Another Dilution Problem... - Molar solutions... (Aug/27/2008 )

I kind of sorted out the problem.. Not sure if its right.. please help me out..

[stock] = 2ug/ul
stock volume = x
[desired] = 10ug/10ml
final volume = 10ml

So Stock volume = [(10ug/10,000ul) x 10,000ul] / [2ug / 1ul]

= [10ug / 2ug] x 1ul

= 5ul...

So I need to add 5ul of my 2ug/ul stock to 10ml to get a final concentration of 10ug??

But wont my drug get completely diluted if add this 5ul (10ug) into 10ml???

BAsically I want my final bath concentration to be 10ug... How to do that??

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StockC=1mM This is C1
requiredC=10pM This C2
requiredV=10ml This is V2

1000000000pM X V1 = 10pM X 10000ul V1=0.0001ul

Now, you went wrong on the direction to move the decimal. You have to remember that there are 1000ul in one mL and 1000mL in one liter so clearly the number as you move to ul to mL to L, the number gets smaller. Say you have 23 ul. This is 0.023mL. So actually, in mL, you need 0.0000001mL to make your dilution. This is why I mentioned earlier you would have to dilute your 1mM stock just to be able to accurately measure the volumes needed to make this dilution.

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The first case: Again, you are moving the decimal in the wrong direction. You have 0.18ug/ul as your final concentration (which is correct). Knowing that a ug is much smaller than mg (and you don't even have one full ug/ul) then the mg must be a much smaller number. In fact it's 0.00018mg/ul.

Next, you can use the equation but it's not necessary if you think it out. You just want a specific amount of the drug in a specific volume. You know you want 10ug so that takes 3.57ul of the stock (10/2.8). If I said I wanted 10ug of this drug in 50ml or 50ul, it doesn't matter. It will still take 3.57ul of the stock to get 10ug.

But...if you want to use the equation:
C1=2.8ug/ul
V1--solving for
C2=1ug/mL<<<--you say you want 10ug in 10ml.
V2=10mL
Change units and the equation is: 2800ug/mL X V1 = 1ug/mL X 10mL V1=0.00357mL which is 3.57ul

Here you need to calculate your final concentration to the mL. Say you wanted 6.5ug in 4.3mL. Your final concentration, C2, is 1.51ug/mL (6.5/4.3). Your V2 is 4.3mL. The equation: 2800ug/mL X V1 = 1.51ug/ul X 4.3mL V1=0.0023mL or 2.3ul

But...I point out that if you wanted just a specific amount of the drug 6.5ug, you can divide by the stock 2.8ug/ul and get 2.3ul.

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C1=2ug/ul
V1= what you are solving for
C2=10ug/10ml or same as 1ug/ml
V2=10mL

2000ug/mL X V1 = 1ug/mL X 10mL V1=0.005 or 5ul

So yes, if you add 5ul of the stock to 10ml, the final concentration is 10ug/10mL.

Don't forget that your stock is ug/uL and you are looking for a final concentration of ug/mL. You want your drug to be very diluted (at least in comparison to the stock concentration!).

Now, looking back you say you want a final concentration of 10ug. Is this per mL???? You must know what the final concentration you want is per unit of volume! What I calculated before was 10ug/10mL which is the same as 1ug/mL. If you want 10ug/mL then you need to add more!
C1=2000ug/mL
V1= what to solve for
C2=10ug/mL
V2=10mL Equation: 2000 X V1 = 10ug/mL X 10mL V1=0.05mL or 50ul

Notice that 10ug/mL is 10X more concentrated than 1ug/mL so you have to add 10X more!

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Hi!

Since highschool, math and I became enemies. Any kind of math was my nemesis, but as I need to use some stuff for lab I bought this book:

http://www.amazon.com/Calculations-Molecul...8584&sr=8-1

Is very basic and simple (and a little expensive too ). It does not have many exercises, but you will get the formulas for most things you need and some useful examples you can extrapolate into your own calculation need. I like it a lot.

Good luck!

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Sorry -- I read ml as ul in my prior post -- good pickup!

Though I hesitate to post this link because, as I said, you need to be comforatble doing these calculations manually, you can use the calculator here to at least check your answers (something I should have done before posting my first "Congratulations!" message)... See the "Dilute a stock solution" section at the bottom of the page.

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I appreciate this link too

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Dear HomeBrew,

I have been using this site to dilute etc etc, but then i felt theres no point in doing something I dont know.. First I wanted to learn the basics of these calculations and then once I master it I wanted to continue using this.. he he..

Today I calculated everythign.. Even things that were already there in the lab I went about calculating etc etc.. he he... I am kind of getting the knack for it..

I shud thank Bioforum and special thanks to RKay447... He is really sweet....

And Thanks Homebrew for the encouragement!!!!

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Thanks a lot bacterie.... Very good suggestion...

Will try to get it... Cheers..

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