Chapter Two 2 LABORATORY EQUIPMENTS AND WARES 1

Chapter- Two 2. LABORATORY EQUIPMENTS AND WARES 1

Acknowledgment n Addis Ababa University n Jimma University n Hawasa University n Haromaya University n University of Gonder n American Society for clinical pathology n Center for disease prevention and control 2

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Learning objectives At the end of this chapter, the student will be able to: ¨ State the different laboratory wares. ¨ Describe the use of laboratory wares. ¨ Explain the general cleaning and care of laboratory wares. 4

Outline 2. LABORATORY EQUIPMENTS AND WARES 2. 1: General laboratory wares 2. 1. 1 Classification of Laboratory glass wares 2. 1. 2 Pipettes 2. 1. 3 Burettes 2. 1. 4 Flasks 2. 1. 5 Beakers 2. 1. 6 Cylinders 5

2. 1: General laboratory wares LABORATORY GLASSWARES AND PLASTICWARES Definition: laboratory glassware and plastic wares are materials used in clinical laboratory for: Ø measuring Ø pipetting Ø transferring Ø Preparation Ø Storage etc. of reagents 6

General laboratory … Ø Most of the routine laboratory wares used to be of glass, but recent advantage made in the use of plastic resin to manufacture a wide range of plastic ware having led to a gradual replacement of glass wares with durable plastic ware. 7

2. 1. 1 Classification of Laboratory glass wares A. can be divided in to five main types according to their composion 1. Glass with high thermal resistance – borosilicate glass can resist about 500 oc 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. 8

Classification of Laboratory glass…… 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 B. Based on their use a) volumetric wares b) Semi-volumetric Glass wares c) Non- volumetric glass wares. 9

Classification of Laboratory glass…… a)Volumetric wares ¨ Apparatus used for measurement of liquids ¨ Can be made either from glass or plastic. it includes : n Volumetric flasks n Graduated centrifuge tubes n Graduated serological pipette n Medicine dropper n Burettes n Micropipettes n Diluting or thoma pipettes etc 10

Classification of Laboratory glass…… 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 ¨ Round ¨ Flat flask bottom flask ¨ Beaker ¨ Centrifuge ¨ Test tube 11

Classification of Laboratory glass…… C ). Semi-volumetric Glass wares: are used for approximate measurement. it includes; n Graduated cylinder n Graduated specimen glass n Beakers n Conical flask n Medicine droppers with or with out calibration mark n Graduated beaker with double beaks n Graduated glass 12

2. 1. 2 Pipettes n There are several types each having their own advantages and limitations. n 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. 13

Pipettes … n Significant errors will result if the temperature of the liquid pipetted is widely different from the temperature of calibration. n The usual temperature of calibration is 20 o. C and this is marked on the pipette. 14

2. 1 Volumetric pipettes are calibrated to deliver a constant volume of liquid. The most commonly used sizes are 1, 5, and 10 ml capacities. Less frequently used sizes are those which deliver 6, 8, 12, and so on ml. They have a bulb mid – way between the mouthpiece and the tip. 15

Volumetric … The main purpose of the bulb is to decrease the surface area per unit volume and to diminish the possible error resulting from water film. The Volume (capacity) and calibration temperature of the pipettes are clearly written on the bulb. They should be used when a high degree of accuracy is desired. 16

Volumetric pipettes…… The pipette is first rinsed several times with a little of the solution to be used, and 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. 17

Volumetric … n N. B: The reliability of the calibration of the volumetric pipette decreases with an increase in size and therefore, special micropipettes have been developing for chemical microanalysis. 18

2. 1. 2. 2 Graduated or measuring pipettes Graduated pipettes consist of a glass tube of uniform bore with marks evenly spaced along the length. n The interval between the calibration marks depends up on the size of the pipette. Two types calibration for delivery are available: A. One is calibrated between two marks on the stem (Mohr). B. The other has graduation marks down to the tip (serological pipette) n 19

Graduated or measuring……. 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. Measuring pipettes are common only in 0. 1, 0. 2, 0. 5, 1. 0 5. 0, and 10. 0 ml sizes. 20

Graduated measuring… 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. 21

A. B C D. A. Volumetric (transfer) B. Ostwald folin (transfer). C. Measuring (Mohr) D. Serological (Graduated) 22

Graduated or… 23

2. 1. 2. 3 Micropipettes n n Micropipettes are frequently used in n Medical chemistry n Virology n Immunology and serology laboratories. This is because in these laboratories often only small quantities of materials are available for measurement. 24

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

Automatic Micropipettes 26

2. 1. 3 Burettes • Burettes are used for measuring variable quantities of liquid that are used in volumetric titrations. • They are made in capacities from 1 to 100 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. Fig. Burette 27

2. 1. 4 Flasks n There are four types of flaks having 25 to 6, 000 milliliter (ml) capacities. 2. 1. 4. 1 Conical (Erlenmeyer) flasks n Conical (Erlenmeyer) flasks are useful for titrations and also for boiling solutions when it is necessary to keep evaporation to a minimum. n Some have a side arm suitable for attachment to a vacuum pump. 28

Flask … 2. 1. 4. 2 Flat bottomed round flasks ¨ Flat-bottomed round flasks are convenient containers to heat liquids. ¨ These flasks are widely used in the preparation of bacteriological culture media. 29

Flasks … 2. 1. 4. 3 Round bottomed flasks ¨ Round bottomed flasks can with stand higher temperatures than the flat- bottomed type. ¨ they may be heated in a necked flame or in an electro - thermal mantle. As a result used for boiling. 30

Flasks … 2. 1. 4. 4 Volumetric flasks n Volumetric flasks are ¨ flat - bottomed ¨ pear-shaped ¨ vessels with long narrow necks fitted with ground glass stoppers. 31

Flasks … Volume metric …. n Most flasks are graduated to contain a certain volume, and these are marked with the liters. n A horizontal line etched round the neck denotes the stated volume of water at given temperature. n They are used to prepare various kinds of solutions. n The neck is narrow so that slight errors in reading the meniscus results in relatively small volumetric differences (minimizes volumetric differences or errors). 32

A. Conical B. Flat bottomed C. Flat bottomed D. Volumetric 33

Flask … Volumetric flask 34

2. 1. 5 Beakers ¨ Beakers have capacities from 5 to 5, 000 ml. ¨ They are usually made up of heat resistant glass and are available in different shapes. ¨ The most commonly used is the squat form, which is cylindrical and has a spout. ¨ There is also a tall form, usually with out a spout 35

Beaker … Beaker 36

2. 1. 6 Cylinders ¨ Cylinders are supplied in 10 to 2, 000 ml capacities. ¨ Some are of heat resistant glass or plastic. 37

Cylinders… q 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. 38

2. 1. 7 Test tubes are made of hardened glass or plastic materials that can withstand actions of chemicals, thermal shock and centrifugal strains. n They are used to hold samples and solutions during medical laboratory procedures. n These include simple round hollow tubes conical centrifuge tubes, vaccutainer tubes. Test tubes can be with or with out rims (lips). n Test tubes with out rim are satisfactory. n 39

Test tube with rack 40

2. 1. 8 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 41

2. 1. 9 Petri dishes q 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. 42

2. 1. 10 Funnels ¨ There are two types of funnels that are widely used in a medical laboratory. These are filter funnel and separating funnel. 2. 1. 10. 1 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. 43

Funnel … 2. 1. 10. 2. Separating funnels ¨ They are used for separating immiscible liquids of different densities. ¨ Separating funnels are used for separating immiscible liquids of different densities. Example, ether and water. 44

2. 1. 11. Pestle and mortar ¨ Pestle and mortar are used for grinding solids, for example, calculi and large crystals of chemicals. ¨ 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. . 45

2. 1. 12 Laboratory Cuvettes (Photometry) ¨ used for photometric readings in instruments or used for measurements of absorbance. ¨ 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. 46

Laboratory Cuvettes … ¨ Can be glass, quartz, or plastic ¨ Require ¨ Should uniform thickness, density, composition be uniformly calibrated 47

2. 1. 13. Pasture pipette n They are non-volumetric glassware used in transferring liquid. n It has a long –drown-out tip with a rubber bulb or teat to suction. n Eye droppers or medicine droppers can use instead of pasture pipettes. 48

Precautions when using glassware 1. All glassware must be handled carefully. 2. Breakage can some times be dangerous and may result in the loss of valuable and irreplaceable materials. 3. Flasks and beakers should be placed on a gauze mat when they are heated over a Bunsen flame. 4. Test tubes exposed to a naked flame should be made of heat resistant glasses. 5. If liquids are to be heated in a bath or boiling water, the glass contents should be heat resistant. 49

2. 2 Medical laboratory Equipments Learning objectives ; § Identify the types and uses of laboratory balances. § Explain the advantages of laboratory refrigerators. § Describe the importance of ovens, water baths and incubators. § State the use of photometers and desiccators. 50

Learning objectives… § Identify the types and uses of microscopes. § State the basic components centrifuge. § Discuss p. H in terms of ion activity and units. § Describe the main components of a p. H meter including their role in analysis. 51

Out line 2. 2 lab equipments 2. 2. 1: Microscope 2. 2. 2: Equipment for purifying water 2. 2. 3: Equipment for weighing 2. 2. 4: Equipment for pipetting and dispensing 2. 2. 5: Laboratory centrifuges 2. 2. 6: laboratory autoclaves, ovens 52

Out line… 2. 2. 7: Incubator, water bath, heat block 2. 2. 8: Colorimeter 2. 2. 9: Mixers 2. 2. 10: Refrigerators 2. 2. 11: Desiccators 2. 2. 12: PH meter 2. 2. 13: Safety cabinets 2. 3: Care and cleaning of laboratory equipments and wares 53

2. 2 Medical laboratory Equipments 2. 2. 1: THE MICROSCOPE ¨ Used to visualize minute objects (animate and inanimate), that cannot be seen by our naked eye. It is a magnifying lens. ¨ It was invented by Anton van Leeuwenhoek –founder of microscope. 54

Microscope … 2. 2. 1. 1 Types of microscope 1. Light field microscope ; - are the group of microscope that uses light. This includes: a. Compound light(bright) field: ¨ Compound microscope is a light microscope, which is routinely used in medical laboratories of hospitals and/or health centers. b. Dark field microscope or dark ground illumination ¨ Makes some living micro-organisms which can not be seen by ordinary transmitted lighting. 55

Microscope … Principle of light microscope ¨ The light enters a special condenser which has a central blacked-out area so that the light cannot pass directly to enter the objective. ¨ The only light entering the eye comes from the micro- organisms themselves, no light entering the eye directly from light source. 56

Microscope … ¨ In the way small micro-organisms are seen brightly illuminated against a black background, like stars in a night sky. Importance of Dark field microscope Used for examiningn Treponema palladium n Borreliae in blood n Microfilariae in blood 57

Microscope … c) Phase contrast microscope ¨ Makes use of this ability of waves to help or hinder each other to produce variations increase the contrast achieved by placing annulus in condenser and phase plate in the objective. 58

Microscope … ¨ Used for examination of § Unstained bacteria § Urine sediments § Haemoparasites § Amoebae in faecal preparations § Trypanosomes in blood, cerebrospinal fluid, lymph gland fluid. 59

Microscope … d) Fluorescence microscope n widely used in the immunodiagnosis Principle: ¨ Ultraviolet light may be used to illuminate particles or micro-organisms which have been previously stained with fluorescing dyes. ¨ These dyes transform the invisible ultraviolet light to visible light. 60

Microscope … ¨ Value n of fluorescence microscope Examination of sputum and c. s. f for acid fast bacilli (AFB) using an auramine staining technique. n Examination of acridine orange stained Trichomonas vaginalis flagellates. 61

Microscope … 2. Electron Microscope: - as the name suggests, employ a beam of electrons produced by an electron gun to produce the magnified image. Mainly used in ¨ Negative ¨ Sample staining stained with potassium phosphotungestate ¨ Examination of viruses NB. The beam can not pass through the metallic back ground of the microscope. 62

Microscope … 2. 2. 1. 2 Major parts of microscope A. Frame work of the microscope This includes: ¨ An arm (stand): - The basic frame of the microscope to which the base, body and stage are attached. ¨ A stage: - the table of the microscope where the slide or specimen is placed. ¨ A foot or base: - is the rectangular part up on which the whole instruments rest. 63

Microscope … B. Focusing system ¨ This encompasses: n Coarse and fine focusing adjustments ¨ Course adjustment: - The course focusing adjustment is controlled by a pair of large knobs positioned one on each side of the body. Give rough image. ¨ Fine adjustment: - it moves the stage so slowly that and give clear image. 64

Microscope … n Condenser adjustments: - The condenser is focused usually by rotating a knob to one side of it. ¨ This moves the condenser up or down. ¨ The condenser aperture is adjusted by the iris diaphragm, which is found just below the condenser. ¨ The principal purpose of the condenser is to condense the light required for visualization. 65

Microscope … C. Magnification system This comprises: ¨ Objectives: - Objectives are components that magnify the image of the specimen to form the primary image. n For most routine laboratory work 10 x, 40 x and 100 x (oil immersion) objectives are adequate. ¨ Eyepiece: - Eyepiece is the upper optical component that further magnifies the primary image and brings the light rays to a focus at the eye point. 66

Microscope … Eye piece: n It consists of two lenses mounted at the correct distance. n It is available in a range of magnifications usually of 10 x, 15 x and sometimes as high as 20 x. N. B: Based on their number of eyepiece microscopes can be classified as monocular, binocular microscopes etc. 67

Microscope … D. Illumination system ¨ Condenser and iris n. Condenser n. The is a large lens with an iris diaphragm. condenser lens receives a beam from the light source and passes it into the objective. n. The iris is a mechanical device mounted underneath the Condenser and controls the amount of light entering the condenser. 68

Microscope … ¨ Mirror n Mirror is situated below the condenser and iris. n It reflects the beam of light from the light source up wards through the iris into the condenser. n The mirror is used to reflect ray or electrical light. 69

Microscope … ¨ Sources ¨Day of illumination Light - A Microscope must not be used in direct sun light. Rather ordinary daylight may be sufficient for some work. ¨Electric light §An ordinary 60 -watt pearl electric bulb placed about 18 inches from the microscope is sufficient for most routine work. 70

Microscope … n Quartz halogen (quartz iodine) are very good light sources because they give excellent white illumination and do not blacken like ordinary tungsten lamps. n Many microscopes are now provided with correctly aligned built-in sources of illumination, which use tungsten or quartz halogen lamps operating on 6, 8 or 12 volts through variable transforms. 71

Microscope … Filters Light filters are used in the microscope to: n Reduce the intensity of light. n Increase contrast and resolution. n Adjust the color balance of the light to give the best visual effect. n Provide monochromic light. n Absorb light. n Transmit light of selected wavelength. n Protect the eye from injury caused by ultra-violet light. . 72 n

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Microscope … 2. 2. 2. 3 Working principle of the microscope ¨ The magnified image of the object (specimen) is first produced by a lens close to the object called the objective. ¨ This collects light from the specimen and forms the primary image. ¨A second lens near the eye called the eyepiece (ocular) enlarges the primary image converting it into one that can enter the pupil of the eye. 75

Microscope … ¨ The magnification of the objective multiplied by that of the eyepiece gives the total magnification of the image seen in the microscope Example: Objective Magnification ¨ 10 X ¨ 40 X ¨ 100 X Eyepiece Magnification 10 X 10 X Total Magnification 100 X 400 X 1000 X 76

Microscope … n Objectives ¨ Low power (10 X) Objective ¨ Used for the initial scanning and observation in most microscopic work. ¨ When using 10 X § Close iris diaphragm. § Lower the condenser. 77

Microscope … ¨ High -dry power (40 X) Objective ¨ Is used to study un stained specimens such as stool and urine sediments for more detailed examination. ¨ When using 40 X § open the iris diaphragm half way. § raise the condenser half way. 78

Microscope … Oil immersion (100 X) Objective ¨ Routinely used for morphologic examination of blood films and microbes. § An oil immersion lens requires that special grade of oil (immersion oil) be placed b/n the objective and the slide. § The oil is used to increase the intensity of light. ¨ When using 100 X § open the iris diaphragm completely. § raise the condenser completely. 79

Microscope … 2. 2. 2. 4 Resolving power of the microscope ¨ It may be defined as the ability to level closely adjacent structural details as being actually separate and distinct. ¨ The increase in magnifying power is always linked to an increase in resolving power. ¨ The higher the resolving power of an objective, the closer can be the fine lines or small dots in the specimen which the objective can separate in the 80

Microscope … n The resolving power of an objective is dependent on what is known as the numerical aperture (NA) of the objective. n The numerical aperture is a designation of the amount of light entering the objective from the microscope field, i. e. the cone of light collected by the front lens of the objective (an index or measurement of the resolving power). 81

Microscope … ¨ Numerical aperture is dependent on the diameter of the lens and the focal length of the lens. E. g. Res. power of: n Human eye- 0. 25 mm n Light microscope- 0. 25µm n Electron microscope- 0. 5 nm 82

Microscope … n Numerical Aperture ¨ Defined as the product of the refractive index of the medium outside the lens (n) and the sine of half the angle of the cone of light absorbed by the front lens of the objective (u) or ¨ Is a number that expresses the ability of a lens to resolve fine detail in an object being observed. 83

Microscope … E. g. 0. 25 on X 10 objective 0. 65 on X 40 objective 1. 25 on X 100 objective ¨ The n greater the N. A the greater the resolving power. The following are the usual numerical apertures of commonly used objectives: n 10 X objective ------ NA 0. 25 n 40 X objective ------ NA 0. 65 n 100 X (immersion oil) objective ------- NA 1. 25 84

Microscope … n Total magnification ¨ is the product of the objective and the eye piece magnification n Useful magnification range ¨ is calculated as: (500 -1000)x NA of that objective E. g. The useful magnification range when an Eyepiece with magnification of 10 x & an objective with magnification 40 x & NA of 0. 65 is: 325 -650. 85

Microscope … n Focal length: ¨ Distance b/n optical center and the point at which parallel rays of light passing through it come to focus. ¨ Larger diameter and long focal length § Higher NA § Higher resolution § Useful magnification 86

Microscope … ¨ Large diameter §Shorter focal length §Very high NA §Very high resolution §Very high useful magnification 87

Microscope … ¨ Small Diameter § Long focal length § Very low NA § Very low r. p § Very low useful magnification 88

Microscope … ¨ Small diameter ¨ Short focal length ¨ Low NA ¨ Low resolution ¨ Low useful magnification n Therefore the wider the angles of the cone of light the higher the NA of the objective and greater is the objectives resolving power and useful magnification. 89

Microscope … 2. 2. 2. 5 Working principle of an oil immersion objective ¨ When a beam of light passes from air into glass it is bent and when it passes back from glass to air it is bent back again to its original direction. ¨ This has effect on oil immersion objective and affects the NA of the objective and consequently it’s resolving power. 90

Microscope … ¨ The bending effect on the objective can be avoided by replacing the air between the specimen and the lens with oil, which has the same optical properties as glass, i. e. immersion oil. ¨ The oil provides better resolution and a brighter image by collecting extra oblique light. 91

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Microscope … 2. 2. 2. 5 Routine use of the microscope n A microscope must always be used with gentleness, care and the following should be noted. 1. Place the microscope on a firm bench so that it does not vibrate. a. Make sure that it is not be exposed to direct sun light. b. The user must be seated at the correct height for the convenient use of the microscope. 93

Microscope … 2. Select the appropriate source of light. 3. Place the specimen on the stage, making sure that the under side of the slide is completely dry. 4. Select the objective to be used. n It is better to begin examination with 10 x objective. 94

Microscope … 5. Bring the objective as close as possible to the slide preparation. 6. Adjust the light source until the illumination of image is at its brightest. 7. Focus the condenser. 8. Adjust the aperture (opening) of the condenser iris according to the specimen being examined. 95

Microscope … ¨ The wider the condenser aperture, the brighter will be the specimen and the smaller be the details, which can be resolved. ¨ The smaller the aperture, the greater will be the contrast. ¨ Certain specimens, example stained and mounted specimens give little glare illuminated image with fine detail. 96

Microscope … q Other specimens, like urine, unstained cerebrospinal fluid and saline mounted fecal specimens give much glare and require a reduced source of light to increase contrast. 9. Examine the specimen by systematically moving the slide with the mechanical stage. N. B: The image of the specimen will be up side down and will move in the opposite direction to the side. 10. For a higher magnification, swing the 40 x objective into place. ¨ Focus the 40 x objective, using the fine adjustment. 97

Microscope … ¨ If for any reason the image is not visible, lower the objective until it is nearly but not quite touching the specimen. ¨ Then looking through the eyepiece, focus up wards with the fine adjustment until the image comes into view 11. For the highest magnification, add a drop of immersion oil to the specimen and swing the 100 x oil immersion objective into place, then open the iris fully to fill the objective with light. n Example. Stained blood smear, acid-fast stain, etc 98

Microscope … 2. 2. 2. 6 Care, Cleaning and Repair of microscope ¨ The microscope is one of the most expensive and delicate instruments. n Good microscopy practice should include: I. Daily cleaning and quality control(QC) check a. Using a clean cloth, wipe any dust from stage and other surfaces of microscope. 99

Microscope … b. Using lens tissue clean dry objective. § Clean 100 X objective with tissue dampened with xylene. § Never use alcohol to clean the oil because it will dissolve the cement holding the lens. c. Carry out a QC check to ensure the lenses are completely clean. 100

Microscope … II- Care when using the microscope 1. 2. 3. 4. 5. 6. 7. Do not use force for any mechanism. Check stage and under side of the specimen, re DRY and CLEAN. Cover wet preparation with cover slip. Use non-drying oil immersion. Put eyepieces that are not in use in closed container. Always lift and carry the microscope well supported with hands. Protect the microscope from dust, moisture and direct sunlight. 101

Precautions when using microscope n Never dip the objectives in xylene or ethanol, as this may cause the lenses to become detached. n Never use ordinary paper to clean the lenses. n Never touch the lenses with your fingers. n Never clean the support or the stage with xylene or acetone. 102

Microscope … III- At the end of the Day’s ¨ Turn the switch off. ¨ Clean ¨ Do using a soft tissue. not leave the objective of eyepiece open. ¨ Decontaminate the stage with 70% alcohol dampened cloth. ¨ Cover with its dust cover. 103

2. 2. 2: Equipment for purifying water 2. 2. 1: DISTILLER ¨A process by which impure water is boiled and the steam condensed on cold surface (condenser) to give pure distilled water is called distillation. ¨ Distilled water is free from dissolved salts and clear colorless, odorless and tasteless. It is sterile too. ¨ The ¨A apparatus is called distiller. considerable volume of cool running water is required to operate or to condense the steam. 104

Equipment for purifying 2. 2. 2: DEIONIZER ¨ Deionizer ¨A is an apparatus used to produce ion free water. deionizer is an apparatus for demineralizing water by means of cartridges filled with ion-exchange resin. ¨ 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 p. H and is free from water-soluble salts but is not sterile. 105

2. 3: Equipment for weighing/Balances ¨ Balances are essential laboratory instruments that are widely used for weighing of various substances (powders, crystals and others) in the laboratory. ¨ For instance, to prepare reagents, stains and culture media, balances are required to weigh accurately and precisely within the needed range. ¨ They should be kept carefully clean and located in an area away from heavy traffic, large pieces of electrical equipment, and open windows. ¨ To minimize any vibration, as interference that may happen, a slab of marble is placed under the balance. 106

Balances … Balances in medical laboratory may be: 2. 3. 1. Rough balances (mechanical balances) 2. 3. 2. Analytical balances/electrical/ 2. 3. 1 Rough balances ¨ Rough balances are several types. Some of them use sliding scale, some have a single or double pan (s) and others utilize dial - operated fractions. ¨ They are used for weighing substances, which do not call for extreme accuracy. 107

Balances … ¨ While operating, they do not require mains electricity or battery power and are currently less expensive than analytical balances of the similar sensitivity. ¨ Some rough balances weigh accurately to 0. 1 gm of a substance. ¨ Two - pan balance is a rough balance, which has two copper pans supported by shafts. n It is used: §To weigh large amounts (up to several kilo grams). §When a high degree of accuracy is not required. 108 n. The sensitivity of a two pan balance is 0. 5 gm.

Balances … ¨ The sensitivity of a balance is the smallest weigh that moves the pointer over one division of the scale. ¨ For routine laboratory purposes the sensitivity of a balance can be considered to be the smallest weigh that it will measure accurately. ¨ Usually the larger the amount of substance to go into a reagent, the least accuracy is required. 109

Rough balances 110

Balances … n 2. 3. 2 Analytical balances Nowadays analytical and electronic balances (single pan balances that use an electron magnetic force instead of weights) are the most popularly used balances in medical laboratories to provide a precision and accuracy for reagent and standard preparation. Ø Analytical balance is a highly sensitive instrument. Ø It may have two pans suspended from a cross beam, inside a glass case. Ø It requires mains electricity or battery (D. C) supplied power. Ø 111

Balances … ¨ These balances are used: 1. To weigh small quantities usually in mili gram (mg) range. 2. When great accuracy is required. E. g. , 2. 750 mg, 0. 330 mg, 5. 860 mg, etc. ¨ Its sensitivity is 0. 5 mg to 1 mg depending on the model. ¨ N. B: The accuracy of a balance should be checked regularly as recommended by the manufacturer. 112

Analytical balance 113

Balances … Use and care of balances ¨A balance is a delicate instrument that requires practical instruction in its correct use. ¨ The following should be applied when using a balance: § Read carefully the manufacturer’s instructions. § Always handle a balance with care. § Position the balance on a firm bench away from vibration, draughts and direct sunlight. 114

Balances … § Before starting to weigh, zero the balance as directed by the manufacturer. If using a beam balance, check the position of the beam. § Weigh the chemicals at room temperature in a weighing scoop or small beaker. And Never put the chemicals directly on the balance pan. 115

Balances … Use and care……. . n When adding or removing a chemical, remove the container to avoid spilling any chemical on the balance. n When using an analytical double pan balance, bring the pans to rest before adding or removing a chemical. n Always use forceps to add or remove weighs. Protect the weights from dust, moisture and fungal growth. 116

Balances … n Use small brush to remove any chemical, which may have been spilt on the balance. n A container of self - indicating silica gel should be kept inside the analytical balance case to remove any moisture present in the atmosphere. n Keeps the balance clean, being particularly careful not to let dirt accumulate near the pivots and bearings. 117

2. 2. 4: Equipment for pipetting and dispensing n There are different types of devices used for pipetting and dispensing specimens. Some of them are: ¨ Simple bulb aspirator- this is simple inexpensive device suitable for use with graduated capillaries. ¨ Thumb wheel aspirator – it can be used with capillaries, shell- back pipettes, example, Sahli or WBC pipettes ad most small bore graduated pipettes, example measuring up to 0. 5 ml. 118

Equipment for pipetting … ¨ Automatic pipetter – it use plastic or glass tips and models are available for measuring single volumes or several different volumes. Automatic pipetters have a greater precision and accuracy. n PVC bulb pipette filler – its tapered and flexible end enables all types of pipettes up to 10 ml volume to be inserted easily and safely in to the end and to be held securely. 119

Equipment for pipetting … n Pi- pump 2500, pipette filler – it is highly recommended for the controlled filling and dispensing of fluid from pipettes. n Bottle top dispenser - it is used to measure a fixed volume of fluid or several different volumes of fluid. 120

Equipment for pipetting and …… n Bottle top hand operated dilutor – this is the most expensive of the devices described above. It is used for measuring accurately and precisely, specimen and reagent. n Plastic bulb pipettes – Plastic bulb pipettes have many uses in a medical laboratory. They can be decontaminated in disinfectant, wash, and reused many times. 121

2. 2. 5: Laboratory centrifuges ¨ Centrifuge: is equipment that is used to separate solid matter from a liquid suspension by means of centrifugal force. ¨ They sediment particles (cells, bacteria, casts, parasites, etc. ) suspended in fluid by exerting a force greater than that of gravity. ¨ The suspended materials are deposited in the order of their weight. ¨ There are many types of centrifuges, but the basic principle is the same, that is, the all use centrifugal force. 122

Centrifuge…. n When a body is rotated in circular movement at speed, centrifugal force is created that drives the body away from the center of the circular movement. n The greater the outward pull due to rotation, that is centrifugal force, the more rapid and effective is the sedimentation. ¨ As a result, heavier elements are thrown to the bottom of the tube followed by lighter particles. 123

Centrifuge…. 124

Centrifuge…. ¨ Centrifugal force increases with the speed of rotation that is the revolution of the rotor per minute and the radius of rotation. ¨ The actual sedimentation achieved at a given speed depends therefore, on the radius of the centrifuge. ¨ Most techniques requiring centrifugation will usually specify the required relative centrifugal force (RCF) expressed in gravity. 125

Centrifuge…. 2. 2. 5. 1 Basic components of centrifuges ¨ Central Shaft: - It is a part that rotates when spinning is effected manually. ¨ Head: - It is a part that holds the bucket and connected directly to the central shaft or spindle. ¨ Bucket or tube: - Are portions that hold test tubes containing a given sample to be spined. 126

Centrifuge…. Specimen Tube Cup Shaft 127

Centrifuge…. 2. 2. 5. 2 Classifications of centrifuges A. Hand centrifuges n These centrifuges are: ¨ Operated by hand or water pressure and they are most commonly used in small laboratory for routine purposes. ¨ Used for preparation of urinary sediments and to concentrate parasites from the given specimen and it is not advisable to use them to separate serum from whole blood. 128

Centrifuge…. B. Electrical Centrifuges ¨ Electrical centrifuges are those centrifuges that are operated by electrical power and produce high centrifugal force. ¨ They are used in most medical laboratories. 129

Centrifuge…. n Based on their tube angle rotation, there are two types. A. Swing out head: - This is the most frequently used type and the head is designed to swing the tubes to the horizontal position during centrifugation process. B. Fixed head: - They have different angles. They are useful for certain laboratory techniques. Example, for agglutination tests in blood grouping using test tube method. 130

Centrifuge…. 2. 2. 5. 3 Kinds of centrifuges 1. Micro-centrifuges ¨ They are used for spinning small tubes as in blood bank laboratories. 2. Medium size centrifuges. ¨ Are used for centrifuging of urine specimens for microscopic analysis of urinary sediments. 131

Centrifuge…. 3. Large centrifuges ¨ They are widely applied in bacteriology and medical chemistry laboratories. ¨ A centrifuge may have a preset speed or more often there is a knob by which the laboratory personnel control the speed. ¨ The speed is given in revolution per minuets (rpm). ¨ Small models are designed to centrifuge volumes up to 200 ml at maximum speeds of 3, 000 - 4, 000 rpm. ¨ Large models will centrifuge volumes up to 2, 200 ml with maximum speeds of 5, 000 rpm. 132

Centrifuge…. ¨A centrifuge may have built in timer or may have to be timed with a watch. Some centrifuges may have a temperature gauge in order to keep the temperature constant as it spines. 4. Cyto-centrifuge n Specific use n Spreading of cells across slide n Body fluids n Microscopic – morphologic slides 5. Ultracentrifuges n High-speed n Up to 90, 000 – 100, 000 rpm; 178, 000 g n More common in research 133

Centrifuge…. 2. 2. 5. 3 Use and care of centrifuges ¨ Although most centrifuges are fitted with an imbalance detector, lid interlock, and an automatic braking system, it is important for laboratory workers to know how to use a centrifuge correctly to prevent it from damage and breakages. n These include: ¨ Reading the manufacturer’s instructions. ¨ Placing a centrifuge on a firm level bench out of direct sunlight, towards the back of the bench. ¨ Whenever possible using plastic tubes made 134 from polystyrene or autoclavable.

Centrifuge…. n Always closing the centrifuge top before turning it on. n Always balancing the tubes that are being centrifuged. n Tubes of the same weight should be placed directly opposite to each other. ¨ Tubes should also be of the same size and should also contain the same amount of liquid. n Increasing spinning speed gradually is important. 135

Centrifuge…. n Give the centrifuge a chance to come up to that speed and then turn up the dial a little further until it reaches the desired 3, 000 rpm. ¨ Five minutes are the usual time required to centrifuge most substances. ¨ Never open the centrifuge while it is still spinning. Never try to slow it down with your hand. Most centrifuges have a brake, which will cause the centrifuge to stop faster. 136

2. 2. 6: laboratory autoclaves, ovens 2. 6. 1 AUTOCLAVE ¨ Autoclave is an instrument that operates by creating high temperature under steam pressure. ¨ Autoclaving is the most common, effective, reliable and practical method of sterilizing laboratory materials. ¨ Temperature of 1210 c, which will kill spores with in 15 minutes and at 15 psi /pound/. ¨ At this particular temperature, pressure and time, all forms of lives are destroyed. 137

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Autoclaves … n Precautions in the use of autoclaves ¨ The following guidelines can help to minimize risks while working with autoclaves. 1. Proper use and care of autoclaves. 2. Regular inspection of the chamber, door seals and gauges. 3. The steam should be saturated and free from chemicals that could contaminate the items being sterilized. 139

Autoclaves … 4. Materials to be autoclaved should be in containers that allow ready removal of air and permit good heat penetration. 5. The chamber of the autoclave should be loosely packed so that steam will reach the load evenly. 6. Operator should wear protective gloves for protection when opening the autoclave. 140

Autoclaves … 6. Thermocouples should be placed at the center of each load in order to determine properating cycles. 7. Ensure that the relief valves of pressure cooker autoclaves do not blocked. 141

2. 6. 2 OVENS ¨ Hot - air ovens are instruments that are used for drying of chemicals and glass wares. ¨ They are also used for the sterilization of various glass wares and metal instruments. ¨ They consist of double walls that are made of copper or steel. ¨ They are heated by circulation of hot air from gas burners between the metal walls or by electrical mains. ¨ There is a thermometer on the top of the ovens and generally an automatic device (thermostat) is fitted to regulate the temperature. 142

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2. 2. 7: Incubator and water bath. 2. 2. 7. 1 INCUBATOR n Incubation at controlled temperature is required for bacteriological cultures, blood transfusion, Serology, Hematology and clinical Chemistry tests. n For bacteriological cultures, an incubator is required whereas for other tests a dry heat block or a water bath may be used. 144

Incubator … n For the incubator, the air inside is kept at a specific temperature (usually at 370 c). When tubes are kept inside the incubator, they take the temperature of the incubator. n The appropriate temperature is obtained by means of temperature regulator and is maintained by a thermostat. This permits a more accurate temperature control. 145

Incubator … n Use and Care of Incubator ¨ Read carefully the manufacturer’s instruction. ¨ Make sure the incubator is positioned on a level surface and that none of the ventilation openings are blocked. ¨ If the incubator does not have a temperature display, insert a thermometer in the vent hole through the roof of the incubator. Adjust thermostat dial until thermometer shows the correct reading, i. e. , 35 - 37 Oc for the routine incubation of bacteriological cultures. 146

Incubator … ¨ Before incubating cultures and tests, check the temperature of the incubator. ¨ Clean the incubator regularly; making sure it is disconnected from its power supply. ¨ Every three to six months check the condition of the incubator ¨ At the time of purchase, it is advisable to buy a spare thermostat and thermometer if these are of special type and are not available locally. 147

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2. 2. 7. 2. WATER BATH ¨ The water bath, like the incubator, is required for controlled temperature incubation of culture and liquids, and many other laboratory tests. ¨ The temperature of the water bath is thermostatically controlled and can be set at any desired level ranging usually from 20 o. C to 100 o. C. ¨ The heating coil may be of immersion type or enclosed in a case, some models have propellers to help to circulated water so that identical temperature is maintained throughout the water bath. 149

WATER BATH … n Use and care of water bath ¨ Maintain the minimum level in the water bath with chemically pure water. Avoid use tap water. Avoid use of water as salts from tap water may get deposited on coil and so affect its function ¨ Always use a thermometer to check that the temperature is stable at the desired level. 150

WATER BATH … ¨ Make sure that the substance being incubated is below the surface of water in the bath ¨ It is advisable to cover the tubes, flasks or plates during incubation to avoid contamination and dilution as a result of condensation of water from the lid of the water bath. ¨ Clean the water bath regularly. 151

2. 2. 8: Colorimeter/ (Photometer) n Colorimeter is an instrument used to measure the concentration of a substance in a sample by comparing the amount of light it absorbs with that absorbed by a standard preparation containing a known amount of the substance being tested. n In a test, a colored solution of the substance being measured or a colored derivative of it is produced this is measured in a colormeter colored solutions absorb light at a given wavelength in the visible spectrum. 152

Colorimeter … ¨ Biological samples contain many substances that can be determined quantitatively or qualitatively ¨ A constant source of radiant energy ¨ Some optics for focusing the light ¨ a colored filter ¨ a cuvette holder ¨ Light- sensitive detector( Converts light energy to electrical energy) ¨ Read out device 153

Spectrophotometer n Is similar to a colorimeter except that instead of using a filter to select the color of the light to pass through the sample, the white light is separated into a rainbow( spectrum of colors) using a prism or diffraction grating. n Continuous adjustment of λ with the help of prisms or diffraction gratings. 154

2. 2. 9: Mixers n are instruments used for preparation of reagents for mixing or dissolving purpose. n Also used for homogenization. 155

2. . 2. 10: Refrigerators ¨ Refrigerators are physical means of preserving various laboratory specimens. ¨ They suppress the growth of bacteria and maintain the specimens with little alteration. ¨ In addition to this, they are also used in the medical laboratory to preserve some reagents such as: ¨Pregnancy tests kits. ¨Rapid plasma reagin (RPR) test kits, ¨Culture media are also preserved. ¨Blood grouping anti sera and others which are kept in the refrigerators to prevent their 156 deterioration.

2. 2. 11: Desiccators ¨ Desiccators are instruments, which are used for drying of chemicals or to keep other chemicals from being hydrated. ¨ As chemicals stay for long period of time out of dessicators, they sometimes absorb water ¨ The chemical is dried in an oven at 110 oc for 1 hour, and then it is placed in a desecrator over night before weighing on the analytical balance. ¨ The purpose of the oven is to remove the water and that of the desicator is to store the chemical at an ambient temperature where it cannot reabsorb water. 157

Desiccator……. ¨A desiccators contains substances called drying agents. ¨ These absorb the water in the air of the desiccators. ¨ The most commonly used drying agents (desiccants) are calcium chloride and concentrated sulfuric acid. ¨ The chemical that is to be dried is placed in another bottle or test tube and is put on top of the desiccants present in a securely closed desiccators. 158

2. 2. 12. PH meter Definition: is an instrument which is used to measure Potential of ion hydrogen (i. e. acidity or alkalinity of a substance) or Is an instrument used to measure the PH or H+ ion concentration. n Potential of hydrogen p. H scale is 0 – 14 n Acid p. H: 0 -6. 9 n Neutral p. H: 7. 0 n Alkaline p. H: 7. 1 -14. 0 159

PH meter … 1. 2. 3. Glass bulb electrode( PH- electrode) Reference( Calomel) electrode Potentiometer (Sensitive meter) which measures the electric volt. n The glass bulb electrode contains a solution of a certain fixed PH or H+ conc. n When the electrodes are placed in a solution of unknown PH, an electrical potential is produced between them( i. e the solution and the H+ ions in the PH-electrode). 160

PH meter … This potential which is proportional to the H+ ion concentration of the test solution, is measured with the aid of reference electrode which is compared to the potential of the PH-electrode. n The mili volt(MV) potential difference is displayed as digital or galvanometric readings(PH 0 -14) OMV=7. 0 n 161

2. 2. 13: Safety cabinets ¨ Safety Cabinets are designed to protect the laboratory personnel, the laboratory environment and work materials from exposure to infectious aerosols and splashes that may be generated when manipulating materials containing infectious agents, such as primary cultures, stocks and diagnostic specimens. ¨ These cabinets could be chemical or biological n N. B: It is extremely important to use gloves as a personal means of protection from various infectious agents while working in medical laboratories. 162

Biological safety cabinets/BSC/ ¨ Are the principal equipment used to provide physical containment ¨ Are used as primary barriers to prevent the escape of aerosols into the laboratory environment. ¨ Certain BSC can also protect the test/specimen from air born contamination n The selection of BSC is based on: ¨ The hazard of the agent in the test ¨ The potential of the laboratory technique to produce aerosols and ¨ The need to protect the test from airborne 163 contamination

BSC … Three types of BSC are available- Class I , Class III. n Class I –BSC ¨ This is an open fronted work chamber which is exhaust ventilated to provide personnel and environmental protection only by means of an inward air flow away from the operator, the exhaust air being filtered through a HEPA filter before being discharged from the cabinet ¨ Are used with agents with low to moderate risk 164

BSC … n Class II- BSC ¨ Is a partially open fronted work chamber which provides protection for personnel and the surrounding environment against biological hazards by means of barrier airflow at the work opening. ¨ A quantity of air equal to the barrier air is exhausted from the cabinet through a HEPA filter. 165

BSC … ¨ Also provides product(test) protection against contamination by means of HEPA filtered air flowing into the cabinet n Class III-BSC ¨ Is a totally enclosed and gas-tight structure ¨ Work procedures in the cabinet are carried out through replaceable arm length gloved sleeves. ¨ Is supplied with air through a HEPA filter and exhausted through two HEPA filters mounted in series ¨ Suitable for use with all categories of biological agents n HEPA- high efficiency particulate air 166

Safety cabinets 167

2. 3: Care and cleaning of laboratory equipments and wares n Care of glassware ¨ All glass ware must be handled carefully. ¨ Breakage can some times be dangerous and may result in the loss of valuable and irreplaceable materials. ¨ Flasks and beakers should be placed on a gauze mat when they are heated over a Bunsen flame. Gauze mat is made from asbestos and its function is to distribute the heat evenly. 168

Care … ¨ Test tube exposed to a naked flame should be made of heat resistant glass such as Pyrex. ¨ If liquid are to be heated in a bath or boiling water the glass contents should be heat resistant. ¨ When diluting concentrated acids, thin walled glassware should be heat resistant. Ø Because the heat evolved by the procedure often cracks thick glassware. 169

Care of … ¨ Containers and their corresponding ground glass stopper should be numbered. Ø Because it is used to ensure direct matching when stoppers are replaced. ¨ Because of the danger of chemical and bacteriological contamination, pipettes should never be left lying on the bench. 170

Cleaning of glass wares ¨ It is clear that volumetric glass wares 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. 171

Cleaning of …. ¨A wide variety of methods have been suggested for the cleaning of most glassware. ¨ Wide varieties of methods have been suggested for the cleaning of most glassware. ¨ In all cases, glassware for the clinical laboratory must be: n Physically clean n Chemically clean n Bacteriologically clean or sterile 172

Cleaning of new glassware ¨ New glass ware should be appropriately treated and cleaned before use. ¨ Newly purchased soft glass ware (soda lime) should be treated overnight with 5% HCl. ¨ This will neutralize free alkali found on the surface. 173

Cleaning of new glassware … ¨ This treatment is not necessary for borosilicate glass (hard glass). ¨ Acid treated glassware must be first rinsed with tap water followed by through rinsing with distilled deionnized water. ¨ Newly purchased borosilicate glass ware is cleaned with detergent followed by washing with tap water and then rinsing with distilled water. 174

General cleaning procedure 1). Preliminary rinsing ¨ Rinse all glassware immediately after use. Remember, dry glassware, like the dry dishes after a meal, is difficult to clean, stains, markings, proteins and other materials may get stubborn due to drying. ¨ Rinse twice in cold or warm water. 2) Soaking in detergent solution ¨ Place in detergent solution (2%). Detergents can be in either solution or powder form. Do not use too concentrate detergent solution which may not be completely removed and this will affect the test result. 175

General…… ¨ Dissolve the detergent completely before putting in the glassware. ¨ Preliminary soaking in the detergent can save time, reduce contamination problems and make the final washing greatly simplified. Soak for one hour. 176

General. . …. 3). Scrubbing ¨ Scrub thoroughly with good quality brush (choose appropriate brush for the type of glassware being cleaned). A milled abrasive may help cleaning but the abrasive should not scratch the glass. ¨ Make sure that the brush reaches all parts of the glassware, inside and the out side. 4). Washing ¨ Wash each glassware one by one under running water. Wash each item 5 times or more. 177

General …… 5). Rinsing ¨ Rinse each glassware with distilled water or deionnized water at least three times. 6). Drying ¨ Place in a wire baskets and dry glassware completely by keeping it in an oven (1400 c). If an oven is not available, dry the glassware on the drying rack at room temperature over night. ¨ Dry the burette in the inverted position on the burette stand. Glassware dried in the hot air oven should be in an inverted position to ensure complete drainage of 178 water as it dries.

General…… 7). Plugging ¨ The clean dry glassware should be put away in a cup board to protect it from dust. ¨ It is recommended that containers should be plugged with non – absorbent cotton wool or the mouth covered with little cups made from wrapping paper or preferably thin sheeting of paraffin wax. 179

Special cleaning of glass ware n n n If the glassware becomes dirty due to coagulated organic matter ( for example dried blood) or other substances , it must be cleaned with chromic acid cleaning solution. Potassium dichromate (or sodium dichromate) and sulphuric acid are both power full corrosive solutions and the mixture makes it even more so. The following cleaning solutions may be used in special cases: n Diluted hydrochloric acid - 50% concentrated HCl in water removes iron stains. 180

Special cleaning … Use nitric acid for stains due to Nesslers reagents (iodine). n Remove grease by boiling with weak alkali solution (sodium carbonate). Never use strong alkalis (sodium hydroxide, potassium hydroxide). n Ordinary grease can also be removed with acetone and ether (flammable). For removing silicone grease use sulphuric acid. Note: All the cleaning reagents must be washed away and the glassware rinsed finally with distilled water or Deionized water. n n 181

1. 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 the 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. 182

Cleaning of pipette… n The pipettes are then soaked in distilled water for at least an hour. n 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. n 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. 183

Cleaning of pipette… ¨ Most laboratories that use large numbers of pipettes daily use a convenient automatic pipette washer. ¨ These devices are made of metal or polyethylene and can be connected directly to hot and cold water supplies. Polyethylene baskets and jars may be used for soaking and rinsing pipettes in chromic acid cleaning solution. 184

2. Cleaning of flasks, beakers, cylinders and other glass wares ¨ Pour warm cleaning solution into each vessel and stopper or cover carefully. ¨ Each vessel should be manipulated so that all portions of the wall are repeatedly brought into contact with the solution. ¨ This procedure should be followed for at least five minutes. 185

Cleaning of flasks … The cleaning solution can be poured from one vessel to another and then returned to its original container. ¨ The vessels should then be rinsed repeatedly with tap water four times and finally rinsed three times with distilled water. ¨ It is important that the necks of volumetric flasks above the graduation mark be clean because when solutions are diluted in the flask drops of water may adhere to an unclean wall and may invalidate the measurement of volume. ¨ 186

3. Plastic wares are usually manufactured from polymers of polyethylene, polypropylene and TEFLON. ¨ These plastics are chemically inert and unaffected by acid /alkali. ¨ Plastic wares includes any article made of plastic that is intended for laboratory use, including, but not limited to beakers, bottles, Petri dishes, flasks, funnels, jars, tubes and stoppers. ¨ 187

4. 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. 188

Cleaning of … ¨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. 189

Summary questions 1. Explain the general cleaning and care of laboratory wares. 2. Explain the general cleaning and care of laboratory wares. 3. Explain the types and uses of microscope. 190

References 1. 2. 3. 4. 5. 6. Linne Jean Jergenson, Basic techniques of medical laboratory 4 th ed. 2000. WHO, Manual of basic techniques for a health laboratory 2000. Chees brough M. District Laboratory manual for tropical courtiers, Cambridge Univerity press, 2000 (Vol ). Chees brough M. District Laboratory manual for tropical courtiers, Cambridge Univerity press, 2000 (Vol II). Seyoum B. Introduction to medical laboratory technology students lecture note series 2002. www. CDC. gov 191

End of slide Next chapter will be : Collection, handling and shipment of laboratory specimens 192