Monolithic chromatograph

Despite many advantages, CEC columns packed with microparticulate sorbents do have some limitations such as the relatively large void volume between the packed particles and the slow diffusional mass transfer of solutes into the stagnant mobile phase present in the pores of the separation medium [83,84]. Alternative approaches to alleviate the problem of mass transfer and intraparticular void volume are the concepts of monolithic chromatographic beds and open-tubular columns. In mono-... 

A. Podgornik and A. Strancar, Convective Interaction Media (CIM)-short layer monolithic chromatographic stationary phases, Biotechnol Annu. Rev., 2005,11, 281-333. 

Podgornik A, Vidic J, Jancar J, Lendero N, Frankovic V, Strancar A. Noninvasive methods for characterization of large-volume monolithic chromatographic columns. Chem Eng Techn 2005 28 1435-41. 

Forcic D, Brgles M, Ivancic-Jelicki J, Santak M, Halassy B, Barut M, et al. Concentration and purification of rubella virus using monolithic chromatographic support. J Chromatogr B 2011 879 981-6. 

In this study, chromatographic experiments were 10 times faster with the monolithic column and results were equivalent to those obtained with the silica-based columns. This approach could be further optimized with faster gradient since flow rate should be increased by a factor 3 or 7 compared to conventional Cig supports [61, 62] and gradient time reduced by the same factor [63] to fully exploit the potential of monolithic supports. 

Chromatographic use of monolithic silica columns has been attracting considerable attention because they can potentially provide higher overall performance than particle-packed columns based on the variable external porosity and through-pore size/skeleton size ratios. These subjects have been recently reviewed with particular interests in fundamental properties, applications, or chemical modifications (Tanaka et al., 2001 Siouffi, 2003 Cabrera, 2004 Eeltink et al., 2004 Rieux et al., 2005). Commercially available monolithic silica columns at this time include conventional size columns (4.6 mm i.d., 1-10 cm), capillary columns (50-200 pm i.d., 15-30 cm), and preparative scale columns (25 mm i.d., 10 cm). 

When two monolithic silica columns were used for two sets of 2nd-D chromatographs (Fig. 7.6c) separating each fraction of the lst-D effluent alternately,... 

Chankvetadze, B., Yamamoto, C., Tanaka, N., Nakanishi, K., Okamoto, Y. (2004). High-performance liquid chromatographic enantioseparations on capillary columns containing monolithic silica modified with cellulose tris(3,5-dimethylphenylcarbamate). J. Sep. Sci. 27, 905-911. 

Kobayashi, H., Kajiwara, W., Inui, Y., Hara, T., Hosoya, K., Ikegami, T., Tanaka, N. (2004). Chromatographic properties of monolithic silica capillary columns for polar and nonpolar compounds in reversed-phase HPLC. Chromatographia 60, S19-S25. 

Leinweber, F.C., Tallarek, U. (2003). Chromatographic performance of monolithic and particulate stationary phases hydrodynamics and adsorption capacity. J. Chromatogr. A 1006, 207-228. 

Oberachert, H., Premstaller, A., Huber, C.G. (2004). Characterization of some physical and chromatographic properties of monolithic poly(styrene-o-divinylbenzene). J. Chromatogr. A 1030, 201-208. 

Schley, C., Altmeyer, M.O., Swart, R., Muller, R., Huber, C.G. (2006). Proteome analysis of Myxococcus xanthus by off-line two-dimensional chromatographic separation using monolithic poly-(styrene-divinylbenzene) columns combined with ion-trap tandem mass spectrometry. J. Proteome Res. 5, 2760-2768. 

One problem is how to optimize throughput (analysis time) without losing peak capacity. Different approaches have been suggested and led to different developments by instrument and column manufacturers. This section will concentrate on the usage of totally porous particle columns for chromatographic separation only. Alternatives are monolithic columns9 and shell packing materials such as Halo or Poroshell.10-13... 

An interesting idea was to use a monolith column to perform dual functions of online SPE and chromatographic separation. Because of the porous structure of a monolith column and its very low backpressure, plasma or diluted plasma can be directly injected. Plumb et al. (2001) used this approach to quantitate an isoquinoline drug and 3 -azido-3 -deoxy thymidine (AZT). Diluted plasma samples (plasma water 1 1) were injected directly into a Chromolith Speed ROD RP-18e column... 

To improve chromatographic separation, another analytical column could be used in addition to the monolith (Xu et al. 2006). The monolith column served as an extraction column only. Hsieh et al. (2000, 2002) utilized a polymer-coated mixed function (PCMF) Capcell C8 column (4.6 x 50 mm, Phenomenex) to provide dual functions—online plasma extraction and analyte separation. The silica was coated with a polymer containing both hydrophilic polyoxythylene and hydrophobic groups. The diluted plasma samples (1 1 to 1 3) were injected directly. No column deterioration was observed after 200 injections. 

Asperger A. et al., 2002. Trace determination of priority pesticide in water by means of high-speed online solid-phase extraction-liquid chromatography-tandem mass spectrometry using turbulent-flow chromatography columns for enrichment and a short monolithic column for fast liquid chromatographic separation. J Chromatogr A 960 109. 

Horvath et al. sintered the contents of a capillary column packed with 6 pm oc-tadecylsilica by heating to 360 °C in the presence of a sodium bicarbonate solution [101]. These conditions also strip the alkyl ligands from the silica support, thus significantly deteriorating the chromatographic properties. However, the performance was partly recovered after resilanization of the monolithic material with dimethyloctadecylchlorosilane allowing the separation of aromatic hydrocarbons and protected aminoacids with an efficiency of up to 160,000 plates/m. 

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