This documet describe about the basic laboratory equipments

1. Basic laboratory equipments and wares
1

2. Learning objectives
At the end of this chapter, the student will be able to:
– State the different types of laboratory wares
– Understand the equipment's used in water purification
– Describe the equipment's used for steralisation
– Describe the use of laboratory glass and plastic wares
– Identify different types laboratory wares
– Explain the general cleaning and care of laboratory wares
2

3. 1. Water purity and distillation system
use
• Quality of water used in the laboratory is very crucial.
• It is used for,
Reagent and solution preparation,
Reconstitution of lyophilized materials and
Dilution of samples demands specific requirements for its purity
• All water used in medical laboratory should be free from substances
that could interfere with the tests being performed.
3

4. Water purity and distillation system use…
• In medical laboratory work, water of an appropriate quality and quantity is
required for the preparation of:
Standard solutions, buffers and controls;
Various laboratory stains;
Reagents used in Clinical Chemistry, Immunology, Hematology and
Microbiology;
Reagents used for culture media;
Reagents used in blood transfusion work and for rinsing of cleaned
glass and plastic wares, cuvettes, etc.
4

5. Purpose of Water Purification
• To remove dirt, chemicals such as ions and substances so
that only pure H2O remains for laboratory uses.
There are different levels of purity:
• Type I
• Type II
• Type III
5

6. Types of water and their uses
• Type III: tap water for washing laboratory ware
• Type II: qualitative urinalysis, rinsing laboratory ware,
qualitative reagents or stains
• Type I: quantitative reagents, dilutions of samples
• Sterilised type I: microbiologic testing
• UV Oxidised sterilised type I: cell culture and nucleic acid
testing.
6

7. Cont…
• For preparation of standard solutions, buffers and controls, the most
pure water quality that is free from bacteria (Type I Reagent Water)
should be used.
• However, for most routine activities carried out in
• Immunology, Urinalysis, Hematology, Microbiology and other
clinical test areas, Type II Reagent Water can be used when the
presence of bacteria is tolerated.
• Type III Reagent Water can be used as a water source for
preparation of ;
• Type I and Type II Water and for washing and rinsing of laboratory wares.
7

8. Water distilling apparatus (Still)
• Is an instrument that is used to purify impure water by a process
known as distillation.
• Distillation is a process by which impure water is boiled and the
steam produced is condensed on a cold surface (condenser) to give
chemically pure distilled water that is water from which non-volatile
organic and inorganic materials are removed.
• Distillation does not remove dissolved ionized gases such as
ammonia, carbon dioxide, and chlorine.
• C:UsershpDesktopDistillation The Operation of a Water
Still.mp4 8

9. Cont…
• Distilled water should be clear, colorless and odorless.
• Distilled water is sometimes found to be contaminated with non-
volatile impurities that have been carried by steam in the form of
spray.
• Example, sodium, potassium, calcium, carbonate ions, sulfate ions,
etc.
• Distillation is an effective water treatment method for removing
contaminants like bacteria, heavy metals, and chemicals.
9

10. Gravity water filter
• Filtration is defined as the passage of a liquid through a filter and
accomplished via gravity, pressure, or vacuum.
• Filtrate is the liquid that has passed through the filter.
• Purpose of filtration is to remove particulate matter from the liquid.
• When using a gravity water filter fitted with and reusable ceramic
candle filter of 0.9 micro meter porosity,
 most bacteria, parasitic microorganisms and suspended particles can
be removed from the water but not dissolved salts.
10

11. Deionizer
• Deionizer is an apparatus used to produce ion free water.
• Deionization is a process in which chemically impure water is passed
through anion and cation exchange resins to produce ion free water.
• Deionized water has;
• low electrical conductivity, near neutral pH and is free from water-
soluble salts but is not sterile.
• Cations, which may be present in the water such as calcium, magnesium
and sodium, are exchanged by the cation resin, which in turn releases
hydrogen ions.
• Anion impurities such as sulfate, bicarbonate, silicate, nitrate and chloride
are exchanged by the anion resin, which in turn releases hydroxyl ions.
11

12. Cont…
• Finally, the hydrogen ions combine with the hydroxyl ions to give
ion - free water.
• N.B: Deionizer resin can cause irritation if it is allowed to enter the
eye or skin.
• It is therefore, advisable to wear plastic gloves and protective eye
goggles when filling the plastic tube.
12

13. UV Oxidation
• Water exposed to UV wavelengths and ozone will sterilize bacteria
but not remove them.
• Type I sterilized water is produced after membrane purification
followed by UV oxidation process.
Disadvantages:
• Very expensive process
• Not commonly available in developing countries
• Filter columns and UV lamp need replacement periodically
13

14. 2. Laboratory sterilizers and autoclave
• Sterilization is the use of a physical or chemical procedure to
destroy all microbial life, including highly resistant bacterial
endospores.
• Disinfection eliminates virtually all pathogenic non-spore-forming
microorganisms but not necessarily all microbial forms on
inanimate objects.
• Effectiveness is influenced by the kinds and numbers of organisms,
• The amount of organic matter,
• The object to be disinfected and chemical exposure time, temperature
and concentration.
14

15. Cont…
• Antisepsis is the application of a liquid antimicrobial chemical to
skin or living tissue to inhibit or destroy microorganisms.
• Swabbing an injection site on a person or animal and hand
washing with germicidal solutions.
• Antisepsis relates to the removal, or elimination, of transient
microorganisms from the skin and a reduction in the resident flora.
15

16. Laboratory Sterilisers
Purpose
• To kill microorganisms and endospores
• To decontaminate reusable equipment, specimens or other infectious wastes prior
to routine disposal
• To prepare sterile media for cell cultures.
Laboratory Sterilizers
There are four main methods to achieve sterilization including:
• Moist heat (autoclave)
• Dry heat
• Chemical sterilization
• Filtration
• The most commonly employed method in medical laboratories is with moist heat,
an autoclave.
16

17. Moist Heat Steriliser/ Autoclave
• a highly effective method of sterilizing and disinfecting objects
through the use of heat in the form of steam plus pressure and time
• The autoclaves can be used in all laboratory applications,
• Sterilization of liquids (such as nutrient and culture media),
• solids (such as instruments, pipettes, glassware),
• waste (destructive sterilization of liquid waste in bottles, or solid
waste in destruction bags) and
• biological hazards in safety laboratories.
17

18. Cont…
• Autoclave sterilization works by using heat to kill microorganisms
such as bacteria and spores.
• The heat is delivered by pressurized steam
• C:UsershpDesktopAutoclave (Moist Heat Sterilization) Working
Procedure (ENGLISH) By Solution Pharmacy.mp4
• C:UsershpDesktopAutoclave Sterilizing.mp4
18

19. Moist Heat Steriliser/ Autoclave….
• These main factors must be considered for sterlisation with an
autoclave:
Temperature, Pressure, Timing
Most Heat Steriliser/ Autoclave can Sterilise:
• Most agar and liquid culture media and swabs for use in microbiology
work.
• Steam media containing heat-sensitive ingredients at 1000C with the
lid left loose to sterilise.
• Specimen containers, pipettes, petri dishes, and other laboratory
glassware or heat-stable equipment using a higher temperature.
19

20. Temperature
• Steam is produced when pure water boils at 1000 C.
• Autoclaving at 1210C for 15-20 min.
• Is required for the fastest route.
• In an autoclave, all air is removed and pressure is used to produce high
temperature steam.
• At a pressure of 15 pounds per square inch (psi), the temperature of
saturated steam rises to 1210C.
• If air remains behind in the steam it will not properly sterilise some
autoclaves have continuous pressure purge which removes cold air
pockets for uniform sterilisation.
• Pressure may be also noted in bars. 1.1 bar is equivalent to 104 k Pa or
15psi.
20

21. Pressure
• At high altitudes, atmospheric pressure is reduced
• The pressure required to achieve 1210C must be increased.
• Pressure should be raised 0.5psi for every 300m (1000 ft) of altitude.
For example, at 2100m (7000ft) a pressure of 18.5 psi is required to raise the
temperature to 1210C.
• An autoclave cycle that ensures a sterilizing temperature of 121°C for at
least 15 minutes at a pressure of 15 psi (100 kPa) is adequate for liquid
reagents;
• For equipment sealed in autoclave bags a temperature of 126°C is
desirable, or 121°C for 20 minutes.
21

22. Timing
 1210C for 15-20 min. is required for the fastest route of
sterilization but a lower temperature and longer sterilization time
can be used.
• It takes certain period of time for the saturated steam to penetrate
the entire load and for heat transfer to occur.
• Time for heat up needs to be added to total time.
22

23. Autoclave saftey
 Follow operating and maintenance instructions supplied by
manufacturer
 To prevent accidents and injury it is important to allow sufficient
time after sterilisation for the pressure to return to zero and for the
load to cool.
 Many newer autoclaves have locks that won’t release until
temperature and pressure have lowered to safe levels.
23

24. Specifications
An autoclave is:
 double walled
 powered by gas, electricity
 containing water reservoirs or inline steam
 some use tap water
 capable for operating a 1210C sterilising cycle.
 typical capacity of 10- 30 L
 fitted with a thermometer and pressure gauge.
24

25. Cont…
• Easy and safe to use with approved lid locking and pressure release
safety valve.
• Supplied with metal tray or wire mesh basket.
• Typical 240 volts and 6.8 amps
• Thermostatically controlled and fitted with an electric cut-out to
prevent the autoclave from boiling dry.
• Set the timer and temperature based on altitude
25

26. Guide for timer, temp at certain altitudes
Altitude Time
Metres (m) minutes
0 15 (121ºC)
500 20 (120ºC)
1000 25 (119ºC)
1500 30 (118ºC)
26

27. Methods of monitoring the performance of
Autoclave
Daily
 Follow manufacturer’s instructions and monitor time,
temperature and pressure gauges
 Simple screen with Sterilisation strip quarterly or annually
 Spore strips or Indicator chemicals
27

28. Quarterly Autoclave Functional Test
Spore strip
 Principle: Bacillis species become nonviable if sterilisation is
effective
 Spore strip or spore-containing ampoules are added with routine
load to be sterilized
 Spores are then tested for viability by routine microbiology
techniques
Problems:
 Depends on time for micro-biology testing to read results
28

29. Alternative Quarterly Autoclave Functional
Test
Browne's indicator tubes
• Principle: Chemical that changes from red to green when the
required temperature has been reached for the correct length of time.
• More practical method
29

30. Weekly Check
Adhesive sterilisation tape
 Principle: Heat and moisture sensitive ink which changes to a dark
colour after autoclaving; often present as bands for high visibility.
Simple method of showing when an article has been autoclaved.
 Problem: not a reliable way of testing whether a sterilising cycles
has been effective.
 Does not record accurately the conditions during the sterilising
cycles
30

31. Care and Maintenance of Autoclave
 Follow the manufacturer’s instructions. Prepare a standard
operating procedure for maintenance and a maintenance log for
documentation.
 Safety: Autoclaves should be allowed to cool to 80°C before
opening and, once removed, sterilised media should be left in a
clean and safe area to cool.
31

32. Other Less Used Sterilisation Methods
Dry Heat (oven) requires 1600C for 120 minutes
• Dry air is blown onto the object that is to be sterilized, passing energy to it
through conduction (forced air).
• Alternatively, an oven could use heated coils instead of fans (static air),
but the forced air type is preferable as it delivers the heat load to the object
with better homogeneity.
 Recommended for sterilisation of some materials prior to use such as
 serum or egg based media
 glassware, petri dishes, inoculating materials that may not withstand
high pressure steam
32

33. Cont…
 using blown hot air to eliminate or deactivate all forms of life inside the
chamber of an industrial oven.
• Typically, the setting must be at 160 °C (320 °F) for a duration of two
hours, 170 °C (340 °F) for one hour, and up to 190°C (375°F) for 6 to 12
minutes.
Advantages of Dry-Heat Sterilization:
• Dry heat ovens are generally cheap to buy
• Cost of operation and heating cycles is generally low
• Heat can go deeply into thick objects, achieving an in-depth
sterilization effect
• Metallic objects that can handle heat well can be sterilized quickly at
high temperatures.
• Dry heat is non-corrosive for metallic materials as it contains too little
moisture. 33

34. Cont…
Disadvantages
• The dry heat can take much more time to achieve sterilization than steam,
flaming, chemical sterilization, or radiation.
• Heat can cause warping to sensitive materials or thin sheets.
• High temperatures can irreversibly damage plastics, rubber, so these are
not suitable for dry heat.
• Overexposure to heat even for materials that can handle it can result in
unwanted changes in the chemical structure of some substances.
34

35. Chemical Sterilisation
 Chemical sterilization involves the utilization of certain
chemicals so as to cause microbial termination.
 Most used chemicals are chlorine, formaldehyde, glutaraldehyde,
quaternary ammonium salts.
 More expensive and some concerns for persistence of chemical
pollution
35

36. Membrane Filtration
• Membrane filters are thin filters that are made of cellulose
• They can be used for sterilization during injection by placing the
membrane between the syringe and the needle
• Seitz filters are usually made of asbestos
• They are pad-like and thicker than membrane filters
 Most frequently used for sterilisation of water prior to
purification
• Membrane filtration traps contaminants larger than the pore size on
the surface of the membrane
36

37. Cont…
Advantages:
 Absolute sterilization - separates particles based on size
 Used for heat sensitive media
 Removal of multiple particle sizes
 Allows for fairly high throughput
Disadvantages:
 Each filter has a specific nominal pore size
 Unable to separate microorganisms that have the same size
 May require a high differential pressure
37

38. 3. General laboratory wares
LABORATORY GLASSWARES AND PLASTICWARES
Definition: laboratory glassware and plastic wares are materials
used in clinical laboratory for:
measuring
pipetting
 transferring
Preparation of reagents
Storage etc.
38

39. LABORATORY GLASSWARES
• Most of the routine laboratory wares used to be of glass,
• But recent advantage made in the use of plastic resin that led to a
gradual replacement of glass wares with durable plastic ware.
Classification of Laboratory glass wares
A. according to their composition, can be divided in to five main types
1. Glass with high thermal resistance – boro-silicate glass can resist about 500oC
and low alkaline contact.
2. High silica glass- contains 96% silicon, It is thermal endurable, chemically
stable and electric resistant.
3. Glass with high resistance to alkali- Boron free, used in strong alkali low
thermal resistance.
39

40. Cont…
4. Low actinic glass – amber color to protect light
5. Standard flint glass- soda lime glass, poor resistance to increased
temp. Contains free soda in its walls
• Hardened glasses, such as
 Pyrex, monax, and firmasil have low soda-line content and are
manufactured especially to resist thermal shock (high temperature).
• The high proportion of boro-silicate increases the chemical
durability of the glassware's.
40

41. Cont…
B . Based on their use
a) volumetric wares
b) Semi-volumetric Glass wares
c) Non- volumetric glass wares.
41

42. Cont…
a)Volumetric wares
– Apparatus used for measurement of liquids
– Can be made either from glass or plastic
– it includes :
• Volumetric flasks
• Graduated centrifuge tubes
• Graduated serological pipette
• Medicine dropper
• Burettes
• Micropipettes
• Diluting or thoma pipettes etc
42

43. Cont…
b). Non- volumetric glass wares: are not calibrated to hold a
particular or exact volume, but rather are available for various
volumes, depending on the use desired.
– Erlenmeyer flask
– Round bottom flask
– Flat bottom flask
– Beaker
– Centrifuge tube
– Test tube
– Pasture pipette
43

44. Cont…
C) Semi-volumetric Glass wares: are used for approximate
measurement.
• it includes;
• Graduated cylinder
• Graduated specimen glass
• Beakers
• Conical flask
• Medicine droppers with or with out calibration mark
• Graduated beaker with double beaks
• Graduated glass 44

45. Pipettes
• There are several types each having their own advantages and
limitations.
• They are designated as class “A” or “B” according to their
accuracy.
 Class “A” pipettes are the most accurate and the tolerance
limits are well defined that is, +0.01, + 0.02 and 0.04 ml for 2,
25, and 50 ml pipettes respectively.
 Class “B” pipettes: are less accurate but quite satisfactory for
most general laboratory purposes.
45

46. Cont…
• Significant errors will result if the temperature of the liquid pipetted
is widely different from the temperature of calibration.
• The usual temperature of calibration is 20o
C and this is marked on
the pipette.
46

47. Volumetric pipettes
• Volumetric pipettes are calibrated to deliver a constant volume of
liquid.
• The most commonly used sizes are 1, 5, and 10ml capacities.
• Less frequently used sizes are those which deliver 6, 8,12, and so on
ml.
• Have a bulb mid – way between the mouthpiece and the tip.
• Purpose of the bulb is to decrease the surface area per unit volume
and to diminish the possible error resulting from water film.
• Volume (capacity) and calibration temperature of the pipettes are clearly
written on the bulb. 47

48. Cont…
• Used when a high degree of accuracy is desired.
• The pipette is first rinsed several times with a little of the solution to
be used, then filled to just above the mark.
• Then the liquid is allowed to fall to the mark and the tip is carefully
wiped with filter paper.
• The contents are allowed to drain in to the appropriate vessel.
• A certain amount of liquid will remain at the tip and this must not be
blown out.
48

49. Cont…
• N.B: The reliability of the calibration of the volumetric pipette decreases
with an increase in size and, therefore, special micropipettes have been
develop for chemical microanalysis.
Graduated or measuring pipettes
• Graduated pipettes consist of a glass tube of uniform bore with
marks evenly spaced along the length.
• The interval between the calibration marks depends up on the size
of the pipette.
49

50. Cont…
• Two types calibration for delivery are available.
• These are:
A. One is calibrated between two marks on the stem (Mohr).
B. The other has graduation marks down to the tip (serological pipette)
• These pipettes are intended for the delivery of predetermined volumes.
• The serological pipette must be blown out to deliver the entire Volume of
the liquid and it has an etched ring (pair of rings) near the mouth end of
the pipette signifying that it is a blow out pipette.
50

51. Cont…
• Measuring pipettes are common only in 0.1, 0.2, 0.5, 1.0 5.0, and
10.0 ml sizes.
• The liquid is delivered by allowing it to fall from one calibration
mark to another.
N.B. The classification of pipettes may not always be based on the
presence or absence of a bulb and etched ring.
51

52. Micropipettes
• Micropipettes are frequently used in;
 medical chemistry,
Virology,
immunology and serology laboratories.
• This is because in these laboratories often only small quantities of
materials are available for measurement.
• Whole blood or serum or plasma is often measured and when such
viscous fluids are used these pipettes are convenient.
52

53. Cont…
• They are found in different capacities such as 5, 10, 25, 50, 100 and
1000 micro liter.
• There are also other kinds of pipettes that are used in medical
laboratories.
• Example; Toma pipette, ESR pipette, Pasteur pipette, automatic
pipettes and others.
53

55. Burettes
• Burettes are used for measuring variable quantities of liquid that are
used in volumetric titrations.
• They are made in capacities from 1to100 milliliters.
• They are long graduated tubes of uniform bore and are closed at the
lower end by means of a glass stopper, which should be lightly
greased for smooth rotation.
55

56. Flasks
• There are four types of flaks having 25 to 6,000 milliliter (ml) capacities.
Conical (Erlenmeyer) flasks
• Conical (Erlenmeyer) flasks are useful for titrations and also for
boiling solutions when it is necessary to keep evaporation to a
minimum.
• Some have a side arm suitable for attachment to a vacuum pump.
56

57. Flat bottomed round flasks
• Flat-bottomed round flasks are convenient containers to heat liquids.
• A gauze mat should be interposed between the flask and flame.
• These flasks are widely used in the preparation of bacteriological culture
media.
Round bottomed flasks
• Round bottomed flasks can with stand higher temperatures than the flat-
bottomed type and
• they may be heated in a necked flame, or in an elector- thermal mantle.
• They can be used for boiling of different kinds of solutions and to make
titration. 57

58. Volumetric flasks
• Are flat - bottomed, pear-shaped vessels with long narrow necks, and are
fitted with ground glass stoppers.
• Most flasks are graduated to contain a certain volume, and these are
marked with the letter “C”.
• Those designed to deliver a given volume are marked with the letter “D”.
• A horizontal line etched round the neck denotes the stated volume of water
at given temperature, for example at 20 degree Celsius
• They are used to prepare various kind of solutions.
• The neck is narrow so that slight errors in reading the meniscus results in
relatively small volumetric differences (minimizes volumetric differences)
58

59. • Fig shows different types of flasks
59

60. Volumetric flask
60

61. Beakers
• Beakers have capacities from 5 to 5,000 ml.
• Made up of heat resistant glass and are available in different shapes.
• most commonly used type is the squat form, which is cylindrical and has a
spout.
• There is also a tall form, usually with out a spout.
• Beakers are often supplied for heating or boiling of solutions.
61

62. Beaker …

63. Reagent bottles
– Reagent bottles are used to store different types of laboratory
reagents.
– They are made from glass or plastics.
– Depending on their use, they are available in various sizes and
type.
Dropping bottle

64. Test tube
• Test tubes are made of hardened glass or plastic materials that
can withstand actions of chemicals, thermal shock and
centrifugal strains.
• They are used to hold samples and solutions during medical
laboratory procedures.
• These include simple round hollow tubes conical centrifuge
tubes, vacutainer tubes.
• Test tubes can be with or with out rims (lips).
64

65. Test tube with rack
65

66. Test tubes
66

67. Cylinders
• Cylinders are supplied in 10 to 2,000 ml capacities.
• Some are made of heat resistant glass or plastic and some are fitted
with ground- glass stoppers
• Measurement of liquids can be made quickly with these vessels, but
a high degree of accuracy is impossible because of the wide bore of
the cylinders.
67

68. Petridishes
• Petri dishes are flat glass or plastic containers, which have a number of
uses in the medical laboratory.
• They are used predominantly for the cultivation of organisms on solid
media.
• They are made with diameters of 5 to 14 centimeter.
• To isolate, identify and study the characteristics of microorganisms
• It is essential to grow them on artificial media, and in routine bacteriology
• The most important requirement of a culture medium is its ability to allow
detectable growth from a minute inoculum within the shortest period of
incubation. 68

69. 69

70. Funnels
• There are two types of funnels that are widely used in a medical
laboratory.
• These are filter funnel and separating funnel.
Filter Funnels
• Filter funnels are used for pouring liquids into narrow mouthed containers,
and for supporting filter papers during filtration.
• They can be made from glass or plastic materials.
Separating funnels
• Separating funnels are used for separating immiscible liquids of different
densities. Example, ether and water. 70

71. Pestle and mortar
• Pestle and mortar are used for grinding solids, for example, calculi and
large crystals of chemicals.
• Those of unglazed portion have porous surfaces, and those of heavy glass
are made with roughened surfaces.
• After each use always clean the pestle and mortar thoroughly.
• This is because chemicals may be driven into the unglazed surfaces during
grinding, resulting in contamination when the apparatus is next used.
71

72. Laboratory cuvettes (absorption cells)
• Cuvettes can be glass cuvettes or plastic cuvettes.
• Glass cuvettes resist many laboratory reagents like organic solvents,
whereas plastic cuvettes are affected by many reagents and become
cloudy, hence affecting the absorbance of the reacting mixture and
so lack accuracy & precision.
• Therefore plastic cuvettes whenever used should be cleaned
immediately.
72

73. Cont…
• If the cuvettes turn to cloudy it should not be used for any analytical
procedures.
• Any scratch or white spot on glass cuvettes cannot be washed out with any
solvent and
• therefore, disturbs absorbance of a given solution.
• Therefore, such cuvettes should be discarded.
• Glass cuvettes are the choice for photometry.
• Absorption cells must be absolutely clean.
• Optical surfaces should not be touched, as grease smudges are difficult to
remove.
73

74. Cleaning of glasswares
• It is clear that volumetric glasswares and glass apparatus must be
absolutely clean, otherwise volumes measured will be inaccurate and
chemical reactions are affected adversely.
• One gross method generally used to test for cleanness is to fill the vessel
with distilled water and then empty it and examine the walls to see
whether they are covered by a continuous thin film of water.
• Imperfect wetting or the presence of discrete of droplets water
indicates that vessel is not sufficiently clean.
74

75. Cont…
• A wide variety of methods have been suggested for the cleaning of
most glassware.
• Chromic-sulfuric acid mixture is the cleaning agent in common
usage.
• It is imperative that glassware cleaning should be as mild as
possible and should be appropriate to the type of contamination
present.
75

76. Cleaning of pipettes
• Pipettes should be placed in a vertical position with the tips up in a
jar of cleaning solution in order to avoid the breakage of their tips.
• A pad of glass wool is placed at he bottom of the jar to prevent
breakage.
• After soaking for several hours, the tips are drained and rinsed with
tap water until all traces of cleaning solution are removed.
• The pipettes are then soaked in distilled water for at least an hour.
76

77. Cont…
• Filing with water, allowing the pipette to empty, and observing
whether drops formed on the side within the graduated portion make
a gross test for cleanness.
• Formation of drops indicates greasy surfaces after the final distilled
water rinse the pipettes are dried in an oven at not more than 110 oc.
• Most laboratories that use large numbers of pipettes daily use a
convenient automatic pipette washer.
• Polyethylene baskets and jars may be used for soaking and rinsing
pipettes in chromic acid cleaning solution 77

78. Plastic wares
• Plastic wares are usually manufactured from polymers of
polyethylene, polypropylene and TEFLON.
• These plastics are chemically inert and unaffected by acid /alkali.
• Plastic wares are durable and suitable to store alkaline solutions.
• However, surface bound may be leached to the solution, absorb
dyes and proteins.
78

79. Cleaning of plastic wares
• After each use Laboratory plastic wares should be immediately
soaked in water or
• If contaminated, soaked overnight in a suitable disinfectant such as
0.5% w/v sodium hypochlorite or bleach.
• Most plastic ware is best clean in a warm detergent solution,
followed by at least two rinses in clean water, and ideally a final
rinse in distilled water.
• The articles should then be left to drain and dry naturally or dried in
a hot air oven, set at a temperature the plastic can withstand.
79

80. Cont…
• Filing with water, allowing the pipette to empty, and observing
whether drops formed on the side within the graduated portion make
a gross test for cleanness.
• Formation of drops indicates greasy surfaces after the final distilled
water rinse the pipettes are dried in an oven at not more than 110 oc.
• A brush or harsh abrasive cleaner should not be used on plastic
ware.
• Stains or precipitates best removed using dilute nitric acid or 3% v/v
acid alcohol.
80

81. 81