Determination of chemical and radiochemical purity of [14C] clozapine by high performance liquid chromatography and liquid scintillation

ABSTRACT

The mechanism of action and metabolism of clozapine, a complex drug used in psychopharmacology, is not completely understood. The effects of this compound in human body are related to some interactions with serotonin and dopamine neurotransmitter receptors. To further elucidate the mechanism of action and to support ongoing drug metabolism studies, [14C] clozapine with suitable radiochemical purity was synthesized in nuclear research center of AEOI. In this report radiochemical and chemical purity of [14C] clozapine were determined by liquid scintillation and reversed phase-HPLC respectively. Separation of [14C] clozapine and its synthesized interface products was carried on C8 optimal column and UV detector at 254nm.The mobile phase consisted of acetonitril-buffered aqueous solution of sodium phosphate with a flow rate of 1ml/min. Detection limit and analytical precision of RP-HPLC method were 0.01micro g/ml and 1-3.4% respectively. The chemical purity of synthesized clozapine was >99%. For determination of activity and radiochemical purity, liquid scintillation spectrometer was used and counting was done by direct addition of samples to ACS [Amersham] solution. Specific activity of synthesized clozapine was 10 micro Ci/mg and radiochemical purity of >99.% was achieved. By separation of [14C] clozapine and its synthesized intermediate products the represented methods, in addition to determination of total yield of reaction, it was possible to determine every step of reaction therefore; it was not nessaseray to use classical methods such as distillation, liquid-liquid extraction, etc. If the HPLC instrument is equipped with radiochemical detector, simultaneous determination of radiochemical as well as chemical yields of products are possible