The internal standard (2, 3-Diphenylquinoxaline) was purchased from Acros
Organics (New Jersey, US). HPLC-grade acetonitrile (HPLC-JT9012) was obtained
from VWR (Pennsylvania, US). Mouse plasma (Na heparinized) from Balb C mice was
procured from Innovative Research (Michigan, US). Human plasma was purchased
from Oklahoma Blood Institute (Oklahoma City, US). All plasmas were stored at
-20°C. All mobile phases and standards were prepared using distilled
water prepared with a Millipore (Milford, US) distillation apparatus.