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At least 937 records · Page 52Linked to original sources
PubMed1987

High-performance liquid chromatographic assay of fenflumizole and its demethyl metabolites in biological samples.

This paper describes sensitive, selective and precise methods for the assay of fenflumizole and its chromatographically verified demethyl and didemethyl metabolites in whole blood, isolated red blood cells, plasma, saliva, urine and tissue (skin and fat) from human subjects. Also conjugates of the two metabolites with glucuronic acid and sulphate were assayable. The compounds were quantitated by means of reversed-phase liquid chromatography after diethyl ether extraction, followed by fluorescence and/or electrochemical detection. The assay using fluorescence detection is quantitative down to ca. 150 pg/ml; with electrochemistry this limit was ca. 600 pg/ml and included the demethyl metabolites only. Proteinaceous materials show an extraction yield of 70-75%, whereas analytes in sample materials without proteins show yields of better than 95%. The precision at concentration levels of ca. 50 ng/ml for the parent compound and ca. 5 ng/ml for the metabolites is at most 6% (relative standard deviation) with both detection modes. The analytical procedures developed were applied after both single and repetitive administration of fenflumizole. The administration of 14C-labelled fenflumizole in the single-dose study revealed the presence in plasma and urine of as yet unknown metabolites. The in vivo retention time of 14C activity was substantially greater in the blood cells than in plasma. Measurements of 14C activity in excreta demonstrated that excretion via the faeces is the preferred route.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1987

High-performance liquid chromatographic quantitation of triacylglycerols containing fenoprofen from biological samples.

A normal-phase high-performance liquid chromatographic (HPLC) method has been developed for the quantitation of radiolabelled triacylglycerols containing fenoprofen, synthesized from [3H]glycerol by isolated hepatocytes and adipocytes. The assay consists of extracting the lipids into diethyl ether, separating triacylglycerols from polar endogenous lipids using silica Sep-Pak cartridges and quantitating endogenous triacylglycerols and triacylglycerols containing fenoprofen by HPLC resolution and scintillation counting. HPLC separation is achieved in less than 10 min. Using [14C]tripalmitin as internal standard the assay has a linear relationship between added triacylglycerol and measured endogenous triacylglycerols and triacylglycerols containing fenoprofen with regression coefficients of 0.997 and 0.998, respectively.

Animals↗
PubMed1987

Determination of cefixime in biological samples by reversed-phase high-performance liquid chromatography.

A simple, accurate and precise isocratic reversed-phase high-performance liquid chromatographic method has been developed and validated for the determination of a new cephalosporin in human serum and urine. Human serum samples, calibration standards and quality control samples (250 microliter) were combined with an equal volume of 6% trichloroacetic acid (TCA). Human urine (0.1 ml) was combined with 6% TCA solution containing the internal standard. The compounds were detected by ultraviolet absorbance set to 280 nm for the serum assay and 313 nm for the urine assay. The method for the determination of cefixime in serum was linear from 100 ng/ml to 30.0 micrograms/ml (r = 0.999), and for the urine assay from 5 micrograms/ml to 100 micrograms/ml (r = 0.999). The minimum reportable quantity for the serum assay was 0.05 microgram/ml. The within- and between-day assay variation for both assays were found to be less than 10% in an extensive assay validation scheme. Results of a storage stability study indicated that human serum and urine samples could be safely stored for up to six months at -18 degrees C and three months at -10 degrees C, respectively.

Cefixime↗
PubMed1987

Sensitive and selective determination of picogram amounts of ciprofloxacin and its metabolites in biological samples using high-performance liquid chromatography and photothermal post-column derivatization.

An analytical method for the detection and quantification of ciprofloxacin and its known metabolites M1, M2, M3 and M4 in urine, serum/plasma, bile, faeces and tissue is described. For the liquid matrices the only sample preparation that is required is dilution. The assay consists of reversed-phase high-performance liquid chromatography and fluorescence detection. For the metabolites M2, M3 and M4 an additional post-column derivatization by successive thermolysis and photolysis is needed. A suitable simple post-column reactor has been constructed. Detection limits for all compounds are between 0.2 and 2.2 ng/ml (absolute detection limits 2-22 pg). Compared with fluorescence detection alone, the derivatization increases the selectivity of detection significantly. The linearity, precision and accuracy of the method were determined.

Bile↗
PubMed1988

Determination of coenzyme Q10, alpha-tocopherol and cholesterol in biological samples by coupled-column liquid chromatography with coulometric and ultraviolet detection.

Coenzyme (Co) Q10, Co Q10H2, alpha-tocopherol and cholesterol were dissociated from lipoproteins in plasma by treatment with 1-propanol. The supernatant obtained was injected directly for determination of Co Q10 and Co Q10H2. Precolumn reduction with borohydride was used for determination of total Co Q10 simultaneously with alpha-tocopherol and cholesterol. Total Co Q10 in freeze-dried myocardial biopsies was determined after extraction with 1-propanol and oxidation of Co Q10H2 with ferric chloride. The chromatographic system comprised two reversed-phase columns and a three-electrode coulometric detector and a UV detector coupled in series. A pre-fractionation on the first column protected the coulometric detector from contamination and reduced the time for analysis by eliminating strongly retained solutes. The coulometric electrodes were operated in the oxidation-reduction-oxidation mode, and the last electrode was used for detection of alpha-tocopherol, Co Q10 and Co Q10H2, while cholesterol was detected by UV at 215 nm. The fast isolation procedure made it possible to determine the reduced and oxidized forms of Co Q10 in plasma. Quantitative recoveries were obtained for all the analytes studied and normal levels were determined with a coefficient of variation of 2-3%.

Cholesterol↗
PubMed1991

High-performance liquid chromatographic analysis of 2',3'-dideoxyinosine in biological samples.

A high-performance liquid chromatographic analysis for the anti-AIDS drug 2',3'-dideoxyinosine (ddI) in rat plasma and urine, with a limit of detection of 0.2 microgram/ml and requiring a sample size of 100 microliters is described. Diluted plasma or urine samples were extracted using a C18 solid-phase extraction column. Retention of ddI on more polar solid-phase extraction columns was insufficient for sample clean-up. This method is useful for pharmacokinetic studies of ddI in small rodents.

Animals↗
PubMed1991

Sanguinarine levels in biological samples by high-performance liquid chromatography.

A high-performance liquid chromatographic method is presented for the analysis of the benzophenanthridine alkaloid, sanguinarine, found in plant extracts. The method is demonstrated to be applicable to analyzing samples such as saliva and gingival crevicular fluid for sanguinarine following a simple acidified methanolic extraction step. The method utilizes an ethyl silane column with acidic and basic ion-pairing reagents in the mobile phase with a limit of detection of 3 ng of sanguinarine in a sample.

Alkaloids↗
PubMed1992

Determination of free N-acetylamino acids in biological samples and N-terminal acetylamino acids of proteins.

N-Acetylamino acids were derivatized with 9-anthryldiazomethane to the corresponding esters. The anthryl esters were separated by high-performance liquid chromatography and detected fluorimetrically (excitation at 365 nm; fluorescence emission measured at 412 nm). N-Acetyl derivatives of Asn, Gln, Ser, Thr, Gly, Ala, Tyr, Pro, Met, Val, Ile and Leu as well as N-formyl-Met could be separated and identified in the same chromatographic run. The detection limit was from 0.10 pmol for AcGln to 5.5 pmol for AcIle and AcLeu. When the acetylamino acids listed above were added to the 700 g supernatant of a rat liver homogenate, the mean recovery was 72%. AcAla and AcTyr were found in free form in baker's yeast. Proteins with an acetylated N-terminus were digested by a protease, and the peptides formed were treated with an N-acylamino acid-releasing enzyme. This method was applied to end-group determination of four proteins (each 0.5 nmol).

Acetamides↗
PubMed1992

Trace quantitation of 4-hydroxy-2-nonenal in biological samples as its oxime-bis-tert.-butyldimethylsilyl derivative using 3-hydroxynonanal as an internal standard.

A gas chromatographic-mass spectrometric method for the determination of the lipid aldehyde 4-hydroxy-2-nonenal (4HNE) in trace quantities is described. The method utilizes the reaction of aldehydes with hydroxylamine leading to the formation of the oxime derivative. The aldehydes are recovered by octadecylsilyl solid-phase extraction and converted to the bis-tert.-butyldimethylsilyl derivatives for analysis using electron ionization. A novel 4HNE analogue, 3-hydroxynonanal, has been synthesized and is used as an internal standard. A limit of detection of approximately 1 pmol of 4 HNE in preparations of approximately 2.10(6) cells or 0.5 ml of whole blood, plasma or serum was observed. Standard addition analysis indicates that the method is accurate at these levels. Replicate analysis of the National Institutes of Standards and Technology Standard Reference Material SRM 909 indicates an average in-run precision of 8.1% and a between-run precision of 13.5% at an average concentration of 82.1 pmol/ml of reconstituted material.

Aldehydes↗
PubMed1992

Simple and sensitive determination of diacetyl and acetoin in biological samples and alcoholic drinks by gas chromatography with electron-capture detection.

Acetoin was quantitatively oxidized into diacetyl by Fe3+ in 1 M perchloric acid. The reaction of diacetyl with 4,5-dichloro-1,2-diaminobenzene afforded 6,7-dichloro-2,3-dimethylquinoxaline (DCDMQ), which was extracted by benzene containing aldrin (25 ng/ml) as an internal standard, and determined by gas chromatography with electron-capture detection. The method is very simple and sensitive. The detection limit of DCDMQ (either diacetyl or acetoin) was 10 fmol/microliters of the benzene extract, and the determination limit of DCDMQ (either diacetyl or acetoin) was 50 fmol/microliters of the extract. Both acetoin and diacetyl could be determined in 0.1 ml of normal human urine or blood, and both were found in rat liver, kidney and brain. The method was also applied to the determination of acetoin and diacetyl in alcoholic drinks.

Acetoin↗
PubMed1992

Determination of D-alanine and D-glutamic acid in biological samples by coupled-column chromatography using beta-cyclodextrin as mobile phase additive.

A high-performance liquid chromatographic assay for monitoring traces of D-alanine and D-glutamic acid in peptide and protein hydrolysates is presented, which uses a two-column set-up with column switching. The main advantage of the proposed method is the higher reliability of the results, compared with the analysis by derivatization and single-column chromatography of the diastereomers. A non-chiral alkyl-silica reversed-phase column is combined with a second column, in which beta-cyclodextrin is used as a chiral mobile phase additive. The amino acids of the hydrolysate are dansylated, and the amino acid of interest is separated from the others on the first column and transferred to the second column where chiral resolution is performed. The transfer volume of ca. 200 microliters is small enough not to cause any peak distortion or dilation in the second column.

Alanine↗
PubMed1992

Evaluation of 2-(2-thiophenecarboxy)benzoic acid and related active metabolites in biological samples.

This paper describes a quantitative assay of 2-(2-thiophenecarboxy)benzoic acid and its systemic metabolites, namely salicylic acid and thiophenecarboxylic acid, by high-performance liquid chromatography with ultraviolet detection at 254 nm. Analytes were extracted from acidified samples with tert.-butylmethyl ether and separated with an RP-18 column (150 mm x 3 mm I.D., 5 microns particle size) with a mixture of 0.01 M potassium phosphate and methanol (70:30, v/v) at pH 3.1. The method proved to have the validation required for pharmacokinetic investigations in animals and humans.

Animals↗
PubMed1992

Methods for chromatographic determination of amanitins and related toxins in biological samples.

Methods for the chromatographic determination of amanitins, toxins of Amanita phalloides (Fr.), Link mushrooms and related toxins are reviewed; particular emphasis is given to high-performance liquid chromatographic methods. The main chemical and toxicological aspects are discussed, but the focus of the present review is on the analytical problems arising in a laboratory charged with the setting up of a procedure which can direct the appropriate clinical management of an intoxicated patient or solve a forensic case.

Amanita↗