Titrimetric analysis of pharma raw materials

In contrast to, for example, HPLC, titration is an absolutemethod and therefore requires no reference method.

The reactionprocesses are known; the titration takes place strictlystoichiometrically and normally very rapidly.

If a titrant with aknown titer is used then the content of the sample can bedetermined directly.

However, this applies only to raw materialsand not to formulations that contain other components that couldreact with the titrant in a similar or identical manner.

It doesnot make sense to qualify the individual components of ananalytical instrument or analysis system separately.

On thecontrary, the complete titration system (titrator, buret,electrode, titration evaluation, sample changer if present) issubjected to a performance check.

The qualification of thetitrator and the validation of the titration method are carriedout at the same time.

General procedure.

Five to ten differentamounts of the sample - in this case ephedrine hydrochloride(ephedrine x HCl, C10H15NO x HCl) - are weighed to the nearest0.1 mg (use a validated balance).

If a 20ml buret is used thenthe sample weights should be chosen to produce a titrantconsumption between 2.5 and 15ml.

The sample is dissolved in theprescribed solvent, the auxiliary solution is added and titrationis performed with c(titrant) = 0.1mol/l.

1ml c(titrant) =0.1mol/l corresponds to 20.17mg ephedrine x HCl MetrohmApplication Bulletin No 252 contains all the necessarycalculation formulae as well as an example of a validationprotocol.