摘要:

In this paper, the separation of fifteen plant auxins by capillary electrophoresis was investigated. A simple and efficient method was developed. The migration behaviour of the auxins under different separation conditions was studied. Optimum separation was obtained with cyclodextrin-modified borate-phosphate buffer. This method was applied to the determination of indole acetic acid (1AA), a well known auxin in plant samples, with cinnamic acid as the internal standard. The method is linear over the range of 0.4–8.0 mg/mL, with 82.4% recovery and a limit of quantitation of 0.4 mg/mL.

ISSN:1082-6076    

DOI:10.1080/10826079608013998

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Many new and complex molecules are being investigated as potential drug candidates. Conventional analytical methodologies may not be suitable for determining the purity, identity, and degradation of these complex molecules. Therefore, new analytical techniques must be developed that address and overcome these problems. Micellar liquid chromatography is such a technique.

ISSN:1082-6076    

DOI:10.1080/10826079608013999

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Isolation of various azadirachtins, ie., Azadirachtin A, B, D, H and I in pure form from neem oil by preparative high performance liquid chromatography procedure is described.

ISSN:1082-6076    

DOI:10.1080/10826079608014000

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

As a part of a study of pesticide migration through a polymer matrix, an HPLC method for analysis of O,O-diethyl-O-(6-methyl-2-(1 -methylethyl)-4-pyrimidinyl)-phosphorothioate, commonly called diazinon) was developed.

ISSN:1082-6076    

DOI:10.1080/10826079608014001

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A new, simple, very sensitive, highly reproducible, isocratic, and reverse phase liquid chromatographic method has been developed for determining urine melatonin concentrations using a fluorometric detector. 6-methoxymelatonin is used as an internal standard. A C18column (150 × 0.46 cm) and a “Waters” fluorometric detector (Model 474 with a 16 uL flow cell are the main components of the liquid chromatographic system. The excitation and emission wavelengths are 285 and 335 nm respectively. Melatonin is extracted from urine at pH 7 using chloroform. The method is sensitive to 0.5 pg. The mean (n=6) inter-assay precision (CV) is 4.3% and intra-assay precision is 5.8%. The mean absolute recovery of the method is about 90%.

ISSN:1082-6076    

DOI:10.1080/10826079608014002

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Solute-micelle association constants and partition coefficients between stationary, aqueous, and micellar phases have been determined for a group of benzene derivatives and polycyclic aromatic hydrocarbons with sodium dodecyl sulphate and hexadecyltrimethylammcnium bromide by Micellar Liquid Chromatography (MLC) with an octylsilica column using micellar mobile phases in absence and in the presence of organic modifiers (methanol, n-propanol, and n-butanol). The retention mechanism of these compounds in the chromatographic system has been studied by comparing experimental capacity factors and selectivity coefficients with those theoretically calculated assuming a direct transfer mechanism. When the surfactant concentration in the mobile phase is increased, a tendency to a change from a three-partition equilibrium mechanism to a direct transfer of solutes from micellar to stationary phase is observed for both surfactants. This change was favored when: (1) the hydrophobic character of the solute increased, (2) CTAB was used as surfactant, and (3) the polarity of the aqueous mobile phase was increased. For highly hydrophobic compounds experiencing a direct transfer mechanism, selectivity coefficients for a pair of solutes can be predicted from the ratio of two stationary-micellarpartition coefficients.

ISSN:1082-6076    

DOI:10.1080/10826079608014003

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A novel high-performance liquid chromatographic (HPLC) method is described for the determination of the alkaloid cuscohygrine [1,3-bis(1-methyl-2-pyrrolidinyl)-2-propanone] in air-dried leaves ofErythroxylum cocavar.coca.The analysis was performed on a weak cation exchange HPLC column using a mobile phase consisting of MeOH: 0.05 M KH2PO4, pH 7 (75:25, v/v) and with UV detection at 220 nm. Cuscohygrine content was determined as 0.21–0.23% inE. cocaleaves.

ISSN:1082-6076    

DOI:10.1080/10826079608014004

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

For compounds containing less than 10% (wt./wt.) nitrogen, the sensivity of nitrogen chemiluminescence detection is limited to concentrations of greater than 0.1 mg/mL under typical operating conditions. For determinations of nitrogen containing surfactants in household products, such sensitivity is not prohibitive due to the high levels of surfactant added to the formulations and is potentially offset by the advantage of the detector's specificity towards nitrogen containing compounds. Lauryl/myristyl monoethanolamide is detected without interfence in a variety of dishwashing liquids and n-methyl glucosamides are detected in liquid laundry detergents. Replicate injections of a single dishwashing liquid preparation indicate a quantitative reproducibility of 8% rsd for lauryl/myristyl monoethanolamide. Performance comparable to HPLC with UV detection has been achieved for methyl neodecanamide in an all purpose cleaner.

ISSN:1082-6076    

DOI:10.1080/10826079608014005

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A method for purification by countercurrent chromatography (CCC) of phosphatidylcholine with high content of DHA is described. Phospholipids were extracted from squidIllex argentinuscharacterized by high performance liquid chromatography and their fatty acids profile determined by gas chromatography. Phosphatidylcholine was primarily represented with 48.3 % (w/w) of total phospholipids and contained 39.7 % of DHA (w/w total fatty acids). The analytical separation of phosphatidylcholine, was achieved on a Kromaton II apparatus, in the systems heptane—ethyl acetate—acetonitrile (1:0.65:1, v/v/v) and isooctane—ethyl acetate—acetonitrile (1:0.65:1, v/v/v), at 550 rpm and 1.5 mL/min flow rate using normal ascending and reversed descending elution modes respectively.

ISSN:1082-6076    

DOI:10.1080/10826079608014006

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Packed column supercritical fluid chromatography of free bile acids is described. Improvement of the separation of isomeric acids is carried out on diol-bonded silica using methanol or isopropanol as modifier of carbon dioxide. These poor UV absorbing analytes were detected by evaporative light scattering detection showing the potentiality of the SFC-ELSD coupling.

ISSN:1082-6076    

DOI:10.1080/10826079608014007

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor