specificity of SIM and the benefits offered by the incorporation of deuterated internal standards make GC--MS-SIM the method of choice for valid identification and precise quantitation of salsolinol, dopamine and dopamine metabolites in a complex sample matrix.

Beer↗
PubMed1981

High-performance liquid chromatography of 25-hydroxyvitamin D2 and 25-hydroxyvitamin D3 in human plasma. Use of isotachysterols and a comparison with gas chromatography--mass spectrometry.

A high-performance liquid chromatographic (HPLC) method for estimating plasma 25-hydroxyvitamin D2 (25-OHD2) and 25-hydroxyvitamin D3 (25-OHD3) is described. The method involves plasma extraction, Lipidex 5000 chromatography and HPLC on straight-phase Zorbax-SIL, collecting the 25-OHD2 + 25-OHD3 fractions. These secosteroids are isomerised to their isotachysterol derivatives and re-run in the same HPLC system, monitoring at 290 nm. 3H-Labelled 25-OHD3 is used as an internal standard. The method was evaluated in terms of reproducibility, and recovery of added secosteroids was quantitative. Values obtained using this method were in close agreement with those values obtained on the same plasma sample using gas chromatography--mass spectrometry.

25-Hydroxyvitamin D 2↗
PubMed1981

Simultaneous determination of blood concentrations of methohexital and its hydroxy metabolite by gas chromatography and identification of 4'-hydroxymethohexital by combined gas--liquid chromatography--mass spectrometry.

A simple, sensitive and selective method is described for the simultaneous determination of low concentrations (less than 50 ng/ml) of underivatized methohexital and its hydroxy metabolite in small (0.1 ml) samples of human and rat plasma or whole blood by gas chromatography with nitrogen-selective detection. Moreover, the main metabolite in rat and man was identified as 4'-hydroxymethohexital by comparison of chromatograms from gas--liquid chromatography (GLC) with data obtained from GLC--mass spectrometry and 1H-nuclear magnetic resonance spectrometry of this metabolite, produced both by incubating methohexital with isolated rat liver microsomes and by isolating this metabolite from rat urine.

Animals↗
PubMed2001

Determination of hydrogen sulfide and acid-labile sulfur in animal tissues by gas chromatography and ion chromatography.

A sensitive and reliable method was developed for the determination of hydrogen sulfide and acid-labile sulfur (ALS) in animal tissues using gas chromatography with flame photometric detector (GC-FPD) and ion chromatography (IC). Hydrogen sulfide trapped in alkaline solution was determined by GC-FPD as hydrogen sulfide or by IC as sulfate after oxidation with hydrogen peroxide. Sodium sulfide used as a source of hydrogen sulfide was standardized by IC. Fresh rat liver and heart tissues contained 112.2+/-23.0 and 274.1+/-34.6 nmol/g of ALS respectively. Free hydrogen sulfide was not detected.

Acids↗
PubMed2001

On the isolation of polychlorinated dibenzo-p-dioxins and furans from serum samples using immunoaffinity chromatography prior to high-resolution gas chromatography-mass spectrometry.

Immunoaffinity chromatography (IAC) for the purification of polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs) from biological samples was explored as a means to simplify the cleanup procedure and thereby decrease the time and cost of dioxin analysis. A monoclonal antibody (DD3) was used to produce IAC columns and to isolate the PCDD/Fs from serum. Native and 13C-labeled PCDD/Fs were spiked at the ppq to ppt range into serum. Quantitation of the PCDD/Fs was performed by a standard dioxin analytical method, i.e. high-resolution gas chromatography-mass spectrometry (GC-MS), which was easily compatible with IAC. Five of the most toxic PCDD/Fs consistently showed acceptable recoveries (>25%) and were reliably quantitated. The congeners specifically recovered by this method represent almost 80% of the toxic equivalency of dioxins and furans present in the serum samples. Dioxin-like polychlorinated biphenyls (PCBs) were not recognized by this antibody column. Compared to conventional dioxin cleanup methods, IAC decreased solvent usage by 1.5 l/sample and took only 2 h to process a sample for analysis.

Benzofurans↗
PubMed1994

High-performance liquid chromatography and micellar electrokinetic chromatography of taxol and related taxanes from bark and needle extracts of Taxus species.

High-performance liquid chromatography (HPLC) and micellar electrokinetic chromatography (MEKC) were applied for the separation of taxol, cephalomannine, and baccatin III in crude extracts from the needle and bark of Taxus species. The chromatogram of the bark extract was cleaner than that of the needle allowing a more reliable detection of taxol and cephalomannine in the bark extract. However, HPLC quantitation of taxol in the needle extract would be difficult due to coeluting taxinines. Nevertheless, this was not a problem in the MEKC experiment. In comparison to HPLC, MEKC offered baseline resolution of taxol from taxinines in the needle extract, less solvent waste, a smaller sample requirement, and the simultaneous detection of taxol, cephalomannine and baccatin III in a relatively simpler electrophoretic run.

Alkaloids↗
PubMed1996

Comparison between gas chromatography-atomic emission detection and gas chromatography-mass spectrometry for the assay of propofol.

Quantitation by gas chromatography-atomic emission detection (GC-AED) is based on the intensity of the signal measured at a wavelength characteristic of an element, after atomisation by the plasma. This response depends only on the number of atoms of this element present in the molecule under investigation, and is independent of the structure of the molecule. This technique was used for the assay of propofol, and the estimation of its two metabolites, after calibration with standard solutions of pure propofol. The results were compared with those obtained by gas chromatography-mass spectrometry (GC-MS). Propofol was quantified with higher precision and accuracy by GC-AED than by GC-MS which exhibited larger residual values. Concentration assessment for two metabolites showed a better agreement with the theoretical value by GC-AED since the response depends only on the number of carbon atoms in each molecule.

Calibration↗
PubMed1997

Determination of S-1 (combined drug of tegafur, 5-chloro-2,4-dihydroxypyridine and potassium oxonate) and 5-fluorouracil in human plasma and urine using high-performance liquid chromatography and gas chromatography-negative ion chemical ionization mass spectrometry.

A high-performance liquid chromatography (HPLC) and gas chromatography-negative ion chemical ionization mass spectrometry (GC-NICI-MS) method was developed for the analysis of the combined antitumor drug S-1 (tegafur, 5-chloro-2,4-dihydroxypyridine and potassium oxonate) and active metabolite 5-fluorouracil in human plasma and urine. Tegafur was fractionated from biological fluids by extraction with dichloromethane and analyzed by HPLC. 5-Fluorouracil and 5-chloro-2,4-dihydroxypyridine were extracted with ethyl acetate from the residual layer after extraction of tegafur, and converted to pentafluorobenzyl (PFB) derivatives. Potassium oxonate was cleaned up with an anion-exchange column (Bond Elut NH2). The extracted potassium oxonate was degraded to 5-azauracil and converted to PFB derivatives. The PFB derivatives were analyzed by GC-NICI-MS. A stable isotope was employed as the internal standard in the GC-NICI-MS analysis. The limits of quantitation of tegafur, 5-fluorouracil, 5-chloro-2,4-dihydroxypyridine and potassium oxonate in plasma were 10, 1, 2 and 1 ng/ml, respectively. The reproducibility of the analytical method according to the statistical coefficients is approximately 10%. The accuracy of the method is good; that is, the relative error is < 10%. The methods were applied to pharmacokinetic studies of S-1 in patients.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1997

Identification of YH439 and its metabolites in rat urine by gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry.

YH439 is a potential drug candidate for the treatment of various hepatic disorders. YH439 and its three metabolites have been identified in rat urine by liquid chromatography-mass spectrometry (LC-MS) and by gas chromatography (GC)-MS. Identification of YH439 and its metabolites was established by comparing their GC retention times and mass spectra with those of the synthesized authentic standards. Both electron impact- and positive chemical ionization MS have been evaluated. The metabolism study was performed in the rat using oral administration of the drug. A major metabolite (YH438) was identified as the N-dealkylation product of YH439. Other identified metabolites were caused by the loss of the methyl thiazolyl amine group (metabolite II) from YH439, the isopropyl hydrogen malonate group (metabolite IV) and the decarboxylated product (metabolite III) of metabolite II.

Administration, Oral↗
PubMed1998

Determination of rat liver triglycerides by gas-liquid chromatography and reversed-phase high-performance liquid chromatography.

Rats fed with a fat-free or an olive oil-rich diet were employed to compare the response of two chromatographic techniques in the determination of rat liver triglyceride (TG) molecular species composition. Gas-liquid chromatography (GLC) on polarizable liquid phase and reversed-phase high-performance liquid chromatography (RP-HPLC) have been commonly employed for TG analysis, obtaining a similar number of chromatographic peaks when used for animal tissue TG determination. In the present study similar results were achieved with regard to most relevant chromatographic peaks, however, important differences were found in the content of minor TGs. Indeed, RP-HPLC permitted separation of long chain polyunsaturated fatty acids, which were not detected by GLC, while the latter technique reported a higher number of myristoyl-containing TG species. RP-HPLC analysis reported a greater number of TGs, with more similarity to a random composition, made up from the liver fatty acid composition. Therefore, it was concluded that utilization of both techniques would be helpful for liver TG analysis as the use of only one of them does not provide a complete profile of liver TGs. Nevertheless RP-HPLC seems to be more useful for this purpose since revealed a more extensive profile.

Animal Nutritional Physiological Phenomena↗