Organic modifier effect values

As above, the log k values of the different types of compounds [alkanols (ROH), polycyclic aromatic hydrocarbons (PAH), alkyl benzenes (RB), and alkyl benzoates (ROB)] each demonstrated a linear relationship with their log P values and this relationship was observed with different ratios of acetonitrile and water. The experiment was then performed in eluents containing different organic modifiers and it was found that the behaviour of analytes containing different functional groups differed and the effect depended on the log P of the analyte. 

One has to emphasize that MS also is associated with several drawbacks when it comes to bioactivity screening. First of all, the optimum, native conditions for bioactivity screening (pH 7.2, addition of 150 mM sodium chloride) are entirely incompatible with optimum conditions for MS detection which, for ESI-MS, typically require acidic pH values and the presence of organic modifiers to enhance ionization properties of the analytes. Assay development for MS-based assays therefore mainly requires the testing of different assay conditions, particularly the replacement of nonvolatile buffers with MS-compatible volatile buffers. Furthermore, it is essential to monitor ion suppression effects, for example, by the... 

Just as different organic modifiers can be employed to generate different selectivities in the RPC separation of peptides, similar effects can be independently achieved through the use of different RPC sorbents. As the hydrophobicity of the stationary phase increases, the X value... 

FIGURE 7 Effect of the organic modifiers on the chiral resolution of aromatic alcohol using Whelk-Ol CSP at different temperatures with negative values of In k indicating the reversal order of elution ( ) ethanol, ( ) 1-butanol, (A) 2-propanol, ( ) 1-propanol, (+ ) trifluoroethanol, and (x) tetrahydrofuran. (From Ref. 138.)... 

The relationships between capacity factor, k , and organic modifier concentration in the mobile phase, and the effect of the column temperature on k for the antibiotics studied have been used to define k as a function of T and V (volume fraction) on the basis of a small number of experimental measurements for a given combination of column, organic solvent, and type of antibiotic. From calculated values of k, resolution values, Rs, may be estimated for adjacent band-pairs under all conditions. The method developed enables the optimization of RP-HPLC separations of the p-lactam antibiotics in the absence of difficult theoretical calculations, using a small number of experimental data, including the influence of the organic solvent in the mobile phase (isopropanol) and the column temperature. 

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