摘要:

4-[(5,6,7,8-Tetrahydro-5,5,8,8-tetramethyl-2-naphthyl)-carbamoyl] benzoic acid (Am-80) is a novel retinobenzoic acid derivative possessing retinoid activity. Plasma concentration of this drug in clinical use is very low, less than 1 ng/ml, and could not be measured with direct immunoassays. A combination of high-performance liquid chromatography (HPLC) and radioimmunoassay (RIA) was developed for this drug in human plasma. Am-80 in 0.5 ml of human plasma was extracted by solid-phase extraction, and the extract was purified by reversed-phase HPLC. The immunoreactivity in the fraction of the eluate was measured by competitive RIA. The within- and between-assay variances were 4.1 to 15.5% and 4.1 to 7.0%, respectively. The limit of quantification was 0.04 ng/ml in human plasma, which was much lower than that of direct RIA, 0.6 ng/ml, previously reported. This assay system could be used to observe the pharmacokinetics of Am-80 in human even after dermal application at very low dose.

ISSN:0003-2719    

DOI:10.1080/00032719608001488

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Unauthorized steroids were administered to volunteers and the presence of anabolic steroids in urine samples were directly confirmed by electrospray ionization mass spectrometry without using the prerequisite steps of enzymatic hydrolysis and trimethyl-chlorosilane derivatization. Further structure determination has been conducted by collisionally induced dissociation in a triple quadrupole tandem mass spectrometer. Overall, the electrospray ionization and tandem mass spectrometry methods prove to be simple, fast and sensitive for the analysis of anabolic steroids in urine samples.

ISSN:0003-2719    

DOI:10.1080/00032719608001489

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The pyridine antihistamines carbinoxamine maleate and doxylamine succinate were derivatized by hydrolysis with cyanogen bromide and coupling with aniline to form a polymethine dye, and determined by colorimetry. In a micellar cationic medium ofN-cetylpyridinium chloride (NCPC), the reaction times were reduced and the sensitivities improved. In 0.1 M NCPC the apparent molar absorptivities of the derivatives were 5,900 and 3,500 M−1cm−1, and the limits of detection (as 3s) were 8.6x10−7M and 1.7x106M, for carbinoxamine and doxylamine, respectively. The sensitivity was enhanced in a three- to six-fold factor with respect to a non-micellar medium. The reproducibility was 0.8% for 1.6x10−4M carbinoxamine, and 1.8% for 1.3x10−4M doxylamine. The procedure was applied to the evaluation of the drugs in pharmaceutical preparations.

ISSN:0003-2719    

DOI:10.1080/00032719608001490

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The paper reviews recent studies on the effect of addition of Ni(II) in the cathodic stripping voltammetry of the following compounds: cysteine, penicillamine, cystine, glutathione (either reduced or oxidised) and N-acetylcysteine. With the exception of N-acetylcysteine, the above compounds give a cathodic stripping peak at -0.6 V (vs. Ag/AgCl, 3 M KCl electrode) which is due to the catalytic reduction of nickel ion. Even in the case of the disulphides the actual catalyst is the thiol produced by the cleavage of the -S-S- bond during the accumulation step. The catalytic peak enables the detection of the analyte with a better selectivity than is obtained with the stripping peak due to the reduction of mercury thiolates. In addition, Ni(II) suppresses the mercury thiolate peak of ligands such as cysteine or penicillamine, but does not modify the behaviour of thiols with low complexing properties (such as N-acetylcysteine). Consequently, compounds such as cysteine and its N-acyl derivatives can be determined simultaneously by means of the catalytic peak and the mercury thiolate peak (at -0.4 V) respectively.

ISSN:0003-2719    

DOI:10.1080/00032719608001491

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A sensitive and selective voltammetric method of analysis is developed for determination of trace amounts of Cr(VI) ions in neutral nitrate phosphate media. This method is based on controlled adsorptive preconcentration of chromium species at Hanging Mercury Drop Electrode (HMDE). The adsorptive stripping response was evaluated with respect to preconcentration time and potential and dependence on composition of supporting electrolyte. As low as 5x10−9mol L−1(0.25 μg/L) and 1x109mol L−1(0.52 μg/L) Cr(VI) can be detected using Cathodic Linear Sweep Stripping Voltammetry (CLSSV) and Differential Pulse Cathodic Stripping Voltammetry (DPCSV), respectively. The precision of the method is satisfactory with a relative deviation of 1.24% with ten experiments at the 0.52 μg 1−1Cr(VI) level. The effect of various cations, anions and surface active substances (SAS) in synthetic aqueous samples has been investigated.

ISSN:0003-2719    

DOI:10.1080/00032719608001492

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A flow-injection analysis (FIA) method for the determination of chlorophenoxyacid herbicides, based on photochemically induced fluorescence (PIF) detection, is described. PTFE tubing was helically coiled around a low-pressure mercury lamp located between the injection valve and the detector. Two analytical procedures are used, either continuous or stopped-flow mode, according to the photochemical behaviour of the analyte. Ultraviolet (UV) photolysis in a 50 % (v/v) MeOH/pH 5 buffer solution provoked a more or less marked increase of the fluorescence signal depending of the herbicide structure. In the stopped-flow mode, UV irradiation times ranged between 90 sec and 12 min. Linear dynamic graphs were established over a concentration range of nearly two orders of magnitude. The FIA-PIF limits of detection ranged from 23 to 98 ng/ml, according to the compound. Relative standard deviations were between 0.7 and 2.7%. The proposed method has been applied to determine these herbicides in spiked river water samples, with mean recoveries ranging from 96 to 108%. It shows the usefulness of this technique for chlorophenoxyacid herbicides analysis.

ISSN:0003-2719    

DOI:10.1080/00032719608001493

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

ISSN:0003-2719    

DOI:10.1080/00032719608001477

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor