Elution nonspecific

Nonsolvent bath, polymer precipitation by immersion in, 15 808-811 Nonspecific elution, in affinity chromatography, 6 398, 399 Nonstationary Poisson process, in reliability modeling, 26 989 Non-steady-state conduction, 9 105 Nonsteroidal antiinflamatory agents/drugs (NSAIDs) 21 231 for Alzheimer s disease, 2 820 for cancer prevention, 2 826 Nonsulfide collectors, 16 649 Nonsulfide flotation, 16 649-650 Nonsulfide mineral flotation collectors used in, 16 648-649t modifiers used in, 16 650, 651t Nonsulfide ores, 16 598, 624... 

The elution volumes of Dextran Blue or DNA are equivalent to the void volume (Vo) of the column. Usually, a small difference appears between the two values due to differences in molecular shape and slight nonspecific interaction with the matrix. 

Figure 6.3 compares nonspecific protein adsorption on a new HIC column vs. the same column after 50 wash cycles. In each case the column was equilibrated, injected with 10 pg of purified IgG, washed, eluted in a linear gradient, and then cycled four more times for a total of five consecutive runs. Eluted peak height was fairly consistent on the new column. Results on the wash-cycled column indicated that significant amounts of protein were being adsorbed. The effect diminished with successive injections so that by the fourth injection, performance was roughly on par with the new column. However, by this time the column had adsorbed about 15 ug of protein. 

Figure 6.3 Nonspecific protein adsorption as a result of column degradation. White circles indicate eluted column peak heights of a new column. Black diamonds indicate eluted peak heights after the column was treated with 50 wash cycles. See text for discussion. (Data from P. Gagnon, 1997, Validated Biosystems Quarterly Resource Guide for Downstream Processing, 2(1), 1, http //www.validated.com/revalbio/library.html.)...

The PO mode is a specific elution condition in HPLC enantiomer separation, which has received remarkable popularity especially for macrocyclic antibiotics CSPs and cyclodextrin-based CSPs. It is also applicable and often preferred over RP and NP modes for the separation of chiral acids on the cinchonan carbamate-type CSPs. The beneficial characteristics of the PO mode may arise from (i) the offset of nonspecific hydrophobic interactions, (ii) the faster elution speed, (iii) sometimes enhanced enan-tioselectivities, (iv) favorable peak shapes due to improved diffusive mass transfer in the intraparticulate pores, and last but not least, (v) less stress to the column, which may extend the column lifetime. Hence, it is rational to start separation attempts with such elution conditions. Typical eluents are composed of methanol, acetonitrile (ACN), or methanol-acetonitrile mixtures and to account for the ion-exchange retention mechanism the addition of a competitor acid that acts also as counterion (e.g., 0.5-2% glacial acetic acid or 0.1% formic acid) is required. A good choice for initial tests turned out to be a mobile phase being composed of methanol-glacial acetic acid-ammonium acetate (98 2 0.5 v/v/w). 

The detection problems. In LC CC, macromolecules elute together or in the vicinity of their initial bulk solvent. The latter exhibits changed composition compared to the mobile phase. This results from the phenomena of preferential solvation (Section 16.2.2) and complicates application of the nonspecific detectors (Section 16.9.1). The detection problem is also evident in the case of LC CC of block copolymers because the detector response as a rule depends or the nature and the relative length of both blocks. 

RP-HPLC with nonaqueous solvents and UVD at 246 nm was developed for the determination of low level POVs of vegetable oils. These measurements are specific for conjugated diene peroxides derived from vegetable oils with relatively high linoleic acid content. These measurements may be supplemented by nonspecific UVD at 210 nm and ELSD for detection of all eluted species. The elution sequence of the triglycerides in a nonaqueous RP-HPLC is linearly dependent on the partition number of each species, Vp, which is defined as = Nq — 2Ni, where Nq is the carbon number and is the double bond number. In the case of hydroperoxides = Nq — 2Nd — Vhpo, where Vhpo is the number of hydroperoxyl groups in the molecule (usually 1 for incipient POV). For... 

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