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71.
Summary A reversed phase liquid chromatographic method is proposed for the analysis of basic hair dyes (raw materials and colourant formulations). The performance of the method was enhanced by introducing post-column on-line photochemical derivatisation in combination with a Diode Array Detector. On-line photoderivatisation provided an effective way of selectively transforming the analytes to compounds with different spectral properties. For each analyte two characteristic UV-Visible spectra (photoreactor on and off) were obtained with the same mobile phase and this information in combination with the chromatographic data (k' at pH 3.0 and 4.5) enabled the unambiguous identification of both commonly used, approved, and banned basic hair dyes. Additionally, this approach was found useful to improve the method sensitivity, allowing the determination of analytes present in low concentration (0.03%) in complex commercial formulations.This work constitutes part of the thesis for the Dottorato di Ricerche of Roberto Gotti. 相似文献
72.
Summary Styrosorb is a beaded microporous polystyrene with particle sizes between 2 and 4 m. In spite of hypercrosslinkage the material was seen to swell in organic solvents. The native material is functionalized with Tris-groups at the outer surface of the particles. The average pore diameter was determined as 1.45±0.3 nm from size exclusion data using polystyrene and polyethylene standards in THF. The reversed phase behavior of the restricted access phase Styrosorb was investigated by injection of two test mixtures. Mixture I contained five aromatic amines, mixture II consisted of AmperozideR and four related compounds. The optimum range of mobile phase composition was assessed so that analytes were separated whilst any proteins present were eluted unretained. Due to the small particle size short columns of 29×4 mm can be used for both sample clean-up and analytical separation of AmperozideR and its metabolite. 相似文献
73.
Summary The aminoacid glutamine in aqueous solution and in conditions of high temperature and long term storage is partly transformed into pyroglutamic acid which exhibits potential neurotoxic effects.Commercially available aminoacid mixtures supplemented with glutamine are heat-sterilized and some losses of glutamine and formation of pyroglutamic acid may occur.The aim of the work was to set up an easy and reliable HPLC method which allows the determination of pyroglutamic acid as a degradation product of glutamine. The column was a 5 m Hypersil ODS (100×4.6 mm) and the mobile phase 100% 0.007 M phosphate buffer pH 3.5.Stability studies in different conditions of temperature and time of storage were performed on aminoacid mixture available in the commerce. 相似文献
74.
Summary The BIAcoreTM Biosensor System utilizes a detection principle known as Surface Plasmon Resonance (SPR) which, in simple terms, detects changes in the refractive index of a solution in contact with a gold film. The gold film is surface modified with carboxymethylated dextran to produce a hydrophillic matrix onto which macromolecules may be covalently immobilized. In this respect, the BIAcoreTM is similar to any other insoluble matrix, such as a chromatographic support. The SPR detection principle, however, allows one to directly visualize the interaction under study, in real time and without the need for reporter molecules such as enzyme-labels. In addition, the very small sample requirements, automated robotics unit and ease of data analysis suggest the potential use of the BIAcoreTM instrumentation for assay development and possibly process development, especially where bio-specific interactions such as immunoaffinity chromatography are used as a step in the process. In this report, we demonstrate the use of the BIAcoreTM SPR detector for the micro-scale determination of conditions for immunoaffinity chromatography of soluble complementreceptor 1, sCR1. 相似文献
75.
Summary We describe here a sensitive, selective and rapid method to quantitate plasma catecholamines, especially dopamine, using high-performance liquid chromatography with electrochemical detection. This method requires a 10-minute run time and has a threshold for detection of 2 picograms, (10pg/ml).A number of commonly employed mobile phases for catecholamine analysis have been tested and have failed to detect dopamine in biological samples. Neither acetonitrile (3–7%) or methanol, (5–8%) in the mobile phase has produced consistently interpretable data either due to inability to detect or interference from co-eluting substances. Optimal detection was achieved with a mobile phase containing sodium acetate (6.8g), citric acid (5.9g), EDTA (48mg), di-n-butylamine (270l), Na-1-octane sulfate (850mg), methanol (100 ml) (amounts refer to 1 liter aqueous solution) (pH 4.3). The mobile phase was passed through a Waters 5 resolve C18 column using a Waters 590 pump and m460 electrochemical detector and 740 data module, Flow rate was 0.9ml/min. Using this method, normal values in human and swine left ventricular myocardium and human and swine plasma have been established for norepinephrine, epinephrine, and dopamine. 相似文献
76.
Summary A sensitive and specific method for quantitation of the steroids betamethasone, prednisolone and cortisone acetate commonly used as adulterants in locally produced herb extracts and in certain homeopathic drugs is described. Reverse-phase liquid chromatography with UV detection has been used. 相似文献
77.
Summary A fully integrated chromatographic system was developed for the determination of leukotrienes in biological samples using
photodiode-array detection (PDAD), which eliminates time consuming manual sample handling steps. A special solid phase extraction,
(SPE) methodology for leucotriene metabolite stability was developed which increased the recoveries and eliminates the contamination
risk of biological samples. The inherent instability (autooxidation) of many of the leukotriene mediators, and the adsorption
effects onto exposed surfaces in vials and in the chromatographic system were found to be very important parameters to control
in order to circumvent high loss of sample analytes. By binding the cell supernatants to the functionalities of the SPE support
stabilised these mediators. Cell culture samples were eluted through a disposable C18 SPE column. The SPE columns were allowed to thaw and deposited in an automated sample handling unit (ASPEC XL). Desorption
of the analytes was followed by a second on-line SPE step, to eliminate remaining interfering matrix compounds. Typical recoveries
when stored at −70°C were in-between 55–97% except for (LTE4) which was found to be around 40% after 72 days of storage. Seven reversed-phase packings were studied. Selectivity factors,
as well as the separation efficiencies, were found to differ for the various C18 bonded silica stationary phases. This integrated on-line column liquid chromatographic system was applied to the determination
of leukotriene B4, leukotriene C4, leukotriene D4, leukotriene and E4 in human cell extracts using prostaglandin B2 as the internal standard. More than 1500 biological samples were analysed. Some validation data are presented for unattended
operations. 相似文献
78.
Composition and hydrolysis products of a biotechnical available complex of macrolides were analyzed by HPLC and ESI-CID-MSn. Major components are leucomycin-type antibiotics (leucomycins A1 (5), A7 (3), A9 (2), 9-desoxy-9-oxo-turimycin H3 (4) and niddamycin B (6). Hydrolysis of the complex mixture yielded 9-, 13-isoforocidins (7, 8, 9, 11) and 9-oxo-forocidin (10). A preparative separation procedure was elaborated furnishing compounds 3 - 11 for semisynthetic experiments.Prof. Dr. Udo Gräfe deceased on 14.2.2003. For obituarity see: Schlegel B (2003) J Peptide Sci 9: 661–661. 相似文献
79.
The potential of micellar electrokinetic capillary chromatography (MEKC) with UV-detection for the simultaneous determination of various selected pesticides in water samples was investigated. The developed method using solid-phase extraction showed high efficiency and good resolution with detection limits in the 0.2 to 0.5 ppm range. Comparison of several SPE cartridges demonstrates their suitability for the extraction of pesticides with different hydrophobicity achieving 5000-fold enrichment. The described method involving SPE procedure and MEKC separation enables the successful determination of a wide spectrum of pesticides in water in the range of maximum residue limits (MRLs). 相似文献
80.
Predicting the selectivity of imprinted polymers 总被引:2,自引:0,他引:2
Summary Imprinted polymers as stationary phases for HPLC separations have been the subject of extensive investigations in recent years.
In order to aid the rational design of synthetic protocols for the preparation of imprinted polymers, a series of calculations
were made to assess the equilibrium concentration of templatemonomer complexes as a function of association constant (K) for the functional groups involved in the interactions and initial concentrations of reactants. This data was then used
to predict the selectivity of polymers prepared under different reaction conditions and the model was tested using an experimentally
determined value ofK and separation factors taken from the literature. 相似文献