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At least 577 records · Page 32Linked to original sources
PubMed1991

Fatty acid composition of glycerophospholipids in seven tissues of cod (Gadus morhua), determined by combined high-performance liquid chromatography and gas chromatography.

A method for the separation from fish tissues of the four main glycerophospholipid classes, phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol and phosphatidylserine, using adsorption high-performance liquid chromatography with ultraviolet detection and consecutive gas chromatographic analysis, based on one injection for their fatty acid compositions, is described. Fatty acid 19:0 was used as an internal standard for the calculation of the relative concentrations of the phospholipids. The patterns of fatty acid distribution within each of the phospholipids from seven cod organs had some general similarities. Phosphatidylcholine had the highest levels of 16:0 and 18:2 n - 6, and the ratio of 20:5 to 22:6 varied between 0.5 and 0.9. Phosphatidylethanolamine had the highest total polyunsaturated fatty acids, (n -3) polyunsaturated fatty acids, and 22:6 n -3, and the ratio of 20:5 to 22:6 varied between 0.2 and 0.5. Phosphatidylinositol showed the highest level of 18:0 and 20:4 n - 6 and had the lowest ratio of (n - 3) to (n - 6). Phosphatidylserine had the highest ratio of (n - 3) to (n - 6) and the lowest ratio of 20:5 to 22:6. A generally low level (less than 1.5%) of the long-chain monoene, 22:1, was found in the phospholipids in all tissues.

Animals↗
PubMed1991

Determination of felodipine and its metabolites in plasma using capillary gas chromatography with electron-capture detection and their identification by gas chromatography-mass spectrometry.

A novel method for the determination of felodipine and its metabolites in plasma by capillary gas chromatography (GC) with electron capture detection was developed. Felodipine and its oxidized metabolite were assayed by capillary GC after solid-phase extraction with the aid of a cool on-column injection technique. Acid metabolites, methyl monoacid and ethyl monoacid and diacid, were extracted with diethyl ether and propylated with 1-n-propyl-3-p-tolyltriazene before being submitted to capillary GC. These methods were very sensitive and useful for the pharmacokinetic study of felodipine. Felodipine and its metabolites were identified by GC-mass spectrometry. The mass spectral patterns of the peaks of extracts from human plasma samples after oral administration of felodipine were in good agreement with those of reference compounds.

Chromatography, Gas↗
PubMed1991

Use of high-performance liquid chromatography-thermospray mass spectrometry and gas chromatography-electron-impact mass spectrometry in the identification of the metabolites of alpha-methylacetohydroxamic acids, potential anti-asthmatic agents.

Two potential anti-asthmatic alpha-methylacetohydroxamic acids, compound 1 and compound II were metabolised to two major products (metabolite 1 and metabolite 2) after oral dosing to rabbits. Metabolite 1, extracted under acid conditions from the plasma and urine of dosed animals, was identified as a glucuronide by incubation with beta-glucuronidase and subsequent high-performance liquid chromatographic-mass spectrometric (HPLC-MS) analysis of the aglycone. HPLC-MS analysis of metabolite 2 suggested that it was the acetamide, however, unequivocal identification was obtained by further analysis using gas chromatography-mass spectrometry (GC-MS) of its trimethylsilyl derivative and by comparison with the mass spectra of the authentic acetamides. This study shows the advantages of combining HPLC-MS with other techniques such as GC-MS for the identification of metabolites.

Animals↗
PubMed1993

Identification and determination of the enantiomers of moprolol and their metabolites in human urine by high-performance liquid chromatography and gas chromatography-mass spectrometry.

A simple and sensitive high-performance liquid chromatographic (HPLC) method using chiral derivatization was developed to screen and determine the enantiomers of moprolol and their metabolites in human urine. The recovery of (+)- and (-)-moprolol from urine was 70.8-81.1% at different concentrations. The coefficients of variation (C.V.) were less than 3.2 and 6.5% for intra- and inter-assays, respectively. Moprolol could be detected in urine up to 24 h after oral administration of a 50-mg dose of moprolol. Unconjugated and conjugated enantiomers of moprolol and their metabolites were analyzed by gas chromatography (GC). A gas chromatographic-mass spectrometric (GC-MS) confirmatory method was established to identify the metabolites of moprolol. The double derivation procedure for moprolol and their metabolites with S-(-)-methyl chloroformate [(-)-MCF] and N-methyl(trimethylsilyl)trifluoroacetamide (MSTFA) gave very good GC-MS properties of the derivatized compounds and provided reliable structural information for their confirmation analysis. This is the first published report on the use of a GC-MS method for the detection of the enantiomers of moprolol and their metabolites in human urine.

Acetamides↗
PubMed1995

Selective extraction of quercetrin in vegetable drugs and urine by off-line coupling of boronic acid affinity chromatography and high-performance liquid chromatography.

Quercetrin, quercetin and chlorogenic acid were measured in urine or in drugs by combination of boronic acid affinity chromatography and HPLC. Simple reversed-phase HPLC with UV detection was used to determine quercetrin in five different Solidago virgaurea drugs. For determination of quercetrin in human urine immobilized boronic acid was applied for sample pretreatment. this procedure leads to a determination limit of 0.01 micrograms/ml with a recovery rate of 95.3%. The first results using this method for quercetrin pharmacokinetics are presented.

Boronic Acids↗
PubMed1995

Determination of chloramphenicol in muscle, liver, kidney and urine of pigs by means of immunoaffinity chromatography and gas chromatography with electron-capture detection.

A rapid and specific clean-up procedure based on immunoaffinity chromatography (IAC) with polyclonal antibodies for the gas chromatographic determination with electron-capture detection of chloramphenicol in pig muscle tissue, organs and urine is described. A commercially available IAC material was used for the analysis. A decrease in the capacity of the column after being used more than 100 times was observed. Mean recoveries were 69, 54, 62 and 95% for spiked pig muscle tissue, liver, kidney and urine, respectively. The limit of detection was 0.2 micrograms/kg for muscle tissue, 2.0 micrograms/kg for liver and kidney and 0.4 micrograms/kg for urine.

Animals↗
PubMed1990

Assay and purity control of oxytetracycline and doxycycline by thin-layer chromatography--a comparison with liquid chromatography.

A thin-layer chromatographic (TLC) method using densitometry is described for the assay and purity control of oxytetracycline and doxycycline. With a mobile phase of dichloromethane-methanol-water (59:35:6, v/v/v) and a silica gel thin-layer, previously sprayed with 10% sodium edetate solution adjusted to pH 9.0, all the potential impurities of oxytetracycline or doxycycline are well separated from the main components and from each other. Results obtained with TLC are compared with those obtained by previously established liquid chromatography (LC) methods using poly(styrene-divinylbenzene) stationary phases. A good correlation was obtained (r greater than 0.9999). For TLC the relative standard deviation (RSD) for the assay of the main component was less than 2%, for LC the RSD was less than 1%.

Chromatography, Liquid↗
PubMed1991

Assay and purity control of metacycline by thin-layer chromatography combined with UV and fluorescence densitometry--a comparison with liquid chromatography.

A thin-layer chromatographic (TLC) method involving UV and fluorescence densitometry is described for the assay and purity control of metacycline. With a mobile phase dichloromethane-methanol-water (58:35:7, v/v/v) and a silica gel thin-layer, previously sprayed with 10% sodium edetate solution adjusted to pH 9.0, all the potential impurities of metacycline were well separated from the main component and from each other. Results obtained with UV densitometry (TLC-UV) and fluorescence densitometry (TLC-F) were compared with those obtained by a liquid chromatography (LC) method using a poly(styrene-divinylbenzene) stationary phase. The correlation coefficients (r) for TLC-UV and LC or TLC-F and LC were better than 0.9999. For TLC-UV the relative standard deviation (RSD) for the assay of the main component was less than 2%, for TLC-F less than 3.0% and for LC less than 1.0%.

Anti-Bacterial Agents↗
PubMed2005

Determination of denaturated proteins and biotoxins by on-line size-exclusion chromatography-digestion-liquid chromatography-electrospray mass spectrometry.

A multidimensional analytical method for the rapid determination and identification of proteins has been developed. The method is based on the size-exclusion fractionation of protein-containing samples, subsequent on-line trypsin digestion and desalination, and reversed-phase high-performance liquid chromatography-electrospray mass spectrometry detection. The present system reduces digestion times to 20 min and the total analysis time to less than 100 min. Using bovine serum albumin and myoglobin as model proteins, optimization of key parameters such as digestion times and interfacing conditions between the different pretreatment steps was performed. The automated system was tested for the identification of infectious disease agents such as cholera toxin and staphylococcal enterotoxin B. This resulted typically in a positive identification by a total sequence coverage of approximately 40%.

Amino Acid Sequence↗
PubMed2004

Thin-layer chromatography of pitch and a petroleum vacuum residue. Relation between mobility and molecular size shown by size-exclusion chromatography.

A coal tar pitch and a petroleum vacuum residue have been separated by TLC using pyridine, acetonitrile, toluene and pentane to develop the chromatograms. The bands of material detected were recovered in 1-methyl-2-pyrrolidinone (NMP) solvent and examined by size-exclusion chromatography (SEC) in NMP eluent. The relation between elution time in SEC and mobility on the TLC plate indicated that molecular size increased steadily with increasing immobility on the plate. This relation was reinforced by UV fluorescence spectroscopy in that the fluorescence moved to longer wavelengths with increasing immobility. The molecular size of the material excluded from the porosity of the SEC column remains undefined; some excluded material was found in all of the fractions from both samples. The valley of zero intensity separating the retained material from the excluded material may suggest a change of structure from near-planar in the retained region to three-dimensional in the excluded region.

Chromatography, Gel↗
PubMed2004

Comparison between high-performance liquid chromatography and gas chromatography methods for fatty acid identification and quantification in potato crisps.

A reversed-phase high performance liquid chromatographic (RP-HLPC) method was compared with a gas chromatography-flame ionization detection (GC-FID) method for determining fatty acids in potato crisps. Different extraction procedures were used. Fatty acids were quantified by linear regression. Both methods presented good precision (R.S.D. < or = 5.88%) and recovery (> or = 82.31%). The precision using HPLC method was slightly better than for GC-FID method. There was good agreement between the fatty acid composition of potato crisps analysed by both methods. For most purposes the HPLC method would be better. However, when more fatty acids need to be analysed, GC is a more suitable method.

Chromatography, Gas↗
PubMed2004

Rapid determination of benzo(a)pyrene in olive oil samples with solid-phase extraction and low-pressure, wide-bore gas chromatography-mass spectrometry and fast liquid chromatography with fluorescence detection.

Benzo(a)pyrene (B(a)P) was extracted from olive oil using solid-phase extraction on columns filled with Florisil and Nucleoprep C18. The extracts were analyzed with GC-MS, using standard capillary column and low-pressure wide-bore column (LP-GC-MS), as well as with HPLC on standard column and short donor-acceptor complex chromatography (DACC) column. Quantitation was done with isotope dilution method (GC-MS and LP-GC-MS) or with internal standard benzo(k)fluoranthene (HPLC). Limits of detection were 1 ng/g for GC-MS on standard column, 1.6 ng/g on LP-column, 0.5 ng/g for HPLC on standard column, and 0.3 ng/g on DACC column, respectively. The applied extraction method allowed handling over 50 samples per day and assured recovery over 80%. Matrix solid-phase dispersion, tried as an alternative isolation method, appeared less advantageous. Fast chromatographic methods (LP-GC-MS and HPLC on DACC) made it possible to reduce analysis time to 8 and 5 min, respectively. The method was applied to routine analysis of B(a)P in olive oil samples.

Benzo(a)pyrene↗
PubMed2004

On-line reversed-phase liquid chromatography-gas chromatography coupled to mass spectrometry for enantiomeric analysis of chiral compounds in fruit beverages.

A method based on the on-line coupling of reversed phase liquid chromatography with gas chromatography/mass spectrometry (RPLC-GC-MS) for the chiral evaluation of characteristic constituents of fruit beverage aroma was investigated. The consideration of a variety of parameters involved in the transfer step allowed to achieve relative standard deviations ranging from 0.4 to 10% in most cases and detection limits from 0.2 to 2.5 mg/l. By applying the developed method to fruit beverages, racemic mixtures of ethyl 2-methylbutanoate and gamma-nonalactone were found. This fact suggests the eventual addition of artificial aromas. The method proposed in the present work can be useful to assess reliably the authenticity of aqueous samples, such as fruit beverages.

Beverages↗
PubMed2005

On-line identification of sugarcane (Saccharum officinarum L.) methoxyflavones by liquid chromatography-UV detection using post-column derivatization and liquid chromatography-mass spectrometry.

Sugarcane (Saccharum officinarum L., Gramineae) bagasse and leaves were investigated for their flavonoid content and transgenic sugarcane ("Bowman-Birk" and "Kunitz") was compared with non-modified ("control") plants. Analyses were carried out by high-performance liquid chromatography coupled to diode array UV detection (LC/UV), also using post-column addition of shift reagents, and tandem MS (atmospheric pressure chemical ionization-MS/MS and collision-induced dissociation-MS). On-line UV and MS data demonstrated the presence of methoxyflavone glycosides and aglycones in a total of seven compounds. Three naturally occurring flavones glycosides and two unusual erythro- and threo-diastereoisomeric flavolignan 7-O-glucosides were identified together with their aglycones.

Chromatography, High Pressure Liquid↗
PubMed2005

Integration of supercritical fluid chromatography into drug discovery as a routine support tool. II. investigation and evaluation of supercritical fluid chromatography for achiral batch purification.

Supercritical fluid chromatography (SFC) has recently been implemented within our analytical technologies department as a purity assessment and purification tool to complement HPLC for isomer and chiral separations. This report extends the previous work to achiral analysis and purification. This internal evaluation explores the potential impact SFC can have on high throughput, batch purification. Achiral methods have been optimised and batches of compounds purified using a retention time mapping strategy. Here the preparative retention time is predicted from a standard calibration curve and fraction windows set to ensure the peak of interest is collected in one of the four available fraction positions. In this contribution, a completely indirect scale up strategy is applied using totally independent analytical and preparative methods. This novel approach allows for fast analytical purity analysis without compromising the ability to scale up to the preparative system. The benefits and limitations of SFC for batch purification are described in comparison to HPLC across a set of standard compounds and a set of 90 research compounds.

Chromatography, High Pressure Liquid↗
PubMed2005

Comparative study of the enantioselective separation of several antiulcer drugs by high-performance liquid chromatography and supercritical fluid chromatography.

A comparative study of the enantiomeric separation of several antiulcer drugs such as omeprazole, lansoprazole, rabeprazole and pantoprazole using HPLC and supercritical fluid chromatography (SFC) on the Chrialpak AD column is presented in this work. The results show that employing the above mentioned column only two compounds (omeprazole and pantoprazole) could be enantiomerically resolved using HPLC, on the contrary SFC allowed the enantiomeric separation of all the compounds studied with higher resolutions and lower analysis times.

2-Propanol↗
PubMed2004

Urinary screening for methylphenidate (Ritalin) abuse: a comparison of liquid chromatography-tandem mass spectrometry, gas chromatography-mass spectrometry, and immunoassay methods.

OBJECTIVE: To develop a routine method for detecting methylphenidate (Ritalin) use among drug abusers using liquid chromatography-tandem mass spectrometry (LC/MS/MS). The new methodology was designed to replace less reliable and/or more expensive and time-consuming techniques (GC/MS and ELISA) currently employed in our laboratory, and to provide a combined one-step screening and confirmation LC/MS/MS method. DESIGN AND METHODS: Because methylphenidate abuse is very prevalent in Saskatchewan, there is a demand to provide high volume urine screening both to detect abuse, and to monitor compliance. Random urine samples sent for drugs of abuse testing, standards, and controls were diluted 1:100 in methanol. Diluted specimens were injected directly into an Agilent 1100 liquid chromatograph coupled to a Sciex API 2000 mass spectrometer. The method utilized selected reaction monitoring (SRM) as well as an electrospray ionization source (EIS) to detect both urinary methylphenidate and the more prevalent metabolite, ritalinic acid (RA). RESULTS: There appeared to be little or no sacrifice in sensitivity because the higher dilutions exhibited much less matrix effect. Limit of quantitation (LOQ) for methylphenidate was 100 nM and 500 nM for RA. Linear calibration curves from 100 to 1000 nM for Ritalin and 500 to 5000 nM for RA were acquired. Imprecision of spiked and true specimens did not exceed 10% and at the LOQ, it was less than 20%. CONCLUSIONS: A rapid, sensitive, reliable, and highly specific method by LC/MS/MS for detecting methylphenidate and its metabolite, RA, were developed. Both the cost and performance of the LC/MS/MS method were superior to GC/MS or ELISA, and it allows use of a single rapid procedure for both screening and confirmation.

Chromatography, Liquid↗
PubMed2006

Determination of plasma thiol bound to albumin using affinity chromatography and high-performance liquid chromatography with fluorescence detection: ratio of cysteinyl albumin as a possible biomarker of oxidative stress.

We examined the influence of oxidative stress on the relative amounts of various albumin-bound thiols in human plasma. To determine the ratio of thiols existing as mixed disulfides following oxidation, we developed a method combining fast purification of albumin using affinity columns and high-performance liquid chromatography (HPLC) with fluorescence detection for low molecular weight thiols which were labeled after reduction. When the effect of exposure of plasma to radical oxygen species on binding of thiols to albumin was determined by the present method, significant increases in the ratio of cysteine bound to albumin (Alb-Cys) to total cysteine were clearly demonstrated.

Adult↗