A Silica Monolithic Column with Chemically Bonded l-Pipecolic Acid as Chiral Stationary Phase for Enantiomeric Separation of Dansyl Amino Acids by CEC–MS

Abstract

A silica monolithic column chemically modified with L-pipecolic acid as chiral stationary phase has been developed for chiral separation of dansyl amino acids by capillary electrochromatography-mass spectrometry (CEC-MS). The monolithic column was prepared by a sol-gel process and subsequent chemical modification by L-pipecolic acid as chiral selector with 3-glycidoxypropyltrimethoxysilane as spacer. Interestingly, it was found that the L-pipecolic acid-modified monolithic column can hold copper(II) ions tightly after loading Cu(II) ions during column preparation and conditioning and allows CEC separation to be conducted based on chiral ligand exchange with MS detection by a mobile phase without copper ions. It has been demonstrated that the chiral monolithic column operates well for enantioseparation of several dansyl amino acids by CEC-MS.

Enantioresolution of Amino Acids: A Decade’s Perspective, Prospects and Challenges

“…The coupling significantly increases signalto-noise ratio, and the ability to simultaneously measure and identify several compounds in the same sample can be obtained using MS 2 experiments [130]. Use of CE-MS in chiral AA analysis has gained attracted attention during the last decade [90,[130][131][132][133][134][135]. Two new electrophoretic techniques have been developed by Liang et al One is microchip capillary electrophoresis based on bovine serum albumin-conjugated Fe 3 O 4 @Au nanoparticles as stationary phase [136] and other is open-tubular capillary electrochromatography using bovine serum albumin-conjugated polydopamine-graphene oxide (PDA/GO) nanocomposites (PDA/GO/BSA) as stationary phase [137].…”

New approaches in sensitive chiral CE

“…However, the peak efficiency obtained by CEC is usually low, while its robustness still needs to be improved. Three works using CEC–MS methodologies for the enantiomeric separation of amino acids ; different neutral, basic, and acidic chiral compounds ; and aminoglutethimide, monomethylamine, and dimethylamine have been reported achieving LODs between 3 × 10 −6 and 8 × 10 −5 M. Thus, Zhang et al described the use of a silica monolithic column chemically modified with l ‐pipecolic acid as chiral stationary phase (CSP) that enabled the chiral separation of three amino acids (phenylalanine, serine, threonine). Nevertheless, with MS detection, no baseline resolutions with analysis times of 100 min were achieved and no application was carried out.…”

Chiral capillary electromigration techniques—mass spectrometry—hope and promise

“…The monolith inside the capillary is then modified with a chiral selector. Zhang and co‐workers modified a preformed silica‐based monolithic column with l ‐pipecolic acid as the chiral stationary phase . The ability of the column to hold copper(II) ions after column preparation and conditioning allowed for chiral ligand exchange separations of racemic dansyl amino acids in the absence of copper‐ions in the mobile phase.…”