Semipermanent capillary coatings in mixed organic–water solvents for CE

Abstract

This report describes the creation of semipermanent capillary coatings that are compatible with organic-water solvent systems in CE. The coatings are created by simply rinsing the fused-silica capillary with long double-chain cationic surfactants, such as dimethyl-ditetradecyl ammonium bromide (2C(14)DAB), dihexadecyldimethyl ammonium bromide (2C(16)DAB), and dimethyldioctadecyl ammonium bromide (2C(18)DAB). These surfactants generate semipermanent bilayer coatings on the capillary surface, which display a high degree of stability in buffers containing up to 60% v/v of organic solvents, such as methanol and ACN. The coating stability increases with increasing hydrophobicity of the surfactant, i.e., with increasing chain length. For instance, the EOF changes by only 1.2% in a 2C(18)DAB-coated capillary after 130 capillary volumes of rinsing with 60% v/v methanol containing buffer. The bilayer coatings allow separations to be performed without the need to regenerate the coating between runs or to maintain the EOF modifier in the run buffer. Rapid separations (<2 min) of anions and basic drugs with migration time reproducibility of less than 0.5% RSD and efficiencies of 0.4-0.6 million plates/m are obtained. In addition, selectivity changes for small anions and cationic drugs are also observed when the organic solvent content is adjusted.

Quaternary ammonium compounds in soil: implications for antibiotic resistance development

“…From Table 1, it is clear that alkyltrimethylammonium compounds (ATMAC) and DADMACs, show correlations exist between increasing hydrophobicity and decreasing critical micelle concentration. Table 1 also illustrates that data on CMC are incomplete and incoherent between authors as experimental setups vary (Asakawa et al 2001;Lemić et al 2005;Marcotte et al 2005;Diress et al 2007;Cepeda et al 2013). Several studies have reported calculated values for the octanol-water partition coefficient for QAACs, although, these are not valid due to the surfactant nature of this compound class.…”

Effect of Cyclodextrins on the Stability of Bilayer: A Novel Electrophoretic Approach

“…2C 18 DAB is a double-chained synthetic surfactant that has frequently been used as a coating agent. [14][15][16][17] The structure of this surfactant resembles 2436 M. Zandkarimi et al phospholipids in a living cell membrane. Double-chained surfactants such as phospholipids or 2C 18 DAB form a flat, uniform, and semi-stable bilayer and make suitable coating agents.…”

Covalent modification of fused silica capillaries with quaternized polyamines to achieve robust and stable anodic electroosmotic flow

“…The results illustrate that methylation to quaternary ammoniums gives a surface with a fixed or permanent charge, and thus constant l eof , in the pH range studied. The decrease in the protonation of imine groups of PEI in the nonmethylated capillary with increasing pH causes the wall to be less positively charged and thus results in a decrease in EOF [1,5,8]. The large deviation at pH 10 in the nonmethylated capillary is not a true SD as it represents a trend to lower EOF over time beginning at -2.64610 -4 cm 2 /Vs and decreases with repeated measurements to -1.86610 -4 cm 2 /Vs.…”