Serial Dilution Concentration Calculation

[meli4]

First Serial Dilution

In a lab I did a serial dilution starting off with a stock solution that was 200 µg/mL. In the first tube I transferred 2 mL from the stock solution and from that one I transferred 1 mL to the following tube and so on. I calculated the following:
Tube 1: 200 µg/mL
Tube 2: 100 µg/mL
Tube 3: 50 µg/mL
etc...
After that dilution I had to add two additional solution to each tube. The total volume of both solutions was 1.1 mL. So, for example, in tube 1 I had 1 mL of the 200 µg/mL solution and to that I added 1.1 mL so it gets diluted even more. I'm confused as to how I calculate the concentration now because I've calculated it different ways and I get different answers. In the second dilution, it says the final volume is 3.1 so does that mean I should just calculate the concentration directly using that volume and forget about the first calculation I did? Or do I have to calculate the concentration in two steps. I emailed my instructor and she said that that image gave me a hint on how to calculate it because it gave me the final volume...I'm assuming she means to use the 3.1 mL.

Please help

[Cat]

The formula is:

C1V1 = C2V2

C1 = Initial concentration
V1 = Initial volume
C2 = Final concentration
V2 = Final volume

So, tube 1 is

200 µg/mL x 1 mL = X µg/mL x 2.1 mL
X = 95.24 µg/mL

You can calculate the rest the same way.

[semac]

hello Meli,

An easy serial dilution tool, freely useable is available on this website http://www.andrewalliance.com/andrew-as ... -download/

give a look it is very easy to use.

Best regards,

Isa

[vanwa71]

https://play.google.com/store/apps/details?id=com.bestserialdilutioncalculator
I use this Android phone calculator. It's fully automated and flexible.