solution preparation steps

Ellyn DaughertySM Biotech Career Pathway

www.BiotechEd.com

www.emcp.com/biotech

www.sargentwelch.com/biotech

[email protected]

• Biotech 1 SLOP

• Text - Chapter 3

• Lab Manual - Chapter 3

• Student CD Tutorials

• Course Planner

5 Steps to Teach Solution Prep

1.What is a solution?

2.Solvent Measurement

3.Measure the Solute

4.Mix the Solute and Solvent

5.Check the Solution Preparation

Five Steps to Teach Solution Prep

• Solutes (usually measured in g)

• Solvents (usually measured in mL)

• Mixed together until solute

dissolves in solvent

• Described by the portion of solute

to solvent usually in one of 3 ways:

- mass/volume

- % mass/volume

- molarity

Step 1. What is a Solution ?

8 mg/mL 4 mg/mL 2 mg/mL

concentration =solute

solution

• 2% glucose solution

• 10% sodium hydroxide solution

•5 g/L protease

•175 mg/mL rennin

•25 !g/!L chymosin

• 1M NaOH

• 50 mM TRIS

• 5 !M CaCl2

Volume of solvent is usually measured using one of 3

instruments. For each, ask:

• What is the total volume that can be measured?

• What is the value of each type of graduation?

Step #2 Solvent Measurement

L mL !L

Review: Metric Measurements and Conversions

1000 1000

92 ml = _________ !L 357 !L = _________ mL

0.5 L = _________ mL 0.557 mL = _________ !L

Step #3 Solute Measurement

Solutes are usually dry chemicals

and their mass is measured on a

scale/balance and reported in

grams (g).

For a specified concentration of a

specified volume of solution, the

technician must determine the

amount of mass of solute need for

the volume of solution at some final

concentration.

3 different equations, one for each

concentration units group

- mass/volume

- % mass/volume

- molarity

Determine the Mass of Solute (g)3 different equations, one for each concentration units group

• mass/volume

• % mass/volume

• molarity

___________ _____________ __________________

concentration desired X volume desired = mass of solute needed

__________ ____________ _________________

conc desired (decimal) X volume desired = mass of solute needed

_________ ____________ __________ __________

concentration X volume desired X molecular weight = mass of solute needed

desired (mol/L) (L) (g/mol) (g)

Measuring for Mass/Volume Solutions

To make 100 mL of a 5 mg/mL hemoglobin solution

___________ _____________ _________________

concentration desired X volume desired = mass of solute to be weighed

5 mg/mL 100 mL 500 mg = 0.5 g


Measuring for % Mass/Volume Solutions

__________ ____________ _________________


To make 100 mL of a 3% CuSO4 solution

3 % = 0.03

0.03 g/mL 100 mL 3 g CuSO4

conc desired X volume desired = mass of solute needed

Measuring for Molar Solutions

To make 300 mL of a 0.5M NaOH solution.

Convert 300 mL = 0.3 L

_________ ____________ __________ _______

concentration X volume desired X molecular weight = mass of solute


Molecular Weight ?

Moles are used to count molecules and atoms since they are too small tocount individually. 1 mole equals the amount of molecules that gives amass, in grams, equal to that substance’s molecular or formula weight.

The formula weight can be determined using a periodic table or by lookingat a chemical reagent bottle.

For Molar Solutions you need the MW

Determine the molecular weight of the solute

The formula weight can be determined using a periodic table or by lookingat a chemical reagent bottle

Measuring for Molar Solutions

To make 300 mL of a 0.5M NaOH solution.


6 g of NaOH is measured on a balance and put into an appropriate vessel.

Then, solvent is added up to the 300 mL graduation.

0.5 mol/L 0.3 L 40 g/mol 6 g



4. Mixing the Solute and Solvent

Mass/Volume solutions

100 mL of a 5 mg/mL hemoglobin solution.

solvent (dH20 or buffer)

0.5 g hemoglobin

100 mL

5 mg/mL 100 mL 500 mg = 0.5 g


250 mL beaker

Mass/Volume Demo

Mixing % Mass/Volume Solutions

100 mL of a 3% CuSO4 solution

3 g CuSO4

solvent (buffer or dH20)

100 mL

0.03 g/mL 100 mL 3 g CuSO4


250 mL beaker

% Mass/Volume Demo

Mixing Molar Solutions

300 mL of a 0.5M NaOH solution.


6 g NaOH

300 mL

solvent (dH20 or buffer)

0.5 mol/L 0.3 L 40 g/mol 6 g



600 mL beaker

Molar Solution Demo

Step 5 Checking the Solution Preparation

I like to teach solution prep with copper sulfate since it is blue

and can be visualized (relative number of molecules compared)

in the Spec 20D+ at 600 nm)

I also check the volume and labels on all tubes.

Other methods of checking solution prep?

Now YOU try it.Make the following solutions but before you do:

• Do all the calculations showing the equations with all the units of measurement shown.

• Diagram how you are going to prepare the solution.

After you prepare the solution, check it in the spec. Demonstrate how to take up and dispense a sample.

• 5 mL of 0.2 g/mL cupric sulfate pentahydrate

• 7 mL of 50 mg/mL cupric sulfate pentahydrate

• 4 mL of 2% cupric sulfate pentahydrate

• 6 mL of 1% cupric sulfate pentahydrate

• 5 mL of 0.5 M cupric sulfate pentahydrate

• 4 mL of 250 mM cupric sulfate pentahydrate

Check each solution in the spec at 600 nm.

Use 3 mL of the solution to be checked, in a 13x100 mm cuvette.

solution preparation steps

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