1. 1 T.Elsarnagawy MLI-mde 210, 311 Laboratory Centrifuges

2. T.Elsarnagawy 2 2 MLI-mde 210, 311 Definition A laboratory centrifuge A laboratory centrifuge is laboratory equipment, is laboratory equipment, driven by a motor, driven by a motor, spins liquid samples at high speed. spins liquid samples at high speed. There are various types of centrifuges, depending on the size and the sample capacity. There are various types of centrifuges, depending on the size and the sample capacity. They vary widely in speed and capacity They vary widely in speed and capacity work by the sedimentation principle, where the centripetal acceleration is used to separate substances of greater and lesser density. work by the sedimentation principle, where the centripetal acceleration is used to separate substances of greater and lesser density. comprise a rotor containing two, four, six, or many more numbered wells within which the samples containing centrifuge tips may be placed. comprise a rotor containing two, four, six, or many more numbered wells within which the samples containing centrifuge tips may be placed. Centrifuges are used in Centrifuges are used in chemistry, biology, and biochemistry for isolating and separating suspensions. chemistry, biology, and biochemistry for isolating and separating suspensions.

3. T.Elsarnagawy 3 3 MLI-mde 210, 311 Operation Increasing the effective gravitational force will more rapidly and completely cause the precipitate to gather on the bottom of the tube as a "pellet". Increasing the effective gravitational force will more rapidly and completely cause the precipitate to gather on the bottom of the tube as a "pellet". The remaining solution is called the "supernate" or "supernatant". The remaining solution is called the "supernate" or "supernatant". The supernatant liquid is then either The supernatant liquid is then either decanted from the tube without disturbing the pellet, or decanted from the tube without disturbing the pellet, or withdrawn with a Pasteur pipette. withdrawn with a Pasteur pipette. The rate of centrifugation is specified by the acceleration applied to the sample, typically measured in revolutions per minute (RPM) or relative centrifugal force (RCF). The rate of centrifugation is specified by the acceleration applied to the sample, typically measured in revolutions per minute (RPM) or relative centrifugal force (RCF).

4. T.Elsarnagawy 4 4 MLI-mde 210, 311 Operation The particles' settling velocity in centrifugation is a function of their The particles' settling velocity in centrifugation is a function of their size and shape, size and shape, centrifugal acceleration, centrifugal acceleration, the volume fraction of solids present, the volume fraction of solids present, the density difference between the particle and the liquid, and the viscosity. the density difference between the particle and the liquid, and the viscosity.

5. T.Elsarnagawy 5 5 MLI-mde 210, 311 Rotor objectives Generally spoken, there are two main types of rotors: Fixed-angle rotor Fixed-angle rotor The rotor (mainly made of aluminium) is very compact. The rotor (mainly made of aluminium) is very compact. There are boreholes with a specific angle (like 45°) within the rotor. There are boreholes with a specific angle (like 45°) within the rotor. These boreholes are used for the sample tubes. These boreholes are used for the sample tubes.

6. T.Elsarnagawy 6 6 MLI-mde 210, 311 Swing-out rotor (= horizontal rotor) Swing-out rotor (= horizontal rotor) The rotor looks like a cross with bucket. The rotor looks like a cross with bucket. Within these buckets, different tubes can be centrifuged. Within these buckets, different tubes can be centrifuged. For a safe centrifugation, a specific adadpter for every tube shape is mandatory. For a safe centrifugation, a specific adadpter for every tube shape is mandatory. Rotor objectives

7. T.Elsarnagawy 7 7 MLI-mde 210, 311 Design Rotor objectives The rotor is closed by a rotor lid. The rotor is closed by a rotor lid. The rotor is located in a rotor chamber which is covered by a metal centrifuge lid. The rotor is located in a rotor chamber which is covered by a metal centrifuge lid. The open lid prevents the motor from turning the rotor when the rotor chamber is open. The open lid prevents the motor from turning the rotor when the rotor chamber is open. During the run, the lid is locked. During the run, the lid is locked. The lid protects the user from being injured by touching a rapidly spinning rotor. The lid protects the user from being injured by touching a rapidly spinning rotor. The rotor chamber and the lid of high quality centrifuges are robust enough to survive a rotor failure at full speed. The rotor chamber and the lid of high quality centrifuges are robust enough to survive a rotor failure at full speed.

8. T.Elsarnagawy 8 8 MLI-mde 210, 311 Design Rotor objectives After a rotor crash, a centrifuge should not be reused as the enormous forces during a crash may have damaged essential parts of the device. After a rotor crash, a centrifuge should not be reused as the enormous forces during a crash may have damaged essential parts of the device. The rotor must be balanced by placing samples or blanks of equal mass opposite each other. Since most of the mass is derived from the solvent, it is usually sufficient to place blanks or other samples of equal volume. The rotor must be balanced by placing samples or blanks of equal mass opposite each other. Since most of the mass is derived from the solvent, it is usually sufficient to place blanks or other samples of equal volume. As a safety feature, some centrifuges may stop turning when wobbling is detected (automatic imbalance detection, see Safety). As a safety feature, some centrifuges may stop turning when wobbling is detected (automatic imbalance detection, see Safety).

9. T.Elsarnagawy 9 9 MLI-mde 210, 311

10. T.Elsarnagawy 10 MLI-mde 210, 311 Theory During circular motion During circular motion  the acceleration is the product of the radius and the square of the angular velocity and it is traditionally named radius and the square of the angular velocity and it is traditionally named "relative centrifugal force" (RCF). "relative centrifugal force" (RCF).

11. T.Elsarnagawy 11 MLI-mde 210, 311 Theory The acceleration is measured in multiples of "g“, the standard acceleration due to gravity at the Earth's surface, or × "g", and it is given by The acceleration is measured in multiples of "g“, the standard acceleration due to gravity at the Earth's surface, or × "g", and it is given bywhere g = acceleration r = rotational radius (centimeter, cm) N = rotating speed (revolutions per minute, r/min)

12. T.Elsarnagawy 12 MLI-mde 210, 311 Calc. of RCF: NOMOGRAM To calculate the RCF value at any point along the tube or bottle: measure the radius, in mm, from the center of the centrifuge spindle to the particular point. draw a line from the radius value on the right hand column to the appropriate centrifuge speed on the left hand column. the RCF value is the point where the line crosses the center column. The nomogram is based on the formula: R = Radius in mm from centrifuge spindle to point in tube N = Speed of spindle in RPM RCF = (11.17 x 10-7) RN 2

13. T.Elsarnagawy 13 MLI-mde 210, 311

14. T.Elsarnagawy 14 MLI-mde 210, 311 Types of centrifuge There are at least five types of centrifuge: preparative centrifuge preparative centrifuge analytical centrifuge analytical centrifuge angle fixed centrifuge angle fixed centrifuge swing head centrifuge swing head centrifuge haematocrit centrifuge haematocrit centrifuge

15. T.Elsarnagawy 15 MLI-mde 210, 311 Centrifuge tubes Centrifuge tubes or centrifuge tips are tapered tubes of various sizes made of glass or plastic. Centrifuge tubes or centrifuge tips are tapered tubes of various sizes made of glass or plastic.glassplasticglassplastic They may vary in capacity from tens of mm, to much smaller capacities used in micro-centrifuges used extensively in molecular biology laboratories. They may vary in capacity from tens of mm, to much smaller capacities used in micro-centrifuges used extensively in molecular biology laboratories. The most commonly encountered tubes are of about the size and shape of a normal test tube (~ 10 cm long). The most commonly encountered tubes are of about the size and shape of a normal test tube (~ 10 cm long).test tubetest tube Micro-centrifuges typically accommodate micro- centrifuge tubes with capacities from 250 μl to 2.0 ml  These are exclusively made of plastic. Micro-centrifuges typically accommodate micro- centrifuge tubes with capacities from 250 μl to 2.0 ml  These are exclusively made of plastic.μlmlμlml

16. T.Elsarnagawy 16 MLI-mde 210, 311 Centrifuge tubes Glass centrifuge tubes can be used with most solvents, but tend to be more expensive. They can be cleaned like other laboratory glassware, and can be sterilized by autoclaving. Glass centrifuge tubes can be used with most solvents, but tend to be more expensive. They can be cleaned like other laboratory glassware, and can be sterilized by autoclaving. Plastic centrifuge tubes, especially micro-centrifuge tubes tend to be less expensive. Water is preferred when plastic centrifuge tubes are used. They are more difficult to clean thoroughly, and are usually inexpensive enough to be considered disposable Plastic centrifuge tubes, especially micro-centrifuge tubes tend to be less expensive. Water is preferred when plastic centrifuge tubes are used. They are more difficult to clean thoroughly, and are usually inexpensive enough to be considered disposable

17. T.Elsarnagawy 17 MLI-mde 210, 311 Centrifuge tubes Three microcentrifuge tubes: 2 mL, 1.5 mL and 200 μL (for PCR).PCR Four screw-top micro-centrifuge tubes.

18. T.Elsarnagawy 18 MLI-mde 210, 311 Safety aspects Centrifuge servicing includes full strip down, chemical cleaning and mechanical breakdown so that each individual component is cleaned and re-calibrated before re-installation. Centrifuge servicing includes full strip down, chemical cleaning and mechanical breakdown so that each individual component is cleaned and re-calibrated before re-installation. Regular servicing and maintenance ensures that your benchtop centrifuge works effectively and provides accurate mixing of samples which can affect results in clinical trials. Regular servicing and maintenance ensures that your benchtop centrifuge works effectively and provides accurate mixing of samples which can affect results in clinical trials.

19. T.Elsarnagawy 19 MLI-mde 210, 311 Safety aspects The load in a laboratory centrifuge must be carefully balanced. Small differences in mass of the load can result in a large force imbalance when the rotor is at high speed. This force imbalance strains the spindle and may result in damage to centrifuge or personal injury. Some centrifuges have an automatic rotor imbalance detection. The control software immediately discontinue the run when imbalance appears. The load in a laboratory centrifuge must be carefully balanced. Small differences in mass of the load can result in a large force imbalance when the rotor is at high speed. This force imbalance strains the spindle and may result in damage to centrifuge or personal injury. Some centrifuges have an automatic rotor imbalance detection. The control software immediately discontinue the run when imbalance appears. Before starting a centrifuge, an accurate check of the rotor lockage as well as the lid lockage is mandatory. Before starting a centrifuge, an accurate check of the rotor lockage as well as the lid lockage is mandatory.

20. T.Elsarnagawy 20 MLI-mde 210, 311 Safety aspects Centrifuge rotors should never be touched while moving, because a spinning rotor can cause serious injury. Centrifuge rotors should never be touched while moving, because a spinning rotor can cause serious injury. Modern centrifuges generally have features that prevent accidental contact with a moving rotor as the main lid is locked during the run. Modern centrifuges generally have features that prevent accidental contact with a moving rotor as the main lid is locked during the run.

21. T.Elsarnagawy 21 MLI-mde 210, 311 Always run the centrifuge with full or evenly distributed sample tubes. Failure to do so can distort the centrifuge rotor and or damage the centrifuge. Sample tubes come in different weights which mean the rotational mass must be equal prior to switching the centrifuge on. Always run the centrifuge with full or evenly distributed sample tubes. Failure to do so can distort the centrifuge rotor and or damage the centrifuge. Sample tubes come in different weights which mean the rotational mass must be equal prior to switching the centrifuge on. Ensure the centrifuge lid is securely shut. Our benchtop centrifuges come with a safety mechanism to prevent operation unless the lid is securely sealed, however it is always advised to check prior to switching on. Ensure the centrifuge lid is securely shut. Our benchtop centrifuges come with a safety mechanism to prevent operation unless the lid is securely sealed, however it is always advised to check prior to switching on. Only use manufacture specific accessories designed to work with your centrifuge, failure to do so can cause damage or injury. Only use manufacture specific accessories designed to work with your centrifuge, failure to do so can cause damage or injury. Ensure your centrifuge is kept clean at all times. Dirt, grease and grime can degrade the efficiency and quality of the centrifuge over time. Regular servicing is paramount. Ensure your centrifuge is kept clean at all times. Dirt, grease and grime can degrade the efficiency and quality of the centrifuge over time. Regular servicing is paramount. Ensure centrifuges are stored in a clean dry area to prevent condensation damage to moving parts. Ensure centrifuges are stored in a clean dry area to prevent condensation damage to moving parts.

22. T.Elsarnagawy 22 MLI-mde 210, 311 Safety aspects Because of the kinetic energy stored in the rotor head during high speed rotation, those who have experienced the loss of a rotor inside of an ultracentrifuge compare the experience to having a bomb explode nearby. Because of the kinetic energy stored in the rotor head during high speed rotation, those who have experienced the loss of a rotor inside of an ultracentrifuge compare the experience to having a bomb explode nearby. When handling dangerous samples (like biohazard), the lid of the rotor needs to have a special gasket (aerosol-tight) to prevent contamination of the laboratory. When handling dangerous samples (like biohazard), the lid of the rotor needs to have a special gasket (aerosol-tight) to prevent contamination of the laboratory. The rotor can be loaded with the samples within a hood and the rotor lid is fixed on the rotor. Afterwards, the aerosol-tight system of rotor and lid is transferred to the centrifuge. Fixation of the rotor within the centrifuge is done without opening the rotor lid again. After the run, the rotor (incl. lid) is removed from the centrifuge to the hood (closed system) for further steps. The rotor can be loaded with the samples within a hood and the rotor lid is fixed on the rotor. Afterwards, the aerosol-tight system of rotor and lid is transferred to the centrifuge. Fixation of the rotor within the centrifuge is done without opening the rotor lid again. After the run, the rotor (incl. lid) is removed from the centrifuge to the hood (closed system) for further steps.