Solution Concentration

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Solution Concentration
OR

• Which Formula
• Should I Use?

2
Solution ConcentrationsUsed in Lab

• Mass/Volume g/L or mg/ml
• Percent
• Molar M, mM or µM

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Mass/Volume Concentration
Expressed as a specific mass per specific
volume Mass may be g, mg, µg, etc Volume may be
to be L, ml, µl, etc Examples X g OR X mg OR
Xµg OR Xµg L ml
µl ml
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Mass/Volume Concentration Tips

• Formula weight does not matter!
• Set up as a fraction
• Convert units as needed to make unit prefixes the
  same in the numerator and denominator
• Simplify the fraction until the denominator is
  equal to 1
• Used to re-hydrate packaged vials and make media

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Percent Solutions
X (w/v) solution X grams solute
100 ml solutionORX (v/v) solution X
ml solute 100 ml solution
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Percent Solutions Tips

• Formula weight does not matter!
• Solid solute indicates w/v
• Liquid solute indicates v/v
• Gel concentrations expressed this way
• Look for

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Molar Solutions
g M FW L g grams of solute to be
weighed out M molarity of the desired
solution FW formula weight of the solute L
volume of desired solution expressed in
liters
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Molar Solutions Tips

• Formula weight does matter
• Solute is dry
• Volume must be expressed in liters
• Usually solving for g
• Add any water(s) of hydration to the FW of the
  solute
• Look for M or mM or µM

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Diluting Solutions
Sometimes you need to dilute a stock solution in
order to make a working solution
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Diluting Concentrated Solutions
C1V1 C2V2 C1 concentration of stock
solution V1 volume of stock solution needed C2
desired concentration of working solution V2
desired volume of working solution
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Diluting Solutions Tips

• Stock buffers diluted this way
• Solute is liquid
• Volume usually expressed in ml
• Usually solving for V1
• Look for X

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Practice!
Now that you know how to use the formulas, lets
practice knowing which formula to use. The
following slides will give you practice problems
for making solutions in the lab. Read each
problem, select which formula you need to apply,
and see if you can solve the problem.
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Directions
Each practice problem will give you four formula
choices. Choose the formula that applies to the
problem. Then solve the problem yourself. On
each CORRECT!! slide, click to see the problem
set-up, then click again for the solution so you
can check your answer. Then click the blue button
to go to the next problem.
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Practice 1
choose formula

• You need to make 1L of LB/Amp media. The
  concentration of Amp in the media should be 0.1
  mg/ml. How much Amp powder do you need to weight
  out?

• g M FW L
• C1V1 C2V2
• X grams solute
• 100 ml solution
• mass/volume

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Practice 2
choose formula

• We purchase PBS
• as a 20X stock solution. How would you make 150
  ml of
• 1X PBS?

• g M FW L
• C1V1 C2V2
• X grams solute
• 100 ml solution
• mass/volume

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Practice 3
choose formula

• Binding Buffer is 4M Ammonium Sulfate
  (NH4)2SO4.
• How would you make 300 ml of
• this solution?

• g M FW L
• C1V1 C2V2
• X grams solute
• 100 ml solution
• mass/volume

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Practice 4
choose formula

• A 30 mg vial of Ampicillin is rehydrated with
• 3 ml of sterile distilled water. What is the
  concentration of ampicillin in this solution?
•  

• g M FW L
• C1V1 C2V2
• X grams solute
• 100 ml solution
• mass/volume

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Practice 5
choose formula

• Methylene Blue is used to stain DNA. How would
  you make 250 ml of a 0.5 solution of Methylene
  Blue using powdered Methylene Blue?

• g M FW L
• C1V1 C2V2
• X grams solute
• 100 ml solution
• mass/volume

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Practice 6
choose formula

• Your protocol calls for a 30 ml, 0.8 DNA gel.
  How much agarose powder do you need?

• g M FW L
• C1V1 C2V2
• X grams solute
• 100 ml solution
• mass/volume

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Practice 7
choose formula

• You need 10 mM EDTA solution to dilute your DNA.
  How would you make 50 ml of
• 10 mM EDTA?

• g M FW L
• C1V1 C2V2
• X grams solute
• 100 ml solution
• mass/volume

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Practice 8
choose formula

• We have 50X TAE. You need 1X TAE to run your
  gel. How would you make 400 ml of 1X TAE?

• g M FW L
• C1V1 C2V2
• X grams solute
• 100 ml solution
• mass/volume

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Practice 9
choose formula

• How would you prepare 250ml of a 40mM solution
  of Magnesium Chloride MgCl26H2O?

• g M FW L
• C1V1 C2V2
• X grams solute
• 100 ml solution
• mass/volume

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Practice 10
choose formula

• We have 2M glucose
• solution. How would you make 100 ml of 2mM
  glucose solution?

• g M FW L
• C1V1 C2V2
• X grams solute
• 100 ml solution
• mass/volume

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CONGRATULATIONS!

• By carefully reading the problems and picking
  out the unknown, you were able apply the correct
  formula and do the math!

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SORRY!
Try Again!
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CORRECT!!

• This is mass/volume.

You need a concentration of 1mg/ml in the media.
1 mg/ml is equivalent to 1 g/L.
Next problem
Since you are making 1 L of media, you would
weigh out 1 g of Ampicillin powder and add it to
the 1 L of media.
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SORRY!
Try Again!
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CORRECT!!

• C1V1 C2V2 is correct

C1 20X PBS C2 1X PBS V2 150 ml
Next problem
(20X)(V1)(1X)(150ml) Cross-multiply divide V1
7.5 ml 20X PBS diH2O qs 150 ml
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SORRY!
Try Again!
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CORRECT!!

• This is a molarity problem.

g M FW L FW for (NH4)2SO4 132 g 300 ml
0.3 L
Next problem
g 4 132 0.3 g 158.4 of (NH4)2SO4 in di
H2O qs 300 ml
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SORRY!
Try Again!
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CORRECT!!

• This is a mass/volume problem.

You are adding 3 ml H2O to a 30 mg vial so you
have 30 mg in 3 ml.
Next problem
Just simplify the fraction 30 mg 10 mg 3
ml (1) ml
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SORRY!
Try Again!
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CORRECT!!

• This is solution.

0.5 solution means 0.5 g in 100 ml of solution.
You need 250 ml of solution so use this
ratio 0.5 g X g 100 ml 250 ml
Next problem
X 1.25 g Methylene Blue diH2O qs 250 ml
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SORRY!
Try Again!
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CORRECT!!

• This is also solution.

0.8 solution means 0.8 g in 100 ml of
solution. You only need 30 ml of solution so use
this ratio 0.8 g X g 100
ml 30 ml
Next problem
X 0.24 g agarose in 30 ml buffer
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SORRY!
Try Again!
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CORRECT!!

• This is a molarity problem.

g M FW L FW of EDTA 372 g 10 mM 0.01
M 50 ml 0.05 L
Next problem
g 0.01 372 0.05 g 0.558g EDTA diH20 qs
50 ml
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SORRY!
Try Again!
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CORRECT!!

• C1V1 C2V2 is correct

C1 50X TAE C2 1X TAE V2 400 ml
Next problem
(50X)(V1)(1X)(400ml) Cross-multiply
divide V1 8 ml 50X TAE diH2O qs 400 ml
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SORRY!
Try Again!
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CORRECT!!

• This is a molarity problem.

g M FW L FW of MgCl26H20 203 g Dont
forget to add the 6 molecules of H20! 40 mM
0.04 M 250 ml 0.25 L
Next problem
g 0.04 203 0.25 g 2.03g MgCl26H20 diH20
qs 250 ml
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SORRY!
Try Again!
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CORRECT!!

• C1V1 C2V2 is correct even
• though we are dealing with
• molar solutions.

First, convert mM to M so units are the same! C1
2M glucose C2 0.002M glucose V2 100 ml
Next problem
(2M)(V1)(0.002M)(100ml) Cross-multiply
divide V1 0.1 ml ml 2M glucose diH2O qs 100
ml