New sorbent for HPTLC--FTIR in situ determination of impurities in flurazepam

An efficient HPTLC--UV/FTIR coupling procedure is presented for the separation and rapid identification of flurazepam hydrochloride and its related substances in bulk powder and capsules. An optimized mobile phase was developed for the separation on specialized plates for HPTLC--FTIR in situ measurement containing a proportion of 50% magnesium tungstate. The proposed procedure shows several advantages to the related compound test of the pharmacopoeia, e.g. baseline separation of the known impurities and detection of the substances as peaks in the UV, Gram-Schmidt or window chromatograms. Furthermore, unambiguous identification is obtained by postrun extraction of the DRIFT spectra and comparison with reference spectra in the library. Quantification of the related compounds was carried out densitometrically. This method shows that the current resurgence of interest in modern instrumental TLC is rightful based on the flexibility and efficiency of this analytical method.