Separation of selected humic degradation compounds by capillary electrochromatography with monolithic and packed columns

Abstract

The separation of selected lignin/humic substance (HS) degradation compounds by capillary electrochromatography (CEC) with a methacrylate-based monolithic column and a conventional column packed with 5 microm octadecyl silica (ODS) particles is presented. The effects of organic modifier concentration, pH of the mobile phase, ionic strength, applied voltage, and temperature on the separation were investigated to determine the optimal separation conditions. With the increase of pH in the mobile phase, some of analytes start to ionize and both chromatographic partition and electrophoresis can play roles in separation simultaneously. Accordingly, different selectivity from high-performance liquid chromatography (HPLC) and capillary electrophoresis (CE) could be achieved. The performances of both kinds of columns were compared. The results showed that the peaks of compounds obtained on the former column were much wider than those on the latter one, although good separation efficiency of alkylbenzenes could be readily achieved; the most probable reasons for this behavior and method to solve this problem were briefly discussed. The CEC of a soil fulvic acid with a monolithic column produced partly resolved broad bands; by means of nuclear magnetic resonance (NMR) analysis a wide range of oxygen derived aromatic substitution patterns was found with prominent contributions from phenolic and carboxylic groups.

On‐line concentration of neutral and charged species in capillary electrochromatography with a methacrylate‐based monolithic stationary phase

“…In order to improve the stability of the monolithic columns, capillaries were treated with 3-(trimethoxysilyl)propyl methacrylate, a bifunctional reagent, prior to polymerization reaction [12]. The methoxy group of this compound reacts readily with the silanol groups at the surface of inner silica wall leaving methoxyloyl end to react with the monomers.…”

Separation of acidic and basic compounds in capillary electrochromatography with polymethacrylate-based monolithic columns

“…In order to improve the stability of the monolithic columns, the capillaries were treated with 3-(trimethoxysilyl) propyl methacrylate, a bifunctional reagent, prior to polymerization [26][27][28]. Briefly, the capillaries were washed with 1 mol l −1 NaOH for 2 h so that siloxane groups at inner surface of raw fused silica capillary could hydrolyze to increase the density of silanol groups serving as anchors for subsequent silanization.…”

Selection of two reliable parameters to evaluate the impact of the mobile‐phase composition on capillary electrochromatography performance with monolithic and particle‐packed capillary columns

“…Moreover, poor wettability [21][22][23] or drying-out of the stationary phase could also occur during CEC process. Then, it appears that suitable systems should not be defined only by the choice of an adequate stationary phase, but rather by selecting mobile-phase conditions that will enable an optimal use of the stationary-phase properties (in terms of efficiency and EOF magnitude).…”