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# simple calculation

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### #1 bio08

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Posted 20 September 2009 - 01:48 AM

I have a 2mM dNTP stock and have only 50 ul/tube of the stock. I have to make 10 mM dNTP (20 ul in a tube).
Is it right if I calculate like : V= 10mM*20ul/2mM=100 ul. Then all I have to do is to take 100ul of the stock dNTP (2mM) and that's it. Now I have 100 ul of 10mM dNTP.
Thanks!

### #2 Gerard

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Posted 20 September 2009 - 03:16 AM

50 ul stock 2mM
100 ul dilution 10mM

Doubled the volume and increased the concentration 5 fold

Take a patent an you get rich

I say check your calculations again there's something wrong

Edited by Gerard, 20 September 2009 - 03:17 AM.

Ockham's razor
Pluralitas non est ponenda sine necessitate
-- "You must assume no plural without necessity".

### #3 helix

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Posted 23 September 2009 - 06:02 PM

Are you sure you're not wanting to make a 10 MICROmolar solution from your 2 MILLImolar stock?

### #4 Dr Teeth

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Posted 24 September 2009 - 04:02 AM

bio08, on Sep 20 2009, 05:48 AM, said:

I have a 2mM dNTP stock and have only 50 ul/tube of the stock. I have to make 10 mM dNTP (20 ul in a tube).
Is it right if I calculate like : V= 10mM*20ul/2mM=100 ul. Then all I have to do is to take 100ul of the stock dNTP (2mM) and that's it. Now I have 100 ul of 10mM dNTP.
Thanks!

So, you are saying that you should take 100 ul from your 50 ul tube of 2 mM dNTP and presto, you will have 100 ul of 10 mM dNTP, which I thought you wanted in tubes of 20 ul total????
If you are diluting your 2 mM stock to a 10 micromolar stock (not 10 mM), you will need only 100 nanoliters of your 2 mM stock in a total of 20 ul.  Since that would be a little difficult to pipet, you will need to do a serial dilution.

Edited by Dr Teeth, 24 September 2009 - 04:03 AM.

Science is simply common sense at its best that is rigidly accurate in observation and merciless to fallacy in logic.
Thomas Henry Huxley

### #5 microgirl

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Posted 24 September 2009 - 05:22 AM

bio08, on Sep 20 2009, 02:48 AM, said:

I have a 2mM dNTP stock and have only 50 ul/tube of the stock. I have to make 10 mM dNTP (20 ul in a tube).
Is it right if I calculate like : V= 10mM*20ul/2mM=100 ul. Then all I have to do is to take 100ul of the stock dNTP (2mM) and that's it. Now I have 100 ul of 10mM dNTP.
Thanks!

Hunh? If your stock is 2 mM you can't make it 10 mM, which is more concentrated. You're question is confusing!!!