Monolithic stationary phases divinylbenzene

A monolithic silica-based CIS stationary phase was used under high flow rate condition (2 mL/min) without significant back pressure in IPC analysis of a recently discovered new drug candidate for the treatment of Alzheimer s disease [15]. Nanoscale IPC using a monolithic poly(styrene-divinylbenzene) (PS-DVB) nanocolumn coupled to nanoelectrospray ionization mass spectrometry (nano-ESl-MS) was evaluated to separate and identify isomeric oligonucleotide adducts. Triethylammonium bicarbonate was used as the IPR. Interestingly, the performance of the polymeric monolithic PS-DVB stationary phase significantly surpassed that of columns packed with the microparticulate sorbents CIS or PS-DVB [16]. 

Hochleitner, E.O. et al. Analysis of isolectins on non-porous particles and monolithic polystyrene divinylbenzene-based stationary phases and electrospray ionization mass spectrometry. Int. J. Mass Spectmm. 2003, 223-224,519-526. 

A typical mobile-phase composition is an acetonitrile-water gradient with a fixed concentration of trifluoroacetic acid (TFA), formic, or acetic acid (typically 0.05-0.5%). TFA acts as an ion-pairing agent and masks secondary interactions with the silica-based stationary phase. TFA may significantly suppress the ESI response in positive-ion mode. To avoid this, either formic acid is preferred or a mixture of 0.02% TFA and 0.5% acetic acid can be used. Some silica-based RPLC materials can be used with a lower TFA concentration (PepMap ). Alternatively, poly(styrene-divinylbenzene) polymeric materials (PS-DVB) can be applied. With a monolithic PS-DVB column, only a small decrease in separation efficiency on the monolithic column was observed when the TFA concentration was reduced from 0.2%to0.05%[51]. 

Xiong, B. etal. Capillary electrochromatography with monolithic poly(styrene-co-divinylbenzene-co-methacrylic acid) as the stationary phase, J. High Resol. Chromatogr., 23, 67, 2000. 

Organic polymers are synthesized within capillaries, with polystyrene-divinylbenzene (PS-DVB) and polymeric methacrylates as the most common stationary phases. The most common process to make capillary monoliths includes opening silanol groups on the fused silica walls with sodium hydroxide, attaching a wall linkage, polymerization with monomer, cross-linker, porogen, and initiator, and sometimes grafting with other functionalities. 

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