Table 4 Procedure for Spiking and Extraction

1

10 g of blended yam samples were weighed in 50 ml centrifuge tubes on Sartorius analytical balance.

2

Blank samples were spiked with 100 μL of mixed standard of the 25 compounds involved in 8 replicates.

3

15 mL of acetonitrile containing 1% glacial acetic acid (v/v) was added in each sample by using a solvent dispenser.

4

Each tube was tightly cupped and shaken for 1 min to ensure contact between the solvent and the sample matrix.

5

6 g anhydrous MgSO4, 1.5 g NaCL, 1.5 g sodium citrate tribasic dihydrate (C₆H₂Na₃O₇ 2H₂O and 0.75 g sodium hydrogen citrate (C₆H₆Na₂O₇ 1.5H₂O) were added and the sample was shaken for 5 min on a mechanical shaker at 300 rpm to enhance sample throughput.

6

The samples were centrifuged at 10,000 rpm for 5 min.

7

5 mL aliquot of extract was taken into a 10 mL test tube.

8

1 mL of the aliquot of extract in the 10 mL tubes was taken into 10 mL flask and diluted to 10 mL with water.

9

1 mL extract was then transferred from the 10 mL flask into an auto sampler vial for LC-MS/MS analysis.