i need to dilute a 1mM solution to 50 and 11000 pmol.. i cant work out a serial dilution can anyone help me?!

Er - welll, I'll have a go.

The SI system goes like this: milli/micro/nano/pico (0.000/000/000/000)
mi mic na pi

Currently you have 1mM, which is 0.001M. You need to dilute this to pico levels. Dilute by 1000, then 1000 again. This gives you a 1 nanomole solution, or 0.000/000/001M. To get this to 50picoM, you need to dilute this nanoM solution by 20, to give:

0.000/000/000/050, or 50pM.

(I think)

well .. you can follow the molarity ratio equation

( M x L )stock soln = ( M x L )prepared soln

so the M and L are known for the prepared soln (50 / 11000pmol) also
the M for the stock soln ... filling the known variables
you will calculate the L (volume) required from the stock
soln to prepare your soln.

if you have 100ml of 0.01M (1mM) and u want to prepare
50 / 11000 pM (50 / 11000 x 10-12 M) in 1L

then = 0.01M x ?ml = 50 / 11000x10-12M x 1000ml

so with doing all the math = you need to take 5x 10-6ml
of your stock to prepare for example the 50pM in 1L soln.

i hope this is right though

My own method would be as follows (although it would be a bit easier to do if I knew what volumes of your final solutions you wanted). Anyway...

For the 1mM -- 50pM dilution, calculate that 1mM = 1,000,000,000pM. I'm not using standard form as it looks untidy on this. Anyway, you're therefore doing a 1 in 20,000,000 dilution. I've always been told that pippetting minute volumes isn't as accurate as adding extra steps, and also the exact way I'd do this depends on how much final volume you want. However, a suggestion is...

First, make up 10ul of your original 1mM solution to 100ml (in water, buffer, or whatever else you use), a 1 in 10,000 dilution, giving you a new conc of 100nM solution.

Then, take 50ul of this second solution, and make up to 100ml with your water/buffer/etc, a 1 in 2,000 dilution. You will then have a 100ml solution of concentration of 50pM (a final dilution from the original of 1 in (10,000 x 2,000) = 1 in 20,000,000.

Two things - first, if mine is wrong, please please tell me, as (a) I don't want to mess someone's work up, and (b) it would get me to do more practice for my own stuff!

Also, lastsamurai, your method appears right. However, you suggest taking 5x10^-6ml of the stock. This is 5nl, and I don't know of any pipette which could accurately dispense such a small amount - I've only gone down to P2 pipettes in the past, which are only really accurate down to about 0.2ul, if that. I think...

Matthew82 .. you are right ... there are no pippette do 5x10-6 .. inorder to go around it by taking 1ml of the 0.1mM stock and dilute it in 1L solution ... and then do the calculations to get 5x10-3 = 5 micorliter .. which you can use the 10micorL pippitte.

thanks for the your comment

let me correct
"... taking 1ml of the 1mM stock and dilute it in 1L solution ... "

PhDgirlie .. please check this with other people .. i also dont want to srew others work ... i am suggesting a mathmatical method not an answer. good luck