Preparation and characterization of monolithic columns for capillary electrochromatography with weak electroosmotic flow

Abstract

Preparation and characterization of monolithic columns for capillary electrochromatography with weak electroosmotic flow Monolithic columns of capillary electrochromatography (CEC) with weak electroosmotic flow (EOF) have been prepared by in situ polymerization of butyl methacrylate and ethylene dimethacrylate, without any charged groups in the reaction mixture. The reproducibility of such columns has been proved good no matter whether they are prepared in the same batch or in different batches. In the case of BMA-EDMA monoliths, besides the traditional ternary mixture -1-propanol, 1,4-butanediol, and water, binary porogenic solvents with only alcohols have also been adopted. Compared with ternary porogenic solvents, the design with binary ones allows for fine control of the pore diameter and the formation of the specific surface of the monolithic polymers. The composition of porogenic reagents has also been shown to have an effect on EOF in the column systems. In addition, the Joule heat effect in such columns has been studied by varying the inner diameter of columns. Through the separation of acidic compounds, monolithic columns with low EOF have shown potential in the analysis of charged samples.

Ecstasy Analysis by Monolithic Materials-Capillary Electrochromatography

“…The monolithic column was performed using the methods basedonthosereportedbyZhanget al 48 andDonget al The polymerization mixture for the positively and negatively chargedmonolithcolumnsconsistedof30%monomermixture, 70% porogens, and 0.5% of initiator with respect to monomer content.Themonomermixturesweremadeupof97%PEDAS and 3% of either METAM or AMPS while the porogens consisted of 77% 1-pentanol and 19% ethylene glycol and 4% water. While the polymerization mixture of the neutral monoliths consisted of 48% monomer mixture, 52% porogens, and0.5%ofinitiatorwithrespecttothemonomercontent.The monomermixturesweremadeupofeither50%LMAorBMA and 50% EDMA while the porogens consisted of 45% 1-propanoland55%1,4-butanediol(all%w/w).…”

“…46,47 Using neutralmonoliths,thehydrophobicinteractionbetweencharged analytes and neutral stationary phase may also be lost and influence the separation efficiency. 43,48 Therefore, the performanceofbothcharged(negativeandpositive)andneutral monolithcolumnswereinvestigatedfortheanalysisofMDMA and its metabolite, MDA (since MDA usually reported both in ecstasytabletsfromsomeregionsandinbiologicalsample),by capillary electrochromatography. The one monolith that provided the highest efficiency with shortest analysis time was then selected for validation and the analysis of ecstasy tablets (MDMA)anditsmetabolitesinurinesamples.…”

Peroxodisulfate as a chemical initiator for methacrylate‐ester monolithic columns for capillary electrochromatography

“…Organic polymer-based monoliths are one of the major categories of monolithic materials, and they are often made by a one-step polymerization of a mixture consisting of one or more functional monomers, including a cross-linker, porogenic solvents, and an initiator. Different types of polymeric materials have been studied depending on the bulk monomers employed in the polymerization mixture, resulting in the following main categories: acrylamide [4][5][6][7][8][9], acrylate [10][11][12], methacrylate [13][14][15][16][17][18][19][20][21][22][23][24][25][26], and styrene-based [27][28][29][30][31] stationary phases. Among these, methacrylate and acrylate monolithic columns have been extensively employed.…”

Photochromic spiropyran monolithic polymers: Molecular photo-controllable electroosmotic pumps for micro-fluidic devices

“…As the SP form of the monolith has no surface charge before flushing with 1 mM HCl there would, theoretically, be no EOF expected from this form of the monolith. It has been previously reported, however, that organic polymer monoliths produce a weak EOF without further modification [41,42] although for the control poly(S-co-DVB) monolith the flow recorded was never higher than ca. 4 nl/min.…”