1. MLAB 2401: Clinical Chemistry
Basic Principles and Practice of Clinical Chemistry
Part One

2. UNITS OF MEASURE Measurement requires a numerical value and a unit
Laboratory results almost always have units of measurement associated with them
SI units:
length ( meter )
mass ( gram )
quantity ( mole )
Volume ( liter )
Time ( second )
Basic units describe unrelated physical quantities

3. Unit of Measure: Prefixes
Common prefixes and abbreviations that are added to units of measure:
deci (d) 10-1
centi (c) 10-2
milli (m) 10-3
micro ( μ) 10-6
nano (n) 10-9
pico (p)
femto (f)
Example: A common unit of liquid measurement is a deciliter( dl ), or one – tenth of a liter
Combine a prefix with a basic unit results in a statement of a specific length, weight or volume
Reporting clinical chemistry results may be in units such as :
mg / dL
g / dL
mEq / L

4. Scientific Notation True scientific notation format: 1.22 X 104
BUT in hemo, for example a hemoglobin result would look like = 12.2 X 103

5. Water Specifications
Tap water is unsuitable for lab use (too many impurities)
Types of water purification techniques
Distillation – removes most organic matter
Reverse osmosis-removes organic, ionic, microbial, and viral contaminants
Ultrafiltration – removes particulate matter, bacteria, emulsified solids
Deionization – ions removed
Reagent Grades of water
Type I Purest – Required for sensitive tests
Type II Acceptable for most uses
Type III OK for washing glassware
CAP - QC of water : pH, electrical resistance, bacterial culture

6. Water filtration system for
Automated chemistry analyzer.

7. Solutions
The clinical lab almost always uses solutions. A solution means that something has been dissolved in a liquid. In the clinical laboratory the solvent we measure most of the time is human plasma. The solute is whatever the substance is we want to measure.
Mixtures of substances – the substances in a solution are not in chemical combination with one another.
Dispersed phase - the substance is dissolved (the solute)
The substance in which the solute is dissolved is the solvent.
Solute + Solvent = Solution

8. Concentration
Amount of one substance relative to the amounts of the other substances in the solution.
Concentration can be measured in many different units
% Solutions: w/w, v/v , w/v (parts of solute / 100 totals parts ) Note: liquids + liquids and solids + solids alters the total parts, but solutes + solvents does not
Molarity: Moles / Liter
Molality: Moles / 1000 grams solvent
Normality: equivalent weight/ liter

9. Expressing Concentration: Percent Solution (parts/100)
% w/w – percentage weight per weight
Most accurate method of expressing concentration, but can be cumbersome (especially with liquids), not often used in clinical labs.
% w/w = gram of solute OR gram of solute per g of solution
100.0 g of solution
How many grams of NaOH are needed to make a 25.0% w/w solution using deionized water as the solvent?
25.0% w/w = X g of solute in 100 g of solution
X= 25.0 g NaOH

10. Expressing Concentration: Percent Solution (parts/100)
% w/v – percentage weight per volume
Easiest & most commonly used, very accurate if temperature controlled.
%w/v= g of solute OR g of solute per mL of solution
100 mL of solution
What is the %w/v of a solution that has 15.0 g of NaCl dissolved into a total volume of 100 mL deionized water?
X% w/v = 15.0 g NaCl
X= 15.0 %

11. Expressing Concentration: Percent Solution (parts/100)
% v/v –percentage volume per volume
Least accurate, but used when both substances are liquids
Note: volumes of liquids are not necessarily additive
%v/v= mL of solute OR milliliter of solute per 100 mL of solution
100 mL of solution
How many milliliters of ethanol are needed to make a 75.0% v/v solution using deionized water as the solvent?
75.0% v/v EtOH = X mL EtOH in 100 mL of solution
= 75.0 mL EtOH

12. Expressing Concentration: Molarity
Three components of Molarity
Gram weight of solute
Solute’s gram molecular weight
Solvent quantity
Number of moles per one liter of solution
Mole = X number of atoms or molecules OR
Mole= Molecular weight in grams

13. Determinig Molarity: First step
Molecular Weight
Sum of the atomic weights of each element in the compound
What is the molecular weight of Na3PO4?
Step 1: Sodium has an atomic weight of 22.99, but there are 3 molecules so *3= 68.97
Step 2: Phosphorus has an atomic weight of 30.97, and only 1 molecule, so *1= 30.97
Step 3: Oxygen has an atomic weight of 16, but there are 4 molecules ,so 16*4= 64.00
Step 4: Add = gram molecular weight

14. Determinig Molarity: Next Step
How many grams are contained in one mole of Na3PO4?
Use the formula for mole calculations
Number grams of solute
Gram molecular weight of solute
1 mole Na3PO4 = X g Na3PO4
gram molecular weight(gmw)
X= g Na3PO4
So, grams of trisodium phosphate are contained in 1 mole of trisodium phosphate or X 1023 trisodium phosphate molecules weigh grams

15. Determinig Molarity: Final Step
Molarity (M) = 1 mole of solute
1L of solution
We are asked to make a 1.00 L volume of a molar solution of trisodium phosphate. How many grams would we need?
M= grams
gmw
1.00 L of solution
0.100 molar= X grams of Na3PO4
gmw of Na3PO4
(0.100M)(1.ooL) = X g
gmw
0.100= X
163.94
(0.100)(163.94)= X
16.39= X

16. Expressing Concentration: Molality
Amount of solute per one kg of solvent
Expressed in terms of weight per weight or moles per 1000 grams of solvent
Used to measure the physical properties of solutions
Molality = 1 mole of solute
1 kg of solvent

17. Expressing Concentration: Normality- First Step
Equivalents Weights / Liter
Equivalent weight is equal to the gram molecular weight of a substance divided by its valence
Valence = the electrical charge of an ion, or the number of moles that react with 1 Mole H+
Example
The MW of calcium = 40 grams
Calcium ions carry a +2 electrical charge ( valence = 2 )
Equivalent Weight of calcium = 40 / 2 = 20 gram equivalent weight

18. Normality: N= number of grams of solute
Gram equivalent weight of solute
1.00 L of solution
Normality (N)
N = Molarity (M) x valence
Molarity = N / valence
M is always < N

19. Solution Properties
Titration – Method of measuring concentration of one solution by comparing it with a measured volume of a solution whose concentration is known
General formula: when you have a volume and concentration of one, and either the volume or the concentration of the other: V1 C1 = V2 C2
For Example:
How many mls of 1.0 N HCl is required to prepare 25 mls of 0.5 N HCl ?
( 1.0 N ) ( ? mls ) = ( 0.5 N ) ( 25 mls)
? mls = mls
You would need to add 12.5 mls of 1.0 N HCl to 12.5 mls of deionized water
( a total volume of 25 mls) to prepare 25 mls of 0.5 N HCl

20. Solution Properties
Density – An expression in terms (usually) of a mass per unit of volume
Many examples - including specific gravity, osmolality

21. pH and Buffers
Buffers resist change in acidity
Buffers are usually weak acids ( or bases) and their salts
pH is the unit used to measure acidity ( Hydrogen ion concentration )
“p” = “negative log” of the concentration of a substance in solution.
Example: pH = - log [H+]
The Hydrogen ion concentration of deionized H2O is 1 x M
The negative log of = 7. The pH of H2O is 7.0
The pH scale ranges from
pH 7 = neutral
pH > 7 = alkaline (basic)
pH < 7 = acid

22. Temperature
Measurement of temperature is an important component of the clinical lab. Instruments, refrigerators and incubators are required to operate within specific temperatures that must be maintained and monitored daily.
Examples
Heat blocks, water baths, and incubators shall be maintained at least +/- 1 degree C. of the desired temperature
Refrigerators shall be maintained at 2 -8 degrees C.
Each laboratory must have a NIST calibrated thermometer in order to ensure the accuracy of other thermometers in the laboratory
Out-of-range temperatures should be addressed asap

23. Temperature
Scientific measurement of temperature is always expressed in the Celsius ( C) scale , not Fahrenheit ( F )
Celsius scale: 0 degrees = freezing point of water
100 degrees = boiling point of water

24. Conversion: Temperature
Conversion of Celsius to Fahrenheit and Fahrenheit to Celsius
F° = ( C ° x 1.8 ) + 32
C° = ( F ° )
1.8
For example:
Your refrigerator at home is probably around 40 ° F. What is that in Celsius?
Celsius= = 4.4
Water boils at 100 ° C. What is that expressed in Fahrenheit?
(1.8)(100) +32 = 212

25. Conversions
Most conversions within the metric system occur in units of TEN where changing a unit of measure to a higher or lower designation requires moving the decimal one place either to the left or to the right.
When converting measures in either the high end of the scale (example kilo to mega) or the low end of the scale (examples milli to micro, micro to nano, etc.) the decimal must be moved three places right or left as the prefix designations are assigned only to every third unit in the extreme ends.

26. Example of a conversion
How many mls are there in 2.5 liters?
The question you have to ask yourself is, what is the relationship between
liters and mls? The answer : 1 liter = 1000 ml
But now what?
We want to get rid of the “liters’ units and end up with “mls” … Right ?

27. 1.25 liters = _____ mls ? Remember, write a fraction that does two things:
1. Equals 1
2. Gets rid of unwanted units and / or adds needed units
100 mg = _________ ug ?

28. Dilutions A ratio of the concentrate to the total (final) volume.
A 1:4 dilution has a 1 volume of sample and 3 volumes of diluent mixed together.
Any volume can be used to create this dilution, but it must be the same unit of volume
Keep in mind the sample size when making your dilution
For example: a 2:3 dilution could contain:
2 mL serum: 1 mL pure water
20 µL of serum: 10 µL of pure water
0.2 mL of serum: 0.1 mL of pure water

29. Dilutions for the Clinical Laboratory
Example:
A technician performed a laboratory analysis of patient’s serum for a serum glucose determination. The patient’s serum glucose was too high to read on the glucose instrument.
The technician diluted the patient’s serum 1:2 and reran the diluted specimen, obtaining a result of 210 g/dl. To correct for the dilution, it is necessary to multiply the result by the dilution factor (in this case x 2).
The final result is 210 g/dl x 2 = 420 g/dl.

30. Examples of dilutions and dilution factors
Parts Parts Total Dilution Dilution
Specimen Diluent Volume Factor
: 2 2
: 3 3
: 4 4 : : : :

31. Serial Dilutions
In these types of questions, you are given a series of tubes.
Each tube having a measured amount of a diluent.
You are instructed to add a specified amount of specimen into the first tube, mix well and transfer a specified amount of the mixture to the next tube, etc.

32. Serial Dilutions Example: 6 tubes, each with 0.5 mL DI water
Add 0.2 mL serum to first tube and serially dilute
Find the dilution in tube # 6
Find the dilution factor (will be the same in each of these tubes)
1/dil factor x 1/dil factor x 1/dil factor (etc. 6 times)
Result multiplying the numerator 1x1x1x1x1x1x1x = 1
Multiplying the denominators
Will give the result as 1 / 1838

33. Resources
Serial dilution

34. References
Bishop, M., Fody, E., & Schoeff, l. (2010). Clinical Chemistry: Techniques, principles, Correlations. Baltimore: Wolters Kluwer Lippincott Williams & Wilkins.
Doucette, L. (2011). Mathematics for the Clinical Laboratory (2nd ed.). Maryland Heights, MO: Saunders.
Sunheimer, R., & Graves, L. (2010). Clinical Laboratory Chemistry. Upper Saddle River: Pearson .