# HELP please! - concentration (Jan/06/2011 )

I need help ASAP.

I am in the middle of Recombineering and I have to make MacConkey agar plates.

The protocol calls for 40g agar in 1L with 1% galactose and 500ul chloramphenicol (final concentration of 12.5ug/ml)

I am making half: 20g in 500ml with 1% but i cannot figure out the chloramphenicol calculations. Our chl is at 50mg/ml. Thank you do much!

-FC

-amarieu-

You need to apply **C1V1 = C2V2**

Where C is concentration and V is volume, and 1 and 2 are the initial and final.

so in your case Chl is at C1=50mg/ml and you wonder V1.

C2=12.5ug/ml and V2=500ml.

All you need to do is put the number in the equation and V1= 0.125ml = 125ul

So you need to add 125ul of Chloranphenicol to your 500ml

-almost a doctor-

almost a doctor on Thu Jan 6 17:52:50 2011 said:

You need to apply

**C1V1 = C2V2**

Where C is concentration and V is volume, and 1 and 2 are the initial and final.

so in your case Chl is at C1=50mg/ml and you wonder V1.

C2=12.5ug/ml and V2=500ml.

All you need to do is put the number in the equation and V1= 0.125ml = 125ul

So you need to add 125ul of Chloranphenicol to your 500ml

Thanks!

I somehow figured it out by doing 50/12.5 and then the volume (500) divided by 4= 125ul

I think it is along the same lines, but I ended up with the same answer! So I think from now, for all volumes if I divide by 4 I will get the amount of chl needed.

-amarieu-