Presampling - Field Sampling: Principles and Practices in Environmental Analysis - page 53

and plastic sieves are also available for more demanding situations in which metal
contamination must be avoided. Metals will normally not be of concern for the samples
analyzed at the field laboratory. In cases in which samples are to be sent to a commercial
laboratory for further analysis, however, contact with metals will be of concern.
Other equipment needed will include a balance and dissolved oxygen and pH meters.
At minimum a top-loading electronic balance having a capacity of several kilograms and
a readability of at least 0.01 g will be needed. Balances with readability of 0.001 g are
readily available, but such sensitivity is not generally needed. A pH meter will be needed
in all field sampling situations, but a dissolved oxygen meter will only be required when
sampling water or water-saturated samples. Inexpensive portable and handheld pH meters
are readily available. The more versatile multifunctional pH meters are more useful and
usually more durable, however. These meters can measure pH and temperature and
accommodate ion selective electrodes (ISE). Ion selective electrodes are available for
measuring ammonia, a wide range of metal cations, and anions, including cyanide,
nitrate, nitrite, and many others. These types of electrodes and measurements can be very
useful, particularly during the transect sampling phase.
Using pH and other electrodes requires filling and standardizing solutions. Most of the
required solutions can be obtained premade, and this is recommended. In no case should
electrode filling solutions be made at the field laboratory. Standardizing solutions for pH
and ISE can be prepared at the field laboratory from premeasured packets of the required
solutes. These are dissolved in the prescribed amount of distilled or DI water, which
should be freshly prepared for this purpose to assure high quality.
An assortment of typical laboratory equipment will also be needed. A shaker for
shaking samples, an oven, and a rack for drying glassware will be useful in the
laboratory. Also, Erlenmeyer flasks, beakers, graduated cylinders, spatulas, weighing
paper, wash bottles, brushes, and laboratory cleaning detergents must be available. In
some cases, other project-specific equipment (e.g., flammable gas detectors for areas
contaminated with fuels) will be needed. Some forethought as to the equipment needed
will allow smooth operation of the field office laboratory. A summary of general
equipment and supplies needed for a field laboratory are given in Table 3.1.
Unless there is some important reason for doing otherwise, only minimal analysis
should be undertaken at the field laboratory. Instrumentation, conditions, and knowledge
are needed for proper operation of sophisticated instrumentation such as spectrometers
and gas chromatographs. Analysis requiring these instruments should be left to the
commercial analytical laboratory.
The operation of any laboratory entails the generation of waste. The waste may be in
the form of broken glassware, discarded excess sample material, chemicals used in
analysis, and innocuous materials, such as paper towels for drying hands. Broken
glassware is the source of cuts in the laboratory, and if not disposed of properly, may be
hazardous to persons handling trash. Special broken-glass containers are available and
should be used for all broken glass. Any samples containing hazardous material either
from samples or from analytical procedures should be disposed of properly. Other
material can be disposed of in local landfills.