lecture 1 module Flashcards
Relative Centrifugal Force (RCF)
describe the force imparted on a particle in suspension during centrifugation
RCF is determined by the mass of the particle (1.118 x10^.5) , the speed of rotation - r and the radius of the rotary head -cm.
rheostat on centrifuge
controlling knob, which controls the amount of line voltage to the motor, and thus regulates the speed of rotation of the shaft.
There are two kinds of centrifuge heads in use in the clinical laboratory:
- Horizontal (swing-out) head
- Fixed-angle head. does not have trunnion rings (the things that make the baskets lie flat during spinnig) like baby centrifuge
rpm
(revolutions per minute) is a measure of the speed of rotation of a centrifuge which can be determined by a device called a tachometer.
Guard Bowl big bowl in cnetrifuge
- It minimizes wind resistance on the rotating head.
- It provides for operator safety. The guard bowl will contain glass and biologicals in the event of breakage, as well as minimizing the spread of aerosols.
two classes of centrifuges
found in the routine laboratory
general purpose centrifuges - bench top
* centrifuges for specialized usage - ultracentrifuge
If breakage occurs, carefully clean the bowl, shields, etc what is the procedure
2% glutaraldehyde solution to clean the centrifuge if potentially infectious
material is present. The gluteraldehyde should be left for a minimum of one hour. The centrifuge may then be wiped clean with soap and water
usually due to
improper balancing, the use of inappropriate, chipped or cracked glassware
- Never open the lid of a centrifuge while it is running. why?
tiny droplets of fluid from the tubes are atomized and carried in the air currents
inside the centrifuge, while it is running. Opening the lid of the centrifuge, during
operation, drives aerosols, into the air around the centrifuge, where they could be inhaled by the operator.
There are two ways to transmit heat
One occurs naturally and is called gravity convection. -hot air (or water) rises and cold air (or water) falls so you put a flame at the bottom of an equipment - small volume capacity
The other is forced and is called mechanical convection. fans and air ducts are used to move the air or water - large scale
The graduated thermometer
heat sensitive fluid such as alcohol, which expands
with the application of heat
thermocouple
measures slight temperature changes It usually
consists of temperature probes which are connected to a meter
When a thermocouple is connected to a recording device (such as a pen on paper) so that the temperature is continually monitored over time it is referred to as a recording thermometer or chart recorder. like the round recorder on the walkins
temperature regulator
Temperature Regulating Devices
control dial, set by the operator, which determines the
temperature to be maintained. It is connected to the thermostat.
thermostat
Temperature Regulating Devices
controls temperature by regulating the flow of electricity (or gas) to the
heating unit. maintains a constant temperature
On some pieces of equipment there are two thermostats; a primary or main thermostat and a
secondary or safety thermostat
primary (main) thermostat regulates the desired temperature by controlling the amount of heat entering the unit - some fridges that have sensitve samples that can be ruined
secondary (safety) thermostat is usually set two degrees higher than the primary
thermostat. - with warning light or alarm
secondary (safety) thermostat is usually set two degrees higher than the primary
thermostat.
hygrometer i
gauge which measures the humidity, usually in % R.H. (Percent Relative
Humidity).
humidistat
regulates (or controls) the amount of moisture entering the unit in order to
maintain a preset value.
GENERAL MAINTENANCE AND QUALITY CONTROL
Daily: * Check thermostat settings
* Record temperature, CO2 and humidity readings
* Check water level
Weekly: * Check proper running of fans, lights
* Check proper functioning of hinges, catches
* Change water (unless connected to a tap)
Monthly: * Clean and disinfect
Six months * Change filters. Many models contain filters to one year: for such things as CO2 input, water input, etc. These must be replaced on a regular basis or they become clogged with impurities.
COMMON TYPES OF THERMAL EQUIPMENT FOUND IN LABORATORIES
Hot plates
Slide warmers
Bacti-cinerators
Incubators
* Waterbaths
Refrigerators
Hot air ovens
Autoclaves
Microwave ovens
Mass/Weight
Mass is the amount or quantity of
matter, while weight reflects the force of gravity that is applied to a given mass.
Sensitivity
Sensitivity is
the smallest weight that can be measured by a balance.
Addition Weighing
Double pan balances are based on the principle of addition weighing. like the traditional scales with one side having calibrated weights
variable load balances
Substitution Weighing
Weighing by substitution also compares two masses on opposite sides of a beam or lever.
However, on one side is a weigh pan and a series of removable calibrated weights, which is exactly balanced by a counterweight on the opposite arm.
an object is put on the scale and calibrated weights have to be pulled off so they are in line with the counter weight on the opposite side
The counterweight is equal to the total of removable weights
constant load balances.
Electromagnetic Force Compensation
top-loading balance
current is proportional to the weight
of the load on the pan and produces a voltage that is converted by a microprocessor and the weight of the mass is displayed on the readout
Two types of balance are commonly used in a modern laboratory
top loading balances (reagent prep) and
analytical balances (more accurate -more decimal places for primary standard prep). The type chosen is dependent on the degree of accuracy required.
make sure there no big temperature differences in what is being weighed and the balance
dont wipe vigorously
use tweezers to handle calibrated weights
always close balance door
cover with dust cover
SIMPLE REFRACTOMETERS
This instrument measures the refractive index of a liquid
mostly used for urine
TYPES OF GLASS
borosilicate, silica, and soda-lime.
High Thermal
Resistant Glass
- Borosilicate * Resists heat, corrosive & thermal shock
- Not affected by temp
- Glassware used for heating & sterilization
- Pyrex & Kimax
- Beakers, flasks
- Pipettes
- Graduated
cylinders
High Silica
- Silica (borosilicate glass with everything removed but silica)
- Extremely stable
- Resists all acids except hydofluoric
- Resists radiation
- Good optical qualities
- High precision analytical work and optical equipment
- Cuvettes
- Microscope lenses
Glass With
Resistance to Alkali
(soft glass)
Boron-free glass
* High resistance to alkali
* Low thermal resistance
* storing strongly alkaline solutions
* Specimen bottles and beakers
Low Actinic Glass
- Low actinic containing color
- Amber or red
- Reduces light transmission
- Holds solutions sensitive to light
- Bottles
Standard Flint Glass
(Cheapest)
- Soda-lime
- Oxides of silicon, calcium & sodium
- Poor resistance to temperature change
- Fair resistance to chemicals
- Non-static
- Bottles and disposable glassware
- Disposable test tubes
- Pipettes
- Weighing bottles
Pyroceram
Mixture of ceramic and glass
* High thermal resistance
* Chemical stability
* Resists corrosion
* Heat exchangers * Hot plates
* Table tops
Polyolefins - plastic type
- Relatively inert
- Generally not affected by
acids, alkalies, salt solutions or most aqueous solutions - Affected by organic acids, essential oils, halogens and strong ozidizing agents
- Bottles, beakers, jars, carboys, funnels, pipettes, baskets, tubing and reagent dispensers
Tygon - plastic type
Non-toxic, clear, flexible
* Can handle most chemicals
* Can be steam autoclaved or chemically sterilized
* Tubing
Cleaning Glassware with Detergents
rinse with tap water or presoak
hot water and 2% detergent, rinse with tap and then distilled water
dry in 90 degree oven but never volumetric glassware - could alter the calibration
Chemical Cleaning
appropriately diluted nitric acid,
hydrochloric acid, and acid dichromate
Beakers
Graduated at very large volume intervals
* Can be made of glass or plastic
Accuracy
* Extremely inaccurate
Uses
* A temporary holding container
* Transfer of small volumes of liquids
Volumetric Flasks
Each consists of a round body and a very narrow, straight neck with a single calibration mark
* Body of the flask is not graduated
* Contains a single, specific volume
* Sizes range from 1 mL to 4 L
Accuracy
* TC (“To Contain”)
* Flask with the highest degree of accuracy
* Class A glassware conforms to National Bureau of Standards (NBS) tolerances (Table 1)
* Very narrow neck with calibration mark facilitates accurate volume measurement
* The correct procedure must be followed in order to obtain an accurate volume
Use
* For preparation of standards and other highly accurate solutions
Erlenmeyer Flasks
- Graduated at very large intervals
Accuracy - Inaccurate; never used to measure volumes
Use - Reaction vessel (conical body and narrow neck facilitates mixing)
Florence or Boiling Flasks
- Elongated neck which is wider than a volumetric flask
- No calibration marking on the neck
Accuracy - Inaccurate
- No graduation markings therefore cannot be used to measure volumes
Use - Reaction vessels widely used as containers in which to heat liquids
Graduated Cylinders
Graduated to intermediate volumes
* Sizes range 10 mL to 4 L
* Can be made of glass or plastic
Accuracy
* Not highly accurate
Use
* Measurement of approximate volumes where a high degree of accuracy is not required
Cuvettes
Similar in appearance to a test tube
* Can have either round or flat sides
* Made of high-quality optical glass (must be handled with care to prevent scratching
optical surfaces)
Use
* To read the absorbance of a solution in a spectrophotometer
DESICCATORS
Contains a desiccant, eg., barium perchlorate, calcium sulfate, calcium chloride or silica gel, covered with a perforated plate on which to set beakers of chemicals
* Maintain a good seal between the jar and the lid by using a lubricant
To keep materials such as chemicals and other powders dry
* After a substance has been heated, storage in the jar will prevent moisture reabsorption during cooling
The large pipettes are divided into two general categories
non-graduated (single volume/transfer pipettes) - volumetric pipette -TD - accuracy and precision, not blown out, freely pour
or graduate (measuring pipettes/various volumes) - Mohr or Serological (has etched ring)
mohr
not calibrated to the tip - do not freely drain
use non viscous liquids
wipe the tip
reagent
Serological
viscous solution
micro and serology
can be plugged with non sterile cotton
calibrated to the tip last bit must be blown out- has etched rings on the mount end of the pipette
dont wipe the tip
least accurate
Tolerance
refer to the accuracy or exactness of the pipette
The allowable variation in a Class A piece of glassware is 0.5%.
micropipettes
calibrated to contain (TC). This means that the exact volume of the pipette is obtained only if it is rinsed out with diluent
Gravimetric calibration
measures the weight of water a pipette dispenses. standard
Photometric techniques
assess pipette performance by comparing the absorbance of a dilute solution of a compound delivered with the test device against that delivered using Class A volumetric glassware
Radionuclide
techniques measure the amount of radioactivity per unit volume of standard fluid delivered
Air Displacement
Semi-automatic pipettors can be classified into two categories:
ie oxford
pocket of air remaining between the plunger and the sample.
* The air pocket can cause sample loss or inaccuracies when pipetting very small volumes or viscous solutions.
* Additional pipetting steps are required since this type of pipette uses disposable tips (increases time and cost).
Semi-automatic pipettors can be classified into two categories Positive Displacement
Teflon-tipped plunger that draws the sample up and contacts the fluid directly
* Capillaries that are not changed between each pipetting must be wiped on the outside, and are therefore not suited to sterile technique.
* Care must be taken when wiping the tip of the pipette so as not to remove any liquid from the capillary with the safety wipe.
PIPETTOR JARS
A jar or bottle can be fitted with a lid containing a plunger apparatus and a dispensing tip.
Pi-pump
bulb This device is also used to eliminate any skin contact with the solution.
If the bulb does become contaminated, it should be rinsed with distilled water and thoroughly air dried.
Propipette
This device is used to eliminate any skin contact with the solution being pipetted, eg., acids, biological material. The flow of the solution can be controlled by the device itself.
the bulbs with the pipes you dont like
Safety Bulb
This device is used when pipetting solutions that are not toxic and will not irritate the skin.
the regular bulbs
volumeteric pipette
wipe the tip
most accurate
standard prep and transfer of exact volumes non viscous
has bulb
