Ratio(ng mL-1)   Recoverya % ± RSD
Amantadine Memantine Amantadine Memantine
1 1   99.79 ± 1.07 99.04 ± 1.89
1 4 100.05 ± 2.00 100.46 ± 1.04
2 1 98.86 ± 1.66 100.18 ± 1.07
aMean of five different experiments.
Table 3: Specificity of the proposed TOF ES-MS method for simultaneous analysis of amantadine and memantine in drug substances.