摘要:

Gravitational Field-Flow Fractionation (GFFF) is a sub-technique of FFF which combines the earth gravitational force with the carrier liquid flow in a horizontal, ribbon-like channel which is well suited for the separation and characterization of monodisperse or polydisperse colloidal materials and macro-molecules.

ISSN:1082-6076    

DOI:10.1081/JLC-100101810

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Benzoin, which reacts specifically with arginine-containing peptides, was used as a pre-column fluorogenic reagent in the HPLC analysis of gonadotropin-releasing hormone (GnRH) and its synthetic analogues in an attempt to improve their detection sensitivity. The reaction kinetics of benzoin with GnRH and its structurally-related analogues, which all contain an arginine residue in the peptide chain, were investigated in this study. A fluorescence detector (ex 325 nm/em 435 nm) was used to detect benzoin-arginine derivatives. Another set of excitation and emission wavelengths (289 nm/344 nm), where fluorescent activity results from the aromatic amino acid residues, such as Tyrosine and Tryptophan, was used for comparison. The derivatization reaction and the fluorescent derivative product were highly affected by peptide concentration and heating time. The reactivity of arginine at position 8 was found to depend on the primary structure of GnRH and its analogues. However, it was observed that GnRH and its analogues were extremely unstable, as indicated by the labile nature of GnRH and its analogues under the derivatization conditions used.

ISSN:1082-6076    

DOI:10.1081/JLC-100101811

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

A simple, fast and precise method for the simultaneous determination of creatinine and uric acid in human urine by capillary zone electrophoresis has been developed. The method only requires filtering urine sample and no other pretreatment. The effect of pH of the background buffer on the existent state of creatinine and uric acid was investigated. Photodiode array detection permitted the rapid identification of creatinine and uric acid in the sample analysed. The linear range, detection limit, precision, and recovery of the method was investigated.

ISSN:1082-6076    

DOI:10.1081/JLC-100101812

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

A new HPLC stationary phase, 1-methylnaphthalene modified Polystyrene-divinylbenzene resin (MNPSDVB), has been prepared to separate C60and C70. High column loading capacity and large separation factor of C60and C70were obtained in MNPSDVB column with the strong solvent, o-xylene, as the mobile phase.

ISSN:1082-6076    

DOI:10.1081/JLC-100101813

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

We have examined the column chromatography using hydrophobic gel carriers, Sephadex LH-20 and HP-Cellulofine, for separation of ten toad poison bufadienolides: resibufogenin, cinobufagin, bufalin, bufotalin, cinobufotalin, telocinobufagin, desacetyl-cinobufagin, desacetyl-bufotalin, desacetyl-cinobu-fotalin, and gamabufotalin (Figure 1). As a result, the use of developing solvents such as n-hexane/CH2Cl2/MeOH(4:5:1), n-hexane/CHCl3/MeOH(4:5:1), and n-hexane/toluene/ MeOH (3:2:1) provided the effective separation of bufadienolides. For separation, we have established the flow speed of developing solvents and the relationship of separation with the diameter and length of column, in addition to the comparison of separation by Sephadex LH-20 and HP-Cellulofine and the relationship with silica gel thin-layer chromatography. Also, we have tested the separability of hydrophobic gel by repeated use and the recovery of bufadienolides on hydrophobic gel column by repeated use.

ISSN:1082-6076    

DOI:10.1081/JLC-100101814

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The chromatographic performance of metal chelating analytes on a C18 functionalized styrene-divinylbenzene stationary phase is studied. The influence of metal ions impurities on their peak shapes and the metal sorption properties of such a stationary phase are investigated. Quantitative evidence is obtained to support the proposition that sorption of metal ions onto the stationary phase results in a chromatographic performance loss of the investigated metal chelating analytes. Since their retention is a function of strong complexing interactions and van der Waals forces, the mixed retention mechanism is best described as one of “metal interaction.” Also when the base material is itself strongly hydrophobic and displays no ionic character whatsoever, pure reversed phase interactions may not be always achievable.

ISSN:1082-6076    

DOI:10.1081/JLC-100101815

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Many mobile phases, including solvent systems with one and two polar modifiers as well as some multiple development techniques and gradient elutions, were examined to select the best thin-layer chromatographic conditions on silica gel F254plates for micropreparative isolation of 10-deacetylbaccatin III (10-DAB III), baccatin III, paclitaxel, and cephalomannine from methanolic extracts obtained from fresh and dried needles and stems ofTaxus baccataL. In case of each solvent system and development technique, RF, k, and α values of 10-DAB III and paclitaxel were determined as well as the separation of compounds coextracted with taxoids, and the whole yew extract. The best mobile phase, benzene-chloroform-acetone-methanol (20:92.5:15:7.5) used twice over a distance of 15 cm was applied for isolation of analyzed taxoids by preparative TLC in connection with RP-HPLC, (C-18) quantitative determination using two mobile phases (30% acetonitrile in water to measure of 10-DAB III levels and 50% acetonitrile in water for baccatin III, paclitaxel, and cephalomannine).

ISSN:1082-6076    

DOI:10.1081/JLC-100101816

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

high performance liquid chromatography (HPLC) with isocratic ion-pair-reversed-phase separation and UV detection at 230 nm is proposed for the determination of creatinine in urine. The analysis is achieved on a C18-Symmetry column (4 μm, 150mm × 3.9mm ID) using a mixture of 10 mM phosphate buffer pH=4, containing 3mM 1-octane-sulfonic acid, sodium salt and methanol (97:3). A flow-rate of 0.5mL/min and a column temperature of 30°C were employed. We validated the method for linearity, precision, and accuracy and the results were found to be excellent. The procedure proposed here is an alternative to less specific colorimetric methods.

ISSN:1082-6076    

DOI:10.1081/JLC-100101817

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

A rapid and selective method for determining a linear alkylbenzenesulfonate (LAS) and its biodegradation metabolites in sea water samples using solid-phase extraction and reversed-phase high performance liquid chromatography with UV detection is proposed. A solid-phase extraction (SPE) procedure is described for concentrating the compounds of interest on Mega Bond Elut C18 mini-column cartridges (2 g of adsorbent). Factors affecting the recovery of the investigated molecules such as conditioning of the SPE cartridge, flow-rate of the sample loaded on the cartridge, volume and pH of the sample, addition of salt to the sample, and elution of the analytes from the SPE cartridge are commented. Most of the tested compounds were extracted at recovery rates of > 70%. The obtained eluates were analyzed on a LiChrospher 100 RP-18 column and a mobile phase gradient of acetonitrile-phosphate buffer (pH=2.2) was used to separate the metabolites. The determination of LAS was made isocratically. Linear calibration curves showed good linearity for each molecule with correlation coefficients greater than 0.998. This method was applied to evaluate the LAS biodegradability in sea water during a laboratory experiment.

ISSN:1082-6076    

DOI:10.1081/JLC-100101818

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

This paper describes a newly developed method to determine Flunarizine (FZ) in rat's brain by high performance liquid chromatography (HPLC) with UV/Vis detection.

ISSN:1082-6076    

DOI:10.1081/JLC-100101819

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor