GC Behavior of disaccharide trimethylsilyl oximes

Twenty-five disaccharides are converted to trimethylsilyl oximes and injected on two capillary columns of different polarities (methyl and phenyl-methyl silicone). Their Kovats retention indices are determined at three temperatures. Multivariate data analysis is used in order to obtain relations between retention and some structural features. Phenylmethyl silicone have better chromatographic characteristics for the assayed compounds. The two columns can provide useful chromatographic information when a very complex disaccharide mixture has to be analyzed.     

Liquid chromatographic assay for constituent disaccharides of hyaluronic acid and chondroitin sulphate isomers

An improved high-performance liquid chromatographic (HPLC) method for unsaturated disaccharides prepared from hyaluronic acid and various chondroitin sulphate and dermatan sulphate isomers was developed, which involves an ion-exchange resin prepared from a sulphonated styrene-divinylbenzene copolymer. The retention times of the individual unsaturated disaccharides were unique and reproducible, the disaccharides appearing in the following order: unsaturated non-sulphated disaccharide derived from hyaluronic acid, then unsaturated 6-sulphated, non-sulphated and 4-sulphated disaccharides from chondroitin sulphate isomers. Unsaturated disulphated disaccharide G had a much shorter retention time than the unsaturated non-sulphated disaccharide derived from hyaluronic acid. The contents of these individual unsaturated disaccharides could be determined with similar sensitivities on the basis of their ultraviolet absorbance. Selective and unique retention times and good resolutions were found for various unsaturated disulphated and trisulphated disaccharides. The proposed method can be used to determine various chondroitin sulphate and dermatan sulphate isomers in addition to hyaluronic acid in amounts as small as 100 ng to 8 micrograms. The practicality of this method was verified by its application to the separation and determination of the different types of chondroitin sulphate and dermatan sulphate isomers derived from human arteries in the presence of appreciable amounts of hyaluronic acid.     

Gas chromatographic-mass spectrometric method for the qualitative and quantitative determination of disaccharides and trisaccharides in honey

An improved method has been developed to identify and quantify honey disaccharides and trisaccharides by gas chromatography and mass spectrometry. The procedure, based on mass spectral and retention data ("retention time windows") determined on two capillary columns with different stationary phases allowed the identification and quantitation in honey of 16 disaccharides and 9 trisaccharides, some of which were not previously identified by GC. The reliability of the analytical results was considerably improved by the use of this procedure: several unidentified disaccharides and trisaccharides were detected, and their presence was taken into account in the quantification.     

The application of retention indices using the alkylarylketone scale to the separation of the barbiturates by HPLC. I. The effect of the eluent

Summary In order to determine the applicability of retention indices, based on the alkylarylketone scale, as the basis of a reproducible method of reporting retentions, the separation of ten barbiturates and a set of column test compounds were examined on an octadecylsilyl bonded silica (ODS-Hypersil) column with methanol-buffer pH 8.5 as eluent. The effects on the capacity factors and retention indices, on changing the eluent composition, pH, ionic strength and temperature, showed that the retention indices of the barbiturates were much less susceptible to minor changes in the eluent than the capacity factors. For non-ionised compounds the retention indices were virtually independent of the experimental conditions. Presented at the 15th International Symposium on Chromatography, Nürnberg, October 1984     

Temperature programmed retention indices: Calculation from isothermal data. Part 1: Theory

Direct conversion of isothermal to temperature programmed indices is not possible. In this work it is shown that linear temperature programmed retention indices can only be calculated from isothermal retention data if the temperature dependence of both the distribution coefficients and the column dead time are taken into account. Procedures are described which allow calculation of retention temperatures and from these, accurate programmed retention indices. Within certain limits the initial oven temperature and programming rate can be chosen freely. The prerequisite for this calculation is the availability of reliable isothermal retention data (retention times, retention factors, relative retention times, or retention indices) at two different temperatures for one column. The use of compiled isothermal retention indices at two different temperatures for the calculation of retention temperatures and thus temperature programmed indices is demonstrated. For the column for which programmed retention indices have to be determined, the isothermal retention times of the n-alkanes and the column dead time as a function of temperature have to be known in addition to the compiled data for a given stationary phase. Once the programmed retention indices have been calculated for a given column the concept allows the calculation of temperature programmed indices for columns with different specifications. The characteristics which can be varied are: column length, column inner diameter, phase-ratio, initial oven temperature, and programming rate.     

Influence of different N- and O-linked carbohydrates on the retention times of synthetic peptides in reversed-phase high-performance liquid chromatography.

Glycopeptides consisting of 6-19 amino acid residues and different mono- and disaccharides attached to single asparagine and serine residues were synthesized on solid-phase and were characterized by reversed-phase high-performance liquid chromatography and circular dichroism. It was shown that the decreased retention times due to glycosylation could be correlated with the increasing length of the sugar moiety. Phosphorylation of the same sequences reduced the retention times 1.6 times more than glycosylation with monosaccharides did. The binding to the column was dependent on the structure of the disaccharide when derivatized and glycosylated asparagine, the building block of N-glycopeptide syntheses was studied. However, this structural dependence of the elution times disappeared in the final glycopeptides. Although both glycosylation and phosphorylation resulted in altered secondary structure of the peptide backbone, it appears that the retention times reflect the increased hydrophilicity more strongly than induced conformational orientation on the surface of the bonded phase.     

The role of electric interaction in the retention index cencept. Universal interaction indices for GLC,HPLC and TLC

Summary New electric interaction indices are proposed which can universally be used in GLC, HPLC and TLC. These indices can easily be calculated from a variety of the commonly used retention parameters, such as Kováts' retention indices, relative retention times, capacity factors, or R_F values, and the average molecular polarizabilities of the reference compounds. Calculation examples for polycyclic aromatic hydrocarbons and n-alkanes are given. Application of the electric interaction indices for studying the retention mechanism is demonstrated.     

直链单烯烃保留指数与分子结构关系的研究

根据同系直链单烯烃保留指数与同碳数正构烷烃保留指数差值与分子碳数间关系曲线拟合,提出预测同系直链单烯烃保留指数的准确公式。在ＳＱ,ＰＦＥ,ＰＥＧ－４０００上,利用所提出的公式对检验集中化合物保留指数预测值与实测值差的标准偏差在±０．９ｉ．ｕ．～±１．５ｉ．ｕ．之间。并且研究发现,同碳数、同几何构型直链单烯烃各位置异构体分子中双键位置与化合物保留指数具有指数关系。首次提出依据分子中双键位置预测其保留指数的准确公式。公式适合各种不同极性固定相。     

Contribution to linearly programmed temperature gas chromatography. Further application of the Van den Dool-Kratz equation, and a new utilization of the Sadtler retention index library

Programmed temperature retention indices (PTRIs) calculated according to the equations of Van den Dool and Kratz, Golovnya and Uraletz, and Erdey et al. (also referred to as Antoine's integrated equation) are used in this work. Precalculation of isotherm retention indices from the results of a linearly programmed temperature GC is also presented. Deviations between experimental and calculated isothermal retention indices are below 2 retention index units. A relative "volatility" retention index is defined, as a function of the "volatilities"of the solute and the bracket reference n-alkanes. The comparison of the "volatility" retention indices with the PTRIs obtained with the other above equations shows absolute deviations of up to 4 retention index units. Based on an earlier "equivalent" temperature concept and on Tekler's proviso, a novel way for the utilization of Sadtler's retention index database, which takes advantage of the 3 data supplied by the library, is proposed.     

Calculation of retention indices by molecular topology. Chlorinated benzenes

A comparative study was undertaken to test the ability of several different topological indices to predict the retention indices of chlorinated benzenes on polar and non-polar stationary phases using both correlation coefficients and correctly predicted elution sequences as criteria of fit. The test was performed on three topological indices: connectivity indices, Wiener numbers, and Balaban indices. The regression analyses showed that the molecular connectivity model predicted the retention indices of chlorinated benzenes more successfully than either Wiener numbers or Balaban indices. The results also demonstrated that the major structural property controlling chromatographic behavior was the size of the chlorinated benzene. In addition, the use of the new non-empirical heteroatom parameterization scheme in the calculation of Wiener numbers and Balaban indices was successfully tested for the first time.     

Gas chromatographic-mass spectrometric characterization of all acyclic C5-C7 alkenes from fluid catalytic cracked gasoline using polydimethylsiloxane and squalane stationary phases

Published retention indices of acyclic alkenes C5-C7 on squalane and polydimethylsiloxane as stationary phases were investigated, and reliable retention indices of alkenes from various sources were converted to separation systems used in a laboratory. Retention indices measured on available authentic commercial alkenes and on alkenic fraction of gasoline, published retention indices as well as means of GC-MS were used for verification of calculated retention indices. Retention of some gas chromatographic unseparated isomer pairs was obtained by mass spectrometric deconvolution using a specific single-ion monitoring. On the basis of these retention data, C5-C7 alkenes were identified and analyzed in the gasoline from fluid catalytic cracking. In the gasoline all 59 acyclic C5-C7 isomeric alkenes were determined at significantly different concentration levels.     

Unified retention indices of hydrocarbons on BP-1 dimethylsiloxane stationary phase

Summary Gas chromatographic retention indices for 23 hydrocarbons were determined on BP-1 dimethylsiloxane between 45 and 65°C. From the data measured unified retention indices were calculated. These values agree well with the corresponding experimental values. The values of unified retention indices obtained on BP-1 are compared with those determined on OV-101 and on squalane. The differences between the unified and the experimental retention indices on BP-1, OV-101 and squalane columns are shown.     

Retention behavior of monosaccharides and disaccharides on titania

Summary The ability of titania to recognize the position of hydroxyl groups was previously found to result from the formation of a chelate ring between a titanium ion and the two oxygen atoms of the hydroxyl group and carboxylate anion of 2-hydroxycarboxylic acids. We investigated how titania could recognize the position of hydroxyl group of monosaccharides and disaccharides. The retention behavior of monosaccharides and disaccharides on titania was found to be characteristic. Thus, sucrose was eluted much faster than the other sugars, whereas D-ribose, D-fructose and L-sorbose were most strongly retained on titania of all of the sugars tested. It is apparent that the sugars strongly retained on titania have an axial hydroxyl group or neighboring hydroxyl groups of the same conformation.     

直链单炔烃保留指数与分子结构关系研究

根据同系直链单炔烃保留指数与同碳数正构烷烃保留指数差值与分子碳数间关系曲线拟合，提出预测同系直链单炔烃保留指数的较准确公式。研究并发现同碳数直链单炔烃各异构体分子中三键位置与化合物保留指数具有指数关系，首次提出了据分子中三键位置预测其保留指数的较准确公式。解决了从低碳数直链单炔烃保留指数预测高碳数直链单炔烃保留指数问题。     

Glycosylidene Carbenes. Part 10. Regioselective Glycosidation of 4,6-O-Benzylidene-D-altropyranosides

Glycosidation by the diazirine 1 , the trichloroacetimidate 4 , and the bromide 5 of the altro-diol 2 , possessing an intramolecular H-bond (HO? C(3) to O? C(1)) in solution, but not in the solid state, proceeds with high and complementary regioselectivity. From 2 and 1 , one obtains mostly the 1,2-linked disaccharides 10 and 11 (β-D > α-D ), together with the 1,3-linked isomers 12 and 13 (α-D > β-D ; 1,2-/1,3-linked products ca. 9:1), the demethylated 1,3-linked disaccharides 24–27 , the trisaccharides 19–22 , the lactone azines 23 , and the hydroxyglucal 18 , while 2 reacted with 4 or 5 to yield mostly the 1,3-linked disaccharides (1,2-/1,3-linked products ca. 1:9). The disaccharides were additionally characterized as acetates (→ 14–17, 28–31 ). Yields and stereoselectivity depended upon the donor, stoichiometry, solvent, temperature, and concentration. Glycosidation of the 1,3-linked disaccharides with 1 yielded the trisaccharides 19–22 . Reaction of the β-D -altro-diol 3 with 1 gave the 1,2- and 1,3-linked disaccharides 32/33 and 34/35 in a 1:1 ratio, characterized as the acetates 36–39 , while glycosidation with 5 according to Lemieux proceeded regioselectively (1,2-/1,3-linked products 91:9). The monotosylates 6 and 7 reacted with 1 to yield the anomeric pairs 40/41 , and 42/43 of the tosylated disaccharides; the oxiranes 44 and 45 were not observed.     

气相色谱灰色分析体系中未知组分保留指数的预测

提出在部分组分已知的气相色谱灰色体系中,利用已知组分的保留指数和保留时间推算死时间和正构烷烃的保留时间,再计算未知组分保留时间的方法,结果显示,在已知组分不是太少的情况下,该方法计算的死时间和正构烷烃的保留时间与实验值吻合,预测的保留指数也有较高的精度.     

Chromatographic characteristics of α-alkynols

Chromatographic retention indices on a standard nonpolar poly(dimethylsiloxane) phase were determined for 33 α-alkynols and their 27 dehydration products (conjugated alkenynes). The resulting data are proposed to be verified using the retention indices of acetylenic alcohols estimated by the additive scheme from the retention indices of isostructural alkynes with the inclusion of increments for secondary and tertiary hydroxy groups. The analogous approach to data the verification of data for alkenynes is based on correlation of their retention indices with normal boiling points.     

Alpha,alpha-trehalose-water solutions. VIII. Study of the diffusive dynamics of water by high-resolution quasi elastic neutron scattering

The present paper shows high-resolution quasi-elastic neutron scattering (QENS) findings on homologues disaccharides (i.e. trehalose, maltose, and sucrose)-water mixtures as a function of temperature. The QENS measurements were performed on both partially deuterated disaccharides in D2O and on hydrogenated disaccharides in H2O to separate the solute dynamics from that of the solvent. The results highlight a noticeable disaccharide kosmotrope character, with results more marked for trehalose. Such evidence accounts for its higher bioprotective effectiveness.