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Working concentration


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#1 EMSA1983

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Posted 18 May 2010 - 08:28 PM

What is working concentration?

how do you improve the working concentration of a stock if a particular concentration is needed but the required volume is v.difficult to pipette?

#2 gebirgsziege

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Posted 18 May 2010 - 11:46 PM

dilute????
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#3 Prep!

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Posted 18 May 2010 - 11:49 PM

What is working concentration?

how do you improve the working concentration of a stock if a particular concentration is needed but the required volume is v.difficult to pipette?


working concentration is sumthing that is a more dilute form of a stock solution (which is obviously more concentrated)

if required volume of stock is too less... there can be two options.. either decrease the stock concentration or increase the working volume!!

suppose u have a 10X solution and you need a 0.001X suppose say 1 ml then you have to aliquot 0.1mcl which might be difficult in that case dilute the stock to a concentration from where the volume required is pipettable!!! (say to 1 X so tat u can pipette 1 mcl now!!)

hope this helps!!
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#4 EMSA1983

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Posted 23 May 2010 - 04:53 PM

thank u?
that is really well explained...

What is working concentration?

how do you improve the working concentration of a stock if a particular concentration is needed but the required volume is v.difficult to pipette?


working concentration is sumthing that is a more dilute form of a stock solution (which is obviously more concentrated)

if required volume of stock is too less... there can be two options.. either decrease the stock concentration or increase the working volume!!

suppose u have a 10X solution and you need a 0.001X suppose say 1 ml then you have to aliquot 0.1mcl which might be difficult in that case dilute the stock to a concentration from where the volume required is pipettable!!! (say to 1 X so tat u can pipette 1 mcl now!!)

hope this helps!!
Best luck!!



#5 HomeBrew

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Posted 23 May 2010 - 06:01 PM

An example of a stock concentration is 50X TAE. A working concentration of TAE would be 1X, therefore, to make your TAE at working concentration, you would dilute your stock concentration 1:50 with water.

Another example is antibiotics. Your stock concentration of ampicillin, for example, might be 100 mg/ml. If your working concentration of ampicillin in media is 100 ug/ml, then your stock concentration is 1000X. Thus you would dilute your stock concentration by adding it to media at 1 ml per liter of media.

If you were trying to add ampicillin to a small volume of media, say 250 ul, this would be difficult to do from your 1000X stock, because you'd have to try and add 0.25 ul to achieve 100 mg/ml. In a case such as this, you could first dilute your stock 1:10 (thus achieving 50 mg/ml) and then add a much more manageable 2.5 ul to your small volume of media (actually, it would be 2.5 ul of antibiotic to 247.5 media to achieve exactly 100 ug/ml, but you get the idea -- if the stock concentration is too high, the amount you need will be too small to measure accurately. In such a case, do an intermediate dilution).

If you have a specific problem, tell us what it is, and we can be of more help.

#6 EMSA1983

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Posted 03 June 2010 - 10:33 AM

An example of a stock concentration is 50X TAE. A working concentration of TAE would be 1X, therefore, to make your TAE at working concentration, you would dilute your stock concentration 1:50 with water.

Another example is antibiotics. Your stock concentration of ampicillin, for example, might be 100 mg/ml. If your working concentration of ampicillin in media is 100 ug/ml, then your stock concentration is 1000X. Thus you would dilute your stock concentration by adding it to media at 1 ml per liter of media.

If you were trying to add ampicillin to a small volume of media, say 250 ul, this would be difficult to do from your 1000X stock, because you'd have to try and add 0.25 ul to achieve 100 mg/ml. In a case such as this, you could first dilute your stock 1:10 (thus achieving 50 mg/ml) and then add a much more manageable 2.5 ul to your small volume of media (actually, it would be 2.5 ul of antibiotic to 247.5 media to achieve exactly 100 ug/ml, but you get the idea -- if the stock concentration is too high, the amount you need will be too small to measure accurately. In such a case, do an intermediate dilution).

If you have a specific problem, tell us what it is, and we can be of more help.


Thanks..
for example, you have a stock of concentration 1 uM. you need to make a 10pM working concentraion in 2 ml of media. The answer will be 0.00002 ml, which will be v difficult to pipette. So how do you do it? how do you dilute the stock?

#7 pito

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Posted 03 June 2010 - 10:50 AM

I cant imagine anyone needing to use 10pM.

But it would be best to dilute your stocksolution first to get a "second stock solution".

Lets say you dilute your stock solution of 1ÁM 1:1000 then you have a stock solution of 1 nanoM.

then you can dilutre further to get 10pM.

A stock solution is just something you can use to make other solutions... but you do not need to start with this stock solution to get your end solution... you can make other "stock" solutions too....

Its always best to make several dilutions and not in 1 step the end solution.

Edited by pito, 03 June 2010 - 10:51 AM.

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#8 HomeBrew

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Posted 03 June 2010 - 06:02 PM

You're still going to make an intermediate dilution -- how much you add depends on whether you're trying to make 2 ml of a solution containing 10pM total, or 2 ml of a solution that's 10pM per ml (thus 20pM total)....

#9 EMSA1983

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Posted 04 June 2010 - 08:09 AM

I cant imagine anyone needing to use 10pM.

But it would be best to dilute your stocksolution first to get a "second stock solution".

Lets say you dilute your stock solution of 1ÁM 1:1000 then you have a stock solution of 1 nanoM.

then you can dilutre further to get 10pM.

A stock solution is just something you can use to make other solutions... but you do not need to start with this stock solution to get your end solution... you can make other "stock" solutions too....

Its always best to make several dilutions and not in 1 step the end solution.


yes got the idea..thanks a lot pito...

#10 EMSA1983

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Posted 04 June 2010 - 08:10 AM

You're still going to make an intermediate dilution -- how much you add depends on whether you're trying to make 2 ml of a solution containing 10pM total, or 2 ml of a solution that's 10pM per ml (thus 20pM total)....


the conc. will be 10 pM for 2 ml..
never mind..i got it..thanks a lot for explaining it so well...




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