Engelhardt test

Both the Engelhardt test and the Neue test capture the total silanol activity at neutral pH. They do not discriminate between addic and regular silanols. Therefore Walter (18) designed a test capable of measuring the amount of addk silanols alone. The test uses a phosphate buffer at pH 3.0 in a methanol/buffer mobile phase. The basic analytes that probe the addic silanols are propranolol and chlorpheniramine, and the neutral reference compound is toluamide. Results of this test were correlated with the metal contamination in the matrix of the parent silica, which is believed to control the addity of the surface silanols. 

Test Mobile phase Engelhardt test MeOH/Wasser 49/51 (w/w), respectively, (55/45 (v/v)) ... 

Engelhardt, G., Schwind, K.-R., and Mulller, B., The testing of chemicals in the Syrian hamster embryo (SHE) cell transformation assay for assessment of carcinogenic potential, Toxicology In Vitro, 8, 213, 2004. 

FIGURE 5.4 Comparison of shape selectivity and planar recognition test procedures SRM 869a test (solutes PhPh, TEN, BaP eluent acetonitrile/water 85/15 (v/v), flow 2 ml/min, detection UV 254 nm) and Tanaka test (solutes o-TER, TRI eluent methanol/water 80/20 (v/v), flow 1 ml/min, detection UV 254 nm. (Reproduced from Engelhardt, H., et al., Chromatographia, A%, 183, 1998. With permission.)... 

Experiments have not been carried out in which the combined effect upon smectite dehydration of increasing temperature, lithostatic pressure, hydrostatic pressure and ionic strength of pore fluid is tested in order to simulate the diagenetic environment. Pairs of these variables have been studied in limited numbers of experiments, some of them difficult to interpret, by Stone and Rowland (1955), Weaver (1959), von Engelhardt and Gaida (1963), Khitarov and Pugin (1966), and Demirel et al. (1970). The accumu-... 

Ln(X) is greater than or equal to the chi-squared value associated f-r degrees of freedom and critical value a (Bain and Engelhardt, 1987). If LLf and LLr are the log-likelihoods for the full and reduced models, respectively, then an alternative form of the likelihood ratio test is given by... 

Bane, L. J., and Engelhardt, M. (1991), Statistical Analysis of Reliability and Life-Testing Models Theory and Methods, 2nd Ed., Marcel Dekker, New York. 

Much of the information on such trends is described in Engelhardt and Michel (1987). The early studies by Smith and Blackwell (1983) and Ramdas and Klinowski (1984). Early studies also suggested correlations of shift with Si-0 distance, but this seems to mainly be associated with the trend with polymerization, although some small dependence may still remain. Some studies have indicated a correlation of the shift with the sum of bond strengths to the four O s of a given silicate tetrahedron (Smith et al. 1983), but this is also clearly related to the polymerization trend. As noted by Kirkpatrick (1988), an empirical correlation of an parameter with a structural or bond parameter does not necessarily imply a cause and effect relationship. One of the main values of quantum mechanical calculations lies in their ability to test such empirical relationships to more deeply understand their foundation. 

Engelhardt - Jungheim test Cr-Cib packing hydrophobic interaction, behavior of basic and acidic analytes (silanophilic interactions) aniline, phenol. o-,m-,p-toluidine, A.A -dimethylaniline, toluene, ethylbenzene, methyl benzoate methanol - water. 50 50 wt % UV (254 nm)... 

Multivariate linear regression can be carried out with common statistics software and was performed in the given example with Statistica 5.0 (StatSoft). Retention factors were measured for a set of selected test solutes using a set of different columns under one fixed set of eluting conditions (acetonitrile/water, 3 7, vjv, without addition of a buffer). A buffer was avoided, since Engelhardt and coworkers reported a marked modulation of column properties by salt or buffer additives this adulterates phase characterization and makes columns look less silanophilic than they actually are [15]. 

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