Quality control of Laboratory Equipment and Instrumentation

Laboratory Equipment and Instrumentation
Verify that each item of equipment meets the user’s needs for precision and minimization of bias. Perform equipment maintenance on a regular basis as recommended by the manufacturer or obtain preventive maintenance contracts on autoclave, balances, microscopes, and other equipment. Directly record all quality control checks in a permanent log book. Use the following quality control procedures:
a. Thermometer/temperature-recording instruments: Check accuracy of thermometers or temperature-recording instruments semiannually against a certified National Institute of Standards and Technology (NIST) thermometer or one traceable to NIST and conforming to NIST specifications. For general purposes use thermometers graduated in increments of 0.5°C or less. Maintain in water or glycerol for air incubators and refrigerators and glycerol for freezers and seal in a flask. For a 44.5°C water bath, use a submersible thermometer graduated to 0.2°C or less. Record temperature check data in a quality control log. Mark the necessary NIST
calibration corrections on each thermometer and incubator, refrigerator, or freezer. When possible, equip incubators and water baths with temperature-recording instruments that provide a continuous record of operating temperature.
b. Balances: Follow manufacturer’s instructions in operation and routine maintenance of analytical and top-loading balances. Balances should be serviced and recalibrated by a manufacturer technician annually or more often as conditions change or problems occur. In weighing 2 g or less, use an analytical balance with a sensitivity less than 1 mg at a 10-g load.
For larger quantities use a pan balance with sensitivity of 0.1 g at a 150-g load. Wipe balance before use with a soft brush. Clean balance pans after use and wipe spills up immediately with a laboratory tissue. Inspect weights with each use and replace if corroded. Use only a plastic-tip forceps to handle weights. Check balance and working weights monthly against a set of reference weights (ANSI/ASTM Class 1 or NIST Class S) for accuracy, precision, and linearity.4 Record results.
c. pH meter: Use a meter graduated in 0.1 pH units or less, that includes temperature compensation. Preferably use digital meters and commercial buffer solutions. With each use, standardize meter with two buffers that bracket the pH of interest and record. Date buffer solutions when opened and check monthly against another pH meter. Discard solution after each use and replace buffer supply before expiration date. For full details of pH meter use and maintenance,
 Media dispensing apparatus: Check accuracy of volumes dispensed with a graduated
cylinder at start of each volume change and periodically throughout extended runs. If the unit is
used more than once per day, pump a large volume of hot reagent water through the unit to rinse
between runs. Correct leaks, loose connections, or malfunctions immediately. At the end of the
work day, break apparatus down into parts, wash, rinse with reagent water, and dry. Lubricate
parts according to manufacturer’s instructions or at least once per month.
g. Hot-air oven: Test performance monthly with commercially available Bacillus subtilis
spore strips or spore suspensions. Monitor temperature with a thermometer accurate in the 160 to
180°C range and record results. Use heat-indicating tape to identify supplies and materials that
have been exposed to sterilization temperatures.
h. Autoclave: Record items sterilized, temperature, pressure, and time for each run.
Optimally use a recording thermometer. Check and record operating temperature weekly with a
minimum/maximum thermometer. Test performance with Bacillus stearothermophilus spore
strips, suspensions, or capsules monthly. Use heat-indicating tape to identify supplies and
materials that have been sterilized.
i. Refrigerator: Maintain temperature at 1 to 4°C. Check and record temperature daily and
clean monthly. Identify and date materials stored. Defrost as required and discard outdated
materials quarterly.
j. Freezer: Maintain temperature at -20°C to -30°C. Check and record temperature daily. A
recording thermometer and alarm system are highly desirable. Identify and date materials stored.
Defrost and clean semiannually; discard outdated materials.