Retention difference between

Despite the lack of solubility of 15 in fluorocarbon solvents, the huge retention differences between organic compounds (solvent front) and fluorous-tagged compounds (>30 min for the longer tags) translate into simple separations by solid... 

SRM 869a Column Selectivity Test Mixture for Liquid Chromatography [44] is composed of three shape-constrained PAHs (phenanthro[3,4-c]phenanthrene, PhPh l,2 3,4 5,6 7,8-tetrabenzonaphthalene, TBN and benzo[a]pyrene, BaP) and is routinely employed to evaluate the shape selectivity of stationary phases. The retention differences between the nonplanar TBN and planar BaP solutes (expressed as a selectivity factor axEN/BaP = provide a numerical assessment of... 

Table 3-4 shows the relative standard deviation in the retention of the same analyte on all columns. For ionized analytes eluted very close to the void volume, the retention difference between all columns is significant, but for analytes retained on the column, the RSD of is much smaller than k and essentially within the experimental error range. 

A 100% methanol mobile phase was used in the study of the retention characteristics for over 50 alkyl-substituted benzenes on a porous graphite column [109]. Retention times varied from 1.8 min k = 0.2) for benzene (just slightly more than the void volume) to 58 min (k = 3 7) for pentamethylbenzene. A distinct advantage of this system over a normal Cjg system was the enhanced selectivity of the graphite column towards both isomeric forms as well as methyl and methylene homo logs. The k values and retention times for all analytes are tabulated. The retention differences between polymethylbenzenes and alkyl-substituted benzenes of the same carbon number (e.g., trimethylbenzenes vs. n-propylbenzene) were studied in detail on Cjg and phenyl columns using an 80/20 methanol/water mobile phase. 

As apparent from Eqs. (11), (12), and (18), the free energy of cavity formation is proportional to the surface area of a protein or peptide. Therefore, retention differences between proteins or peptides will reflect the incremental changes in their surface areas as a consequence of adsorption to the stationary phase ligands. In the presence of an organic solvent in RPC, or when the salt concentration is sufficiently high in HIC, the retention relationship for a specific protein or peptide takes the simplified linear form [8,160,207]... 

Wescan 269-001 [64], the once popular silica-based ion exchanger, which was based on a macroporous substrate with a pore width of 300 A, is not manufactured anymore. A specific feature of this column was the large retention difference between mono- and divalent anions with a negative signal appearing in the chromatogram after the elution of sulfate at about 20 min. This peak is called system peak (see Section 3.7.4.2), which is inevitable when employing phthal-ates as eluents. 

Thus, the retention difference between fluoride and chloride, which is less than 2 minutes under the same conditions on an AS4A column, may be expanded to more than 20 minutes with the CarboPac PAl. Figure 3-122 illustrates an example of the baseline-resolved separation of various monocarboxylic acids, which would elute as one peak close to the void volume when using an AS4A column. Monocarboxylic acids are relevant in many of today s analysis problems this procedure provides an elegant solution. Amidosulfonic acid, for example, is one of the many components in flue gas scrubber solutions from desulfurization devices, which require frequent analysis. 

If two data input runs are used, the only requirement is that they differ significantly in temperature conditions. In general, the calculation error for a particular compound decreases as the retention time difference between the two runs increases. For example, if data input run 1 was mn isothermally at 100°C, and data input run 2 was run isothermally at 105°C, the retention differences between the two mns would be rather small and may introduce more error that if data input mn 2 was mn isothermally at 150°C. The two runs can be any combination of isothermal and/or ramp segments as needed, and there is no requirement that either mn be made under the same temperature range or the same number of isothermal and ramp segment combinations. 

Nikula KJ, Avila KJ, Griffith WC, Mauderly JL. Lung tissue responses and sites of particle retention differ between rats and cynomolgus monkeys exposed chronically to diesel exhaust and coal dust. Fundam Appl Toxicol 1997 37 37-53. 

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