Studies on the analytical performance of a non-covalent coating with N,N-didodecyl-N,N-dimethylammonium bromide for separation of basic proteins by capillary electrophoresis in acidic buffers in 25-and 50-μm capillaries

Abstract

Capillaries (25- and 50-microm inner diameter) coated with a double-alkyl-chain cationic surfactant N,N-didodecyl-N,N-dimethylammonium bromide (DDAB) were used for the separation of four basic standard proteins in buffers of pH 4 at various ionic strengths. The choice of buffer is critical for the analytical performance. Ammonium ions must be avoided in the buffer used in the non-covalent coating procedure owing to competition with the surfactant. Phosphate buffer gave a better separation performance than some volatile buffers; the reason seems to be a complex formation between the proteins and dihydrogenphosphate ions, which decreases tendencies for adsorption to the capillary surface. The DDAB coating was easy to produce and stable enough to permit, without recoating, consecutive separations of the proteins for up to 100 min with good precision in migration times and peak areas. A strong electroosmotic flow gives rapid separations, which is of special importance when commercial instruments are used, since the choice of the length of the capillary is restricted.

Cationic poly(amidoamine) dendrimers as additives for capillary electroseparation and detection of proteins

“…Therefore, the influence of PAMAMs as additives on separation performance varies with buffer pH. On the other hand, buffers of wide pH range have been employed for high performance separation of proteins by CE/CEC, from extremely acidic [15], mild acidic [16][17][18][19][20] to neutral [12,[21][22][23][24], mild alkaline [25,26] and extremely alkaline [27]. Therefore, examining the properties of PAMAM dendrimers as additives in different pHs is helpful in extending their potential applications in protein analysis.…”

Interactions of Proteins with the Acidic Components of the Electrolyte Solution and Their Role in the Performance of Separations by CZE

“…In addition, the TMBD-DIEN solution contains a high concentration of phosphate anions that are expected to strongly interact with the positively charged proteins. The formation of strong complexes between phosphate ions and proteins has been largely documented in literature [34] and already associated with the explanation of changes in the migration behavior of proteins in CZE [29,[35][36][37].…”

Effect of coating electrolytes on two-tailed surfactant bilayer coatings in capillary electrophoresis

“…Efficiencies of about 1 million plates/m [2,3] and quantitative recoveries [4,5] have been observed for separations of basic proteins on didodecyldimethyl ammonium bromide (DDAB)-coated capillaries. Further, the amphiphilic nature of surfactants enables them to effectively coat hybrid microfluidic channels [6].…”

“…Two-tailed cationic surfactants such as DDAB [2,9] and dioctadecyldimethylammonium bromide (DODAB) [3,9,10] form supported bilayers on the capillary wall [5]. The stability of these bilayers allows two-tailed surfactants to be used as semi-permanent coatings, wherein the capillary or microfluidic channel is pre-rinsed with a surfactant solution to form the coating followed by flushing the non-sorbed surfactant from the capillary.…”