August 13, 2024, 05:21:50 PM
Forum Rules: Read This Before Posting

### Topic: Dilution help  (Read 4495 times)

0 Members and 1 Guest are viewing this topic.

• Very New Member
• Posts: 2
• Mole Snacks: +0/-0
##### Dilution help
« on: September 19, 2023, 12:33:44 AM »
Hello! I have a TNF-a stimulation that has a stock concentration of 10ug/mL. I want to have a final concentration in my 100uL well of 10ng. I have no idea how to solve for the amount of PBS I need to add to the stock so that after I add to the well it is at the 10ng concentration. Any one can help explain?

#### Hunter2

• Sr. Member
• Posts: 2259
• Mole Snacks: +185/-49
• Gender:
• Vena Lausa moris pax drux bis totis
##### Re: Dilution help
« Reply #1 on: September 19, 2023, 02:16:49 AM »
Convert  10 μg/ ml to ng/μl to have the same unit like 10 ng/100 μl

How much is it.

• Very New Member
• Posts: 2
• Mole Snacks: +0/-0
##### Re: Dilution help
« Reply #2 on: September 19, 2023, 07:40:47 AM »
1 want to add between 1-8ul to the well

#### Hunter2

• Sr. Member
• Posts: 2259
• Mole Snacks: +185/-49
• Gender:
• Vena Lausa moris pax drux bis totis
##### Re: Dilution help
« Reply #3 on: September 19, 2023, 07:47:33 AM »
10 μg/ml = 10 ng/ μl

To get 10 ng/100 μl  you have to add 1 μl  of the stock to 99 μl of the solvent.

#### Babcock_Hall

• Chemist
• Sr. Member
• Posts: 5662
• Mole Snacks: +328/-24
##### Re: Dilution help
« Reply #4 on: September 19, 2023, 12:38:27 PM »
When I teach dilutions, I suggest to students that they draw a picture of what is going on.  With respect to your example, I suggest starting with the idea that the mass of material in the pipet tip (1) is equal to the mass of material in the well (2).  Putting this idea into a formula:  Mass1 = Mass2.   The mass of TNFα is equal to the concentration of a solution times the volume of the same solution.  Try writing an equation that expresses this idea.  Making a picture minimizes plugging incorrect numerical values into a formula.