The hydrolytic stability of poly(2-(dimethylamino)ethyl methacrylate) was investigated and compared with the stability of its monomer 2-(dimethylamino)ethyl methacrylate (DMAEMA), with 2-(dimethylamino)ethyl isobutyrate (DMAEIB), representing the repeating unit in the polymer, and with the related 3-(dimethylamino)propyl methacrylate (DMAPMA) (H 0/pH range −0.5 to +12, at 37 °C, in aqueous solution). At pH < 3, the unsaturated DMAEMA and DMAPMA were more stable than the saturated DMAEIB. At pH 4−8, DMAEMA and DMAEIB were equally stable, but less stable than DMAPMA. This has been ascribed to a coordination of the protonated dimethylamino group and the ester carbonyl, rendering the ester more susceptible to nucleophilic attack of a hydroxyl ion. At alkaline pH (>pK a) no differences in stability between the compounds were found. P(DMAEMA), either in its free form or complexed to DNA, was substantially more stable to hydrolytic degradation than DMAEMA and DMAEIB. Fluorescence measurements performed with a copolymer of DMAEMA and dansyl ethyl methacrylamide showed that the dielectric constant (εr) experienced in the environment of the polymer backbone, was low (about 7). This microenvironment might be the reason for the hydrolytic stability of the polymer, since the hydrolysis of the monomer decreased substantially with decreasing εr of the medium. Accelerated degradation (80 °C, pH 1 and 7) of p(DMAEMA) and poly(2-(dimethylamino)ethyl acrylate), p(DMAEA), showed that p(DMAEA) was more sensitive to hydrolysis. This can be explained by the assumption that, due to the lack of the methyl group, the εr in the environment of the acrylate backbone is higher than the εr in the environment of the p(DMAEMA) backbone.

The kinetics of the hydrolysis of glycidyl methacrylate derivatized dextran (dex-MA), hydroxyethyl methacrylate derivatized dextran (dex-Hema, and hydroxyethyl methacrylate (HEMA) were systematically investigated in aqueous solution in the H0/pH range of -1.8 to 10.4 at 37 degrees C. The degradation products were quantified with reversed-phase HPLC and used to calculate the residual amount of dextran-bound methacrylate esters. In all compounds the degradation reactions follow first-order kinetics, the rate constants being susceptible to both specific acid and specific base catalysis. The reaction rate constant was independent of both the dex-MA concentration and the degree of substitution. The log Kobs-pH profiles can be divided into three parts: a proton-catalyzed, a solvent-catalyzed, and a hydroxyl-catalyzed section. At high acidities, dex-HEMA and HEMA are equally stable, but about seven times less stable than dex-MA. At alkaline pH, the order of stability is HEMA > dex-MA > dex-HEMA. This demonstrates that at alkaline pH dex-HEMA is predominantly degraded by hydrolysis of the carbonate ester, whereas at low pH, hydrolysis of the methacrylate ester is the main degradation route of this compound.

This survey as a sequel of two earlier reports gives an overview of recent developments, starting from 1999, in the use of derivatization protocols in capillary electrophoretic (CE) analysis. Derivatization is mainly used for enhancement of the detection sensitivity in CE, for which a combination of fluorescence labeling and laser-induced fluorescence detection is favorable. Moreover, especially in the field of saccharide assay, derivatization to introduce charge into the molecule, is common. Derivatization procedures are classified in tables, focused on precapillary, on-line, on-capillary and postcapillary arrangements and divided in sections concerning the functional group that is derivatized. The most frequently reported groups are amines and the reducing end of (oligo)saccharides, but thiols, carbonyl and carboxyl groups, steroids and inorganic ions have also been reported about. Other reasons for derivatization are to enhance chiral separation, introduction of a suitable charge into the molecule or to improve mass spectrometric detection. The use of derivatization techniques for special cases, such as the analysis of neurotransmitters, insulin antibodies and mitochondria has also been incorporated as well as a study on the adsorption of proteins onto capillary walls during CE in which derivatization plays a role.

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