Solution Preparation Steps

5 Steps to Teach Solution Prep • • • • •

Ellyn Daugherty SM 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

Five 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

Step 1. What is a Solution ? • Solutes (usually measured in g) • Solvents (usually measured in mL) • Mixed together until solute dissolves in solvent

solute concentration = solution • Described by the portion of solute to solvent usually in one of 3 ways: - mass/volume

•5 g/L protease •175 mg/mL rennin •25 !g/!L chymosin

- % mass/volume - molarity

• 2% glucose solution • 10% sodium hydroxide solution

• 1M NaOH • 50 mM TRIS • 5 !M CaCl2

8 mg/mL

4 mg/mL

2 mg/mL

Step #2 Solvent Measurement 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?

Review: Metric Measurements and Conversions

L

1000

92 ml = _________ !L 0.5 L = _________ mL

mL

1000

!L

357 !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 ___________ _____________ __________________ concentration desired X volume desired = mass of solute needed

• mass/volume

__________

• % mass/volume

conc desired (decimal) X volume desired

_________

• molarity

____________

concentration desired (mol/L)

____________ X

__________

_________________ =

mass of solute needed

__________

volume desired X molecular weight = mass of solute needed (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 concentration desired X volume desired = mass of solute to be weighed

Measuring for % Mass/Volume Solutions To make 100 mL of a 3% CuSO4 solution 3 % = 0.03 __________

____________

conc desired (decimal)

0.03 g/mL conc desired

X

volume desired

100 mL X

volume desired

_________________ =

mass of solute needed

3 g CuSO4 = 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

desired (mol/L)

(L)

(g/mol)

(g)

Molecular Weight ? Moles are used to count molecules and atoms since they are too small to count individually. 1 mole equals the amount of molecules that gives a mass, in grams, equal to that substance’s molecular or formula weight. The formula weight can be determined using a periodic table or by looking at 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 looking at a chemical reagent bottle

Measuring for Molar Solutions To make 300 mL of a 0.5M NaOH solution. Convert 300 mL = 0.3 L

0.5 mol/L concentration desired (mol/L)

0.3 L X

40 g/mol

6g

volume desired X molecular weight = mass of solute (L)

(g/mol)

(g)

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.

4. Mixing the Solute and Solvent Mass/Volume solutions 100 mL of a 5 mg/mL hemoglobin solution. 5 mg/mL 100 mL 500 mg = 0.5 g concentration desired X volume desired = mass of solute to be weighed

250 mL beaker 100 mL solvent (dH20 or buffer) 0.5 g hemoglobin

Mass/Volume Demo

Mixing % Mass/Volume Solutions 100 mL of a 3% CuSO4 solution 0.03 g/mL conc desired (decimal)

100 mL X

volume desired

3 g CuSO4 =

mass of solute needed

250 mL beaker 100 mL solvent (buffer or dH20) 3 g CuSO4

% Mass/Volume Demo

Mixing Molar Solutions 300 mL of a 0.5M NaOH solution. Convert 300 mL = 0.3 L

0.5 mol/L concentration

0.3 L X

40 g/mol

6g

volume desired X molecular weight = mass of solute

desired (mol/L)

(L)

(g/mol)

(g)

600 mL beaker

300 mL solvent (dH20 or buffer) 6 g NaOH

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.