摘要:

Identification of the molecular species of phosphatidylcholines (PCs) is important for studies of lipid metabolism and the structure of cell membranes. The high performance liquid chromatography (HPLC) separations of the intact molecular species of PCs used earlier were mostly on reversed-phase C18(octadecyl silica) columns, usually with isocratic elution. The eluent used contained a silanol suppressing agent. Volatile silanol suppressing agents are preferred for the purification of PCs because they can be removed from the HPLC fractions easily by nitrogen stream. They must be used when liquid chromatography-mass spectrometry (LC-MS) and evaporative light scattering detector (ELSD) are used because non-volatile silanol suppressing agents cause high background. For the identification of radioactive metabolites, using both the UV detector at 205 nm and radioactivity flow detector sequentially, we recommend the separation on a C8(octyl silica) column, eluted with a gradient of methanol-water containing conc. NH4OH as silanol suppressing agent.

ISSN:1082-6076    

DOI:10.1081/JLC-100101491

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The majority of chiral HPLC separations are performed in the normal-phase mode using alcohol-modified hexane mobile phases. Normal-phase chiral HPLC methods are not routinely coupled with electrospray ionization mass spectrometry (ESI-MS) because of the mobile phase incompatibility. In this study, we investigated the use of ESI-MS compatible mobile phases for chiral HPLC methods. This would enable the sensitivity and selectivity of LC/MS to be applied to chiral HPLC analyses.

ISSN:1082-6076    

DOI:10.1081/JLC-100101492

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The separation of oxybutynin enantiomers (racemic mixture of two enantiomers) was studied on an ovomucoid column. The optimized chiral separation baseline resolved the enantiomers in less than 10 minutes. Chromatographic variables that were found to have an effect on the chiral separation were studied and include: mobile phase pH, mobile phase ionic strength, type and concentration of organic modifier added to the mobile phase, column temperature, and the amount of analyte injected.

ISSN:1082-6076    

DOI:10.1081/JLC-100101493

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Chromatographic RMwand log k'wparameters have been used as alternatives to the shake flask n-octanol/water partition coefficient method to study the lipophilic character of several known pyrimidinic nucleoside derivatives and two novel ones. The RMand log k' values were measured by means of reversed-phase thin-layer chromatography (RP-TLC) and reversed-phase high performance liquid chromatography (RP-HPLC) respectively. Good linear relationships were observed between log P values obtained from the classical shake flask method (log Po/w) and each one of those obtained by chromatographic techniques (log PRP-TLCand log PRP-HPLC) and by theoretical calculations using the CLOGP program (log PCLOGP). The RMwand log k'wvalues have proven to be reliable parameters for describing the lipophilic properties of this family of compounds.

ISSN:1082-6076    

DOI:10.1081/JLC-100101494

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The fundamental chemical interactions governing the retention of 15 solutes in 40 micellar reversed-phase liquid chromatographic systems using sodium dodecyl sulfate (SDS), cetyltrimethylammonium bromide (CTAB), methanol, n-propanol, and n-butanol as mobile phase additives are studied using linear solvation energy relationships (LSERs). The influence of solute properties on retention in MLC and the trends in the coefficients as a function of SDS and CTAB concentrations are investigated. The ability of the LSERs to account for the chemical interactions underlying solute retention is shown.

ISSN:1082-6076    

DOI:10.1081/JLC-100101495

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The present work is the first attempt to use countercurrent chromatography for xenobiotics extraction and separation from complex natural matrices without sample pretreatment. A procedure has been developed for the direct extraction and separation of some PAHs from a sewage sludge medium being in fact a concentrated suspension. The sewage sludge and aqueous solutions containing the trace amounts (0.01–10 μg/mL) of PAHs were used as the stationary phase in the column whereas organic solvents (n-heptane, dichloromethane) or their mixture were used as mobile phase.

ISSN:1082-6076    

DOI:10.1081/JLC-100101496

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

A series of solvent systems was developed for CCC to separate mixtures containing variable amounts of artemisinin, artemi-sitene, and arteannuin B. To purify multigram quantities of artemisinin by CCC it was necessary to maximize the amount of a mixture that could be dissolved in a fixed quantity of the solvent mixture.

ISSN:1082-6076    

DOI:10.1081/JLC-100101497

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

A high performance liquid chromatography method was developed for the determination of organic acids in commercial samples ofGarcinia cambogiaextracts. The major organic acid in commercially available extracts ofGarcinia cambogiahas been found to be (-) hydroxycitric acid present to the extent of 51–55%. Tartaric, citric, and malic acids are present in small quantities and have been detected by using 6 mMsulfuric acid as the mobile phase with a flow rate of 1.0 mL/min and UV detection at 210 nm.

ISSN:1082-6076    

DOI:10.1081/JLC-100101498

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Evaporative light scattering detection (ELSD) is an inexpensive “universal” mode of optical detection for LC. We report here on ELSD as a useful adjunct to UV detection for the RP-HPLC peptide mapping of proteins. We use peptide mapping as a “finger-printing” technique to detect post-translational modifications and other small changes to recombinant protein pharmaceuticals. UV absorption and ELSD modes were run in series for a RP-HPLC tryptic map of the small “model” protein, cytochrome c. We also report preliminary ELSD data for the RP-HPLC tryptic map of an IgG1 monoclonal antibody.

ISSN:1082-6076    

DOI:10.1081/JLC-100101499

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The retention behavior of ten iridoid glucosides on reversed octadecylsilane and normal diol stationary phases is compared. To consider in quantitative terms the experimental results, structure-retention relationships have been studied. When free rotation around σ-bonds in the solute molecule during the chromatographic process was taken into account, increased accuracy of calculated retention was obtained. The values of positive, respectively negative contribution of the same functional groups to the solute molecule retention on each column were calculated.

ISSN:1082-6076    

DOI:10.1081/JLC-100101500

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor