Common Operations and Wet Chemical Methods in Environmental Laboratories - Fundamentals of Environmental Sampling and Analysis - page 134

so that water wets it immediately and forms a uniform film upon emptying. This thin
film will not be a part of the delivered volume. If the glassware is designated TC, it is
calibrated that the film should be part of the contained volume. Pipets marked with
TC are designed to transfer usually viscous solutions, and a thin film remaining
inside should be flushed out with a suitable solvent.
Practical tips
To calibrate a volumetric device, weigh a certain volume of water on
analytical balance. For instance, a 1-mL water should be close to 1.0000 g.
To minimize error with measuring pipets, it is a good practice not to use the
tip portion of the pipet. For instance, use only a maximum of 4 mL for a 5-ml
pipet. Alternatively, since almost all serological pipets have an additional mL
marked above the 0 mL line, the accuracy can be improved by not using the
1 mL liquid near the tip.
Do not use disposable pipet for certain hydrophobic solvents such as hexane
and chloroform. These harsh solvents will dissolve disposable pipets, there-
fore, glass pipets are recommended.
Do not submerge the marked portion of the pipets in the liquid as they may
contaminate the solution.
6.1.4 Laboratory Health, Safety, and Emergency
First Aid
A safe and healthful practice is no doubt the most important and should be an
integral part of all activities in environmental sampling and analysis. Although the
victims, as a result of unsafe and health hazardous operations are the people who
are directly involved in the first place, the presence of any safety and health
hazard should be prevented and is the responsibility of all parties including the
organization, the project manager and the lab manager. In the United States,
the minimum standard of practice for health and safety activities is detailed in
government documents (OSHA 29 CFR 1910.1450). Prior training for all parties is
required and a written laboratory hygiene plan (LHP) or chemical hygiene plan
(CHP) should always be developed and implemented within an organization.
Prior to sampling and analytical work, one should always make efforts in
identifying any potential safety and health hazards and should be knowledgeable
about the methods of prevention. These safety and health hazards could be related to
chemical hazards (strong acids/bases, perchloric acid and other highly reactive
chemicals, organic solvents and reagents), physical hazards (electrical, mechanical,
radiation- or compressed gases-related), or biological hazards (infectious biological
samples). For chemical hazards, a good lab practice is to know your chemicals
through the material safety data sheet (MSDS) for their potential toxicity and other
hazards.