Stress hormone metabolite levels in feathers represent an integrated picture of hormone physiology during feather growth. We address several current methodological issues and provide suggestions for future research.

Electrokinetic chromatography (EKC) is a powerful analytical technique that uses an ionic pseudo-stationary phase (PSP) to separate neutral compounds. Although anionic surfactants are the most common choice for PSP, cationic latex nanoparticles are an attractive alternative. Reversible addition-fragmentation chain transfer (RAFT) polymerization was used to synthesize several types of diblock copolymers that self-assemble into latex nanoparticles, which were characterized by a variety of techniques including diffusion NMR. The performance of each nanoparticle as a PSP was studied by using a homologous series of ketones and linear solvation energy relationships (LSER) analysis. A cationic homopolymer coating was found to be necessary to prevent band broadening caused by analyte interactions with nanoparticles adsorbed to the capillary surface. No significant difference in methylene selectivity or LSER parameters was observed between nanoparticles with different cationic shells, but differences were observed between nanoparticles with different hydrophobic cores. Cationic latex nanoparticles behaved more like anionic latex nanoparticles than like cationic surfactants, suggesting that selectivity is primarily driven by the hydrophobic portion of a PSP. Cationic latex nanoparticles in combination with a homopolymer cationic capillary coating are an excellent choice for EKC analyses where an anodic electroosmotic flow is required.

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Capillary electrophoresis and electrokinetic chromatography are typically carried out in unmodified fused-silica capillaries under conditions that result in a strong negative zeta potential at the capillary wall and a robust cathodic electroosmotic flow. Modification of the capillary wall to reverse the zeta potential and mask silanol sites can improve separation performance by reducing or eliminating analyte adsorption, and is essential when conducting electrokinetic chromatography separations with cationic latex nanoparticle pseudo-stationary phases. Semipermanent modification of the capillary walls by coating with cationic polymers has proven to be facile and effective. In this study, poly([2-(acryloyloxy)ethyl]trimethylammonium chloride) polymers were synthesized by reversible addition-fragmentation chain transfer polymerization and used as physically adsorbed semipermanent coatings for capillary electrophoresis and electrokinetic chromatography separations. An initial synthesis of poly([2-(acryloyloxy)ethyl]trimethylammonium chloride) polymer coating produced strong and stable anodic electroosmotic flow of -5.7 to -5.4 × 10 cm /V⋅s over the pH range of 4-7. Significant differences in the magnitude of the electroosmotic flow and effectiveness were observed between synthetic batches, however. For electrokinetic chromatography separations, the best performing batches of poly([2-(acryloyloxy)ethyl]trimethylammonium chloride) polymer performed as well as the commercially available cationic polymer polyethyleneimine, whereas polydiallylammonium chloride and hexadimethrine bromide did not perform well.

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