Quantitative Structure—Retention Relationship Modeling of the Retention Behavior of Selected Antipsychotic Drugs in Normal-Phase Thin-Layer Chromatography

JPC – Journal of Planar Chromatography – Modern TLC -     

Investigations of Retention Rule in Reversed-Phase High Performance Liquid Chromatography——Theoretical Consideration of Retention Convergence and Experimental Verification

This paper studied the effect of different chromatographic parameters in RP-HPLC (for example,composition of mobile phase, temperature, number of carbon atoms within the solute molecules, solvent molecules and alkyl ligand on bonded phase surface) on the retention convergence based on the displacement adsorption multi-interaction model,and derived a few retention convergent equations by using thermodynamic method,which have been verified by a great deal of experimental data of homologous series.Moreover,we have developed a general method, which can calculate the coordinate values of various retention convergent points by computer directly from experimental data,and the results predicted are in good agreement with that obtained by using plotting method.     

A Study of Retention Time Gradient Effect of Gradientally Loaded Columns

In this work, the "retention time gradient effect" of gradient GC columns is intensively studied to establish some equations and formulas for structure calculation of chromatographic columns. In addition, the relevant computer programs are designed.     

Retention behaviour of carboxylic acid methyl esters in supercritical fluid chromatography

The study on retention behavior in supercritical fluid chromatography (SFC) is necessary to understand the mechanism of the various interactions in SFC. The retention of SFC in carboxylic acid methyl ester/polymethylsiloxane/CO2 system was studied systematically and the retention behavior of this kind of compounds under various typical operation conditions was described using the method of an alternative unified theory of chromatographic retention. The results illustrated that expression: Ink.= a + b/T + cp + dp/T + ep2/T can be used to describe quantitatively the retention behavior of carboxylic acid methyl ester/polymethylsiloxane/CO2 system in the ranges of reduced density from 0.549 to 1.411. It was also found that the entropy of solute in stationary phase is dependent on the density of supercritical fluid (SF) under typical operating conditions of SFC.     

Retention Behaviors of Uronic Acid-containing Polysaccharides and Neutral Polysaccharides in HPGPC

The determination of molecular weights (Mw) of polysaccharides has served as an important process since the physical properties of the polysaccharides are closely related to their Mw and/or molecular weights distribution (MWD). For Mw and MWD determinations, high performance gel permeation chromatography (HPGPC) has gained wide acceptance as a preferred method due to its high sensitivity, speed and reproducibility. In chromatography, it is well known that the molecular weights are determ…     

Retention studies following (n, γ) activation of rare earth bromates

The initial retentions (at ∼20°C) of (n, γ) activated rare earth bromates were studied using a²⁵²Cf fission neutron source with respect to⁸⁰Br,^80mBr and⁸²Br. They lay over the ranges 19–23, 21–23 and 28–32%, respectively. On heating, retention progressively increases and closes on ∼100% for Sm-bromate while for other systems the optimum values reach <85%. Thus, cation effect becomes more pronounced during thermal annealing. The isothermal data show that the weight-loss is due to dehydration. The cation effect on retention is discussed in the light of various parameters like lanthanide contraction, crystal structure, lattice energy, crystal water, properties of anion and mode of thermal decomposition.     

Prediction of Retention Time of Solutes under Linear Gradient Elution Conditions in RP-HPLC

A model for prediding retention time of solutes undeir linear gradient elulioa conditions has been established. In this model,the theorelkal expressions under different eluflon modes were derived and tested with the retention behaviors of p-hydroxy-benzaldehyde, vanilUn, biphenyl, phenanthrene in gradient elution. With halting into account the dwell time of the instrumeatal system, the theoretically predicted retention times agreewell with those experimentally determined.     

Retention properties of novel β-CD bonded stationary phases in reversed-phase HPLC mode

With the given special structures, the CD bonded stationary phases are expected to have complementary retention properties with conventional C18 stationary phase, which will be helpful to enhance the polar selectivity in RP mode separation. In this work, two β-cyclodextrin (β-CD) bonded stationary phases for reversed-phase HPLC, including 1, 12-dodecyldiol linked β-CD stationary phase (CD1) and olio (ethylene glycol) (OEG) linked β-CD stationary phase (CD2), have been synthesized via click chemistry. The resulting materials were characterized with FT-IR and elemental analysis, which proved the successful immobilization of ligands. The similarities and differences in retention characteristics between the CD and C18 stationary phases have been elucidated by using comparative linear solvation energy relationships (LSERs). The force related to solute McGowan volume has no significant difference, while the hydrogen bonding and dipolar interactions between solutes and CD stationary phases are stronger than between solutes and C18, which is attributed to the special structures (CD and triazole groups) of CD stationary phases. Chemical origins are interpreted by comparison between CD1 and CD2. Similar dispersive interactions of CD1 and CD2 are attributed to their similar length of spacer arms. CD2 which contains OEG spacer arm has relative weaker HBD acidity but stronger HBA basicity. CD stationary phases display no serious different methylene selectivity and higher polar selectivity than in the case of C18. Higher acid selectivity and lower basic selectivity are observed on CD2 than on CD1. Distinctive retention properties and good complementary separation selectivity to C18 make the novel CD bonded stationary phases available for more application in RPLC.     

Retention behavior of the inclusion complexes of some polycyclic aromatic hydrocarbons with β-cyclodextrin

Summary The retention behaviour of a group of polycyclic aromatic hydrocarbons having nearly equal ionization potentials but different molecular polarizability values was investigated by reversed-phase HPLC and gas chromatography, using -cyclodextrin as a selective inclusion reagent. In HPLC, the cyclodextrin was applied as an additive to the ethanolwater binary mobile phase, while in gas chromatography -cyclodextrin served as the stationary phase coated on an inert support. The relationships between the capacity factors, molecular polarizabilities and the shape parameter of solute molecules is discussed.     

Retention Time Locking in the Determination of Narcotic Drugs by Chromatography and Chromatography–Mass Spectrometry

The use of retention time locking (RTL) in the development of unified procedures for the detection and quantitative determination of drugs in biological fluids was considered. With consideration for the use of RTL, a chromatographic procedure with flame-ionization and mass-selective detection was developed for the detection and quantitative determination of opiates and their synthetic analogs; phenylalkylamine derivatives; cocaine; ketamine; and other narcotic drugs, their derivatives, and metabolites in urine. The analytical ranges for chromatography–mass spectrometry were 0.05–1000 and 0.005–1000 g/mL under the conditions of total ion current (TIC) scanning and selected ion monitoring (SIM), respectively. With flame-ionization detection (GC–FID), the analytical range was 0.5–1000 g/mL.     

Use of Large Retention Index Database for Filtering of GC–MS False Positive Identifications of Compounds

The use of the large retention index database for identification and filtering of false positive hits in GC–MS analysis of the ylang-ylang essential oil is illustrated. Differences between experimental retention indices and database values of retention indices of candidate compounds provide additional constraints on the list of candidates for a target compound. Over 100 components of ylang-ylang essential oil (total grade) were identified. The main components, with concentrations more than 4?%, are β-caryophyllene, germacrene D, benzyl benzoate, linalool, geranyl acetate, α-(E,E)-farnesene and isobornyl acetate.     

The Choice of Polar Stationary Phases for Gas–Liquid Chromatography by Statistical Analysis of Retention Data

We have studied the retention indices of 127 volatile substances on a C₇₈-paraffin and on its seven nearly isochor and isomorphous polar derivatives over a temperature range of 90–210 °C. The retention index of a substance on the C₇₈ paraffin has been considered as the standard. The additional retention on the polar derivative was given by the difference of its retention index on the polar solvent and on the C₇₈-paraffin. Statistical analyses of the additional retention have shown that with respect to retention, the seven polar solvents can be classified into three groups: Type I: TTF (tetrakistrifluoromethyl), MTF (monotrifluoromethyl), Type II: PCN (primary cyano), PSH (primary thiol) and Type III: TMO (tetramethoxy), SOH (secondary alcohol) and POH (primary alcohol). It is shown that these three types are best represented by the solvents TTF, PCN and TMO. PSH (primary thiol) is aligned with PCN at temperatures up to about 150 °C, but is similar to TMO at 210 °C.     

Reproducibility of Programmed-Temperature Retention Indices under Average Linear Velocity Carrier Gas Control of GC and GC�CMS

Programmed-temperature retention indices (PTRIs) are useful for the identification and quantification of chemicals by means of GC and GC/MS. To obtain reproducible PTRIs, we studied the influence of average linear velocity and column length under the constant average linear velocity control (CVC) using 55 pesticides and 33 fatty acid methyl esters. The PTRIs decreased with increasing average linear velocity, and the degree of decrease differs with the compounds. The PTRIs, however, were almost constant as long as the same average linear velocity was used even if the column length was changed. In addition, the correlation between the variation ratio in PTRI and the increase in average linear velocity was linear. Using the linear relationship between PTRIs and average linear velocities under CVC, highly reproducible PTRIs were obtained even if the capillary column length changes. Furthermore, the PTRIs determined by GC with FID, ECD, and FPD under atmospheric pressure were applied to GC/MS under vacuum or vice versa. From these results, it was confirmed that because CVC provides reproducible retention indices, CVC is advantageous for qualitative and quantitative analysis by GC and GC/MS.     

Pd-catalyzed oxidative olefination of arenes with olefins via C–H activation: Retention of the leaving group

Russian Journal of Applied Chemistry - Pd-catalyzed direct oxidative olefination of arenes with olefins via C–H activation is described in the absence of any chelating directing groups. For...     

An Enhanced Adsorption in Puerarin Retention on Oligo-β-Cyclodextrin Grafted Poly(Glycidyl Methacrylate) Media

The poly(glycidyl methacrylate) adsorbents P(GMA–EDMA) and P(GMA–DVB) were synthesized by the radical suspension–polymerization method and farther coupled by oligo-β-cyclodextrin (CDP) to obtain P(GMA–EDMA)–CDP and P(GMA–DVB)–CDP. The synthesized polymeric media were characterized by Fourier transform infrared (FTIR) spectrometer, scanning electron microscopy, and BET surface area. The adsorption of puerarin from aqueous solution onto the four media, i.e., P(GMA–EDMA), P(GMA–DVB), P(GMA–EDMA)–CDP, and P(GMA–DVB)–CDP, was studied. An enhanced adsorption of puerarin apparently presented on grafted media. The interaction between the polymeric media and the puerarin was researched by FTIR. The result shows that the adsorption efficiency on P(GMA–DVB)–CDP driven by multiple weak interactions is much higher than that on P(GMA–EDMA) driven by hydrogen bonding interaction only and on P(GMA–DVB) or P(GMA–EDMA)–CDP driven by two interactions.