The separation of diastereoisomers of polystyrene oligomers in reversed phase HPLC

Selectivity of phase system is of primary concern when designing a 2-D separation, as it affects the 2-D system orthogonality and consequently the peak capacity controlling the number of peaks that can be separated in the available 2-D retention space limited by the time of analysis. Possibilities for characterization of LC phase system selectivity with respect to different polar and nonpolar structural units are compared, with special attention to multidimensional samples with various types of repeat groups, such as homopolymers, (co)polymers, fatty acid esters with various acyl lengths and number and position of double bonds, etc. Possibilities of the 2-D LC separations of these and other sample types, including pharmaceuticals, natural phenolic compounds, biopolymers, etc., using various combinations of separation modes are reviewed. Rules for design of comprehensive 2-D LC x LC systems are discussed, with respect to mobile phase compatibility in the two systems and modulation techniques suppressing band broadening connected with the sample fraction transfer from the first to the second dimension. Pitfalls connected with online connection of normal-phase and RP LC systems and their possible practical solutions are addressed and illustrated by practical examples.

Section: Sec6np Sec6rp and Rp6np 2-d Separations Of Synthetic Polymmentioning

confidence: 98%

Column selectivity for two‐dimensional liquid chromatography

Jandera¹

2006

“…An Onyx C18 monolith (100 mm64.6 mm) was purchased from Phenomenex (Lane Cove, NSW, Australia). Carbon clad zirconia (3 lm particle diameter) was purchased from ZirChrom Separations (Anoka, MN, USA) and packed into columns (100 mm64.6 mm) using methods previously described [13]. The stationary phase material was used as supplied from the manufacturer.…”

Section: Chemicalsmentioning

confidence: 99%

Two‐dimensional HPLC analysis of oligostyrenes: Comprehensive and online heart‐cutting techniques

Shalliker

2009

2-D HPLC incorporating two reversed phase (RP) environments was employed for the isolation of oligomers and their diastereomers of low molecular weight oligostyrenes. The operation of a comprehensive method of analysis was compared to a heart-cutting approach. The comprehensive approach employed a high resolution diastereomer separation in the first dimension and a low peak capacity C18, high speed separation according to molecular weight. Because of solvent incompatibility between the dimensions in the comprehensive method, successful separation of the diastereomers of the oligomers was not possible. The heart-cutting approach used a C18 monolith in the first dimension, which was selective only for molecular weight. Entire molecular weight fractions were then transported to the second dimension in an online heart-cutting process for the separation of diastereomers. The heart-cutting process was more successful in that 228 components of the 511 within the sample were recognized. This series of separations was undertaken in less than 6 h.

“…A Phenomenex Luna C18 column (15064.6 mm, 5 lm particle diameter) (Phenomenex, Torrance, CA, USA) was used in the first separation dimension. Carbon clad zirconia (CCZ) (3 lm particle diameter), which was used as the stationary phase in the second dimension, was purchased from ZirChrom Separations, Inc. (Anoka, MN, USA) and packed into columns (5064.6 mm) using methods previously described [26]. The stationary phase material was used as supplied by the manufacturer.…”

Section: Chemicalsmentioning

confidence: 99%

Multidimensional liquid chromatography for sample characterisation

Toups

Gray

Dennis

et al. 2006

While LC finds enormously widespread use in almost all areas of chemical science, the technique is limited as a means of identification because compounds do not elute with unique retention times. This limitation spurred the growth of hyphenated instrumental methods of analysis, such as LC-MS/MS, which because of the MS/ MS detection became a method of identification. However, techniques like LC-MS/ MS are specialised and require high initial purchase and running costs, inhibiting the more widespread growth of the technique. In an attempt to increase the separation power of LC, multi-dimensional LC was developed. This expanded the separation space and subsequently has allowed the development of methods with fingerprinting ability due to the lower probability of component overlap. The work in this study illustrates the application of 2-D LC as a means of chemical fingerprinting. We employed a sample base of various low molecular weight oligostyrenes and their diastereomers that represent a population of compounds whose selectivities in a one-dimensional separation are almost unity and hence essentially impossible to separate. Yet in a 2-D domain almost all individual components occupy unique 2-D retention times.