The Pirkle Type Stationary Phases

The so-called Pirkle stationary phases (named after their inventor W. M. Pirkle) consist of relatively small molecular weight chiral substances covalently bonded to silica. Each bonded moiety contains a limited number of chiral sites (sometimes only one). Nevertheless, on account of their small size, there will be a larger number of interactive groups bonded to the silica and thus the probability of the solute interacting with a chiral centre is still very high. In addition, as the interacting molecule is relatively small, the extra-chiral contributions to retention are also comparatively small, and consequently the chiral interactions themselves represent a higher proportion of the total. It follows that chiral selectivity becomes a more dominant factor controlling retention with the Pirkle phases.

The Pirkle phases have also been used very successfully for the separation of many free and derivatized amino acids. The separation of the p-bromophenyl derivatives of the enantiomers of a number of amino acids is shown in Figure 1. The stationary phase was a naphthyl urea Pirkle stationary phase multiply-bonded to the silica. All of the enantiomers were separated and the analysis time was less than 50 min. Elution was achieved by progressively increasing the dispersive character of the mobile phase. Consequently, the chiral selectivity was probably dominated by polar interactions.

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

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