Discriminators stability

Cool on-column >250 pm column (i.d.) 1 ppm (FID) Reduced thermal degradation and discrimination Wide range of analyte concentrations High sample capacity (LVI) Autosamplers Direct quantification Excellent precision Control of operational conditions (initial oven temperature) Optimisation required Not applicable for polar solvents Column contamination by dirty matrices Poor long term stability... 

In the preceding section, the interaction energy between two reacting molecules has been discussed with the assumption of no nuclear configuration change. In the donor-acceptor interaction the delocalization stabilization is dominant. Eq. (3.25) indicates the importance of HO and LU in the donor-acceptor interaction. But the expression of Eq. (3.21) shows that in general cases the contribution of HO and LU to the quantity D is not so discriminative as those of the other MO s. 

There are two main factors that influence the selectivity of a sensor limits in discrimination of an interfering ion and upper limits in stability constant of an analyte-ionophore complex. While an ideal ionophore does not form complexes with interfering ions, too strong complexation with the primary ion leads to a massive extraction of analyte into membrane phase coupled with a coextraction of sample counter-ions, known as Donnan exclusion failure. In such cases, at high activities and lipophilicities of sample electrolytes, fli(org) increases and a breakdown of membrane permselectivity prevents the Nemst equation to hold. 

Taken together, the equilibrium spreading pressures of films spread from the bulk surfactant, the dynamic properties of the films spread from solution, the shape of the Ylj A isotherms, the monolayer stability limits, and the dependence of all these properties on temperature indicate that the primary mechanism for enantiomeric discrimination in monolayers of SSME is the onset of a highly condensed phase during compression of the films. This condensed phase transition occurs at lower surface pressures for the R( —)- or S( + )-films than for their racemic mixture. 

When compressed to surface pressures greater than their stability limits (see Table 10), diastereomeric mixtures of /V-(a-methylbenzyl)stearamides with both stearoylalanine and stearoylserine methyl esters provided clear evidence of chiral discrimination. Force-area isotherms at 35°C for homochiral and heterochiral pairs of N-(a-methylbenzyl)stearamide and stearoylalanine methyl ester show differences in both their lift-off and touchdown (the area per molecule where the surface pressure returns to zero on the expansion arm of the isotherm) areas per molecule (Fig. 32). In addition, monolayers of the heterochiral pair could be compressed to lower areas per molecule than monolayers of the homochiral pair. 

Abstract Humans produce temporarily stable, genetically mediated odour signatures and possess the ability to recognise, discriminate and identify other people through the sense of smell. The capability of self, gender, kin and non-kin odour recognition plays a role in social interactions. It seems that despite the stability of olfactory cues, the hedonic quality of body odour may vary over time. 

Lai, M.C., Hageman, M.J., Schowen, R.L., Borchardt, R.T., Laiard, B.B., and Topp, E.M. 1999b. Chemical stability of peptides in polymers. 2. Discriminating between solvent and plasticizing effects of water on peptide demidation in poly(vinyl pyrrolidone). J. Pharm. Sci. 88, 1081-1089. 

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