Small molecule separation columns

Aqueous SEC is widely used for the determination of MWDs of a variety of synthetic and naturally occurring water soluble polymers, as well as for separations of small molecules. The column requirements for aqueous SEC are very demanding to eliminate ionic and hydrophobic effects. 

Other applications that utilize different types of reversed-phase columns in both dimensions have been advocated by Carr (Stoll et al., 2006) for metabolomics work in small-molecule separations. These stationary phases include a pentafluorophenyl-propyl stationary phase in the first dimension and a carbon-coated zirconia material stationary phase in the second dimension. A common mistake in 2D method development is to mismatch the solvent system the two solvent systems must be miscible as discussed below. 

In contrast to IEX, RPLC protein separations show good efficiency using either nonporous (Wall et al., 2000) or porous (Liu et al., 2002 Millea et al., 2005) silica columns, with peak capacities of approximately 100. Although not equivalent to small molecule separations, including peptides, this performance is not the main... 

First, mobile phase and column we saw that most of the small molecule separations could be made on a C18 column in An/buffer water, with the exception of charged molecules and carbohydrates, which are too water soluble. We saw a range of polarity from fat-soluble vitamins, steroids, triglycerides, chlorinated pesticides eluting in 60-80% An/water, to carbamate, phosphate pesticides, anticonvulsants, antidepressants at 40-50% An/water, to nucleosides, nucleotides, aspirin, and water-soluble vitamins at 5-10% An/water. If you know something about the compound s structure or its solubility, you have a good clue as to what mobile phase can be used for its separation. 

Agilent Technologies currently offers commercial nanospray HPLC-ChipR and HPLC-Chip CubeR MS and MS/MS systems. Chips come with standard Cis packing or can be custom packed with standard HPLC column materials. They are aimed at proteomic labeling studies, and small molecule separations. 

The nature and characteristic of column packing containing the stationary phase is critical to the column performance and success of the intended applications.13 Common types and characteristics of column packings in use today for small molecule separations are summarized below. Details are discussed further in this section. 

Another type of packed column particle useful for relatively small molecule separations is a porous polymer . Trade name Porapack . These are like the molecular sieve, but made of organic polymers or resins with larger sized pores. Highly volatile molecules larger than the fixed gases, but of a size containing only a few atoms, are... 

Preliminary data (27) suggest that stationary-phase diffusion is about one-third as fast for ion-exchange HPLC as for RPLC, whiph appears reasonable on the basis of the results discussed for small molecules separated on Silica column packings (see Section III,A). Therefore,... 

The development of HPLC columns for small-molecule separations is today well advanced, and it is likely that further iminovements are somewhat limited. Thus advances in column technology during the past decade... 

The first criterion for column selection is the molecular weight of the sample to be analyzed. For some applications in which resolution is required over a relatively narrow molecular weight range, individual pore size packings are suitable. This is particularly the case for small-molecule separations, as shown in Figure 5. For polymer analyses in which resolution is required to cover several decades of molecular weight, mixed gel or linear columns are widely applicable. 

Gel permeation chromatography, exclusion chromatography. gel filtration chromatography. A technique for separating the components of a mixture according to molecular volume differences. A porous solid phase (a polymer, molecular sieve) is used which can physically entrap small molecules in the pores whilst large molecules pass down the column more rapidly. A solvent pressure up to 1000 psi may be used. 

The gel-like, bead nature of wet Sephadex enables small molecules such as inorganic salts to diffuse freely into it while, at the same time, protein molecules are unable to do so. Hence, passage through a Sephadex column can be used for complete removal of salts from protein solutions. Polysaccharides can be freed from monosaccharides and other small molecules because of their differential retardation. Similarly, amino acids can be separated from proteins and large peptides. 

The mechanism of separation is the same for Zorbax PSM columns as it is for other types of SEC columns. As the mobile phase flows through the column, large molecules are forced down the column at faster rates than small molecules because the large molecules have less access to the column volume inside the pores. Consequently, molecules that are too large to permeate any of the pore... 

The analysis demonstrates the elegant use of a very specific type of column packing. As a result, there is no sample preparation, so after the serum has been filtered or centrifuged, which is a precautionary measure to protect the apparatus, 10 p.1 of serum is injected directly on to the column. The separation obtained is shown in figure 13. The stationary phase, as described by Supelco, was a silica based material with a polymeric surface containing dispersive areas surrounded by a polar network. Small molecules can penetrate the polar network and interact with the dispersive areas and be retained, whereas the larger molecules, such as proteins, cannot reach the interactive surface and are thus rapidly eluted from the column. The chemical nature of the material is not clear, but it can be assumed that the dispersive surface where interaction with the small molecules can take place probably contains hydrocarbon chains like a reversed phase. 

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