Science Lab Tech Part 2 Lecture PDF

Science Laboratory Technology (SLT) Part (2) Autoclave Autoclave Cutaway illustration of a jacketed rectangular-chamber autoclave Cutaway illustration...

Science Laboratory Technology (SLT) Part (2) Autoclave Autoclave Cutaway illustration of a jacketed rectangular-chamber autoclave Cutaway illustration of a cylindrical-chamber autoclave An autoclave is a machine used to carry out scientific processes requiring elevated temperature and pressure in relation to ambient pressure and/or temperature. Autoclaves are used before surgical procedures to perform sterilization. Many autoclaves are used to sterilize equipment and supplies by subjecting them to pressurized saturated steam at 121 °C (250 °F) for around 30-60 minutes at a pressure depending on the size of the load and the contents. The name comes from Greek auto-, ultimately meaning self, and Latin clavis meaning key, thus a self-locking device. Uses Sterilization autoclaves are widely used in microbiology and mycology and medicine. They vary in size and function depending on the media to be sterilized and are sometimes called retort in the chemical and food industries. Typical loads include laboratory glassware, other equipment and waste, surgical instruments and medical waste. A notable recent and increasingly popular application of autoclaves is the pre-disposal treatment and sterilization of waste material, such as pathogenic hospital waste. Machines in this category largely operate under the same principles as conventional autoclaves in that they are able to neutralize potentially infectious agents by using pressurized steam and superheated water. A new generation of waste converters is capable of achieving the same effect without a pressure vessel to sterilize culture media, rubber material, gowns, dressings, gloves, etc. It is particularly useful for materials which cannot withstand the higher temperature of a hot air oven. Autoclaves are also widely used to cure composites, especially for melding multiple layers without any voids that would decrease material strength, and in the vulcanization of rubber. The high heat and pressure that autoclaves generate help to ensure that the best possible physical properties are repeatable. Manufacturers of spars for sailboats have autoclaves well over 50 feet (15 m) long and 10 feet (3 m) wide. In research Autoclaves used in education, research, biomedical research, pharmaceutical research and industrial settings (often called "research- grade" autoclaves) are used to sterilize lab instruments, glassware, culture media, and liquid media. Research-grade autoclaves are increasingly used in these settings where efficiency, ease-of-use, and flexibility are at a premium. Research-grade autoclaves may be configured for "pass-through" operation. This makes it possible to maintain absolute isolation between "clean" and potentially contaminated work areas.  Laboratory centrifuge ment, driven by a motor, which spins liquid samples at high speed. There are various types of centrifuges, depending on the size and the sample capacity. Like all other centrifuges, laboratory centrifuges work by the sedimentation principle, where the centripetal acceleration is used to separate substances of greater and lesser density. Types Laboratory centrifuge There are various types of centrifugation:  Differential centrifugation, often used to separate certain organelles from whole cells for further analysis of specific parts of cells  Isopycnic centrifugation, often used to isolate nucleic acids such as DNA  Sucrose gradient centrifugation, often used to purify enveloped viruses and ribosomes, and also to separate cell organelles from crude cellular extracts There are different types of laboratory centrifuges:  Microcentrifuges (devices for small tubes from 0.2 ml to 2.0 ml (micro tubes), up to 96 well-plates, compact design, small footprint; up to 30,000 g)  Clinical centrifuges (moderate-speed devices used for clinical applications like blood collection tubes)  Multipurpose high-speed centrifuges (devices for a broad range of tube sizes, high variability, big footprint)  Ultracentrifuges (analytical and preparative models) Because of the heat generated by air friction and the frequent necessity of maintaining samples at a given temperature, many types of laboratory centrifuges are refrigerated and temperature regulated. Safety An Eppendorf laboratory centrifuge The load in a laboratory centrifuge must be carefully balanced. This is achieved by using a combination of samples and balance tubes which all have the same weight or by using various balancing patterns without balance tubes. 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 the centrifuge or personal injury. Some centrifuges have an automatic rotor imbalance detection feature that immediately discontinues the run when an imbalance is detected. Before starting a centrifuge, an accurate check of the rotor and lid locking mechanisms is mandatory.  A ThermoFisher laboratory bench-top centrifuge. Shaker (laboratory) A temperature-controlled shaker, as used in biochemistry work A shaker is a piece of laboratory equipment used to mix, blend, or agitate substances in a tube or flask by shaking them. It is mainly used in the fields of chemistry and biology. A shaker contains an oscillating board that is used to place the flasks, beakers, or test tubes. Although the magnetic stirrer has lately come to replace the shaker, it is still the preferred choice of equipment when dealing with large volume substances or when simultaneous agitation is required. Types Vortex shaker A vortex shaker is a usually small device used to shake or mix small vials of liquid substance. Its most standout characteristic is that it works by the user putting a vial on the shaking platform and turning it on; thus, the vial is shaken along with the platform. A vortex shaker is very  variable in terms of speed adjustment, for the shaking speed can be continuously changed while shaking by turning a switch. Vortex shaker Platform shaker A platform shaker has a table board that oscillates horizontally. The liquids to be stirred are held in beakers, jars, or flasks that are placed over the table or, sometimes, in test tubes or vials that are nested into holes in the plate. Shaking incubator for culture flasks Orbital shaker An orbital shaker has a circular shaking motion with a slow speed (25- 500 rpm). It is suitable for culturing microbes, washing blots, and general mixing. Some of its characteristics are that it does not create vibrations, and it produces low heat compared to other kinds of shakers, which makes it ideal for culturing microbes. Moreover, it can be modified by placing it in an incubator to create an incubator shaker due to its low temperature and vibrations.  Thermal shaker for test tubes Incubator shaker An incubator shaker (or thermal shaker) can be considered a mix of an incubator and a shaker. It has an ability to shake while maintaining optimal conditions for incubating microbes or DNA replications. This equipment is very useful since, in order for a cell to grow, it needs oxygen and nutrients that require shaking so that they can be distributed evenly around the culture. Anyone employing an incubator shaker (thermal shaker) to grow yeast or bacteria in the laboratory needs to beware that under the usual conditions encountered in the lab, the rate at which oxygen diffuses from the gaseous phase into the shaken liquid phase is too slow to keep up with the rate at which the oxygen is consumed by, for example, E. coli dividing every half hour or Saccharomyces cerevisiae dividing every hour. If the investigator measure the oxygen in the shake flask on the shaker -- polarographically, for example -- at mid-exponential phase of growth, the dissolved oxygen concentration will turn out to be zero. Shaking incubator for culture tubes Refrigerator Food in a refrigerator with its door open Exterior of a Samsung refrigerator A refrigerator, colloquially fridge, is a commercial and home appliance consisting of a thermally insulated compartment and a heat pump (mechanical, electronic or chemical) that transfers heat from its inside to its external environment so that its inside is cooled to a temperature below the room temperature. Refrigeration is an essential food storage technique around the world. The lower temperature lowers the reproduction rate of bacteria, so the refrigerator reduces the rate of spoilage. A refrigerator maintains a temperature a few degrees above the freezing point of water. The optimal temperature range for perishable food storage is 3 to 5 °C (37 to 41 °F). A similar device that maintains a temperature below the freezing point of water is called a freezer. The refrigerator replaced the icebox, which had been a common household appliance for almost a century and a half. The United States Food and Drug Administration recommends that the refrigerator be kept at or below 4 °C (40 °F) and that the freezer be regulated at −18 °C (0 °F). The first cooling systems for food involved ice. Artificial refrigeration began in the mid-1750s, and developed in the early 1800s. In 1834, the first working vapor-compression refrigeration system was built. The first commercial ice-making machine was invented in 1854. In 1913, refrigerators for home use were invented. In 1923 Frigidaire introduced the first self- contained unit. The introduction of Freon in the 1920s expanded the refrigerator market during the 1930s. Home freezers as separate compartments (larger than necessary just for ice cubes) were introduced in 1940. Frozen foods, previously a luxury item, became commonplace. Freezer units are used in households as well as in industry and commerce. Commercial refrigerator and freezer units were in use for almost 40 years prior to the common home models. The freezer-over-refrigerator style had been the basic style since the 1940s, until modern, side-by-side refrigerators broke the trend. A vapor compression cycle is used in most household refrigerators, refrigerator–freezers and freezers. Newer refrigerators may include automatic defrosting, chilled water, and ice from a dispenser in the door. Domestic refrigerators and freezers for food storage are made in a range of sizes. Among the smallest are Peltier-type refrigerators designed to chill beverages. A large domestic refrigerator stands as tall as a person and may be about one metre (3 ft 3 in) wide with a capacity of 0.6 m3 (21 cu ft). Refrigerators and freezers may be free-standing, or built into a kitchen. The refrigerator allows the modern household to keep food fresh for longer than before. Freezers allow people to buy perishable food in bulk and eat it at leisure, and make bulk purchases. Styles of refrigerators In the early 1950s most refrigerators were white, but from the mid-1950s to the present day, designers and manufacturers have put color onto refrigerators. In the late-1950s/early-1960s, pastel colors like turquoise and pink became popular, and brushed chrome-plating (similar to a stainless steel finish) was available on some models. In the late 1960s and throughout the 1970s, earth tone colors were popular, including Harvest Gold, Avocado Green and almond. In the 1980s, black became fashionable. In the late 1990s stainless steel came into vogue. Since 1961 the Color Marketing Group has attempted to coordinate the colors of appliances and other consumer goods. Freezer Freezer units are used in households and in industry and commerce. Food stored at or below −18 °C (0 °F) is safe indefinitely. Most household freezers maintain temperatures from −23 to −18 °C (−9 to 0 °F), although some freezer-only units can achieve −34 °C (−29 °F) and lower. Refrigerator freezers generally do not achieve lower than −23 °C (−9 °F), since the same coolant loop serves both compartments: Lowering the freezer compartment temperature excessively causes difficulties in maintaining above-freezing temperature in the refrigerator compartment. Domestic freezers can be included as a separate compartment in a refrigerator, or can be a separate appliance. Domestic freezers may be either upright, resembling a refrigerator, or chest freezers, wider than tall with the lid or door on top, sacrificing convenience for efficiency and partial immunity to power outages. Many modern upright freezers come with an ice dispenser built into their door. Some upscale models include thermostat displays and controls, and sometimes flat screen televisions as well. Newer refrigerators may include:  Automatic defrosting  A power failure warning that alerts the user by flashing a temperature display. It may display the maximum temperature reached during the power failure, and whether frozen food has defrosted or may contain harmful bacteria.  Chilled water and ice from a dispenser in the door. Water and ice dispensing became available in the 1970s. In some refrigerators, the process of making ice is built-in so the user doesn't have to manually use ice trays. Some refrigerators have water chillers and water filtration systems.  Cabinet rollers that lets the refrigerator roll out for easier cleaning  Adjustable shelves and trays  A status indicator that notifies when it is time to change the water filter  An in-door ice caddy, which relocates the ice-maker storage to the freezer door and saves approximately 60 litres (2 cu ft) of usable freezer space. It is also removable, and helps to prevent ice-maker clogging.  A cooling zone in the refrigerator door shelves. Air from the freezer section is diverted to the refrigerator door, to cool milk or juice stored in the door shelf.  A drop down door built into the refrigerator main door, giving easy access to frequently used items such as milk, thus saving energy by not having to open the main door.  A Fast Freeze function to rapidly cool foods by running the compressor for a predetermined amount of time and thus temporarily lowering the freezer temperature below normal operating levels. It is recommended to use this feature several hours before adding more than 1 kg of unfrozen food to the freezer. For freezers without this feature, lowering the temperature setting to the coldest will have the same effect.  Freezer Defrost: Early freezer units accumulated ice crystals around the freezing units. This was a result of humidity introduced into the units when the doors to the freezer were opened condensing on the cold parts, then freezing. This frost buildup required periodic thawing ("defrosting") of the units to maintain their efficiency. Manual Defrost (referred to as Cyclic) units are still available. Advances in automatic defrosting eliminating the thawing task were introduced in the 1950s, but are not universal, due to energy performance and cost. These units used a counter that only defrosted the freezer compartment (Freezer Chest) when a specific number of door openings had been made. The units were just a small timer combined with an electrical heater wire that heated the freezer's walls  for a short amount of time to remove all traces of frost/frosting. Also, early units featured freezer compartments located within the larger refrigerator, and accessed by opening the refrigerator door, and then the smaller internal freezer door; units featuring an entirely separate freezer compartment were introduced in the early 1960s, becoming the industry standard by the middle of that decade. Energy efficiency A European energy label for a fridge Display of modern American-style / side-by-side refrigerators, available for purchase in a store Because of the introduction of new energy efficiency standards, refrigerators made today are much more efficient than those made in the 1930s; they consume the same amount of energy while being three times as large. Auto defrosting If the defrosting system melts all the ice before the timed defrosting period ends, then a small device (called a defrost limiter) acts like a thermostat and shuts off the heating element to prevent too large a temperature fluctuation, it also prevents hot blasts of air when the system starts again, should it finish defrosting early. On some early frost-free models, the defrost limiter also sends a signal to the defrost timer to start the compressor and fan as soon as it shuts off the heating element before the timed defrost cycle ends. When the defrost cycle is completed, the compressor and fan are allowed to cycle back on.[citation needed] Frost-free refrigerators, including some early frost-free refrigerators/freezers that used a cold plate in their refrigerator section instead of airflow from the freezer section, generally don't shut off their refrigerator fans during defrosting. This allows consumers to leave food in the main refrigerator compartment uncovered, and also helps keep vegetables moist. This method also helps reduce energy consumption, because the refrigerator is above freeze point and can pass the warmer-than-freezing air through the evaporator or cold plate to aid the defrosting cycle.[citation needed] ULT freezer A standard upright negative 80 degree freezer An ultra low temperature (ULT) freezer is a refrigerator that stores contents at between −40 to −86 °C (−40 to −123 °F). An ultra low temperature freezer is commonly referred to as a "minus 80 freezer" or a "negative 80 freezer", referring to the most common temperature standard. ULT freezers come in upright and chest freezer formats. Application  A scientist placing samples into a negative 80 degree freezer In contrast to short term sample storage at +4 to −20 °C (39 to −4 °F) by using standard refrigerators or freezers, many molecular biology or life science laboratories need long-term cryopreservation (including "cold chain" and/or "colder chain" infrastructures) for biological samples like DNA, RNA, proteins, cell extracts, or reagents. To reduce the risk of sample damage, these types of samples need extremely low temperatures of −80 to −86 °C (−112 to −123 °F). Mammalian cells are often stored in dewars containing liquid nitrogen at −196 °C (−320.8 °F).[failed verification] Cryogenic chest freezers can achieve temperatures down to −150 °C (−238 °F), and may include a liquid nitrogen backup. Biological samples in ULT freezers are often stored in polymer tubes and microtubes, generally inside storage boxes that are commonly made of cardboard, polymer plastics or other materials. Microtubes are placed in storage boxes containing a grid of dividers that typically permit 64, 81, or 100 tubes to be stored. Standard ULT freezers can store approximately 350 to 450 microtube boxes. Boxes commonly used for storage of samples in laboratory freezers ULT freezers are widely used in fish and meat preservation. The tuna fishing industry requires the use of ULT freezers.[citation needed] ULT freezers are commonly fitted with alarm systems that will remotely alert designated parties in the case of a freezer failure.[citation needed] Pull down time The pull down time is defined as the necessary time to cool down the ULT freezer from ambient temperatures to the selected temperature of −80 to −86 °C (−112 to −123 °F). The time strongly depends on the type of insulation, the efficiency of the compressor system as well as the installed metal shelves within the freezer. At the start of the twenty-first century, ULT freezers were able to cool down within 3 to 5 hours. Warm up time is typically 1/8 °C per minute.[citation needed] Incubator (culture) Interior of a CO2 incubator used in cell culture An incubator is a device used to grow and maintain microbiological cultures or cell cultures. The incubator maintains optimal temperature, humidity and other conditions such as the CO2 and oxygen content of the atmosphere inside. Incubators are essential for much experimental work in cell biology, microbiology and molecular biology and are used to culture both bacterial and eukaryotic cells. An incubator is made up of a chamber with a regulated temperature. Some incubators also regulate humidity, gas composition, or ventilation within that chamber. The simplest incubators are insulated boxes with an adjustable heater, typically going up to 60 to 65 °C (140 to 150 °F), though some can go slightly higher (generally to no more than 100 °C). The most commonly used temperature both for bacteria such as the frequently used E. coli as well as for mammalian cells is approximately 37 °C (99 °F), as these organisms grow well under such conditions. For other organisms used in biological experiments, such as the budding yeast Saccharomyces cerevisiae, a growth temperature of 30 °C (86 °F) is optimal. More elaborate incubators can also include the ability to lower the temperature (via refrigeration), or the ability to control humidity or CO2 levels. This is important in the cultivation of mammalian cells, where the relative humidity is typically >80% to prevent evaporation and a slightly acidic pH is achieved by maintaining a CO2 level of 5%.  A Bacteriological incubator Incubators serve a variety of functions in a scientific lab. Incubators generally maintain a constant temperature, however additional features are often built in. Many incubators also control humidity. Shaking incubators incorporate movement to mix cultures. Gas incubators regulate the internal gas composition. Some incubators have a means of circulating the air inside of them to ensure even distribution of temperatures. Many incubators built for laboratory use have a redundant power source, to ensure that power outages do not disrupt experiments. Incubators are made in a variety of sizes, from tabletop models, to warm rooms, which serve as incubators for large numbers of samples.