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 163 records · Page 9Linked to original sources
PubMed1994

Determination of beta-sympathomimetics in liver and urine by immunoaffinity chromatography and gas chromatography-mass-selective detection.

A specific and sensitive method for the determination of several beta-agonistic drugs in liver and urine is described. Following clean-up by immunoaffinity chromatography and two different derivatizations, gas chromatography-mass spectrometry with electron-impact ionization is performed. The immunoaffinity chromatography columns were packed with Sepharose-immobilized polyclonal antibodies raised against the beta-agonist clenbuterol. Owing to the high clean-up efficiency of the immunoaffinity column large sample volumes can be used (up to 100 ml urine or 25 gram liver). The immunoaffinity sample pretreatment is highly specific and no further sample pretreatment was necessary. Due to the combination of two different derivatizations only GC-MS with electron-impact ionization is necessary to fulfil legal requirements. The first confirmation step consists of a derivatization reaction between the hydroxyl group of the parent compound and trimethylsilane. The second confirmation method is a derivatization to a cyclic derivative with the hydroxyl group and the aliphatic nitrogen group. Limits of determination in liver as well in urine are at the 10 ng/kg or ng/l (ppt) level with acceptable signal-to-noise ratio. The method is suitable for identification and quantification of trace amounts of several similar beta-agonistic drugs either used separately or in combination and can be used also for quantification of clenbuterol in liver with regard to levels exceeding the maximum residue limit (MRL) of 1 microgram/kg (ppb).

Adrenergic beta-Agonists↗
PubMed1997

Isolation and measurement of urinary 8-iso-prostaglandin F2alpha by high-performance liquid chromatography and gas chromatography-mass spectrometry.

8-iso-Prostaglandin F2alpha (8-iso-PGF2alpha) is a product of free radical-catalyzed peroxidation of arachidonic acid. Measurement of its urinary excretion has been proposed as an index of oxidative status in vivo. A stable isotope dilution method for its quantification by gas chromatography-electron capture chemical ionization mass spectrometry is described. Sample cleanup required the combined use of high-performance liquid chromatography and thin-layer chromatography. The inter-assay R.S.D. in two separate determinations was 1.6 (n=4) and 2.3% (n=4). The accuracy of the assay was evaluated through recovery experiments. The equation of the regression plot correlating the amounts added and recovered was y=0.91x-0.31, r=0.9916 (n=12). The pair of fragment ions ([M-181]-) at m/z 569 and m/z 573 was monitored for quantification. The mean 8-iso-PGF2alpha excretion rate was 528 +/- 127 (S.D.) ng per day in five male volunteers and 730 +/- 305 ng per day in six females. Intake of 80 mg of lycopene per day by eleven volunteers for four weeks resulted in a non-significant reduction of 8-iso-PGF2alpha excretion.

Adult↗
PubMed2004

Protein-doped monolithic silica columns for capillary liquid chromatography prepared by the sol-gel method: applications to frontal affinity chromatography.

The development of bioaffinity chromatography columns that are based on the entrapment of biomolecules within the pores of sol-gel-derived monolithic silica is reported. Monolithic nanoflow columns are formed by mixing the protein-compatible silica precursor diglycerylsilane with a buffered aqueous solution containing poly(ethylene oxide) (PEO, MW 10,000) and the protein of interest and then loading this mixture into a fused-silica capillary (150-250-microm i.d.). Spinodal decomposition of the PEO-doped sol into two distinct phases prior to the gelation of the silica results in a bimodal pore distribution that produces large macropores (>0.1 microm), to allow good flow of eluent with minimal back pressure, and mesopores (approximately 3-5-nm diameter) that retain a significant fraction of the entrapped protein. Addition of low levels of (3-aminopropyl)triethoxysilane is shown to minimize nonselective interactions of analytes with the column material, resulting in a column that is able to retain small molecules by virtue of their interaction with the entrapped biomolecules. Such columns are shown to be suitable for pressure-driven liquid chromatography and can be operated at relatively high flow rates (up to 500 microL x min(-1)) or with low back pressures (<100 psi) when used at flow rates of 5-10 microL x min(-1). The clinically relevant enzyme dihydrofolate reductase was entrapped within the bioaffinity columns and was used to screen mixtures of small molecules using frontal affinity chromatography with mass spectrometric detection. Inhibitors present in compound mixtures were retained via bioaffinity interactions, with the retention time being dependent on both the ligand concentration and the affinity of the ligand for the protein. The results suggest that such columns may find use in high-throughput screening of compound mixtures.

Buffers↗
PubMedDate not supplied

Separation of pure and immunoreactive virus-like particles using gel filtration chromatography following immobilized metal ion affinity chromatography.

A purification process was developed to obtain highly pure rVP2H particles, formed by a structural protein (VP2) of the infectious bursal disease virus (IBDV) with six additional histidine residues at its C-terminus. The ultimate goal was the development of an efficient subunit vaccine against IBDV infection. The particles within the infected High-Five (Hi-5) cell lysates were partially purified by employing immobilized metal ion (Ni(2+)) affinity chromatography (IMAC). The initial step could recover approximately 85% of immunoreactive rVP2H proteins but failed to separate the rVP2H particles from the free rVP2H proteins or its degraded products. To separate the particulate form from the free form of rVP2H, an additional step was added, which used either gel filtration chromatography or CsCl density gradient ultracentrifugation. Both were able to produce extremely pure rVP2H particles with a buoyant density close to 1.27 g/cm(3). However, the former method can process a larger sample volume than does the latter. By integrating IMAC and gel filtration chromatography, 1 mg of extremely pure rVP2H particles was routinely obtained from a 500 mL Hi-5 cell culture broth. The separation of the particulate form from the free form of rVP2H proteins exposes their respective immunogenicity to induce the virus-neutralizing antibodies and the ability to protect chickens from IBDV infection. Additionally, the abundant quantities of pure rVP2H particles coupled with their uniform dimensions facilitates an understanding of higher order structure of the immunogenic particles and can therefore result in improved vaccines against the virus.

Baculoviridae↗
PubMed2002

Determination of semivolatile compounds in Baltic herring (Clupea harengus membras) by supercritical fluid extraction-supercritical fluid chromatography-gas chromatography-mass spectrometry.

The on-line supercritical fluid extraction-supercritical fluid chromatography-gas chromatography method was applied to the determination of volatile compounds of raw and baked Baltic herring (Clupea harengus membras). The analytes were extracted with supercritical carbon dioxide at 45 degrees C and 10 MPa pressure. After extraction, the volatiles and coeluted lipids were separated on-line using supercritical fluid chromatography and the volatile fraction was introduced directly into a gas chromatograph. In all, 30 compounds were identified from fish samples with mass spectrometry. The most abundant compounds in the fresh Baltic herrings were heptadecane and 1-heptadecene. When the fish were stored for 3-6 days at 6 degrees C, the total peak area of the volatiles began to increase and the proportions of short chain acids (acetic, propanoic, 2-methylpropanoic, and 3-methylbutanoic) also increased. After 8-9 days of storage, 3-methylbutanoic acid comprised about 36 and 40% of all volatiles in raw and baked herring, respectively.

Acetic Acid↗
PubMed2004

Preliminary studies on selenium-containing proteins in Brassica juncea by size exclusion chromatography and fast protein liquid chromatography coupled to ICP-MS.

An approach for screening and resolving selenium-containing plant proteins was developed based on the combination of sample preparation and multi-dimensional liquid chromatography coupled to ICP-MS. Different protein extraction protocols were investigated. A 24 h dodecylsulfate-mediated protein extraction in a sonication bath followed by acetone precipitation was found to be optimal. The use of different protein precipitate solubilizing agents (sodium dodecyl sulfate media and Tris-HCl buffer) demonstrates possible fractionation of the selenium-containing proteins. Selenium-containing protein screening and fractionation were carried out by means of SEC-ICP-MS. High molecular weight selenium containing proteins were solubilized with a sodium dodecyl sulfate-containing buffer, whereas the low molecular weight compounds were released into a Tris-HCl buffer. Size exclusion chromatography-fast protein liquid chromatography coupled to ICP-MS allowed separation and detection of several selenium-containing proteins in Se-supplemented wild type Brassica juncea plant, a fast growing selenium accumulator.

Chromatography, Gel↗
PubMed1981

Hydrophobic-interaction chromatography and anion-exchange chromatography in the presence of acetonitrile. A two-step purification method for human prolactin.

Described is a two-chromatographic-step preparative-scale technique for the purification of human prolactin from a frozen pituitary homogenate. The method utilizes hydrophobic interaction chromatography on the mildly hydrophobic adsorbent phenyl-Sepharose CL-4B and anion-exchange chromatography on DEAE-cellulose in the presence of acetonitrile. Human prolactin was solubilized at pH10.0 after a prior extraction of pituitaries at pH4.0, the acid pH being ineffective at solubilizing human prolactin but capable of solubilizing large amounts of interfering protein. An 11-fold increase in the potency of the solubilized human prolactin was achieved in this manner. Prolactin could be adsorbed to phenyl-Sepharose at low ionic strengths (I<0.01); few other proteins were adsorbed under these conditions. This is a demonstration of the hydrophobic nature of human prolactin. The amount of phenyl-Sepharose was limited to the minimum (35mg of protein/g of phenyl-Sepharose) necessary to adsorb human prolactin, further reducing the uptake of other pituitary protein. Desorption was achieved by using an acetonitrile gradient (0-30%, v/v), resulting in a purification of human prolactin of 85-fold and recovery of 78%. Acetonitrile (20%, v/v) was also included in all buffers for DEAE-cellulose chromatography, increasing the resolution and recovery of human prolactin, apparently by minimizing non-ionic interactions with the matrix. Prolactin (10mg) was recovered from 63g if pituitaries, an overall recovery of 58%. It was homogeneous by gel filtration and sodium dodecyl sulphate/polyacrylamide-gel electrophoresis, contained less than 0.1% somatotropin (growth hormone), on iodination demonstrated more than 95% binding to excess anti-(human prolactin) serum and could be displaced from anti-(human prolactin) serum in a manner indistinguishable from the serum of a patient with a human prolactin-secreting adenoma.

Acetonitriles↗
PubMed1988

Comparative analysis of glycosylated hemoglobins by ion-exchange column chromatography and high-performance liquid chromatography in patients with hemoglobinopathies.

Cation-exchange chromatography gives falsely decreased values for glycosylated hemoglobins (GHbs) in patients with abnormal hemoglobins (Hbs) such as S, D, G, C, E, and O. This decrease is thought to be proportional to the percentage of abnormal Hb present. In the authors' study, cation-exchange column chromatographic GHb values on 84 nondiabetic patients heterozygous for Hb S, 28 AS diabetic patients, and 23 nondiabetic patients heterozygous for Hb C were calculated to account for the percentage of abnormal Hb, and the resulting values were compared with the GHb values obtained by high-performance liquid chromatography (HPLC). There existed a good correlation between the calculated GHb and the GHb obtained by HPLC (r = 0.92 for AS and r = 0.94 for AC). In patients with elevated Hb F, chromatographic GHb values are falsely high. In such cases, correction can be made by subtracting the Hb F value from the observed GHb. In laboratories where cation exchange chromatography is used, accurate determination of GHb can be made by adjusting observed values for portion of the abnormal Hb present.

Chromatography, High Pressure Liquid↗
PubMed2000

The quantitation of 2-oxo-3-hydroxy lysergic acid diethylamide (O-H-LSD) in human urine specimens, a metabolite of LSD: comparative analysis using liquid chromatography-selected ion monitoring mass spectrometry and liquid chromatography-ion trap mass spectrometry.

This paper compares the potential forensic application of two sensitive and rapid procedures (liquid chromatography-mass spectrometry and liquid chromatography-ion trap mass spectrometry) for the detection and quantitation of 2-oxo-3-hydroxy lysergic acid diethylamide (O-H-LSD) a major LSD metabolite. O-H-LSD calibration curves for both procedures were linear over the concentration range 0-8,000 pg/mL with correlation coefficients (r2) greater than 0.99. The observed limit of detection (LOD) and limit of quantitation (LOQ) for O-H-LSD in both procedures was 400 pg/mL. Sixty-eight human urine specimens that had previously been found to contain LSD by gas chromatography-mass spectrometry were reanalyzed by both procedures for LSD and O-H-LSD. These specimens contained a mean concentration of O-H-LSD approximately 16 times higher than the LSD concentration. Because both LC methods produce similar results, either procedure can be readily adapted to O-H-LSD analysis for use in high-volume drug-testing laboratories. In addition, the possibility of significantly increasing the LSD detection time window by targeting this major LSD metabolite for analysis may influence other drug-free workplace programs to test for LSD.

Chromatography, High Pressure Liquid↗
PubMedDate not supplied

Conversion of tibolone to 7alpha-methyl-ethinyl estradiol using gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry: interpretation and clinical implications.

OBJECTIVE: Tibolone, a hormone therapy drug, is used to treat climacteric symptoms. This drug is rapidly metabolized into three major metabolites (3alpha-hydroxytibolone, 3beta-hydroxytibolone, and Delta4-tibolone). One clinical study provided evidence of conversion of tibolone to another estrogenic metabolite, 7alpha-methyl-ethinyl estradiol (MEE). However, no evidence of MEE formation was found in another study using the human aromatase enzyme. Because MEE was analyzed by gas chromatography-mass spectrometry (GC-MS), which requires derivatization, together with the fact that derivatization of some steroids may lead to aromatization, it is feasible that the MEE detected resulted from an artifact generated during the derivatization process. Hence, our objective was to assess whether tibolone is converted to MEE. DESIGN: We assayed MEE formation in a nonbiological system using GC-MS after derivatization and by analyzing MEE formation using liquid chromatography-mass spectrometry (LC-MS) in nonderivatized samples. RESULTS: MEE formation was evident in tibolone samples derivatized with either pentafluoropropionic anhydride or trimethylsilyl and analyzed by GC-MS. The amount of MEE formed increased with increasing amounts of tibolone (0.5, 1, 2.5, and 5 microg) derivatized; however, relative to tibolone, the percentage of MEE formed remained constant and ranged between 0.22% and 0.29% of tibolone. In contrast to GC-MS, no MEE formation was seen when tibolone was analyzed by liquid chromatography-mass spectrometry without derivatization. CONCLUSIONS: Our findings prove that conversion of tibolone to MEE is an artifact that is generated in a GC-MS system and is largely due to the intense heating step involved in GC-MS. Caution should be exercised to extrapolate clinical implications from existing data on MEE formation using a GC-MS system.

Chromatography, Liquid↗
PubMed1985

Identification and measurement of 4-oestren-3,17-dione (19-norandrostenedione) in porcine ovarian follicular fluid using high performance liquid chromatography and capillary gas chromatography-mass spectrometry.

4-Oestren-3,17-dione (19-norandrostenedione) has been identified as a major steroid in porcine ovarian follicular fluid for the first time. This steroid was isolated by C18 reverse-phase high performance liquid chromatography (HPLC) and its structure was established unambiguously by capillary gas chromatography-mass spectrometry. The mean concentration in pooled fluid obtained from prepubertal gilts determined by HPLC and capillary gas chromatography was 1.71 mumol/l. The leve of this steroid in fluid obtained from large preovulatory follicles of sows exceeded 21.0 mumol/l on days 19 and 20 of the oestrous cycle. The high levels of this steroid within the follicle during the follicular phase might imply a possible biological role in follicular development and oocyte maturation.

Androstenedione↗
PubMed2004

[Simultaneous determination of the residues of pyrethriods, organochlorines and polychlorinated biphenyl congeners in unpolished rice by gas chromatography with gel permeation chromatography purification].

The separation behaviors of organochlorine pesticides, pyrethriod pesticides, polychlorinated biphenyl congeners (PCBs) and unpolished rice matrixes were systematically investigated with gel permeation chromatography (GPC) because of its outstanding capability in removing lipid and pigments from sample solutions. A separation method was proposed for the quantitative determination of 35 pesticides and PCBs in unpolished rice by GPC and gas chromatography simultaneously. Samples were extracted with ethyl acetate, purified by GPC, and then determined by gas chromatography and electron capture detection (GC-ECD). With external standard method, the recoveries of 3 standard addition levels of low, medium, high concentrations were 70.1% - 107.4%, 70.3% - 109.9%, 70.8% - 109.5%, respectively with relative standard deviations from 2.3% to 13.3%. The detection limits were 0.07 microg/kg for organochlorines and PCBs, and 0.44 microg/kg for pyrethriods.

Chromatography, Gas↗
PubMed1992

Molecular dosimetry in rat urine of aflatoxin-N7-guanine and other aflatoxin metabolites by multiple monoclonal antibody affinity chromatography and immunoaffinity/high performance liquid chromatography.

The development of molecular dosimetry methods will simplify the identification of people at high risk for cancer. A combined monoclonal antibody immunoaffinity chromatography/high performance liquid chromatography method has been devised to isolate and quantify aflatoxin-DNA adducts and other metabolites in rat urine samples. We report the production of 11 different monoclonal antibodies recognizing aflatoxin B1, aflatoxin Q1, aflatoxin G1, aflatoxicol, and aflatoxin M1 and the application of these antibodies to a multiple monoclonal antibody affinity chromatography technique. Using the multiple monoclonal antibody affinity column with rat urines obtained from dosed animals, between 90 and 95% of total aflatoxin metabolites can be bound to the column and isolated. Analytical immunoaffinity chromatography/high performance liquid chromatography analysis of these isolated aflatoxins reveals that more than 55% of the aflatoxins in rat urine are aflatoxin-dihydrodiol, aflatoxin-N7-guanine, aflatoxin Q1, aflatoxin M1, aflatoxin P1, and aflatoxin B1, accounting for 1.5, 9.6, 1.8, 34.5, 8.0, and 1.0% of the total aflatoxins, respectively. Further, a perchloric acid digestion of the aflatoxin-N7-guanine peak was used to confirm its identity by its conversion to guanine. The measurement of aflatoxin-N7-guanine excretion in rat urine was examined to assess its utility as a marker of DNA adduct formation in the liver, and a dose-dependent excretion in urine was found with a correlation coefficient of 0.99. A comparison of the dose-dependent residual levels of aflatoxin binding to liver DNA with the amount of aflatoxin-N7-guanine excreted in urine showed a correlation coefficient of 0.98. Besides the nucleic acid adduct excretion data, aflatoxin M1 and aflatoxin P1 were evaluated as molecular dosimeters in the urine. Aflatoxin M1 was found to be an excellent marker, whereas no linear relationship between dose and aflatoxin P1 excretion in urine was found.

Aflatoxin B1↗
PubMedDate not supplied

Identification and quantitation of sulfamethazine metabolites by liquid chromatography and gas chromatography-mass spectrometry.

Methods for the identification and quantitation of carbon-14 labeled sulfamethazine [4-amino-N-(4,6-dimethyl-2-pyrimidinyl)benzenesulfonamide], N4-acetylsulfamethazine, the N4-glucose conjugate of sulfamethazine, and desaminosulfamethazine in swine tissue are described. Tissues are ground and extracted with methanol, and the 14C-labeled compounds are purified by XAD-2 column chromatography and C-18 reverse phase liquid chromatography (LC) and the 14C-labeled compounds are then methylated and identified by gas chromatography-mass spectrometry analysis. Quantitation is accomplished by measuring the amount of 14C-activity that cochromatographs (C-18 reverse phase LC) with reference compounds.

Animals↗
PubMed1977

Gas-liquid chromatography and liquid chromatography of ethylenethiourea in fresh vegetable crops, fruits, milk, and cooked foods.

The Onley-Yip procedure for determining ethylenethiourea (ETU) in milk and crops was modified to reduce interferences by the ethylenebisdithiocarbamates (EBDCs). A 20 g crop-methanol extract is cleaned up by adsorbing the sample onto Gas-Chrom S. desorbing ETU, and eluting ETU from aluminum oxide with chloroform containing ethanol. ETU is converted to the S-butyl derivative for gas-liquid chromatography (GLC) and flame photometric detection (sulfur mode). For liquid chromatography (LC), ETU is cleaned up on another aluminum oxide column and injected directly. LC and GLC results are confirmed by thin layer chromatography. A cooking procedure based on conversion of EBDCs to ETU is included for surveying crops for possible EBDC content. Recoveries from 8 crops and milk fortified at 0.05 ppm ETU ranged from 73 to 100%.

Animals↗
PubMed1978

Determination of zearalenone in cornflakes and other corn-based foods by thin layer chromatography, high pressure liquid chromatography, and gas-liquid chromatography/high resolution mass spectrometry.

A simple cleanup procedure based on pH adjustments was used to obtain extracts of corn foods. The method gave good recoveries of zearalenone determined by thin layer chromatography (TLC) and high pressure liquid chromatography (HPLC). As little as 5 ng zearalenone was detected by TLC, using Fast Violet B Salt as the spray reagent; the lower limit of detection in cornflakes was about 20 microgram/kg. With HPLC on Spherisorb silica (5 micrometer) and detection by fluorescence at an excitation maximum of 310 nm as little as 5 microgram zearalenone/kg cornflakes could be determined. While the TLC method was also applicable to corn chips, cornmeal, popcorn, and frozen corn, an interference was observed in HPLC of the latter 3 products. This interference was separated from zearalenone by adding a second HPLC analytical column (Spherisorb ODS). Gas-liquid chromatography coupled with mass spectrometric single ion monitoring at high resolution, although of limited availability, was shown to be the most sensitive and selective method for determining zearalenone in corn foods. The natural occurrence of zearalenone in a sample of cornflakes (13-20 microgram/kg) was demonstrated by all 3 detection procedures.

Chromatography, Gas↗
PubMed1977

Trace analysis of zearalenone and/or zearalanol in animal chow by high pressure liquid chromatography and gas-liquid chromatography.

An analytical method is described for determining residues of the estrogens zearalenone and/or zearalanol in animal chow at levels as low as 10 ppb. The chow is extracted with methanol and cleaned up by a 3-step procedure employing a Sephadex LH-20 column, liquid-liquid partitioning at pH 13 and 8.3, and a silica gel column. Residues of the 2 compounds, separated on silica gel, are assayed by using high pressure liquid chromatography with ultraviolet detection. Additional data are also included concerning p-values of the compounds in several solvent systems, Rf values from thin layer chromatography with 9 solvent systems, solubilities in 3 solvents, and a procedure for preparing their pentafluoropropionyl derivatives for analysis by electron capture gas-liquid chromatography.

Animal Feed↗
PubMed2006

Development of an efficient method for the preparative isolation and purification of chlorophyll a from a marine dinoflagellate Amphidinium carterae by high-speed counter-current chromatography coupled with reversed-phase high-performance liquid chromatography.

In our research into chlorophylls of marine dinoflagellates, chlorophyll a was separated rapidly from the hexane extract of Amphidinium carterae in three steps. The first step was silica gel column chromatography, where elution was performed with 0-50% ethyl acetate in n-hexane. The second was high-speed counter-current chromatography using a two-phase solvent system consisting of n-hexane-ethyl acetate-methanol-water (5:5:5:1, v/v), and the third step was preparative reversed-phase high-performance liquid chromatography using a solvent system of acetone-water (89:11, v/v). HPLC analysis showed that the purity of chlorophyll a from the second step was over 83%, and after the third it was over 99%. Thirty milligrams of chlorophyll a was isolated from a crude sample of 250 mg of chlorophylls, and its structure was identified by analyzing its MS, 1H NMR and 13C NMR spectra.

Animals↗