Development and Validation of a Stability Indicating LC Method for the Assay and Related Substances Determination of a Proteasome Inhibitor Bortezomib

Table 3

Mass balance study.

Stress condition	Time	Assay of active substance (% w/w)	Total impurities (% w/w)	Mass balance (assay + total impurities) (% w/w)	Remarks
Thermal treatment (105°C)	7 h	92.4	7.0	99.4	Imp-A, Imp-E and Imp-G were major degradation products
Photo degradation (Open stress)	7 days	96.9	2.4	99.3	Imp-A, Imp-E and Imp-G were major degradation products
Acid hydrolysis (5.0 M HCl, 70°C)	72 h	96.2	3.0	99.2	Imp-B was major degradation product.
Base hydrolysis (0.1 M NaOH, 25°C)	7 h	94.4	5.3	99.8	Imp-A, Imp-B and Imp-D were major degradation products
Oxidation (3% H2O2)	Immediately	81.9	17.9	99.8	Imp-E was major degradation product.
Water hydrolysis (70°C)	72 h	97.4	2.1	99.5	Imp-A, Imp-B and Imp-E were major degradation products