metrology - los angeles mission college

MetrologyChapter 2

Biotechnology: A Laboratory Skills Course | explorer.bio-rad.com2

What is Metrology?

▪ Metrology is the science of measurement.

▪ Most common types of measurements:

–weight, distance, volume, temperature, pH

▪ Scientific system of measurement:

Metric System


Importance of Accuracy

▪ Accuracy in measurement is key to the generation of a

consistent product.

–accuracy depends on a regular process of testing and

calibrating (adjusting) instruments to be within an established

margin of error

• Random Error – fluctuations from measurement to measurement

• Systematic Error – consistent errors due to state of instrument

***Testing and Calibration typically involves following an SOP***


Margin of Error Example (Micropipets)


Equipment for Measuring Weight

▪ Triple beam balance

Photo courtesy of Ohaus Corporation

▪ Electronic balance



▪ Analytical balance

–Most accurate, measures to the

most significant figures (to the 10th

of a milligram or 0.0001)

–Contains an enclosure to eliminate

air currents


▪ Substances are never weighed directly onto the scale

but into:

–weigh boats

–weigh papers

–other vessels such as a beaker

–scale must be zeroed or tared with the empty

paper/boat/vessel first



Equipment for Measuring Volume

▪ Graduated cylinders

–generally range in capacity from

10 ml to 1 liter or more

–best choice for larger volumes

–measured by the bottom of the

meniscus


The Meniscus of a Measured Liquid

measure

bottom of

meniscus

A meniscus is the curved upper surface

of a liquid due to surface tension with

regard to the container (usu. glass).


▪ Serological pipets

– require motorized or manual pipet

pumps or bulbs

–generally range in capacity from

1 ml to 25 ml



▪ Transfer pipets

–used for convenience, not

accuracy

–generally range from 1 to

3 ml in capacity

–may or may not be

graduated



▪ Adjustable-volume micropipets

–most accurate way to measure

volumes from less than 1 ml to

1000 ml

– require disposable pipet tips



▪ Erlenmeyer flasks, beakers

–generally used for mixing and short term

storage of solutions

–not very accurate for measuring


beakers

Erlenmeyer flask


▪ Reagent bottles

–used exclusively for long term

storage, not good for measuring

–requires proper labeling• name of solution

• concentration

• date made

• initials of person who made it

• potential hazards if necessary

Equipment for Storing Liquids

metrology - los angeles mission college

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