Search results for "PERFORMANCE"

Application of molecularly imprinted polymers in supercritical fluid chromatography

2000

Molecularly imprinted polymers (MIPs), for the templates free base racemic propranolol and the L-enantiomer of phenylalanine anilide (L-PA), were investigated as stationary phases in supercritical fluid chromatography (SFC). Large retention differences were observed on the propranolol MIP for both the template molecule and the structural analogue metoprolol compared to that observed on the corresponding blank polymer. Mobile phase composition and solute concentration were found to affect this retention behaviour. The phenylalanine anilide MIP (L-PA MIP) was found to be enantioselective in SFC with stronger retention observed for the template enantiomer. Throughout the study, characteristic …

Environmental analysis of chlorinated aromatic thioethers, sulphoxides and sulphones

1993

Abstract Chlorinated aromatic thioethers discussed here are polychlorinated dibenzothiophenes, thianthrenes and diphenylsulphides. Relatively little is known about their occurrence, behaviour and fate in the environment. Polychlorinated dibenzothiophenes and diphenylsulphides have recently been found to be formed in waste combustion and analysed in pulp mill effluents. Chlorinated sulphoxides and sulphones are usually metabolites or oxidation products of different chlorinated aromatic compounds. Different gas chromatographic-mass spectrometric techniques are used in the analysis of the chlorinated thioethers. The sulphoxides and sulphones, because of their higher polarity, can be isolated f…

Transformation of Iodide in Natural and Wastewater Systems by Fixation on Humic Substances

2000

Separation of different fractions of humic substances (HS) by their molecular weight was carried out by size exclusion chromatography (SEC). The fixation of inorganic iodide by HS of these fraction...

Imprinted chiral stationary phases in high-performance liquid chromatography

2001

Polymers imprinted with chiral templates offer a new generation of tailor-made chiral stationary phases (CSPs) with predictable selectivities. This review summarizes the present state of the art of molecular imprinting to generate tailor-made CSPs and provides an overview of the main factors involved in the manufacturing process that are crucial to the chromatographic performance of the phases.

Fast high performance liquid chromatography analysis in lipidomics: Separation of radiolabelled fatty acids and phosphatidylcholine molecular species…

2006

Abstract HPLC procedures using conventional C 18 columns are usually used to separate simple and complex lipid mixtures but these methods of separation remain often laborious and very slow. Here, monolithic columns were successfully applied to separate lipids – radiolabelled fatty acid mixtures and individual phosphatidylcholine (PC) molecular species. For that, isocratic elution was performed using two Chromolith™ Performance RP-18e columns connected in series. Detection was achieved by online measurement of radioactivity for radiolabelled fatty acids and by UV absorbance at 205 nm for PC molecular species. The performances of such silica rods were compared to conventional reverse-phase si…

Separation of polycyclic aromatic hydrocarbons under isocratic conditions by a column switching technique

1994

A simple and efficient method of separating a 20-component PAH-mixture (RSM 1647 standard mixture +benzene, toluene, perylene and coronene) by RP-HPLC is described. Separation was by using two Superspher-100 RP-18 cartridges thermostatted at different temperatures under isocratic conditions with water-acetonitrile eluent. The analysis time with complete resolution of all components can be reduced to 15 min.

Reversed-phase liquid chromatography of biotin-labelled nucleotides

1985

Native and modified alumina, titania and zirconia in normal and reversed-phase high-performance liquid chromatography

1996

Chromatographic properties of silica, alumina, titania and zirconia have been investigated in normal phase mode in the separation of test mixtures of basic, neutral and acidic compounds. In contrast to silica the chromatographic behaviour revealed the basic properties of the alumina, titania and zirconia surfaces. Therefore, separation of basic compounds on these packings seems very promising. Lypophilic packings have been synthesized by modification of titania, zirconia and alumina with organosilanes and polymers and tested for the separation of basic compounds and proteins. High hydrolytic stability of the modified packings was observed during separations with strong alkali and acidic elu…

Distribution of Δ5-olefinic acids in the triacylglycerols fromPinus koraiensisandPinus pinasterseed oils

1996

Purified triacylglycerols (TAG) fromPinus koraiensis andP. pinaster seed oils, which are interesting and commercially available sources of Δ5-olefinic acids (i.e.,cis-5,cis-9,cis-12 18:3 andcis-5,cis-11,cis-14 20:3 acids) were fractionated by reversed-phase high-performance liquid chromatography, and each fraction was examined by capillary gas-liquid chromatography for its fatty acid composition. A structure could be assigned to more than 92% of TAG from both oils. In both instances, ca. 48% of the TAG were shown to contain at least one δ5-olefinic acid. In the great majority of TAG, our data showed that there is only one molecule of δ5-olefinic acid per molecule of TAG. This is compatible …

Prediction of the retention in reversed-phase liquid chromatography using solute-mobile phase-stationary phase polarity parameters.

2002

Abstract A previously reported algorithm, based on the equation: log k=( log k) 0 +p(P N m −P N s ) , that relates the retention in reversed-phase liquid chromatography with solute (p), mobile phase (PmN) and stationary phase (PsN) relative polarity parameters, is improved. The retention data reported by several authors for different sets of compounds, eluted with acetonitrile–water and methanol–water mixtures, are used to test the algorithm and elaborate a database of p values. The methodology is successfully applied to predict the retention using PmN values calculated as PmN=1.00−(2.13ϕ)/(1+1.42ϕ) for acetonitrile–water and PmN=1.00−(1.33ϕ)/(1+0.47ϕ) for methanol–water, ϕ being the organi…