This reference described in the European Pharmacopoeia as a resolution test for use in derivative spectroscopy.
Description and Discussion
0.020% v/v solution of toluene in methanol, permanently sealed by heat fusion into a far UV quartz cell. Supplied with a methanol blank.
In derivative spectroscopy, absorption spectra aretransformed into first-, second- or higher-order derivatives.This technique facilitates the resolution of two or more peaksthat overlap and become merged into a composite curve, andare represented by shoulders on that curve rather than asindividual peaks. By calculating the derivative, the underlying individual spectra can be more readily identified. Probably themost used is the second order, i.e d2 A/dλ2.
When this reference material is scanned in 2nd derivative mode against the methanol blank, the resulting spectrum should be similar to that shown, with a small negative extremum. ( ) at 285 nm between two larger negative extrema at 261 nm and 268 nm.
To meet the requirements of the Pharmacopoeia, the ratio A/B should be greater than 0.2:
Toluene in methanol cell with methanol blank cell