is it okay to prepare serial dilution a day prior to spread plating? can we refrigerate?
how do you know how much to take from the stock solution? or you just assume and take 1 ml always?
Ten fold dilution means you dilute it 10 times. Each of the test tubes already contains 9ml of the broth. So adding 1ml of the inocculum and then vortexing it makes it 10 times diluter than the previous test tube.
Suppose if you had 90ml of broth, you would need to add 10ml of inocculum from the previous test tube and that would make it 10 times diluter. We simply use the dilution formula commonly written as:
C1 . V1 = C2 . V2
Where
C1 : initial concentration
V1 : volume to be taken from the previous test tube
C2 : desired concentration
V2 : volume of desired concentration that you want to make up.
Hope it helps.
Great video :)