Laboratory Instrument Use And Care PDF

LABORATORY INSTRUMENT USE AND CARE Dr SKB Bani  LABORATORY INSTRUMENT USE AND CARE INSTRUMENT is a tool or mechanical device, especially one used for precision work in science, medicine or technology.  A device used for measuring.  Something used as a means or agent of achieving a d...

LABORATORY INSTRUMENT USE AND CARE Dr SKB Bani  LABORATORY INSTRUMENT USE AND CARE INSTRUMENT is a tool or mechanical device, especially one used for precision work in science, medicine or technology.  A device used for measuring.  Something used as a means or agent of achieving a desired result or accomplishing a particular purpose. CARE Concern  LABORATORY INSTRUMENT USE AND CARE Instruments are important in the functioning of labs. Manual procedures gradually giving way to automated equipment. Most of these automated analysers are computerised, making it necessary for laboratory staffs to become computer literates. Advantages of instruments 1. Improves efficiency 2. Reduces patient’s waiting time. 3. Minimise cost (reduced reagent usage, re-usable automatic pipettes and cuvettes).  LABORATORY INSTRUMENT USE AND CARE Plastic and Glassware Plastics are gradually replacing glassware. Plastic wares are 1. Safer to use 2. Cheaper to buy 3. Disposable or single use (prevent spread of infections and ensure accuracy of measurement eg pipette tips) 4. Eliminates cost of cleaning cos they are disposable. Glasswares are autoclavable, expensive to buy, easily damaged.  LABORATORY INSTRUMENT Use clean and unbroken glassware in the lab (prevent contamination and injury and ensure accurate measurement of substances) Glassware must be microbiologically clean (sterilised after use) Chemically clean before use (clean before use). Glassware can better withstand strong disinfectants and chemicals than plastics.  LABORATORY INSTRUMENT Never allow dirty glassware to dry out cos dirt is not easily removed when it is dried to a surface. Wash immediately after use or soak in soaking jar. A new glassware is alkaline and should be soaked in dilute HCl (approximately 1%), then washed and rinsed thoroughly with distilled water.  LABORATORY INSTRUMENT Decontaminate glassware used for patient samples by first pre-soaking in 5% hypochloride soln or boiling, autoclaving. Cleaning is easier if glassware is soaked in detergent soln. Plasticware is given the same treatment as above, except some are not AUTOCLAVABLE.  LABORATORY INSTRUMENT USE Equipment for weighing (balance) Analytical balance 1. Two pan analytical balance 2. One pan analytical balance  LABORATORY INSTRUMENT USE AND CARE Basically two-pan balance known weights is added to one pan while the substance been measured is added to the other pan. This type of balance is fast fading out. A modification of the analytical balance is the single-pan balance.  LABORATORY INSTRUMENT Electronic balance  Uses a microprocessor.  It is a mono-pan balance.  supported by an electric coil which is suspended in an electromagnetic field.  Adding weight to the pan causes the coil to move.  the movement changes the electric current in the electromagnetic field.  This change is proportional to the weight of the substance being measured.  and its measured with an indicator system (analog or digital display).  though expensive, electronic balances offer accuracy, speed and ease of operation.  LABORATORY INSTRUMENTS As a means of measuring force, the analytical balance (electromagnetic balance) method utilizes the electromagnetic force generated from a magnet and coil to compute the weight/mass of substances.  LABORATORY INSTRUMENT The electrical resistance wire method (electronic balance)  CARE OF THE BALANCE  Place on a vibration free, even surface.  Level with. the help of a spirit level by adjusting the screws on the stand/bottom.  Zero the balance b4 weighing  Always add weighs by means of forceps in the case of pan balance and spatula in the case of electronic balances.  Never weigh any substance directly on the pan of the balance, use a weighing container.  CARE OF THE BALANCE Keep the balance and the pan free of chemicals by brushing the particles off after use.. Always keep a desiccant in the cabinet of analytical balances to prevent corroding and aid easy movement at the pivot. Check the accuracy of the balance regularly When not in use, protect the balance with a cover.  CARE OF THE BALANCE.  CENTRIFUGES Rapidly sediment particles (cells) suspended in fluid.. It exerts centrifugal force which is greater than the force of gravity. This causes the cells to sediment. The higher the centrifugal force, the faster and more effective the sedimentation...  TYPES OF CENTRIFUGE Fixed angle centrifuge the cups are held at a fixed angle.. This position makes the centrifugation more rapid than the swing out type. In this type, there is less likelihood of the sediment being disturbed when centrifugation stops. Swing out centrifuge The tubes are in a vertical position in the resting state but occupy a horizontal position when the centrifuge is in use.  fixed angle centrifuge.  swing out centrifuge.  TYPES OF MODELS OF CENTRIFUGE Hand centrifuge fixed to the bench and the handle is rotated manually. It gives low speed only. It is found in. rural areas where there is no electricity or where electricity supply is erratic. Battery operated bench centrifuge this is operated by battery. It needs a lot of power so the battery must be charged and recharged. Electric bench top centrifuge most popularly used in laboratories. It uses electricity.  handheld centrifugation. Microhaematocrit centrifuge Used to spin capillary tubes. Used mostly to estimate PCV and the concentration of certain blood parasites. Mostly electric. but can also be battery operated. Ultracentrifuge Allows refrigeration at high speeds while protecting the sample from the heat generated by the rotor. The temperature ranges between -15 to -25 during centrifugation. Cytocentrifuge Special centrifuge used in the transfer of cells in suspension to a circumscribed area in a glass slide. The centrifuge concentrates the cells and prevent their damage.... Care for centrifuges Balance the centrifuge by ensuring that the buckets or tubes opposite to each other are of the same weight. Check that the buckets are properly positioned.. When filling the tube, make sure to leave the fluid about 2cm below the rim of the centrifuge tube. Cap the tubes or bottles when using a potentially infectious material. When using a swing out rotor head centrifuge, check that the tubes are of the proper length so that they will not break while centrifuging due to swinging out of the tubes.  Care for centrifuges Do not try to stop the centrifuge by hand when it is still rotating. Do not open a centrifuge until the rotor has completely come to a rest.. Some centrifuges have a locking device that prevents the centrifuge from opening while the rotor is rotating. Use a non-corrosive disinfectant to clean the centrifuge from time to time. Follow maintenance procedure as prescribed in the manufacturer’s manual.  Autoclave For sterilizing particles and media by steam under pressure.. Incubator Keep tests under controlled temperature esp microbiological cultures. Mostly electric but there are a few model use batteries. Follow manufacture’s manual.  WATER BATH Required for controlled temperature incubation for laboratory tests. Water temperature is thermostatically controlled. Can be set at any desired level ranging usually from 20–100 degree Celsius Some models have propellers to help circulate water in the bath in other to have an identical temperature. Maintain a minimum level of chemically pure water. Avoid the use of tap water to prevent the deposition. of salts on the coil, which can affect the function of the coil and corrode it. Always use a thermometer to check the temperature of the water bath is stable at the desired level. Make sure that the sample being incubated is below the water surface in the bath.. Cover tubes and flasks or plates during incubation to avoid contamination, dilution as a result of condensation of water from the lid of the bath. Clean the water bath regularly, following the manufacturer’s instructions of how to clean the bath WATER BATH  A water bath is an instrument where water is heated and the set temperature is maintained at a constant level. It is used to incubate liquid substances.  When only a few samples in tubes require incubating, it is more convenient and less expensive to use a dry heat block (dry bath incubator).  Chemical tests react best at a specific temperature. Many tests react at room temperature (18 to 220C) and others require a specific temperature as body temperature (35 to 370C).  Such requirements are better met by using water bath. When the reactants in tubes are placed in a water bath, the water surrounding the tubes warms the substances in the tube and imputes same temperature to the test solution. USE AND CARE OF A WATER BATH 1. Read the manufacturer’s instructions carefully. 2. Fill the bath and maintain its level with distilled water if unavailable, fill with boiled water, preferably boiled and filtered rainwater. This is necessary to minimize salts depositing on the heater. 3. To minimize the growth of microorganisms in the water, add a bactericidal agent such as merthiolate at a dilution of 1 in 1000 to the water. 4. Before incubating samples check that the temperature of the water is correct using thermometer. 5. Ensure that the level of the water is above the level of whatever is being incubated. USE AND CARE OF A WATER BATH 6. Use the lid to prevent loss of heat from the bath and to minimize particles from entering the water. When removing the lid after incubation, take care to avoid any water entering uncapped tubes. Whenever possible, use capped tubes. 7. Clean the water bath regularly, taking care not to damage the heating unit. If there is a build up of scale on heater and sides of the bath, this can be removed by using lemon juice. 8. Unplug the bath from the wall socket when not using it, when there is an electric storm, and when cleaning the bath and carrying out any maintenance work. 9. Every three to six months, check the bath for correction. Note: If you are using a boiling water bath and ovens, be sure you use heat resistant glass or plastic wares. STILLS AND DE-IONIZERS  Many laboratory tests require chemically pure water, especially in clinical chemistry.. DISTILATION  Water is boiled and the vapour is condensed to produce pure water. The instrument used is called a still.  Distilled water is free from salts, clear, odourless, colourless, tasteless. It is pyrogen free when collected into a sterile container.  Pyrogen is a substance which can cause fever when introduced into the body esp endotoxins (polysaccharides) produced by some GNB bacteria eg E. Coli. TESTING DISTILLED WATER Tests. for chlorides add a few drops of 10% silver nitrate to about 500ul of distilled water. A good distilled water should not develop cloudiness. Test for sulphates add a few drops of 10% barium chloride to about 500ul of distilled water. A good distilled water should not show precipitates. DE-IONISED WATER  Another way to get chemically pure water. This process involve passing tap water tru anion and cation. exchange resins. 2+ 2+ +  Cations such as Mg Ca Na are removes and replaces with + 2- - - H while anions such as SO4 , Cl , HCO3 and silica are - replaced by OH. + -  H + OH = H2O. De-ionise water is free from H2O soluble salts but it is not pyrogen free. It is there4 not used for the preparation of intravenous infusions and injections. TYPES OF DE-IONISERS  Hand held de-ionisers  Bench top.  Wall mount de-ionisers.  You can regenerate the cation resin by passing HCl tru it and regenerate the anion resin by passing NaOH tru it.  And then rinsing thoroughly with distilled water. TESTING FOR DE-IONISE WATER  De-ionise water has a very high resistance to electricity..  Measuring the resistance of de-ioniser water tells you its quality.  The conductivity meter is usually part of the de- ioniser.  Generally, a conductivity of 1.5-2.0 milli Ohms per ml is acceptable. FREEZERS AND FRIDGES 1. Preservation of laboratory reagents, e.g. 4°C±2°C. 2. Culture media and bacterial cultures are refrigerated to avoid contamination and to preserve them. 3. Blood bank for preserving blood for transfusion FREEZERS AND FRIDGES Temporal storage usually done at -20 while long term storage is. done at -80.  Avoid over load of freezers and fridges.  Always keep the freezers and the fridges clean  Use a solution of warm water and baking soda to clean the inside and outside surfaces  Provide a power stabiliser. Refrigerators Refrigerators are physical means of preserving various laboratory specimens. They suppress the growth of bacteria and maintain the specimens with little alteration. used in the medical laboratory to preserve reagents  test kits test samples blood grouping anti sera and others are kept in the refrigerators to prevent their deterioration at room temperature. Refrigerators Culture media are also preserved in refrigerators to avoid bacterial contamination and growth. For routine uses, refrigerators are commonly set at a temperature of 2 to 80C. There are also other deep freeze refrigerators with different ranges of temperature for example 0 0 0 C to -70 C, which are mostly utilized for research purposes. N.B: When whole blood is preserved in refrigerators, it is essential that the temperature is maintained at 2 to 80C to avoid damage of red blood cells. Ovens  Hot - air ovens are instruments that are used for drying of chemicals and glasswares.  They are also used for the sterilization of various glasswares 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.  There is a thermometer on the top of the ovens and thermostat is fitted to regulate the temperature. Incubator Incubation at controlled temperature is required for bacteriological cultures, blood transfusion, Serology, Hematology and Medical Chemistry tests. For bacteriological cultures, an incubator is required whereas for other tests a dry heat block or a water bath may be used. For the incubator, the air inside is kept at a specific temperature (usually at 370C). When tubes are kept inside the incubator, they take the temperature of the incubator. The appropriate temperature is obtained by means of temperature regulator and is maintained by a thermostat. This permits a more accurate temperature control. Use and Care of Incubator 1.Read carefully the manufacturer’s instruction. 2. Make sure the incubator is positioned on a level surface and that none of the ventilation openings are blocked. 3. If the incubator does not have a temperature display, insert a thermometer in the vent hole through the roof of the incubator. Adjust the thermostat dial until the thermometer shows the correct reading, i.e., 35 - 37OC for the routine incubation of bacteriological cultures. Use and Care of Incubator 4. Before incubating cultures and tests, check the temperature of the incubator. 5. Clean the incubator regularly; making sure it is disconnected from its power supply. 6. Every 3 to 6 months check the condition of the incubator. 7. 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. COLORIMETER (PHOTOMETER)  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.  In a test, a colored solution of the substance being measured or a colored derivative of it is produced. This is measured in a color meter. Colored solutions absorb light at a given wavelength in the visible spectrum.  Biological samples contain many substances that can be determined quantitatively or qualitatively. VISIBLE LIGHT SPECTRUM When a beam of light passes through a colored solution, it interacts with matters in the solution and the result may be refraction, reflection, absorption and transmission among others. Refraction: - is defined as sudden change in the direction of the beam when the light passes from one medium to another with a different physical density. Reflection: - is a condition where the beam returns back towards its source. Example mirror. Absorption: - is a situation where some components of the light (colors) are retained or absorbed. Visible light spectrum  Transmission: - refers to the situations where some portions of the light permitted to pass through a given medium.  Radiation is characterized by waves on which basis the electromagnetic radiation spectrum could be divided in many regions including gamma rays, x-rays, ultra violet rays, visible, infrared, microwaves and radio waves.  Of the above, the visible region is the radiant energy to which the human eye responds and their wavelength varies between 400 and 700nm.  Wavelength of about 700nm are seen by the eyes as red colors while those of progressively shorter wavelengths give in descending order to orange, yellow, green, blue, and finally violet colors which is produced in the short wavelength of 400nm. Beer’s and Lambert’s Law Most colorimetric analytical tests are based on the Beer’s – a Lambert’s law which states that under the correct conditions the absorbance of a solution when measured at the appropriate wavelength is directly proportional to its concentration and the length of the light path through the solution. Using a standard, this law can be applied to measuring the concentration of a substance in unknown (test) solution by using the formula:At/As=Ct/Cs In colorimetric tests, the path is kept constant by using optically matched cuvettes usually of 10 mm light path distance or tubes of known light path distance. In selecting the correct band of wavelength to use, both the maximum absorbance and selectivity of the wavelengths for a particular substance need to be considered. For the Beer’s - Lambert’s law to hold true, both the solution being tested and the instrument used to measure the absorbance must meet certain requirements. These include: A. Solution Requirements The solution must be the same through out (homogeneous) and the molecules it is composed of must not associate or dissociate at the time absorbance is being measured. The substance being measured in the solution should not react with the solvent. Reagent blanks must be used to correct for any absorption of light by solvents. A reagent blank solution contains all the reagents and chemicals used in the chemical development of the color but lack the substance being assayed. B. Instrument Requirement The instrument used in colorimetric tests must show satisfactory accuracy, sensitivity and reproducibility at the different wavelengths used. The cuvettes used in the instrument must be optically matched, free from scratches, clean. Measuring instruments  Different types of instruments are produced for measurement of substances in a given colored solution, including colorimeter, spectrophotometer, absorptiometer, spectrometer and flame photometer.  Some of the biochemical methods provide solutions of colored compounds while others are involved in a chemical reaction to yield colored solutions for the quantitative measurement of substances.  Elementary colorimeter was used previously for the analytical purpose, but it is now totally superseded by the modern ones. Elementary colorimeters are prone to errors that may result due to differences in the individual ability to visually identify colors. So it is replaced by the modern photoelectric instrument, which measures the intensity of the transmitted or absorbed light not merely, color.  Photoelectric instruments used in colorimetry are: A. Absorptio - meter or filter absorption spectrophotometer or filter photometer. B. Spectro photometer or absorption spectrometer. Measuring instruments A. Absorptiometer  It is called absorptiometer because it is the amount of absorbed light, which is, measured not merely color development.  It provides a wider band of wavelength to determine the complementary diffracting radiation.  The components of this instrument include: Light source; Filter cells (cuvettes); Photosensitive detector system and; Galvanometer to measure the out put of photo sensitive element. Measuring instruments Theory of Absorptiometry  On passing white light through a colored solution, some part of the white light will be absorbed while the others are transmitted depending on their frequencies (wavelengths).  For analytical purposes, we are interested in the extent of absorption of light energy by solutions of the same compound in known and unknown concentrations under identical conditions, which can be used to determine the unknown concentration. Measuring instruments Theory of Absorptiometry B. Spectrophotometer Spectrophotometer is an instrument, which measures light absorbance at various wavelengths by producing a monochromatic light using a diffraction grating or glass prism. Light is passed through a monochromator to provide selection of the desired wavelength out of the spectrum to be used for the measurement. Slits are used to isolate a narrow beam of light and improve its chromaticity. The light is then passed through the cuvette, where a portion of the radiant energy is absorbed depending on the nature of the substances in a solution. Any light not absorbed is transmitted to a detector, which converts light energy to electrical energy. Measuring instruments Theory of Absorptiometry B. Spectrophotometer  A monochromator is a system of isolating radiant energy of a desired wavelength and excluding that of other wavelengths. Spectral isolation can be accomplished by various means including the use of filters, prisms and diffraction grating.  Method of producing the monochromatic light is different in spectrophotometers and absorptiometer. Filter photometer (absorptiometer) uses filter for wavelength isolation while a spectrophotometer isolates the light by a prism or diffraction grating system.  The color intended to be measured should be due to the substance under investigation but not due to any of the reagents used. This is controlled by using reagent blank. Measuring instruments Theory of Absorptiometry Flame photometry or flame emission spectroscopy Flame photometry is a spectral method in which excitation is caused by spraying a solution of the sample in a hot flame. A characteristic radiation is emitted in a flame by individual elements and the emission intensity is proportional to the concentration of the element introduced into the flame. Each element emits a radiant power with a specific wavelength. Using different filters, elements in a mixture can be analyzed at different wavelength. Measuring instruments Theory of Absorptiometry Flame photometry or flame emission spectroscopy FLAME PHOTOMETRY is used for the determination of electrolytes in a given solution. It is most commonly used for the quantitative analysis of sodium and potassium ions in body fluids. Solutions that contain Sodium and potassium ions when placed in a Bunsen burner produce characteristic colors and the brightness of the flame varies according to the concentration of the elements in solution. Measuring instruments Theory of Absorptiometry Flame photometry or flame emission spectroscopy The instrument measures individual elements by correlating with the intensity of emitted radiation. Lithium releases a red, sodium a yellow, potassium a violet and magnesium a blue color in a flame when placed in an ordinary burner. The color helps for the qualitative analysis while the flame emission spectroscopy reading is needed for the quantitative analysis of the elements. 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. When we are weighing chemicals where a very high degree of accuracy is needed, as sodium chloride (NaCl) used as a standard for the chloride test, the chemical must not contain water.  The chemical is dried in an oven at 110oC for 1 hour,  then it is placed in a dessictor over night before weighing on the analytical balance.  The purpose of the oven is to remove the water and that of the dessicator is to store the chemical at an ambient temperature where it cannot reabsorb water. DESICCATORS  A dessicator contains substances called DRYING AGENTS. These absorb the water in the air of the dessicator.  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 dessicator. Instruments and materials used for pH determination p Meter H pH meter is an instrument used to measure the p or H hydrogen ion concentration of a given solution by the potential difference between two electrodes. Major components of p meter are: H Glass bulb electrode; Reference (calomel) electrode and; Potentio meter (sensitive meter) which measures the electric volt. Instruments and materials used for pH determination p Meter H p is the universal accepted scale for the concentration of hydrogen H ion in aqueous solution, which gives a measurement of the acidity or alkalinity of a given solution. p is defined as the negative logarithm of the molecular concentration H of the active hydrogen ions, p = - log. H H+ The p of a given solution is measured by the p meter and displayed as H H digital or galvanometric reading by converting the milli volt (Mv) difference between the two electrodes to p value. If the potential H difference is zero milli volts between the two electrodes, the corresponding value of p is 7.0. H INSTRUMENTS AND MATERIALS USED FOR PH DETERMINATION pH Meter  The pH of any solution will be in the range of 0 to 14.0. If pH of a solution is less than 7.0, it is known as acidic, whereas, pH value greater than 7.0 is considered as basic. A mixture with pH value of 7.0 is a neutral solution.  pH value may change inversely with changes in temperature. For optimum readings it is better to use a temperature of 25oC.  The glass electrodes of a pH meter may be affected by the following conditions: Continuous use; Protein solution that can interfere with the glass membrane; Dehydrating agents; Change of temperature and; Scratching or fracturing of the glass membrane. Instruments and materials used for pH determination pH Meter When not in use, electrodes should be immersed in distilled water. New electrodes can be generated by immersing in 0.1 Molar solution of hydrochloric acid over night. Washing of the electrodes with distilled water before and after use is very important. Standard short-range p strips H Uses: Dip a small piece of strip into a given solution Compare the color change on the strip with the standard chart or paper strip Approximate values of p can be found from H this technique. Use of different buffers Universal indicator and series of buffers with different pH value are used; The universal indicator solution is added in the different pH solutions as well as in unknown solution under the procedure; The color of the unknown solution is compared with the color of series of buffers; The pH of the unknown solution is considered as the same with the pH of buffer, which gave us similar color with the solution to be determined. Precautions while using buffers 1. Calibrate with buffers having pH values that bracket the pH of the sample. For example, if the expected pH value is between 8.0 and 9.0 calibrate with pH 7.0 and 10.0 values. 2. Before starting calibration, be sure that the sensor and the buffer are at the same temperature. 3. If possible, calibrate with buffers having the same temperature as the process. If the buffer and the process temperature differ by more than about 150C, an error as great as 0.1 pH may result. 4. Buffers have limited shelf lives. Do not use a buffer if the expiration date has passed. 5. Store buffers at controlled room temperature. 6. Do not return used buffer to the stock bottle. Discard it immediately. 7. Protect buffers from excessive exposure to air. Atmospheric carbon dioxide lowers the pH of alkaline buffers. N.B: Calibration is to mean that the reading in the display on a measuring instrument is checked against a standard; any deviation that exists between the true value and the value displayed in the reading is determined. Instruments for purifying water The quality of water used in the laboratory is very crucial. Its use in 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. 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. Instruments for purifying water  For preparation of standard solutions, buffers and controls, the most pure water quality that is free from bacteria (Type I Reagent Water, reagent grade 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. Depending on the requirements, available facilities and quality of the laboratory’s water supply, the following instruments can be used to obtain water of adequate purity and quality. WATER DISTILLING APPARATUS (STILL)  Water distilling apparatus 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. WATER DISTILLING APPARATUS (STILL)  Distillation does not remove dissolved ionized gases such as ammonia, carbon dioxide, and chlorine.  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. 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. The 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. 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 1. low electrical conductivity, 2. near neutral pH and 3. is free from water-soluble salts but is 4. not sterile. Deionizer  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.  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 Care, cleaning, and repair of the microscope 1. Care and cleaning A microscope is a delicate instrument both mechanically and optically. Therefore, the following important points should be taken into considerations. 1. Always carry a microscope using both hands. 2. When not in use, a microscope should be protected from dust, moisture, direct sunlight and put in microscope case. 3. Keep it standing in place ready for use, but protected by light cover. 4. In humid climate it is necessary to cover the microscope in a plastic bag with a drying agent (silica gel) over night to avoid molds growing on the lenses. 5. At the end of each day’s work, the surface lenses of the objectives, eyepieces, and condenser should be cleaned using lens tissue. N.B: Never clean the lens of the objectives and eyepiece with alcohol. 2. Repair of the microscope Except for obvious and simple measures, if a microscope becomes damaged optically or mechanically, it is better to send it or the damaged part to a reliable scientific instrument repairer or preferably to the manufacturer. Polymerase chain reaction (PCR) machine  PCR is a machine that is widely employed in the molecular biology laboratory.  It helps to detect and amplify small fragments of nucleic acid (DNA/RNA) of interest from various clinical samples. Polymerase chain reaction (PCR) machine Steps in PCR technique: 1. Denaturation of double stranded DNA into single stranded DNA. 2. Annealing or primer binding. 3. Final extension or DNA synthesis. Flow cytometery  Flow cytometery is an instrument used to measure and quantify cells that are suspended in fluid medium.  Example, determination of gametocytes (white blood cell types) from whole blood samples. Automated analyzers Automated analyzers are instruments that are used in medical laboratories to process a large number of laboratory tests quickly (i.e. hundreds or even thousands of tests can be done within an hour). The methods avoid the use of manual methods such as: 1. Measuring and adding reagents; 2. Mixing samples and reagents; 3. Calibrating the assay; 4. Recording, 5. Analyzing and 6. storing sample data etc thereby improving efficiency