Micro scale analytical derivatizations on solid phase

Abstract

Analytical derivatization (AD), a subset of functional group analysis, alters the structure of an analyte to a product more suitable for analysis. The reactions impart stability to the product and a functionality that enhances sensitivity and specificity to the determinations. By targeting the functional groups for labeling AD adds selectivity to the measurements. Associated with these advantages, however, is the additional step required in sample preparation. The issue of the extra step was resolved by solid phase analytical derivatization (SPAD) which combined the extraction and derivatization step or limited the process to a one-pot reaction in which extraction and derivatization occurred on the solid phase without intermediate isolation of the analyte. Within the broad class of organic acids, SPAD provides conditions that can: derivatize both functionalities; selectively derivatize carboxylic acids in the presence of phenols by reaction at neutral pH which does not ionize phenols; derivatize phenols in the presence of acids by selectively inhibiting derivatization of carboxylic acids at alkaline pH. These reaction characteristics hold whether carboxylic acids are on different compounds or on the same compounds. In the case of carbonyls, SPAD enhances the reaction rate over solution chemistry so that both aldehydes and the usually slower reacting ketones are rapidly extracted/derivatized in one step. The derivatization incorporates chromophores, fluorophores and electrophores for purpose of detection, as well lipophilicity for purpose of extraction. In the case of primary and secondary amines, SPAD functional groups that enhance sensitivity and/or lipophilicity. Initially, SPAD was a batch process but transitioned into a microextraction/derivatization and an automated technique.