Volume Fraction Of Modifier Research Articles

Optical Properties of Binary Mobile Phases as Constituent Objective Functions in Optimizing the Conditions for High-Performance Liquid Chromatography of Hydrophobic Phenol-Like Compounds

The dependence of the absorbance and the UV absorption limits of typical binary mobile phases for high-performance liquid chromatography (HPLC) on the volume fraction of modifiers was analyzed. The applicability of the found relationships to the multiparametric optimization of the mobile-phase composition with a generalized objective function using the Microsoft Excel 2000 spreadsheet program was considered by the example of microcolumn HPLC of hydrophobic phenol-like additives.

Prediction of peptide retention times in normal-phase liquid chromatography with only a single gradient run

Previous studies of peptide separation by normal-phase liquid chromatography have shown a linear relationship between the logarithm of the capacity factor and the logarithm of the volume fraction of modifier in the mobile phase. This permitted the use of a model to predict isocratic and gradient retention times based on data obtained by two initial gradient runs. In the present study, chromatographic behavior of 25 peptides in normal-phase liquid chromatography with isocratic elution have been studied and a linear relationship between the slope ( S) and intercept [log k(0)] was obtained. This relationship was combined with the algorithm of prediction reported in the previous paper. The prediction of peptide retention times with only a single experimental gradient retention data was investigated.

Prediction of peptide retention time in normal-phase liquid chromatography

Peptide separation by normal-phase liquid chromatography was studied in my two previous papers. The present study shows a linear relationship between the logarithm of the capacity factor and the logarithm of the volume fraction of modifier in the mobile phase. This permitted the use of a model to predict isocratic and gradient retention times following two initial gradient runs. An algorithm for predicting was based on a modification of the ion-exchange model reported in the previous paper. Observed retention times were in reasonably good agreement with those predicted.

Rheological properties and the interface in polycarbonate/impact modifier blends: Effect of modifier shell molecular weight

Core-shell impact modifiers are used to enhance the impact strength of thermoplastics such as polycarbonate. The shell of the modifier is designed specifically to interact with the matrix polymer because interfacial adhesion between the modifier and matrix is important in improving the impact strength. Several methods have been proposed to study the interactions at the modifier/matrix interface. One measure of this interaction is the strength of lap joints. The degree of interactions at the interface can be characterized as the thickness of the interfacial region where the chains of the two polymers mix. Yet another aspect is related to the effect of interfacial interactions on the dynamic mechanical properties of the blend. Previous studies have shown that the viscoelastic properties of these blends deviate from the emulsion models that have been proposed for such blends. The deviation of the measured viscoelastic behavior of these blends compared to that predicted by the models has been attributed to the formation of network structure of particles in the blend. The formation of the network structure is a consequence of larger effective volumes of the particles due to interactions at the interface with the matrix. This study provides a means of using rheological properties and the emulsion models to estimate the extent of interaction at the modifier/matrix interface. In blends used in this study it can be shown that the interactions between the modifier and matrix extend far beyond the boundary between the two and the estimated effective volume fraction of modifier is much larger than the actual modifier content in the blend. The effective volume fraction is frequency dependent and decreases with increasing frequency. The data suggest that beyond certain frequencies the modifier no longer interacts with the matrix and the system has properties similar to the matrix with holes. The data are presented which indicate that, within the range studied, lower modifier shell molecular weight results in a higher level of interaction with polycarbonate. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1095–1105, 1998

Separation of inorganic anions by reversed-phase ion-pair chromatography with direct UV detection

In this paper, a separation method of the inorganic anions including I−, NO 2 − , NO 3 − , IO 3 − and SCN− on the reversed-phase ion-pair chromatography with direct UV detection has been developed, and the limits of detection of these inorganic anions were determined. The effects of the organic modifier volume fraction and concentration of the ion-pair reagent on the retention of inorganic anions were discussed.