Nonaqueous electrochromatography on continuous bed columns of sol-gel bonded large-pore C30 material: Separation of retinyl esters

Abstract

A nonaqueous electrochromatographic reversed‐phase separation method for retinyl esters using continuous bed columns has been developed. The packing material was C30 modified material large‐pore silica (5 μm Nucleosil 4000 Å). The continuous bed columns were prepared by sol–gel bonding in 180 μm inside diameter fused silica capillaries. The mobile phase consisting of 2.5 mM lithium acetate in N,N‐dimethylformamide‐acetonitrile‐methanol (2+7+1, v/v) gave rise to an electroosmotic flow of 1 mm/s at 350 V/cm and 40°C. Using a 36 cm effective length column separation of the commercially available and synthesized standards (all‐trans‐retinyl acetate, palmitate, heptadecanoate, stearate, oleoate, and linoleoate) was obtained within 12 min. Separation of isomeric retinyl palmitate (13‐cis‐ and all‐trans‐retinyl palmitate) was also obtained. The selectivity was found to be temperature dependent in the temperature range investigated (30–60°C). The within‐day and between‐day variations (n=3) of retention times of all‐trans‐retinyl palmitate were 0.2% relative standard deviation (RSD) and <2.5% RSD, respectively. Further, the within‐day and between‐day variations (n=3) of peak areas were in both cases <4% RSD using injection. The column examined was stable for more than 1 month of extensive use. Liver extracts from arctic seal were analyzed. © 2001 John Wiley & Sons, Inc. J Micro Sep 12: 561–567, 2000

Temperature-programmed non-aqueous electrochromatographic separation of retinyl esters

“…An isothermal electrochromatographic separation method for retinyl esters was previously described [48]. An isothermal electrochromatographic separation method for retinyl esters was previously described [48].…”

“…In a commercial CEC system (open system, no connections) at the same operating conditions, an h of 3.9 was obtained [48]. In a commercial CEC system (open system, no connections) at the same operating conditions, an h of 3.9 was obtained [48].…”

“…The C 30 packing material was prepared using 5 lm Nucleosil 4 000 (Machery-Nagel, Düren, Germany) and triacontyltrichlorosilane (ABCR, Karlsruhe, Germany), as previously described [48]. Fused silica capillaries of 180 lm internal diameter (ID)/350 lm outside diameter (OD) (Composite Metal Services, Hallow, Worcester, UK) were washed with 1 M KOH and water, respectively, and dried with nitrogen at 1208C, according to Ref.…”

Temperature programming in liquid chromatography

“…Temperature-responsive stationary phases have provided another means of changing resolution [102]. Currently attempts are being made to provide a new platform for separation of proteins and peptides by electrochromatography, using elevated temperatures [69,71]. In an application area where there is a considerable need for fast separation methods, the preliminary results are very promising, with high resolution and efficiency and reduced analysis times.…”

Recent applications of capillary electrochromatography

“…The conditions previously applied on a Hypersil ODS column were transferred to the analysis of retinyl ester standards and liver extracts of arctic seal on a capillary column packed with 5 mm C30 particles. The same samples were analyzed on a column with sol-gel bonded Nucleosil silica, modified with C30 [76]. The use of sol-gel bonded C18 as a continuous bed was investigated for the same analysis [75].…”