Neue 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. 

It is important to note the difference between the example of the Waters-Neue test and the example that was discussed in Section 2.3.1.2. In the previous discussion, the pH was closer to the of the respective substances whose retention was significantly changed by small variations of the two parameters. The strong bases in the Waters-Neue test have values that are about four pH-units higher than the applied pH = 7. In this scenario, the conditions are completely different from those observed when there was a very strong dependency on the dissociation and the pH (see Figure 2.7). 

Test Mobile phase Neue test MeOH/20 mM Phosphate buffer pH = 7, 59.4/40.6 (w/w) ... 

FuBganger R, Schaumann O (1931) liber ein neues Lokalanas-thetikum der Novokainreihe (Pantokain). Naunyn-Schmiedeberg s Arch exp Path Pharmakol 160 53-65 Hoppe JO, Alexander EB, Miller LC (1950) The use of the trypan blue and rabbit eye tests for irritation. J Am Pharm Assoc Sci Ed 39 147-151... 

Such national formularies are good starting points for formulations as they may have been tested or supported by published or validated formulae. A secrnid example is the German Formulary (Neues Rezeptur-Formularium, see Sect. 39.4.2). In the UK, the Handbook of Extemporaneous Preparation (see Sect. 39.4.6) also lists a selectimi of 50 commonly used formulae, and the British Pharmacopoeia has a small number of formulatirMis detailed. The existence... 

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