The plasma proteins needed to be precipitated from the plasma because they interfere with the sample running on the TLC plate due to their hydrophilicity and high concentration. The extraction solution consisted of a mixture of acetonitrile:methanol (2:1) (v:v) . A 100µl sample of plasma was placed in a 15ml tube followed by a sample of 250 µl of the extraction solution. The sample was aspirated 3 times, vortexed at maximum speed for 10 min and finally spun down at 5000rpm/5025g for 5 min. The resulting supernatant containing the extracted drugs was carefully removed leaving the precipitant pellet at the bottom of the tube. This supernatant was then placed in a glass vial for analysis.