Medical laboratory instrumentation

1. Introduction into
Clinical
Laboratory
instrumentation
Prepared and Presented by :
Amany Mohamed Elshamy
Department of Medical
Laboratories
Badr Academy

2. Outlines
• Introduction
• Centrifuge
• Weighting Balance
• Thermometry
• pH meter
• Summary
• Questions
2

3. Introduction
• A medical or clinical laboratory is
a laboratory where tests are done
on clinical specimens in order to
obtain information about the
health of patients as pertaining
to the diagnose, to evaluate
effectiveness of therapy and
prevent the disease.
3

4. Concepts
Laboratory Instrument is any implement, tool, or utensil used for
laboratory test.
An instrument is a device that measures a physical quantity, such
as flow, concentration, temperature, level, distance, angle, or
pressure.
Laboratory equipment is the measuring tools that usually used in
a laboratory.
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5. Concepts
• Laboratory techniques: are the
sum of procedures used on applied
sciences in order to conduct an
experiment and performed on
patient specimens to detect
biomarkers and diagnose diseases.
Such as:
Techniques for Extraction & Storage of
Biomolecules, Gel Electrophoresis,
Microscopic techniques.
5

6. Lab Instruments
examples
• Microscopes
• Blood analyzers (i.e., cell
counters)
• Electrolyte, glucose, and oxygen
analyzers
• Equipment for urinalysis
• Various immunoassays
• Gel electrophoresis equipment
for analyzing DNA.
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7. Considerations for purchasing
a clinical chemistry
instrument?
• The several factors should
be taken into consideration.
• Know what types of
materials will be analyzed
and the kind of analysis that
will be done on them. The
volume of patient analysis to
be done and the time
constraints being worked
within should also be
considered.
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8. Steps to achieve successful purchasing
1.Establish the need
2.Define the requirements
3.Define the resources
4.Call tenders
5.Evaluate tenders
6.Select
7.Purchase
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9. Repair and maintenance
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10. Operations in a Clinical Laboratory
Sample handling Performing tests Discards used samples safely Information management (
Analyzes and reports results –
Stores results in a data base).
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11. Centrifuge
• Centrifugation: is the
process of using
centrifugal force to
separate the lighter
portions of a solution,
mixture, or suspension
rom the heavier portions.
11

12. Centrifuge function
1. Remove cellular elements
from blood to obtain cell-free
plasma or serum or analysis.
2. Concentrate cellular elements
and other components of
biological fluids or microscopic
examination or chemical
analysis.
3. Remove chemically
precipitated protein from an
analytical specimen.
4. Separate protein-bound or
antibody-bound ligand from free
ligand in immunochemical and
other assays.
5. Extract solutes in biological
fluids rom aqueous to organic
solvents
6. Separate lipid components
such as chylomicrons from
other components o plasma or
serum, and lipoproteins from
one another. 12

13. Types of centrifuge
• Types of centrifuges used in the clinical laboratory
include:
(1) Horizontal-head or swinging-bucket
(2) Fixed-angle or angle head
(3) Ultracentrifuge
13

14. Swinging-bucket
Fixed-angle
Fixed-angle microcentrifuge
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15. 15

16. Laboratory
centrifuges:
1. Microcentrifuges (devices for
small tubes from 0.2 ml to 2.0
ml (micro tubes), up to 96 well-
plates, compact design, small
footprint; up to 30,000 g).
2. Clinical centrifuges (moderate-
speed devices used for clinical
applications like blood
collection tubes).
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17. Principles of Centrifugation
• The correct term to describe the force required to separate two phases
in a centrifuge is relative centrifugal force (RCF), also called relative
centrifugal field.
• Units are expressed as number of times greater than gravity (e.g., 500
× g).
• RCF is calculated as follows:
RCF= 1.118 × 10−5 ×r × rpm2
17

18. Principles of Centrifugation
Where,
1.118 × 10−5 = an empirical factor;
r = radius in centimeters from the center of rotation to the bottom of the
tube in the rotor cavity or bucket during centrifugation.
rpm = the speed of rotation of the rotor in revolutions per minute.
18

19. Principles of Centrifugation
• The RCF of a centrifuge may also be determined by
manufacturers of centrifuges. RCF is derived from the distance
from the rotor center to the bottom of the tube, whether the tube
is horizontal to, or at an angle to, the rotor center.
• The time required to sediment particles depends on:
(1) rotor speed
(2) radius of the rotor
(3) effective path length travelled by sedimented particles.
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20. Weighting Balances
Types of Balances:
• Double-pan
• Single-pan
• Electronic balances
They are frequently used in the clinical
laboratory.
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21. Types of Balances
Electronic Balance
• In an electronic balance, an electromagnetic force is applied to
return the balance beam to its null position.
• Most electronic balances have a built-in provision or taring, so
that the mass of the container is subtracted easily from the total
mass measured.
• In addition, in many modern balances, a built-in computer
compensates or changes in temperature and provides both
automatic zero tracking and calibration.
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22. Thermometry
• Water baths and
heated cells where
reactions take place are
examples of such
devices.
• Different types of water
baths may be required
depending on the
application.
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23. Types of Laboratory Water Baths
1. Unstirred water baths
2. Stirred water baths
3. Circulating Water Baths
4. Shaking water baths
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24. 1. Unstirred water
baths
1. They are the cheapest
laboratory baths and have
the least accurate
temperature control
because the water is only
circulated by convection and
so is not uniformly heated.
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25. 2. Stirred water baths
They have more accurate
temperature control. They can
either have an in-built
pump/circulator or a removable
immersion thermostat /
circulator (some of which can
pump the bath liquid externally
into an instrument and back
into the bath).
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26. 3. Circulating Water
Baths
Circulating water baths (also
called stirrers ) are ideal for
applications when temperature
uniformity and consistency are
critical, such as enzymatic and
serologic experiments. Water is
thoroughly circulated
throughout the bath resulting in
a more uniform temperature.
26

27. 4. Shaking water
baths
They have a speed controlled
shaking platform tray (usually
reciprocal motion i.e. back and
forwards, although orbital motion is
available with some brands) to
which adaptors can be added to
hold different vessels.
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28. pH meter
• pH meter systems measure
hydrogen ion concentration;
electrochemical.
• NB; The pH of some solutions
changes with temperature
28

29. pH meter
• The pH of solution is defined as the
negative logarithm of the hydrogen
ion concentration, in an aqueous
solution.
• pH is the unit of measure that
describes the degree of acidity or
alkalinity. It is measured on a scale of 0
to 14.
• The pH value of substance is directly
related to the ratio of hydrogen ion
[H+] and the hydroxyl ion [OH-]. 29

30. pH meter
(H+) is the hydrogen ion concentration of the solution in moles
per liter.
In an aqueous solution, the product of hydrogen ion
concentration and hydroxyl ion concentration is constant.
30

31. pH meter
• Convenient way to express hydrogen ion concentration, or
acidity
pH = - log[ H+]
• Where concentration is expressed in moles/liter.
• pH 5.0 solution has ten times more hydrogen ions than pH 6.0
solution. As hydrogen ion concentration, or acidity, increases,
the pH value decreases.
• The [H+] of pure water is 1 X 10-7 mole/L What is pH?
• Answer; The pH of pure water is 7
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32. pH scale
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33. pH scale
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34. 34

35. pH meter
• In the laboratory, hydrogen ion
concentration is controlled with
buffers.
• Buffers are defined as a
solution containing either a
weak acid and its salt or a weak
base and its salt, which is
resistant to changes in the pH
of a system.
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36. pH meter principle
• To measure a pH value, a measuring electrode (pH electrode) and
a reference electrode are needed.
• In many cases, a combination electrode, housing both measuring
and reference elements, is used.
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37. 37

38. Glass electrode
38
The glass electrode is constructed from a special soft
glass of high electrical conductance. It consists of a
bulb that contains a solution of constant hydrogen
ion concentration.

39. Glass electrode
• A 'gel layer' develops on the pH-sensitive glass membrane when
a pH glass electrode meets an aqueous measuring solution. Such
a 'gel layer' arises also on the inside of the glass membrane
which is in contact with a defined buffer solution (the inner
buffer).
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40. Glass electrode
• The H+ ions either diffuse out of the gel layer, or into the gel
layer, depending on the pH value of the measured solution. In the
case of an alkaline solution the H+ ions diffuse out and a
negative charge is established on the outer side of the gel layer.
40

41. Glass electrode
• Since the glass electrode has an internal buffer with a constant
pH value, the potential at the inner surface of the membrane is
also constant during the measurement. The total membrane
potential is a result of the difference between the inner and outer
charge.
41

42. Reference electrode
• Every reference electrode consists of a reference element
which is immersed in a defined electrolyte. This electrolyte must
be in contact with the measured solution. This contact most
commonly occurs through a porous ceramic junction.
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43. Reference electrode
• Of the many reference systems, only the mercury/calomel and
the silver/silver chloride systems, along with certain
modifications of them, have attained practical importance. Due to
environmental considerations, however, the mercury electrode is
rarely used today.
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44. Reference
electrode
44

45. Reference electrode
• The potential of the reference electrode system is defined by
the reference electrolyte and the reference element (e.g.
silver/silver chloride). Here it is important that the reference
electrolyte has a high ion concentration which results in a low
electrical resistance.
45

46. pH measurements
ΔE = E − E1 = 0.059 (pH − pH1)
46

47. Combination electrodes
•Since the combination electrode is much easier to handle than
the separate electrodes.
•In the combination electrode the glass electrode is concentrically
surrounded by the reference electrolyte.
47

48. Combination electrodes
• Three-in-one electrodes
• A recent innovation is the addition of a temperature sensor to
the pH combination electrode. By housing the temperature sensor
in the same body as the pH and reference elements, temperature
compensated readings. 48

49. Combination
electrodes
49
The reference electrodes
in combination
electrodes are protected
against light using Ruby
red glass.
Good choice for storing
combination electrodes is
in a buffer solution having
pH4

50. Application
The main applications are
• Control of industrial processes;
• Analysis of foods and cosmetics;
• Clinical analysis;
• Environmental analysis;
• Microelectrode measurements;
• Measurement of soil pH level by glass electrode is an important
process to observe soil acidity.
50

51. Which of the following cannot form the
inner reference electrode in glass
electrodes?
a) Silver electrode
b) Copper electrode
c) Calomel electrode
d) Silver chloride electrode
51

52. Questions
1. RCF is measured in which o the ollowing units?
a. Gravities (g)
b. Centimeters (cm)
c. RPMs
d. Forces ( f)
52

53. Questions
2. What is the pH of a solution with an H+ ion concentration of 10-
4 mole/L?
3. What is the pH of solution with an H+ ion concentration of 5.0
X 10-6 mole/L?
53

54. Questions
4. Which of the following statements is FALSE?
A. An acid is a proton donor and a base is a proton acceptor.
B. An acidic solution has a pH greater than 7, and a basic solution
has a pH less than 7.
C. Neutralisation of an acid by a base gives a solution of salt in
water.
D. The pH of the stomach is normally in the range of 1.6–1.8.
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55. 5. What does the pH of a buffered solution depend on?
A. The ratio of the components of the buffer solution
B. The amount of acid added to the buffer solution
C. The amount of base added to the buffer solution
D. The amount of acid and of base added to the solution
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56. 56
6. Acidity is stated as a pH value. If the pH of urine
sample “A” is 6 and the pH of urine sample “B” is 7, then
which of the following is true?
• A. The most acidic sample is sample B.
• B. Sample A has ten times the hydroxide ion concentration of sample
B.
• C. Sample B has ten times the hydrogen ion concentration of sample
A.
• D. Sample A has ten times the hydrogen ion concentration of sample
B.

57. 57
7. Which of the following is not the characteristic of a
reference electrode?
• a) It must have a known output potential
b) It must have a constant output potential
c) Its output potential is dependent on the composition of the solution
d) It is employed in conjunction with the indicator or working electrod