Separation and analysis of cis-diol-containing compounds by boronate affinity-assisted micellar electrokinetic chromatography

Abstract

Cis-diol-containing compounds (CDCCs) are usually highly hydrophilic compounds and are therefore difficult to separate by conventional reversed-phase-based micellar electrokinetic chromatography (MEKC) due to poor selectivity. Here, we report a new method, called boronate affinity-assisted micellar electrokinetic chromatography (BAA-MEKC), to solve this issue. A boronic acid with a hydrophobic alkyl chain was added to the background electrolyte, which acted as a modifier to adjust the selectivity. CDCCs can covalently react with the boronic acid to form negatively charged surfactant-like complexes, which can partition into micelles formed with a cationic surfactant. Thus, CDCCs can be separated according to the differential partition constants of their boronic acid complexes between the micellar phase and the surrounding aqueous phase. To verify this method, eight nucleosides were employed as the test compounds and their separation confirmed that the combination of boronate affinity interaction with MEKC can effectively enhance the separation of CDCCs. The effects of experimental conditions on the separation were investigated. Finally, the BAA-MEKC method was applied to the separation and analysis of nucleosides extracted from human urine. BAA-MEKC exhibited better selectivity and improved separation as compared with conventional MEKC and CZE. Successful quantitative analysis of urinary nucleosides by BAA-MEKC was demonstrated.

Boronate affinity adsorption of cis‐diol‐containing biomolecules in nonaqueous solvent

“…Specific capture and effective enrichment of these biomolecules are therefore critical in their isolation/separation and analysis (Li et al ., ). Boronic acids can bind with compounds containing cis ‐diol moieties with high affinity through reversible ester formation in alkaline conditions, while dissociations occur in acidic conditions, thus boronic acids have specific selectivity for the cis ‐diol‐containing compounds (Wang et al, , , ; Li and Liu, ). Boronate affinity adsorption has been broadly used for isolation/enrichment of hydrophilic molecules containing cis ‐diols (Wang et al, , , ; Li et al ., ; Cetinkaya et al ., ).…”

“…Boronic acids can bind with compounds containing cis ‐diol moieties with high affinity through reversible ester formation in alkaline conditions, while dissociations occur in acidic conditions, thus boronic acids have specific selectivity for the cis ‐diol‐containing compounds (Wang et al, , , ; Li and Liu, ). Boronate affinity adsorption has been broadly used for isolation/enrichment of hydrophilic molecules containing cis ‐diols (Wang et al, , , ; Li et al ., ; Cetinkaya et al ., ). However, the traditional boronate affinity adsorption has seldom been applied to hydrophobic molecules, owing to their poor solubility in aqueous solutions (Wang et al, , , ).…”

Boronate affinity‐assisted MEKC separation of highly hydrophilic urinary nucleosides using imidazolium‐based ionic liquid type surfactant as pseudostationary phase

“…Most of the boronate affinity chromatography applications are based on phenylboronate moieties with very few reports concerning the applicability of alkylboronates . It was recently reported that the association constant between 1‐butylboronate and different nucleosides is in the range of 200–205 M −1 at pH 10.0, and it was found that the six nucleosides studied exhibit only slight variations in their association constant with 1‐butylboronate .…”

“…It was recently reported that the association constant between 1‐butylboronate and different nucleosides is in the range of 200–205 M −1 at pH 10.0, and it was found that the six nucleosides studied exhibit only slight variations in their association constant with 1‐butylboronate . Based on these data, a method called ″boronate affinity assisted MEKC″ has been developed to improve the selectivity of the separation of nucleosides compared to MEKC methods without employing a boronate . In , the authors have reported that alkylboronates can be used in combination with the traditional cationic surfactant, cetyltrimethylammonium bromide (CTAB), in the separation of urinary nucleosides.…”

“…Based on these data, a method called ″boronate affinity assisted MEKC″ has been developed to improve the selectivity of the separation of nucleosides compared to MEKC methods without employing a boronate . In , the authors have reported that alkylboronates can be used in combination with the traditional cationic surfactant, cetyltrimethylammonium bromide (CTAB), in the separation of urinary nucleosides. They have found that the introduction of 1‐butylboronic acid (BBA) at 25 mmol/L, urea (2 mol/L), and CTAB (25 mmol/L) to the BGE (200 mmol/L CHES) affords the best resolution between the studied analytes.…”