2.4. Sample collection and extraction
Blood samples for pharmacokinetic analysis were
obtained prior to administration of a single intravenous dose of actinomycin D (0.75 or 1.50 mg/m
2
)
and at 15 min, 30 min and 1, 2, 4, 6 and 24 h
post-administration. Blood samples (2 ml) were collected in heparinised tubes and centrifuged at 1200 g
for 10 min at 4
◦
C. Plasma was separated and frozen
at−20
◦
C prior to analysis. Extraction of actinomycin
D from human plasma (500l) involved addition
of 100l of the internal standard working solution
(5.0g/ml), and 3 ml of acetonitrile, added in three
1 ml aliquots while vortex mixing the tube for approximately 30 s. Following extraction, samples were
centrifuged at 1200×gfor 5 min at room temperature and 3 ml of supernatant transferred to clean glass
tubes and evaporated to dryness under nitrogen at
37
◦
C. Samples were resuspended in 200lofmobile phase (acetate buffer pH 4.0:methanol; 35:65),
transferred to Eppendorf tubes and microfuged at