摘要:

An automated reverse phase high performance liquid chromatography (HPLC)—photodiode array method using a multi linear gradient elution is described for the simultaneous analysis of nine xanthines: xanthine, 7-methylxanthine, 3-methylxanthine, 1-methylxanthine, isocaffeine, theobromine, paraxanthine, theophylline and caffeine. The separation method development was based on mobile-phase optimisation and off-line solid-phase extraction (SPE) from human biological fluids: blood serum and urine. Eluent consisted of 0.05 M CH3COONH4and methanol (90:10 v/v) changing to (70:30 v/v) over a period of 20 min. Identification of xanthines was achieved by photodiode—array detector and quantitation was performed at 270 nm. Isocaffeine was used as internal standard at a concentration of 3.06 ng/μL. High extraction recoveries were achieved from Merck RP-18 cartridges using 1% hydrochloric acid as eluent, requiring small volumes, 40 μL of blood serum and 100 μL of urine.

ISSN:1082-6076    

DOI:10.1080/10826079608014038

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Four reversed phases were tested in RPLC of newly synthesized diphenylmethane derivatives. Non-deactivated Kromasil C-8 and Beckman C-18 and deactivated Supelco LC-8-DB and Supelco LC-18-DB reversed phases were evaluated. Column supplier, deactivation and the presence of amine modifier (triethylamine, TEA) were used as variables and capacity factors (k) and asymmetry factors (As) were measured. Two different mobile phase systems were used: Acetonitrile: ammonium acetate (0.1 M) and methanol: potassium dihydrogen phosphate (0.02 M). According to the results of this comparative study, non-deactivated Kromasil C-8 and Beckman C-18 were found to be the most suitable phases for our applications e.g., synthesis purity and lipophilicity studies concerning antihistamine-like compounds. For most of the compounds involved in this study, the use of these phases requires TEA as an amine modifier. Addition of the amine also made it possible to use the deactivated phases, e.g., Supelco C-8 and C-18 columns. The RPLC method was used to evaluate the lipophilicity of some DPPE derivatives, compared to known antihistaminergics.

ISSN:1082-6076    

DOI:10.1080/10826079608014039

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The quantitative determination of pregnenolone in rat brain was done using reverse phase high performance liquid chromatography with fluorescence detection and the internal standard method. The desired fraction was obtained from a rat brain with the combined use of a Bond Elut C8 cartridge for the solid-phase extraction and a lipophilic gel (piperidino-hydroxypropyl Sephadex LH-20) for the ion-exchange chromatography. The fraction was derivatized with 1-anthroyl cyanide followed by purification with 2 successive silica gel columns to remove the excess or decomposed reagent. Separation of the compounds was performed on a J'sphere ODS-L80 column and the calibration graph was linear from 10 to 60 ng/tube (ca. 1 g tissue of brain). The method was applied to the determination of pregnenolone in rat brains of Wistar and Sprague-Dawley strains, most of which showed much lower amounts than that previously reported.

ISSN:1082-6076    

DOI:10.1080/10826079608014040

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A method for the determination of teflubenzuron and Diflubenzuron in fish tissues by HPLC is presented. The samples were extracted with acetone—tetrahydrofuran. Employing traditional liquid-liquid extraction and using a Si and C8solid phase extraction column, a clean extract was obtained. The lower limit of quantification for teflubenzuron was 20 ng/g (mL) for muscle, liver and plasma and for diflubenzuron in muscle and liver, the limit of quantification was 25 ng/g.

ISSN:1082-6076    

DOI:10.1080/10826079608014041

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The organic acids quinic, malic, shikimic and citric were separated on a packed reverse phase fused-silica capillary column using 0.01 M K2HPO4/H3PO4at pH 2.7 as eluent at a flow rate of 2 μL/min, and determined with UV detection. Conventional liquid chromatographicequipment was adapted for such purposes.

ISSN:1082-6076    

DOI:10.1080/10826079608014042

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A rapid and selective high performance liquid chromatography method for the simultaneous quantification of zopiclone and zolpidem has been developed. Signals are monitored by a photodiode-array detector with a main 305 nm wavelength and a bandwidth of 10 nm. After one step liquid phase extraction, samples of 100 μL are injected into a 5 μm ODS-2 column (30 cm × 4.6 mm I.D.). Drugs are eluted with a mobile phase containing potassium dihydrogen phosphate buffer, 0.01 M, methanol and tetrahydrofuran (30: 65: 5, V/V/V). Retention times of zopiclone and zolpidem are, respectively, 4.5 min and 5.5 min. The procedure has the necessary sensitivity and precision for pharmacokinetic studies (within day coefficients of variation < 7.1% and between-day coefficients of variation < 12.1%). The linearity and the rapidity of this method are especially attractive for toxicological quantification in emergency toxicology.

ISSN:1082-6076    

DOI:10.1080/10826079608014043

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A dynamic chiral stationary phase (CSP 7) for resolving racemic α-amino acids have been prepared by hydrophobically loading (S)-N,N-carboxymethyl dodecyl leucinol monosodium salt onto a commercial reverse phase octadecyl silica gel column. CSP 7 was successfully employed in resolving various racemic α-amino acids. The chromatographic results for resolving various racemic α-amino acids on CSP 7 have been found to be generally better as expected from the chiral recognition model proposed than those on the previously reported dynamic CSP (2), (R)-N,N-carboxymethyl dodecyl alaninol monosodium salt which is hydrophobically bound onto a commercial reverse phase octadecyl silica gel column. Especially, CSP 7 seems to be more attractive than CSP 2 in that CSP 7 shows reasonably good resolving ability for the broad range of racemic α-amino acids at the high content of organic modifier (20% CH3CN) in the aqueous mobile phase while CSP 2 shows very poor resolving ability.

ISSN:1082-6076    

DOI:10.1080/10826079608014044

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A simple liquid chromatographic method was developed to study the pharmacokinetics of scoparone in the rat plasma. After addition of an internal standard (ferulic acid), plasma was deproteinized by acetonitrile for sample clean-up. The drugs were separated on a reverse phase column and detected by UV detection at a wavelength 340 nm. Acetonitrile-water (30:70, v/v, pH 2.5 adjusted by orthophosphoric acid) was used as a mobile phase. It was applied to the pharmacokinetic study of scoparone in rats after a dose of 5 mg kg−1intravenous administration. A biphasic phenomenon with a rapid distribution followed by a slower elimination phase was observed from the plasma concentration-time curve.

ISSN:1082-6076    

DOI:10.1080/10826079608014045

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A high-performance liquid chromatographic method is described for the determination of mitomycin C (MMC) in rabbit ocular tissues. The optimial conditions were 20 mM sodium phosphate buffer, pH 7.0—methanol (70:30) in isocratic elution (flow rate lmL/min). The detection limit of MMC of this method is 0.02 μg/g for conjunctive and sciera or 0.02 μg/mL for aqueous humor. The effect of pH value and temperature on the stability of MMC was investigated. Acetonitrile was used for extracting MMC from conjunctiva and sclera, and ethyl acetate for aqueous humor. Recoveries ranged from 49% to 92% over a wide range of concentrations (0.1–400 μg/g). The half-life of MMC, after cellulose sponge administration, is 0.58 hours for the conjunctiva and 0.45 hours for the sclera. The peak concentration of MMC in aqueous humor is 1 hour.

ISSN:1082-6076    

DOI:10.1080/10826079608014046

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A highly sensitive and selective HPLC-MS-MS method was developed for the determination of terfenadine in human plasma. The analytes, terfenadine and terfenadine related compound A (internal standard), were extracted from human plasma by methyl t-butyl ether/methylene chloride/n-butyl chloride (3:2:1). The organic solvent is evaporated to dryness and reconstituted in 100 μL of acetonitrile/0.02 M ammonium acetate buffer pH 3.5 (50:50). Chromatographic separation is achieved on a TSK. gel ODS-80TScolumn with a mobile phase composed of acetonitrile/1% formic acid/0.01 M ammonium acetate pH 4.0 (85:13:2). The analytes were detected by HPLC in conjunction with electrospray tandem mass spectrometry. The assay was linear in the concentration ranges of 0.2 to 50 ng/mL. The analysis of pooled quality controls demonstrated excellent precision with relative standard deviations being less than 5.2%. The method is accurate with all intraday and over-all mean values being less than 5.3% from theoretical.

ISSN:1082-6076    

DOI:10.1080/10826079608014047

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor