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

1. You are provided with an antibody solution Ab that has a concentration 600 ug/ul. For lab it is necessary to make thefollowing dilutions.

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

b. 20 ul of 1:20 +40 ul of buffer to make a 1:60 dilution at __________ ug/ul.

c. 5ul of 1:60 + 5ul of buffer to make a ________ dilution at _________ug/ul.

It seems I am missing dome concepts. Could someone help?

This is homework - tell us what you think and we will help correct/expand your answers.

This is the second one today... as I said: on our times we did our HWs alone or googled for the answers. Not asked directly others. How will you learn?

I did not answer the question at first this is how I did it

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

add the buffer, which is 190 ul, to 10ul to get 200 total ul.

6000ug/200= 30 ug/ul

I don't understand how do we know that it is 1:20 dilution.

b. 600ug/ul/ 20=30 ug/ul

30 ug/ul times 20ul=600ug/ 60 ul= 10 ug/ul

I don't understand why the it is a 1:60 dilution. I don't understand why 1:60 dilution was given. I did not use it in solving the question, but my answer is correct.

Am I missing something.

c. 600ug/ul/60=10ug/ul times 5ul=50 ug

50 ug/10ul= 5ug/ul I could not figure out the dilution.

uzalive on Tue Sep 25 22:08:35 2012 said:

I did not answer the question at first this is how I did it

a. 30 ug/ul

I don't understand how do we know that it is 1:20 dilution.

Correct. Dilution ratios work like fractions 1:20 is a 1 part in 20 therefore 600/20 = 30ug/ul...

uzalive on Tue Sep 25 22:08:35 2012 said:

b. 10 ug/ul

I don't understand why the it is a 1:60 dilution. I don't understand why 1:60 dilution was given. I did not use it in solving the question, but my answer is correct.

Am I missing something.

1:60 of the original solution. 600/60 = 10 ug/ul.

uzalive on Tue Sep 25 22:08:35 2012 said:

c. 600ug/ul/60=10ug/ul times 5ul=50 ug

50 ug/10ul= 5ug/ul I could not figure out the dilution.

To calculate the ratio do the inverse of what you would do for working out the concentration- so 600ug/ul / 5 ug/ul =...

One comment, 1/20 is not 1:20

1/20 -> one part of *x* IN 20 parts

1:20 -> one part of *x* AND 20 parts of *y*

Most people would use 1 part with 19 parts diluent to give 1:20, as in the example questions above.

El Crazy Xabi on Wed Sep 26 04:44:39 2012 said:

One comment, 1/20 is not 1:20

1/20 -> one part of

*x*IN 20 parts

1:20 -> one part of

*x*AND 20 parts of

*y*

You would think so, but no. 1:20 when talking about dilutions is 1 part in 20 (or 1 part X + 19 parts Y)

It looks like a mathematical ratio but it's never used like one.

1:20 is a confusing notation and should be abandoned. Because you're never really sure if it's a dilution or a ratio of solute and solvent.

Why can't just people say '20 times diluted' or '1 in 20 dilution'?

Astilius on Wed Sep 26 11:14:52 2012 said:

El Crazy Xabi on Wed Sep 26 04:44:39 2012 said:

One comment, 1/20 is not 1:20

1/20 -> one part of

*x*IN 20 parts

1:20 -> one part of

*x*AND 20 parts of

*y*

You would think so, but no. 1:20 when talking about dilutions is 1 part in 20 (or 1 part X + 19 parts Y)

It looks like a mathematical ratio but it's never used like one.

Maybe you don't, but I use both notations. It's not the first time finding mixes with 70:25:5 of x,y and z and similar. That's why I keep the ration and fraction notation separated. Also because I learned it in that way. It can also be a cultural stuff like the number of continents or the number of lives of cats

Textbook: http://www.hofstra.edu/pdf/Tec_nyscate_solutions_and_dilutions.pdf

see page 29 (It's not what I think, it's also in a book)

There is an old thread about and each people use one or another

http://www.protocol-online.org/biology-forums/posts/31255.html