Question

You will prepare a serial dilution with 6 tubes. Into tube 1 you add 0.9 ml NaCl and you add 0.5 ml NaCl into tubes 2-6. Next you add 0.1 ml of serum to tube 1 and mix and transfer 0.5 ml to tube 2. Continue making serial dilutions through tube 6 (discarding 0.5 ml from tube 6). Finally, you add 0.5 ml of sheep RBCs to EACH tube (1-6)

What is the final dilution in each tube after the addition of sheep blood cells?

Answer 1

Dilution factor = initial volume/ final volume

Dilution factor for tube 1 = 0.1/1

= 1/ 10

Next Dilution factor for the next 5 tubes is = 0.5 /1

= 1/2

Now 0.5 ml of RBC added to each tube ,the dilution factor for each tube would be 1/2

So final dilution in tube 1 is = 1/10 * 1/2(this is the dilution factor for blood)

= 1: 20

for tube 2,

Final dilution factor = 1/10 * 1/2 *1/2

= 1: 40

for tube 3 ,

Final dilution factor =

= 1/10* 1/2* 1/2 *1/2

= 1: 80

similiarly for tube 4 ,

= 1/10 * 1/2 *1/2*1/2*1/2

=1: 160

for tube 5,

= 1/10*1/2*1/2*1/2*1/2*1/2

=1: 320

For tube 6,

=1/10*1/2*1/2*1/2*1/2*1/2*1/2

=1: 640