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At least 397 records · Page 22Linked to original sources
PubMed2004

Quantification of urinary excretion of 1,N6-ethenoadenine, a potential biomarker of lipid peroxidation, in humans by stable isotope dilution liquid chromatography-electrospray ionization-tandem mass spectrometry: comparison with gas chromatography-mass spectrometry.

Etheno DNA adducts are promutagenic DNA lesions derived from exogenous as well as endogenous sources. The levels of etheno adducts in tissue DNA are elevated in cancer prone tissues, and the urinary excretion of etheno adducts is associated with oxidative stress. In this report, a new assay based on isotope dilution liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) is developed for the quantification of 1,N(6)-ethenoadenine (epsilonAde) in human urine samples without the need for derivatization. Sample purification before analysis by MS only requires a reversed phase solid phase extraction column. Two multiple reaction monitoring transitions with two product ion fragments generated from a common parent ion were used to quantify urinary epsilonAde. The detection limit of epsilonAde using LC-ESI-MS/MS is 2 pg injected standard epsilonAde on-column, and the assay allows accurate quantification of urinary epsilonAde at concentrations higher than 10 pg/mL. The presence of epsilonAde in human urine is confirmed by the collision-induced daughter ion spectrum. Using this assay, the levels of epsilonAde in the 24 h urine samples from 18 healthy individuals are determined, and the results are in very good agreement with those obtained using isotope dilution gas chromatography-negative ion chemical ionization-mass spectrometry. The high specificity and simple sample pretreatment of this LC-ESI-MS/MS method render it a valuable tool in measuring epsilonAde in the complex mixture of human urine as a promising noninvasive biomarker for DNA damage associated with oxidative stress and for cancer chemoprevention studies.

Adenine↗
PubMed1994

Determination of anabolic esters in oily formulations and plasma in husbandry using high-performance liquid chromatography and gas chromatography-mass selective detection.

Two different analytical methods are described for the analysis of anabolic steroid esters in oily formulations for veterinary use and animal plasma samples, respectively. For the determination of anabolic steroid esters in oily formulations (at mg kg-1 levels) a reversed-phase high-performance liquid chromatographic method with gradient elution is described. Gradient elution is performed owing to the relatively large variations in polarity of the investigated anabolic steroid esters. For the analysis of anabolic steroid esters in plasma (at ng ml-1 levels) two different strategies are applied. After solid-phase extraction, the plasma samples are introduced into the high-performance liquid chromatography (HPLC) system where the obtained fractions are then analysed by using gas chromatography-mass selective detection (GC-MSD). An alternative method is direct analysis of plasma samples after solid-phase extraction by using GC-MSD without any further clean-up procedure. Prior to GC-MSD the samples are derivatized to corresponding trifluoroacyl (TFA) derivatives. The calibration graph for HPLC is rectilinear over the range 25-150 ng ml-1 plasma and the analytical recoveries for medroxyprogesterone acetate (MPA) and testosterone propionate (TP) are more than 95%. The detection limits for both analytes in GC-MS are 2.5 ng ml-1 plasma for MPA and 0.5 ng ml-1 plasma for TP with an acceptable signal-to-noise ratio (calculated for the derivatized relative molecular mass). In the analysis of plasma obtained from animal experiments concentrations of 6.5 ng ml-1 are found for MPA by using GC-MSD and 5.0 ng ml-1 are found for nortestosterone laurate (NL) by using HPLC.

Anabolic Agents↗
PubMed1994

Determination of succinonitrile in horse urine by gas chromatography-nitrogen-phosphorus detector and gas chromatography-mass spectrometry.

A chromatographic method was developed to detect and confirm the presence of succinonitrile (SDN) in horse urine samples, for antidoping control. The urine samples (5 ml) were extracted with diethyl ether and screened by gas chromatography-nitrogen-phosphorus detector and the confirmation of the drug's presence was accomplished by using gas chromatography-mass selective detection. The recovery of extraction was 78 and 81% for 1.0 and 2.0 micrograms ml-1 (relative standard deviation, < 10%), respectively. Urine samples collected after the administration of Energisan were positive for SDN (1-30 h) in all samples analysed.

Animals↗
PubMed1994

Determination of xanthines by high-performance liquid chromatography and thin-layer chromatography in horse urine after ingestion of Guaraná powder.

The seeds of Guaraná are rich in xanthines and are used for the preparation of guaraná powder which is very commonly given to horses as a 'tonic' in Brazil. In this paper, the xanthine content of guaraná powder was determined, in addition to its clearance time in horses. Thin-layer chromatography was used as a screening procedure and high-performance liquid chromatography was performed to quantify the drugs in both the powder and urine samples. The guaraná powder was found to contain 2.16, 1.10 and 36.78 mg g-1 of theobromine (TB), theophylline (TP) and caffeine (CF), respectively, and in urine it was possible to detect TB and TP up to 13 d and CF up to 9 d after the administration of guaraná powder.

Administration, Oral↗
PubMed2000

Solid-phase microextraction coupled with high performance liquid chromatography: a complementary technique to solid-phase microextraction-gas chromatography for the analysis of pesticide residues in strawberries.

Solid-phase microextraction coupled with high performance liquid chromatography has been studied for the analysis of methiocarb, napropamide, fenoxycarb and bupirimate in strawberries. The strawberries were blended and centrifuged. Then, an aliquot of the resulting extracting solution was subjected to solid-phase microextraction (SPME) on a 60 microns polydimethylsiloxane/divinylbenzene (PDMS/DVB) fibre for 45 min at room temperature. The extracted pesticides on the SPME fibre were desorbed into SPME/high performance liquid chromatography (HPLC) interface for HPLC analysis with diode-array detection (DAD). The method is organic solvent-free for the whole extraction process and is simple and easy to manipulate. The detection limits were shown to be at low microgram kg-1 level and the linear response covered the range from 0.05 to 2 mg kg-1 of pesticides in strawberries with a regression coefficient larger than 0.99. A good repeatability with RSDs between 2.92 and 9.25% was obtained, depending on compounds.

Chromatography, Gas↗
PubMed2006

Multi-residue method for the determination of 450 pesticide residues in honey, fruit juice and wine by double-cartridge solid-phase extraction/gas chromatography-mass spectrometry and liquid chromatography-tandem mass spectrometry.

A multi-residue method was developed for the determination of 450 pesticide residues in honey, fruit juice and wine using double-cartridge solid-phase extraction (SPE), gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-tandem mass spectrometry (LC-MS-MS). The method development was based on an appraisal of the characteristics of GC-MS and LC-MS-MS for 654 pesticides as well as the efficiency of extraction and purification from honey, fruit juice and wine. Samples were first diluted with water plus acetone, then extracted with portions of dichloromethane. The extracts were concentrated and cleaned up with graphitized carbon black and aminopropyl cartridges stacked in tandem. Pesticides were eluted with acetonitrile + toluene, and the eluates were concentrated. For 383 pesticides, the eluate was extracted with hexane twice and internal standard solution was added prior to GC-MS determination. For 67 pesticides, extraction was with methanol prior to LC-MS-MS determination. The limit of detection for the method was between 1.0 and 300 ng g(-1) depending on each pesticide analyte. At the three fortification levels of 2.0-3000 ng g(-1), the average recovery rates were between 59 and 123%, among which 413 pesticides (92% of the 450) had recovery rates of 70-120% and 35 pesticides (8% of the 450) had recovery rates of 59-70%. There were 437 pesticides (97% of the 450) with a relative standard deviation below 25%; there were 13 varieties (3% of the 450) between 25.0 and 30.4%.

Beverages↗
PubMed1979

Metabolic fate of aromatic hydrocarbons in aquatic organisms: analysis of metabolites by thin-layer chromatography and high-pressure liquid chromatography.

Aquatic organisms convert aromatic hydrocarbons into a variety of conjugated and nonconjugated derivatives. Analytical techniques based on thin-layer chromatography (TLC) and high-pressure liquid chromatography (HPLC) were employed to separate, identify and quantitate individual metabolites from fish exposed to radiolabeled naphthalene and 2,6-dimethylnaphthalene. Significant differences in profiles of individual metabolites were found in relation to the type of biological sample analyzed. Liver of naphthalene-exposed salmonids contained eight polar derivatives, as shown by HPLC. Two nonconjugates (1-naphthol and 1,2-dihydro-1,2-dihydroxynaphthalene) and three conjugates (1-naphthyl glucuronic acid, 1-naphthyl sulfate and 1-naphthyl glucoside) were identified. HPLC revealed that brain of 3H-naphthalene-exposed trout contained essentially the nonconjugated derivatives, 1-naphthol and 1,2-dihydro-1,2-dihydroxynaphthalene. TLC showed that the metabolites from trout urine were 1-naphthol, 1,2-dihydro-1,2-dihydroxynapthalene, and 1-naphthyl glucuronic acid (99% of the total metabolites detected). Major components of the metabolite fractions of tissues and biological fluids were 1,2-dihydro-1,2-dihydroxy and glucuronic acid derivatives. Dihydrodiol derivatives arise from the corresponding arene oxides, some of which have been shown to be cytotoxic to certain mammalian systems.

Animals↗
PubMed1981

Monitoring bacterial metabolites in cultured buttermilk by high performance liquid chromatography and headspace gas chromatography.

A commercial buttermilk culture was added to Grade a skim milk. Samples were analyzed hourly for a total of eighteen hours. Headspace gas chromatography measured changes in acetaldehyde, acetone, ethanol, and diacetyl concentrations. High performance liquid chromatography measured changes in orotic, citric, pyruvic, lactic, uric, acetic, and propionic acid concentrations. Consumption of orotic acid and citric acid substrates was noted. Production of diacetyl, ethanol, pyruvic, lactic, acetic, and propionic acids was observed. Acetaldehyde concentration increased initially and then decreased as ethanol was formed. Acetone and uric acid concentrations remained constant during fermentation. In addition, chemical changes occurring during refrigeration were measured after seven days. Acetaldehyde, ethanol, and acetic acid increased in concentration; diacetyl, orotic, citric, pyruvic, lactic, and propionic acids decreased in concentration. Also, a headspace gas chromatographic test was done for the quantitation of acetoin.

Animals↗
PubMed1998

Enantiomer analysis of chiral lactones in foods by on-line coupled reversed-phase liquid chromatography-gas chromatography.

A new application is proposed for the on-line coupling of reversed-phase liquid chromatography to gas chromatography (RPLC-GC) that allows the GC chirospecific analysis of gamma-lactones in fruits and commercially available fruit-containing products. The use of a programmed temperature vaporizer as an interface with the system makes the transfer of large volume fractions (i.e., 2520 microL) of aqueous eluents from LC to GC possible (speed of sample transfer, 1800 microL/min). Relative standard deviations obtained for the investigated lactones under the experimental conditions vary from 7 to 14%. The described system enlarges the LC-GC application field and overcomes the limitations reported thus far concerning the use of typical normal-phase eluents (i.e., the transfer of rather small volume fractions at low speeds of sample introduction).

Chromatography, Gas↗
PubMed2000

Separation and tentative identification of the main pigment fraction of raisins by thin-layer chromatography-Fourier transform infrared and high-performance liquid chromatography-ultraviolet detection.

The soluble color pigments of raisin are separated by reversed-phase thin-layer chromatography (TLC), and the capacity of TLC-Fourier transform infrared (FTIR) with both on-line and off-line coupling is assessed for the identification of the main fraction. TLC has also been used as a pilot technique for the development of a gradient elution method for the separation of pigments by high-performance liquid chromatography (HPLC). On-line TLC-FTIR cannot be used for identification because of the strong adsorbance of the stationary phase. Off-line TLC-FTIR combined with the retention behavior of the main pigment fraction indicates that it is a polymer, caramel-like compound composed of erythrose and fructose monomers. Baseline separation of pigments is achieved by HPLC using TLC as a pilot method.

Chromatography, High Pressure Liquid↗
PubMedDate not supplied

Simultaneous determination of bromvalerylurea, bromodiethylacetylurea, and allylisopropylacetylurea in serum and urine by high-performance liquid chromatography with a multiwavelength UV detector and thin-layer chromatography.

A method for rapid detection and identification of bromvalerylurea (BVU), bromodiethylacetylurea (BDU), and allylisopropylacetylurea (AIU) in serum and urine by high-performance liquid chromatography (HPLC) with a multiwavelength UV detector after Sep-Pak C18 cartridge extraction is reported. A Jasco Finepak C18 reversed-phase column was used for the separation. Acetonitrile-distilled water (1:1, v/v) was used as a mobile phase. There was no significant absorption of the three hypnotics in the UV spectra (210-350 nm). However, the absorption of each was higher at the shorter wavelengths. The quantifications for the three hypnotics detected at 210 nm by the chromatogram were linear over the range 0.2-4 micrograms/mL and the detection limits of BVU, BDU, and AIU were 5, 10, and 10 ng as absolute amounts, respectively. The mean recovery yields of BVU, BDU, and AIU by Sep-Pak C18 cartridge extraction were 85.7 +/- 4.1, 98.6 +/- 2.2, and 95.1 +/- 3.5% (n = 5) in serum and 79.5 +/- 3.8, 95.7 +/- 1.8, and 93.0 +/- 4.2% (n = 5) in urine, respectively. An optimal system of thin-layer chromatography for the identification of the hypnotics is also discussed.

Bromisovalum↗
PubMed1997

The use of ELISA tests and immunoaffinity chromatography combined with reversed-phase high-performance liquid chromatography for dexamethasone detection in equine urine.

Dexamethasone is a corticosteroid drug widely used in racehorses because of its anti-inflammatory effect. It is, therefore, frequently detected in antidoping tests. A method for the antidoping control of dexamethasone in equine urine using screening by ELISA and confirmation by immunoaffinity chromatography combined with reversed-phase high-performance liquid chromatography-diode array detection (HPLC-DAD) is described. The ELISA test is frequently used in antidoping tests for its sensitivity, relative speed, and low cost. The test showed linearity in the range of 4-500 ng/mL of urine, and the intra-assay and interassay imprecision were 9.4 and 9.7%, respectively. The confirmation method showed a limit of detection of 4 ng/mL for dexamethasone. The intra-assay and interassay imprecisions were 10.3 and 14.4%, respectively. The HPLC-DAD showed a limit of detection of 5 ng and linearity in the range of 25-500 ng of dexamethasone. The absolute method recovery was 56.4%. The proposed method detected dexamethasone up to 52 h after administration and proved to be adequate for the antidoping control.

Animals↗
PubMed1997

Determination of buprenorphine in human plasma by gas chromatography-positive ion chemical ionization mass spectrometry and liquid chromatography-tandem mass spectrometry.

Buprenorphine is used for the management of pain and has been advocated for the treatment of opioid addiction. Therapeutic doses result in low plasma concentrations of buprenorphine. In order to assess the safety and efficacy of buprenorphine, sensitive analytical methods are needed. Until recently, gas chromatography-positive ion chemical ionization mass spectrometry (GC-PCI-MS) offered the most sensitive method to selectively quantitate buprenorphine. We have developed and validated a sensitive liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS-MS) method for buprenorphine. The method is described and compared with a GC-PCI-MS method validated in this laboratory. One-milliliter aliquots of plasma are required for the LC-ESI-MS-MS method and 2-mL aliquots for the GC-PCI-MS method. Buprenorphine-d4 is used as internal standard for both methods. Derivatization with pentafluoropropionic acid anhydride is used for the GC-PCI-MS method, in which the derivatized protonated molecular ions after loss of water are monitored at m/z 596 and 600. For LC-ESI-MS-MS, the parent protonated molecule ions are monitored at m/z 468 and 472. A single-step extraction of basic plasma with n-butyl chloride provided recoveries of 70-87%. Although a limit of quantitation (LOQ) of 0.1 ng/mL could be established for LC-ESI-MS-MS, we could only achieve an LOQ of 0.5 ng/mL with the GC-PCI-MS assay. The GC-PCI-MS method has a linear range of 0.5 to 40 ng/mL (mean r2 = 0.998, n = 7). For quality control samples at 1.0, 2.5, and 12.5 ng/mL, the intra- and interassay coefficients of variation (CV) did not exceed 14%, and percent of targets were within 16%. The LC-ESI-MS-MS method had a linear range of 0.1 to 10 ng/mL (mean r2 = 0.999, n = 7). For quality control samples at 0.25, 2.5 and 7.5 ng/mL, the intra- and interassay CVs did not exceed 4%, and percent of targets were within 12%. Stability studies demonstrated buprenorphine was stable for up to 24 h, 125 days, and 55 days when stored at room temperature, 4 degrees C, and -20 degrees C, respectively. The utility of the lower LOQ was demonstrated in 40 plasma samples collected up to 96 h after a sublingual dose of buprenorphine; 10 were quantitatable using GC-PCI-MS and 38 using LC-ESI-MS-MS.

Administration, Sublingual↗
PubMedDate not supplied

Screening for basic drugs in 2-mL urine samples by dual-plate overpressured layer chromatography and comparison with gas chromatography-mass spectrometry.

A dual-plate overpressured layer chromatography (OPLC) method was evaluated for broad-scale screening of basic drugs in 2-mL autopsy urine samples. Extraction was carried out by mixed-mode solid-phase extraction, and identification was based on automated comparison of corrected Rf values (hRfc) and in situ UV spectra with library values by dedicated software. The day-to-day precision of hRfc values was good in both OPLC1 and OPLC2 systems with median relative standard deviations of 2.4% and 3.4%, respectively. Both Rf and hRfc values were independent of the amount of analyte (0.5-10 microg) applied to the plate. Detection limits were determined for 47 drug substances in 2-mL urine samples, and they varied between 0.05 and 3.5 mg/L with a median of 1.0 mg/L. The performance of OPLC was evaluated by analyzing 30 autopsy urine samples by both OPLC and gas chromatography-mass spectrometry (GC-MS). The majority of findings by OPLC were in agreement with GC-MS. Some substances with low concentrations were not detected by OPLC, whereas GC-MS failed to detect a few polar substances. The OPLC method thus provides an alternative for current planar and column liquid chromatographic drug screening methods with the possibility of lowering detection limits by using a larger sample size.

Chromatography, Liquid↗
PubMedDate not supplied

Rapid determination of N,N-diethyl-m-toluamide and permethrin in human plasma by gas chromatography-mass spectrometry and pyridostigmine bromide by high-performance liquid chromatography.

A rapid and highly sensitive gas chromatography-mass spectrometry (GC-MS) method for simultaneous determination of N,N-diethyl-m-toluamide (DEET) and permethrin with (2)H(10)-phenanthrene (98 atom %) as an internal standard and a separate external standard high-performance liquid chromatography (HPLC) method for pyridostigmine bromide (PB) determination in human plasma were developed and validated. The GC-MS method for DEET and permethrin quantification utilizes a one-step extraction with tert-butylmethylether. The HPLC method for PB quantification involves a solid-phase extraction and UV detection. The range of the analytical method for DEET and permethrin was 1 ng/mL to 100 ng/mL and for PB was 5 ng/mL to 100 ng/mL. Recovery from plasma proved to be more than 80%. The intraday precision ranged from 1.3% to 8% for DEET, from 2.1% to 11.4% for permethrin, and from 3.0% to 4.8% for PB. The interday precision was 3% for DEET, ranged from 5% to 9% for permethrin, and from 5% to 9% for PB. The accuracy for the limit of quantification was 92% +/- 8% relative standard deviation (RSD) for DEET, 112% +/- 11% RSD for permethrin, and 109% +/- 5% RSD for PB. All 3 compounds were stable in human plasma at -80 degrees C for at least 12 months and after 2 freeze-thaw cycles with RSD values ranging from 7.1% (DEET, 80 ng/mL) to 8.1% (DEET, 8 ng/mL), from 2.3% (permethrin, 80 ng/mL) to 11.6 % (permethrin, 8 ng/mL), and from 0.2% (PB, 80 ng/mL) to 3.6% (PB, 8 ng/mL). Both methods were successfully applied to pharmacokinetic/ pharmacodynamic studies of combined exposure of DEET (skin application), permethrin (treated uniforms), and PB (30 mg orally three times/day for four doses) in healthy volunteers (n = 81).

Chromatography, High Pressure Liquid↗
PubMedDate not supplied

Detection of ritalinic acid in urine by thin-layer chromatography and gas chromatography.

A new method for the analysis of ritalinic acid, the major metabolite of methylphenidate in urine, is described. The procedure involves solid-phase extraction of ritalinic acid from urine using C-18 reverse phase columns. The ritalinic acid is methylated to form methylphenidate which, together with an internal standard, is then extracted into chloroform and analyzed by gas chromatography using a flame ionization detector. This procedure gives essentially quantitative recovery of ritalinic acid from 10 mL urine and is linear in the range of 0 to 10 micrograms/mL. A positive analysis for ritalinic acid is confirmed by thin-layer chromatography. Detection sensitivities of greater than or equal to 1 micrograms/mL urine were observed for both procedures.

Chromatography, Gas↗
PubMed1995

Propofol concentration monitoring in plasma or whole blood by gas chromatography and high-performance liquid chromatography.

We compared the measurement of propofol concentrations in plasma or whole blood by high-performance liquid chromatography (HPLC) to that of gas chromatography (GC). Blood samples were collected from patients who had received bolus injection or continuous infusion of propofol. The results showed that the two methods correlated well both in plasma and whole blood samples. However, significant biphasic differences of propofol concentrations between plasma and whole blood specimens were observed in the bolus injection group. Differences were larger in the infusion group. This discrepancy in concentrations resulted from the infusion or clearance of propofol, and the lag of redistribution across blood cell membranes. In conclusion, monitoring of propofol concentrations by the methods of GC and HPLC gives equivalent results. For propofol concentration monitoring, plasma samples are preferred, but immediate centrifugation is needed.

Adult↗
PubMed1987

Honeydew sugars in wild-caught Phlebotomus ariasi detected by high performance liquid chromatography (HPLC) and gas chromatography (GC).

Phlebotomus ariasi Tonnoir sandflies were caught in light traps hung in oak trees and in a house in the Cévennes focus of leishmaniasis in the South of France. The flies were cryopreserved either immediately on removal from the traps, or after starvation for 6-7 days, or after 6-7 days starvation followed by exposure to oak infested with the aphid genera Lachnus or Thelaxes. After transportation to the laboratory, the sandflies were thawed and aqueous extracts of the crushed flies were analysed for their carbohydrate content using high performance liquid chromatography (HPLC) and gas chromatography (GC). Starved female sandflies lacked significant amounts of any saccharides. Four types of sugar, melezitose and its hydrolysis products turanose, glucose and fructose, were observed in flies which had been starved previously and then placed with Lachnus infested oak. The results also indicate the presence of hydrolysis products of melezitose: (a) in flies previously starved and placed with Thelaxes infested oak, (b) in P.ariasi cryopreserved direct from the light traps hung in oak trees infested with Lachnus and Thelaxes, and (c) flies caught in a house. Unidentifiably small quantities of a trisaccharide were also detected in the latter groups of flies. In previous tests, sugars were detected in P.ariasi after their exposure to aphid-infested oak (Quercus ilex L.), but not when P.ariasi females were exposed to washed oak leaves without aphids. The results indicate that P.ariasi feed on melezitose and/or turanose, the main local source of which is aphid honeydew. A better understanding of sugar meal sources of sandflies using HPLC and GC techniques will assist in our understanding of sandfly/Leishmania relationships, parasite transmission and epidemiology.

Animals↗