Comparison on photo-initiators for the preparation of methacrylate monolithic columns for capillary electrochromatography

Towards highly specific aptamer-affinity monolithic column by efficient UV light-initiated polymerization in "one-pot"

Time-consuming or tedious operation in multiple-step process might is the obstacle for efficiently preparing aptamer-affinity monolithic column. Here, a new and facile strategy to prepare aptamer-based hybrid affinity monolith in "one-pot" at room temperature was exploited, in which UV light-initiated free-radical polymerization and "thiol-ene" click reaction were implemented simultaneously. Only 7 min was cost for finishing the polymerization reaction, which was only 1/100 of that for the traditional thermal polymerization. Using ochratoxin A (OTA) as the model analyte, the recipe for photo-initiated polymerization was optimized, and SEM morphology, FTIR, EDS, pore size distribution and specific recognition performance were also studied. Compared with traditional thermal polymerization, the resultant monolith was achieved more facilely and displayed better results such as more homogeneous skeleton structure, higher reaction efficiency of aptamer (>88.2%) and better specific selectivity to OTA. Besides, an extremely low nonspecific adsorption of analogues was obtained and showed a level at only 1/25 of that in the similar aptamer-affinity monolith prepared by thermal polymerization. Applied to beer and red wine samples, good recovery yields about 99.7 ± 4.0% -101.2 ± 2.3% (n = 3)was achieved with the acceptable RSDs. It would open up a rapid and promising access to efficiently preparing high-performance aptamer-based affinity monolithic columns for online specific recognition.

Preparation of Benzyl Quinine-modified Monolithic Column for Reversed-phase Capillary Electrochromatography

N-Benzylquininium chloride is a versatile functional monomer with quinoline and benzyl groups, which is beneficial for reversed-phase chromatography. In this study, a novel monolithic column with reversed-phase mode was synthesized using N-benzylquininium chloride as the monomer and 3-(acryloyloxy)-2-hydroxypropyl methacrylate as the cross-linker in a binary porogenic solvent consisting of PEG 400 and a 0.05 M sodium hydroxide aqueous solution. The alkaline solution were found to be useful for the improvement of the mechanical stability of the porous monoliths. The monolithic column showed excellent reversed-phase selectivity and various compounds, such as alkylbenzenes, phenols and polycyclic aromatic hydrocarbons, were separated successfully. The highest column efficiency was 1.75 × 10⁵ N m^-1. The relative standard deviations of the migration time for thiourea and four alkylbenzenes were all less than 5.0%, which indicates the monolithic column has good stability. The application of the monolithic column for the analysis of polycyclic aromatic hydrocarbons in spiked lake water samples illustrated its great potential for practical application.

Influence of photo-initiators in the preparation of methacrylate monoliths into poly(ethylene-co-tetrafluoroethylene) tubing for microbore HPLC

In this study, poly(butyl methacrylate-co-ethyleneglycol dimethacrylate) polymeric monoliths were in situ developed within 0.75 mm i.d. poly(ethylene-co-tetrafluoroethylene) (ETFE) tubing by UV polymerization via three different free-radical initiators (α,α'-azobisisobutyronitrile (AIBN), 2,2-dimethoxy-2-phenylacetophenone (DMPA) and 2-methyl-4'-(methylthio)-2-morpholinopropiophenone (MTMPP). The influence of the nature of each photo-initiator and irradiation time on the morphological features of the polymer was investigated by scanning electron microscopy, and the chromatographic properties of the resulting microbore columns were evaluated using alkyl benzenes as test substances. The beds photo-initiated with MTMPP gave the best performance (minimum plate heights of 38 μm for alkyl benzenes) and exhibited a satisfactory reproducibility in the chromatographic parameters (RSD < 11%). These monolithic columns were also successfully applied to the separation of phenylurea herbicides, proteins and a tryptic digest of β-casein.

An innovative reversed-phase monolithic column modified with 4-vinylbiphenyl and ionic liquid stationary phases for capillary electrochromatography

A poly(VBP-co-EDMA-co-IL) monolithic column was used for electrochromatographic separation.

Photoinitiated polymerization of cationic acrylamide in aqueous solution: synthesis, characterization, and sludge dewatering performance

A copolymer of acrylamide (AM) with acryloyloxyethyl trimethyl ammonium chloride (DAC) as the cationic monomer was synthesized under the irradiation of high-pressure mercury lamp with 2,2-azobis(2-amidinopropane) dihydrochloride (V-50) as the photoinitiator. The compositions of the photoinduced copolymer were characterized by Fourier transform infrared spectra (FTIR), ultraviolet spectra (UV), and scanning electron microscope (SEM). The effects of 6 important factors, that is, photo-initiators concentration, monomers concentration, CO(NH₂)₂ (urea) concentrations, pH value, mass ratio of AM to DAC, and irradiation time on the molecular weight and dissolving time, were investigated. The optimal reaction conditions were that the photo-initiators concentration was 0.3%, monomers concentration was 30 wt.%, irradiation time was 60 min, urea concentration was 0.4%, pH value was 5.0, and mass ratio of AM to DAC was 6 : 4. Its flocculation properties were evaluated with activated sludge using jar test. The zeta potential of supernatant at different cationic monomer contents was simultaneously measured. The results demonstrated the superiority of the copolymer over the commercial polyacrylamide as a flocculant.

Reversed-phase monoliths prepared by UV polymerization of divinylbenzene

Many different techniques have been developed to prepare monolithic materials specifically for chromatographic techniques. The two most popular polymerization techniques being thermal or via ultra violet (UV) light. Whereas thermal polymerization is easily employed for a whole variety of monomer and porogen systems, UV polymerization has been limited to methacrylate-based systems, and styrenic systems have been avoided due to their strong absorbance at low wavelengths. By careful consideration of wavelength, initiator and other system components, it was proven that reversed-phase columns for the separation of proteins and peptides can be prepared using divinylbenzene through UV initiation of 2-methyl-4'-(methylthio)-2-morpholinopropiophenone at a wavelength of 350 nm.