serial dilution - basic question (Jul/23/2010 )

If I have a sample that has been diluted 1:50 already, and I need to make a 1:75 dilution, I will just take 1ul from the 1:50 dilution and add it into 25ul of water to make a 1:75 dilution. Is this right?

claritylight on Jul 23 2010, 06:16 PM said:

NOOOOOOO!!!!!
a 50 times diluted solution and u diluting it 25 times now so it will be 50X25 and not 50+25!!!!
u have to dilute it 1.5 times now to make it a 75 times dilution.. i.e. take 50 mcl from 1:50 and 25 mcl diluent!!!
Hope tat helps!!!
Best luck!!

Prep! on Jul 23 2010, 08:03 AM said:

Can I just add 25ul to the 1:50 dilution itself? Meaning, that right now, there is 50ul total in the 1:50 diluted sample, so if 25ul is added, it will make a 1:75 dilution right?

If I take 1ul from the 1:50 dilution and add it into 25ul of water, what is the final dilution called?

claritylight on Jul 23 2010, 04:59 AM said:

1:1300 dilution.

1ul is a significant fraction of 25ul. So the volume of 1ul must be taken into account, total volume is 26ul

claritylight on Jul 23 2010, 06:29 PM said:

yes u can directly add 25 mcl to ur solution

claritylight on Fri Jul 23 11:46:51 2010 said:

No its not right

You need to dilute your 1:50 sample 2:3 times to obtain 1:75 dilution. Add 1 volume of water to 2 volumes of your sample to do this.

So if you need 6 ul of 1:75 diluted sample:
4ul 1:50 sample
2ul H2O