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# dna concentration

5 replies to this topic

### #1 biogirl1230

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Posted 01 June 2009 - 03:13 PM

hello,
please help. i have a 1000ng/ul stock dna, i need to get it down to 50ug in 100ul final volume. How do I do this or please give me the formula? thanks.

Edited by biogirl1230, 01 June 2009 - 03:14 PM.

### #2 bob1

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Posted 01 June 2009 - 04:22 PM

c1*v1=c2*v2

Where c = concentration and v=volume, 1 and 2 are initial and final respectively.

### #3 biogirl1230

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Posted 02 June 2009 - 03:55 AM

c1*v1=c2*v2

Where c = concentration and v=volume, 1 and 2 are initial and final respectively.

a typo - the stock is 1000ug/ml, not 1000ng/ml

Is this right:

V1 = (50ug)*(0.100ml) / (1000ug/ml)

V1 = 0.005ml = 5ul of stock DNA + 95ul water

### #4 juanboja

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Posted 02 June 2009 - 09:03 AM

Yes biogirl, that is correct.

### #5 almost a doctor

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Posted 02 November 2009 - 07:20 AM

Yes biogirl, that is correct.

actually, that is not correct. I know this is an old post, but as I've just been redirected to it from another post about dilutions and concentrations, I thought I should reply and ammend the mistake as you guys are mixing conentrations with absolute amounts.

From biogirl1230, your stock DNA is at 1000ug/ml = 1mg/ml = 1µg/µl.

Now, you say you need 50µg in 100µl, which means your final concentration is 50µg/100µl = 0.5µg/µl. This is the concentration you have to use for C1V1=C2V2 so in this case: V1= (0.5µg/µl * 100µl )/ 1µg/µl = 50µl You need 50µl of your stock solution + 50µl of water. It's actually a simple 1:2 dilution.

A different way to look at it is: your solution is at 1µg/µl. you need 50µg. Independently of your final volume you need 50µl of this initial stock to have 50µg, and whatever the final volume you need (in this case 100µl) you top up with buffer (or water).

I know is late for whatever the experiement was, but hopefully this is of general help anyway.

### #6 gogreen

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Posted 03 November 2009 - 02:36 AM

Yes biogirl, that is correct.

actually, that is not correct. I know this is an old post, but as I've just been redirected to it from another post about dilutions and concentrations, I thought I should reply and ammend the mistake as you guys are mixing conentrations with absolute amounts.

From biogirl1230, your stock DNA is at 1000ug/ml = 1mg/ml = 1µg/µl.

Now, you say you need 50µg in 100µl, which means your final concentration is 50µg/100µl = 0.5µg/µl. This is the concentration you have to use for C1V1=C2V2 so in this case: V1= (0.5µg/µl * 100µl )/ 1µg/µl = 50µl You need 50µl of your stock solution + 50µl of water. It's actually a simple 1:2 dilution.

A different way to look at it is: your solution is at 1µg/µl. you need 50µg. Independently of your final volume you need 50µl of this initial stock to have 50µg, and whatever the final volume you need (in this case 100µl) you top up with buffer (or water).

I know is late for whatever the experiement was, but hopefully this is of general help anyway.

Thats right 'almost a doc', I always go with the second way of doing it...
@ Biogirl1230, there was no typo in ur first post, 1000ng/ul and 1000ug/ml are both the same!!

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