100 micro molar to 250 micro molar - (Sep/25/2012 )

Interesting. Though, component ratios (e.g. 1:2:1:5) are not the same as dilutions.
The obvious difficulty lies if it's a two component ratio, the resulting notation could easily be ambiguious.

Looking at everyone's favourite, Wikipedia, I see this: http://en.wikipedia....#Dilution_ratio

But yes, there is often much confusion with this, but it should be clear, either by declaration or context if a ratio or dilution were involved.

I also think Trof is onto something -- I have seen many, many people confused over this and the notation isn't helping. Someone want to write up a letter and submit a suggestion of new notation to Nature?

There's also the point that after a certain level of dilution, it really doesn't matter whether you are using the fraction or ratio. For example, 1:5 (one part and 5 parts) is 0.166, whereas 1/5 is 0.2, sure biggish difference, but when you get out to say 1:100 (0.0099) vs 1/100 (0.01) really, what's the difference?

Difference is when people don't understand dilution factor notation at all, they may actually use it wrong when it matters.
Besides, for some applications it does matter even then, for example if you're doing standard curve by serial dilution, you better have the exactly correct ratio, otherwise your results would be screwed.

You have an antibody solution that has a concentration of 600 ug/ul. You want to make th following dilutions.

10 ul of 600 ug/ul Ab +190 ul of buffer to make a 1:20 dilution at ________ ug/ul.


This is how I did it.

1. 600 ug/ul times 10 ul= 6000 ug

2. 6000 ug/200ul= 30ug/ul


I know that this answer is correct because I checked. I don't understand how this gives you a 1:20 dilution. Why is the 1:20 given? I did not use it in my calculations. It seems that I am missing some concept. Can someone clarify this. I would have thought that you would divide 30 ug/ul by 20.

Uzalive

if you go from 6000µg to 30µg, then you diluted it 20 times.
6000/20 = 30

and where does the 1:20 comes from (without making the math of the antibody) 10 µl and 190 µl , is 10 µl in 200 µl in total, its 1:20 , 1 part of 20 parts in total or 10 parts of 200 parts in total.

uzalive on Sat Sep 29 18:02:27 2012 said:

Dear Uzalive,

Dilution factors are always what students and some researchers have problems with. Large volumes are sometimes easier to deal with than smaller ones. The problem with research is that the antibody, drugs and compounds we use are expensive and therefore we cannot make up litres just to keep the maths easy. With dilution factors:-

1:10 is 1ml to 9mls of diluent (total 10mls of solution)
1:10 is 0.1ml (100ul) to 0.9ml (900ul) total = 1ml
1:10 is 0.01ml (10ul) to 0.09ml (90ul) total = 0.1ml

With your antibody at a concentration of 600ug/ul, a 1:20 dilution is:-
1ml to 19ml
0.1 to 1.9mlml
0.01 (10ul) to 0.19ml (190ul)
Giving you a final concentration of diluted antibody of 30ug/ul

You have to practise and be able to convert/look at different ways of stating the same volume, measurement etc

Hope this is useful

Kindest regards

Neale

I have 100 micro molar dNTP stock, how do i convert it to 250 micro molar as i need 250 micro molar for my PCR?

Please help me with the calculations

You can't go from less concentrated to more...

however, you probably want 25 uM rather than 250... so read the rest of this thread...