Monolithic Phases

Xu R.N. et al., 2006. A monolithic-phase based online extraction approach for determination of pharmaceutical compounds in human plasma by HPLC-MS/MS and a comparison with liquid-liquid extraction. J Pharm Biomed Anal 40 728. 

Future directions in these phases include metal oxide monoliths, phases with smaller pores and larger surface areas for preparative separations, and exploration of MS-compatible phases. 

Yang et al. (1992a, b) also utilised a combination of experiment and calculation to critically determine the phase region for the /9-NiAl, 7 -Ni3AI and j0 -Ni2AlTi phases. The philosophy of their approach was to produce an alloy with high levels of /3 and 0, as mixtures of these phases had been shown to have enhanced creep resistance in comparison to the monolithic phases themselves (Polvani et al. 1976). The combination of experiment and calculated phase % vs temperature plots (Figs. 

Strategies for the Preparation of Molecularly Imprinted Monolithic Phases... 58... 

The molecular imprinting strategy can be applied for the recognition of different kinds of templates from small organic molecules to biomacromolecules as proteins. Some examples of separations investigated with MIP monoliths in CEC and LC are shown in Table 2. The influence of the imprinted monolithic phase preparation procedure and of the separation conditions on the selectivity and chromatographic efficiency have been widely studied [154, 157, 161, 166, 167, 192]. The performance of imprinted monoliths as chromatographic stationary phase has also been compared to that of the traditional bulk polymer packed column [149, 160]. It was shown that the monolithic phases yielded faster analyses and improved chiral separations. 

The thermoelectric properties of doped and sintered samples are presented in Table 1. The electrical resistivity of the composite made by those doped powders become very high, compared to monolithic phases. So far, we consider the results to have been caused by Ge diffusion between SiGe/ PbTe interface. By EPMA analysis, 0.9-3.5at% of Ge were probed in PbTe phase. After the experimental work by T.Abakumowa [12] such Ge atoms could work as donor site in PbTe lattice. 

The electrical resistivity of the composite made by those doped powders become very high, compared to monolithic phases. We consider the results to have been caused by Ge diffusion between SiGe/ PbTe interface. 

K.C. Saunders, A. Ghanem, W.B. Hon, E.F. Hilder, P.R. Haddad, Separation and sample pre-treatment in bioanalysis using monolithic phases a review, Anal. Chim. Acta 652 (2009) 22. 

Both open and packed columns have been demonstrated on LC and CEC chips. Strategies for making stationary phases in microchannels are few, and fall basically into three categories (a) standard HPLC packings, (b) monolithic phases, and (c) wall coatings or bonded, each of which is now discussed in turn. 

Fig. 11 Top SU-8 based microfluidic system, which includes an enzymatic microreactor, a chromatographic device, and an integrated ionization emitter tip. Bottom SEM photograph of a section of a monolithic phase prepared from LMA/EDMA. Reproduced from [133]...

Scheme 12 Immobilization of palladium(O) particles onto the monolithic phase inside the microreactor...

SilicaROD The stationary phase is constituted as a solid rod no classical particles (..monolithic phases ). 

GaAs MMICs Monolithic microwave integrated circuits have been fabricated using ion implantation. This renders feasible the fabrication of monolithic phased array radars. These circuits incorporate active devices, RF circuitry, and bypass capacitors (53-54). 

There are three possibilities for the implementation of SPE in microfluidic devices, namely, (1) to fill a channel with particles that serve as the extraction material, (2) coat the channel wall with the extraction material, and (3) fill a channel with a polymeric rod (monolithic phase) extraction material. 

To increase the surface-to-volume ratio in the preconcentration channel without the need for particles, the channel can be filled with a polymeric rod. These are formed by in situ polymerization, during which the polymer material also reacts with the wall of the channel. As a result, no frits are needed to hold the material in place. Columns filled with a polymeric rod, so-called monolithic columns, were originally developed for conventional liquid chromatography. They are made by sol-gel technology, " which enables the formation of a highly porous material containing macropores and mesopores in its structure. The use of a monolithic phase circumvents the problems encountered when packing a column with particles. 

Yu et al. described the integration of ion-exchange and hydrophobic concentrators based on a methacrylate-based monolithic phase in a chip made of glass. With this device, they were able to concentrate a hydrophobic tetrapeptide, Coumarin 519, and green fluorescent protein (GFP) by a factor of 1000. 

More recently, columns have been developed where the stationary phase is formed of a porous polymer network inside the capillary. These are called monolithic phases, and have emerged as an alternative to traditional packed bed columns for use in micro-HPLC. They hold many advantages over traditional packed bed columns, being easy to manufacture since the monolith is formed in situ, often via a one-step reaction process, and its properties such as porosity, surface area, and functionality can be tailored. Another major advantage is that they eliminate the need for retaining frits. These columns can be manufactured from a variety of materials, but the most common include sol-gel, methacrylate-based, acrylamide-based, and styrene-based polymeric structures. 

These two disadvantages are less pronounced with solid core particles than with silica-based monolithic phases. Moreover, the retention behavior of every monolithic column can be considered one of a kind given the manufacturing process for the bonding. There are three more considerations with monolithic columns ... 

The aim of this entry is to provide an overview of the monolithic phases that are most commonly or widely used (silica- and polymer-bases) in chromatography. In describing these materials, the focus will be on highlighting the differences between the phases and finally providing key applications to demonstrate the use of material. 

This contribution aims to present the framework for the analytical assessment of strengthened structures when the intervention methods adopted result in composite members with multiple monolithic phases. The slippage introduced... 

The success of repair/strengthening, as quantified by the improvement of strength and stiffness of the retrofitted members, depends on its entirety on the degree of collaboration between the various monolithic phases of the composite member. The response of the retrofitted member is modified proportionally to the slip that takes place along the interface. The calculation of slip... 

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