摘要:

Many chiral thiols such as cysteine, homocysteine, N-acetylcysteine (NAC), and penicillamine are biologically important compounds. Among other roles, they act as antioxidants, therapeutic agents and indicators of disease. When analyzing low levels of these compounds, they are often derivatized in order to increase the sensitivity of the determination. However, it is generally an associated amine functional group that is derivatized. By selectively derivatizing only the thiol moiety with a fluorescent group, one is able to eliminate the large number of amine containing background compounds that are present in biological samples. However, there have been few reports on the enantiomeric resolution of thiol containing amino acids in which the fluorescent tag is linked exclusively through the sulfhydryl group. The first HPLC enantioresolution of N(1-pyrenyl)maleimide (NPM) and ThioGlo™3 derivatized compounds is reported on Teicoplanin and naphthylethyl-carbamate-β-cyclodextrin (NEC-β-CD) chiral stationary phases.

ISSN:1082-6076    

DOI:10.1081/JLC-100100463

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The recovery of particles of the colloidal components subject to separation by the potential barrier sedimentation field-flow fractionation (PBSdFFF) is of great significance in separation science. For the recovery studies in PBSdFFF, monodisperse submicron spherical particles of poly(methyl methacrylate) (PMMA) were used. The extent of the PMMA particles' adhesion and detachment on and from the Hastelloy C channel wall depends on the ionic strength of the suspending medium. The presence of the indifferent electrolyte of Ba(NO3)2in the suspending medium, which influences the total potential energy of interaction between the PMMA particles and the channel wall, leads to the partial or total adhesion of the PMMA particles on the channel wall. Finally, the ideal experimental conditions for improving the recovery of the colloidal particles under study in PBSdFFF were investigated.

ISSN:1082-6076    

DOI:10.1081/JLC-100100464

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

A chromatographic method based on a combination of single-column ion-chromatography separation with a bulk-acoustic-wave double-cell quartz crystal (DCQC) detector quantification for the determination of cyclamate in foodstuffs and body fluids was developed. The chromatographic system involves the use of a Shimadzu IC-A1 column with 5mM o-phthalic acid/methanol (90:10 V/V) as a mobile phase. The method exhibits an acceptable detection limit and anti-interference ability. The DCQC detector has a low temperature coefficient and high conductance sensitivity. Foodstuff and body fluid sample such as ice cream, beverage, dried fruit ofAreca catechuL., and urine were analysed successfully.

ISSN:1082-6076    

DOI:10.1081/JLC-100100465

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Preparative scale purification of PEG-protein conjugates by centrifugal precipitation chromatography is discussed. By utilizing the transport of ammonium sulfate across a membrane and the centrifugal force, an ammonium sulfate gradient is formed and used for differential precipitation of PEG-protein conjugates. Native proteins can be separated from PEG-protein conjugates by using this technique.

ISSN:1082-6076    

DOI:10.1081/JLC-100100466

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

A simple, selective, and reproducible method was developed for the quantitative determination of β-phenylethylamine (PEA) in human plasma. The method involved sample clean-up procedure by a solid-phase extraction using a Sep-Pak C18cartridge in the presence of phenylpropylamine (PPA) as an internal standard followed by pre-column fluorescence derivatization witho-phthalaldehyde, 2-mercaptoethanol. PEA and PPA were separated by reversed-phase high performance liquid chromatography (HPLC) on a C18reversed-phase column with a mobile phase consisting of a 0.0375 M acetate (pH 5.5)/acetonitrile (50:50, v/v) buffer and detected fluorometrically. A linear relationship was achieved between the peak area ratios of PEA/PPA and PEA concentrations over the range of 250 to 2000 pg/injection (one injection=40 μL). The limit of detection for PEA at a signal-to-noise ratio of 3 was 4 pg/injection (100 pg/mL) in a standard solution. Total analysis was achieved in less than 25 minutes with the average PEA recovery of 94.1%. The reproducibility and the repeatability of the method, assessed by calculating the mean C.V. of peak area ratio (PEA/PPA) and that of the retention times of the analytes, were in the range of 1.1–3.3% and 0.14–0.42%. The average plasma PEA level in healthy volunteers was 1129.8 ± 268.1 pg/mL (n=40, age 39.3 ± 10.3 years (mean ± S.D.)).

ISSN:1082-6076    

DOI:10.1081/JLC-100100467

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Separation of selected lanthanoid elements was performed by high-speed countercurrent chromatography (CCC) equipped with a small coiled column of a 10 cm3capacity. A hexane solution of 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (EHPA) was retained in the tubing column as the stationary phase. The stationary phase retention increased with increasing rotational speed and with decreasing flow rate of the aqueous mobile phase. Mixtures of lanthanoids (Gd, Tb and Dy) were chromatographically eluted in the increasing order of extractability by introducing the buffered mobile phase, and excellent separation of lanthanoids was achieved.

ISSN:1082-6076    

DOI:10.1081/JLC-100100468

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Six synthetic gastrointestinal drugs, cimetidine, homatropine, metoclopramide, pirenzepine, ranitidine, and scopolamine butylbromide, which can be found as adulterants in traditional Chinese medicines were assayed simultaneously, within 6 min., using high performance capillary electrophoresis. The electrolyte was a buffer solution containing 100 mM phosphate buffer (NaH2PO4/H3PO4, pH 2.5) and 5 % acetonitrile. Applied voltage was 20.5 kV and temperature was 30°C. 3-Benzyl-5-(2-hydroxyethyl)-4-methylthiazolium chloride was used as an internal standard and the detector was set at 214 nm. The effects of buffer pH and acetonitrile concentration on separation are important. The relative standard deviations of these gastrointestinal drugs for intra-day and inter-day analyses were 0.78–2.15 % and 1.10–2.75 %, respectively. The recoveries of the synthetic drug adulterants in traditional Chinese medicinal formula ranged from 97.3 to 102.4 %.

ISSN:1082-6076    

DOI:10.1081/JLC-100100469

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Commercial soybean products for human consumption (soybeanprotein isolate, soybean flour, textured soybean, and soybean powdered milks)are characterized for the first time by Sodium Dodecyl Sulphate PolyacrylamideGel Electrophoresis (SDS-PAGE) using the PhastSystem®, a semi-automaticelectrophoretic system. It makes SDS-PAGE very fast and gives very sharp bandsthat simplify the identification. The time from loading the gel to characterizationis less than 1 hour and the resolution is similar to that of large conventionalgels. Proteic fractions obtained from these commercial soybean products byusing a fractionation procedure described in literature are also analyzed.The electrophoretic patterns of these globulin fractions exhibited some differenceswhich were attributed to the different technological process used for thepreparation of each product investigated. Furthermore, the electrophoreticpatterns obtained for commercial soybean products enabled the differentiationbetween products derived from soybean protein isolates and those prepareddirectly from whole soybeans.

ISSN:1082-6076    

DOI:10.1081/JLC-100100470

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

A highly sensitive method of simultaneous separation and determination of Pb2+, Cu2+, Cd2+, Co2+, and Ni2+was developed and evaluated by on-line sample pretreatment of chelation ion chromatography. Bulk quantities of anions, alkali metals, alkaline earth metals, tervalence cations, and other interfering components were eliminated by pyrophosphoric acid / ammonium acetate buffer solution (pH 5.5), while retaining heavy and transition metals on iminodiacetate-based resins. Then, they were disabsorbed and transferred to sulfonated cation exchangers.

ISSN:1082-6076    

DOI:10.1081/JLC-100100471

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

An improved high performance liquid chromatography (HPLC) method for the analysis of the main organic compounds in musts and wines is presented. A column packed with hydrogen sulfonated divinyl benzene-styrene copolymer and two detectors connected in series were used (UV at 210 nm and RI, respectively). The addition of acetonitrile (6%) to the mobile phase (0.045NH2SO4) allowed the simultaneous separation and quantification of several organic acids, glucose, fructose, glycerol, and ethanol. Direct injection and sample clean-up with a SAX cartridge was tested and compared. The SAX fractionation gave satisfactory results, however the direct injection of diluted wine (1:20) provided the best precision (CV ≤ 2.1%) and accuracy of analysis. Statistical analysis (paired t-test) disclosed significant differences only for glucose, fructose, α-ketoglutaric, and pyruvic acid. The role of column temperature for the analysis of vitamin C (ascorbic acid) was also investigated. Vitamin C underwent thermal degradation during analysis with column temperature ≥ 30°C.

ISSN:1082-6076    

DOI:10.1081/JLC-100100472

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor