T. Hanai

Characterization of bonded-amine packing for liquid chromatography and high-sensitivity determination of carbohydrates.

Abstract Characterization of bonded-amine packing was achieved with an organic-aqueous eluent by use of aromatic compounds as standard samples. The results indicate that the main interaction between the stationary phase and the solute is hydrogen bonding, hydrophobicity of the packing being negligible. The amine packing was also employed for an analysis of carbohydrates. A colorimetric detection of a reduced form of Tetrazolium Blue served for the determination (limit of detection: 10 ng of saccharide). The separation time was reduced by gradient elution. An oligosaccharide of d.p. 20 was eluted in less than 40 min.

Prediction of retention times for aromatic acids in liquid chromatography

Abstract The chromatographic behaviour of 30 aromatic acids was examined in a system of fine particle macroporous polystyrene-divinylbenzene copolymers and acetonitrile-water mixtures at different pH as eluents. The acids were benzoic, phenylacetic, cinnamic, mandelic, naphthoic and hippuric acids, and their hydroxy and/or methoxy derivatives. At low pH, the logarithm of the capacity ratios of these acids was linearly related to the logarithm of their partition coefficients in the octanol-water system calculated after Rekker. By combining the above result and the dissociation constant of the acid, it was possible to predict the retention times of the acids at a given pH of the eluent.

Selectivity of a phenyl-bonded silica gel☆

The selectivity of a phenyl-bonded silica gel was examined as the difference between the capacity ratios of five groups of compounds in acetonitrile- and tetrahydrofuran-water mixtures, in pure tetrahydrofuran and in n-hexane. The five groups were polyaromatic hydrocarbons, alkylbenzenes, halogenated benzenes, aliphatic alcohols and alkanes. In the reversed-phase mode, the polyaromatic hydro- carbons were retained more than the other groups, as expected, but selectivity was clearly observed in the chromatographic behavior of the chlorobenzenes. The use of the π energy effect obtained from the Van der Waals volume and the delocalization energy of solutes was tested for the optimization of reversed-phase liquid chromatography.

Retention versus van der waals volume and π energy in liquid chromatography

A system in which only the size and the π energy of the molecules may be involved, is examined by reversed-phase liquid chromatography using octadecyl bonded silica gels as the packing. If hydrogen bonding and Coulombic forces are negligible, the retention of molecules depends upon their size, and the presence of π electrons enhances the selectivity. Therefore, the difference between the logarithm of the capacity ratios of alkanes and polycyclic aromatic hydrocarbons (PAH) was defined as the π energy effect and log k′ (PAH) = log k′ (Van der Waals volume) — log k′ (π energy effect). The π energy effect calculated for alkylbenzenes and chlorobenzenes from the capacity ratios obtained on different packings in acetonitrile—water mixturs was constant. Therefore, the prediction of the retention time of these compounds was also possible from their Van der Waals volumes and π energy. The solvent effects of tetrahydrofuran and n-hexane are also discussed.

Hydrophobicity and Retention in Reversed Phase Liquid Chromatography

Abstract Reversed phase liquid chromatography retention data for several compounds are examined in relationship to their hydrophobicities. Alcohols and various aromatics are used to compare hydrophobicities in aliphatic and aromatic compounds. Capacity factors, k1, can be correctly evaluated by using the hydrophobic factors (log P) derived from the hydrophobic fragmental constants. Appropriate solvent mixtures to achieve good separations can be choosen from graphical data.

Hydrophobicity and chromatographic behaviour of aromatic acids found in urine

Abstract In reversed-phase liquid chromatography, the capacity ratios of urinary compounds were related with their hydrophobicity calculated by Rekkers hydrophobic fragmental constants. The retention behaviour of these compounds differed from that of non-ionizable compounds whose retention time can be predicted in different mixtures of acetonitrile and water as eluent and on an octadecyl silica packing from their calculated hydrophobicity. However, the calculated values for hydrophobicity and/or those derived from the results obtained for non-ionizable compounds could be useful to analyze the metabolites of acidic compounds in urine. The retention behaviour of all the compounds on gradient elution is also discussed.

Liquid Chromatographic Behavior of Nitrogen Compounds

Abstract Chromatographic behavior of nitrogen compounds differed from others. The column efficiency was poor for the compounds and sometimes solutes were not eluted out from a column. Therefore, the elution volume of alkylamines, anilines, pyridines, pyrazines, quinolines and aminopolyaromatic hydrocarbons was measured on a methacrylate gel and octadecyl bonded silica gels in pH controlled acetonitrile/water mixtures. The solvent effect on the dissociation constant differs from that obtained for aromatic acids. The values in acetonitrile/water mixtures are smaller than those obtained in 100% water. The linear relation between log P and log k′ values is obtained in eluents of pH 7 where the retention of these compounds is maximized. Some hydrophobic fragmental constants are proposed from this result. Prediction of retention time of these compounds from their log P values can be done in the individual groups on octadecyl bonded silica gels in pH controlled acetonitrile/water mixtures.

Systematic Liquid Chromatographic Separation of Poly-, Oligo-, and Monosaccharides

Abstract High speed separations of poly-, oligo-, and monosaccharides were achieved on Chromosorb LC 9, Toyo Soda Starch Gel TSKLS17OP5, and Hitachi 3013N packings. Post column reaction system with tetrazolium blue was used to obtain a low detection limit for oligo-, and monosaccharides. Polysaccharides were analysed within 20 min by gel permeation chromatography over TSKLS17OP5 gel. DP 30 oligosaccharide was eluted in 30 min on Chromosorb LC 9 using a gradient of acetonitrile/water. Finally monosaccharides were separated in 25 min on Hitachi 3013N macroporous anion exchange resin.

Dependence of the retention of phenols upon van der waals volume, π-energy and hydrogen-bonding effects

Abstract The retention of polyaromatic hydrocarbons (PAHs) and alkylbenzenes (PhR) can be predicted from their Van der Waals volume and π-energy effect, and that of alkyl alcohols (ROH) from their Van der Waals volume and hydrogen-bonding effect. The maximum retention is related to the Van der Waals volume, log k ′ (VWV). Retention is reduced by the π-energy effect, log k ′ (π), or the hydrogen-bonding effect, log k ′ (HB). Therefore, the retention time is given by log k ′ (PAH and PhR)  log k ′ (VWV)  log k ′ (π) or log k ′ (ROH)  log k ′ (VWV)  log k ′ (HB) Furthermore, the retention of phenols (PhOH) is given by log k ′ (PhOH)  log k ′ (VWV)  log k ′ (π)  log k ′ (HB) in acidic acetonitrile—water mixtures on octadecyl-bonded silica gels.

Chromatography of aromatic acids on ion exchangers

Abstract The chromatographic behaviour of aromatic acids was determined on an octadecyl- (TSK LS 410), a propylamino- (Chromosorb LC-9), a diethylaminoethyl- (TSK IEX 540 DEAE) and a sulphonyl-bonded silica gel (TSK IEX 510 SP) in sodium phosphate buffer with acetonitrile. The dissociation constants and the maximum capacity ratios are related to the pKa and log P values. The maximum capacity ratios correlate well with their log P values on the octadecyl-bonded packing. The pKa values obtained on ion exchangers correlate well with those obtained on the octadecyl-bonded packing. The pKa values decrease on anion exchangers in the order 510 SP > 410 > 540 DEAE > Chromosorb NH2.