Peak compression in linear gradient elution liquid chromatography.

An expression for peak compression factor based on temporal peak widths is proposed which can be measured directly. The relationship between it and peak compression factor based on spatial peak widths is given. The experimental data presented in the Neue's work are reevaluated.

Influence of the pre-elution of solute in initial mobile phase on retention time and peak compression under linear gradient elution.

Under gradient elution the solute will firstly migrate in initial mobile phase due to dwelling time (t) of the system. The pre-elution of solute in initial mobile phase can be accounted for by a dimensionless value of t/(tk), where t and k denote dead time and retention factor in initial mobile phase, respectively. The influence of t/(tk) on retention time (t) and peak compression factor (G) are discussed under linear gradient elution.

[Analysis of alkaline CuO degradation products of acid detergent fiber from tobacco leaves by using liquid chromatography].

The acid detergent fiber (ADF) from tobacco leaves was obtained by treating the sample with petroleum ether-ethanol (6:4, v/v), 30 g/L sodium dodecylsulfate and 0.5 mol/L sulphuric acid containing 20 g/L hexadecyl trimethyl ammonium bromide successively. The ADF was degraded by the alkaline CuO oxidation procedure.

[Influence of the distortion of gradient profile on peak width in gradient liquid chromatography].

In gradient liquid chromatography, the gradient profile may be distorted because of the effects of solvent mixing and axial dispersion. Such effects will be significant especially when stepwise gradient and linear gradient with high slope are applied. In this work, we discussed the influence of the distortion of gradient profile on the peak width.

Equivalence between the equilibrium dispersive and the transport model in describing band broadening in analytical gradient liquid chromatography.

It is shown that the transport (TR) model may be equivalent to the equilibrium dispersive (ED) model in analytical gradient liquid chromatography when the column efficiency is not small. This result is obtained by assuming that the gradient profile is not distorted, the injection is an impulse, and the apparent axial dispersion coefficient (Da) of the ED model or the lumped kinetic coefficient (kfL) of the TR model varies with mobile phase composition. According to this equivalence, the plate height equation derived from the TR model in our previous work (Eq.

Evaluation of the peak variance in gradient liquid chromatography.

The peak variance obtained under single stepwise (SS), single linear (SL) and ladder-like (LL) gradient conditions was evaluated by taking into account the variation of plate height with mobile phase composition. LC tests were performed on a C18 column using a mixture of methanol and water as the mobile phase and six aromatic compounds (anisole, o-cresol, biphenyl, phenol, aniline and acetophenone) as the model samples. It was found that the relationship between the retention factor and mobile phase composition could be described by the linear solvent strength model.

Poly[[diaqua-hemi-μ(4)-oxalato-μ(2)-oxalato-praseodymium(III)] monohydrate].

In the title complex, {[Pr(C(2)O(4))(1.5)(H(2)O)(2)]·H(2)O}(n), the Pr(III) ion, which lies on a crystallographic inversion centre, is coordinated by seven O atoms from four oxalate ligands and two O atoms from two water ligands; further Pr-O coordination from tetra-dentate oxalate ligands forms a three-dimensional structure. The compound crystallized as a monohydrate, the water mol-ecule occupying space in small voids and being secured by O-H⋯O hydrogen bonding as an acceptor from ligand water H atoms and as a donor to oxalate O-acceptor sites.