to 1 102 g of an analyte per sample. Method
Power supply
8021 uses a gas chromatograph/photoionization
GCs require a stable, continuous power sup-
and/or electrolytic conductivity (GC/PID/ECLD)
ply, especially if an autosampler is used to con-
analyte separation and detection system. These de-
tinue the analytical sequence overnight. Instru-
tection system can be used for many VOCs and
ments powered down each night will require time
has a lower limit of detection around 1 1010 g of
during the next morning to warm up before cali-
an analyte per sample. However, like the MS de-
bration can be performed. This will cut into the
tection system, these detectors have a limited
work day. Power can be supplied by portable gen-
range of linear response, often less than two or-
erators, either gasoline or diesel, or by heavy duty
ders of magnitude.
electrical cords tied into existing site power. When
using generators, it is important to size the gen-
erator to the power requirements of the labora-
On-site analysis of groundwater samples by
tory. If the fuel reservoir is too small, it may need
purge-and-trap (i.e., Method 5030) can also be
refilling during the middle of the night to keep
coupled with any of the following accepted meth-
the instruments running. Be aware that in heavily
ods of analyte detection, Methods 8260B, 8015B,
grassed, dry areas, there is always the danger of
or 8021B. See the Soil Sample section for a brief
causing a fire from the use of gasoline generators.
description of these methods. As with soil analy-
Check with site personnel during the planning stage
sis a stable laboratory temperature must be main-
to identify site specific hazards or regulations.
tained to meet the quality assurance requirements.
Since this system can be equipped to handle a 25-
Laboratory supplies
mL aliquot, detection limits can be increased by
Because water for VOC analysis can easily be
about a factor of five, as compared to those of the
contaminated by gasoline and diesel fumes, the
soil samples.
water supply should be checked frequently. When
an on-site source of distilled water is not avail-
able, a water supply can be acquired through the
purchase of commercial bottled water. Several lo-
LOGISTICS
cal brands of distilled water may have to be pur-
On-site analysis has been greatly facilitated by
chased and tested to find a suitable water source.
the increase in field portable analytical instrumen-
Bottled distilled water treated by ozonation fre-
tation and methodologies. The quality of data ob-
quently will be the best choice.
tained from on-site activities, whether centered
To avoid costly delays, bring extra quantities
around a mobile laboratory or a permanent on-
of all supplies needed, including sampling vials,
site laboratory, can be greatly increased through
purge and trap grade methanol, vials of standards,
careful planning and by taking a few precautions.
gas-tight and Luer Lok syringes, and spare parts
for analytical instrumentation. Even in an area
with a local source, you could spend several hours
Location and climate control
In many cases, a mobile laboratory can be
obtaining the needed supplies.
driven directly to the sampling site. When park-
During the planning stage locate a supplier of
ing, try to orient the door so that the prevailing
gases of the proper purity. Welding supply stores
wind does not blow exhaust fumes from opera-
are usually a good source. Make arrangements
tions into the laboratory and possibly compromise
ahead of time to ensure the gas you need is avail-
the quality of the samples, the analysis, or the
able. When inquiring, discuss price. A transient
water supply. Also, try to level the laboratory as
customer could be charged two or three times the
much as possible or have leveling benches. Be-
price a regular customer is charged. In some cases,
cause of the nature of GC analysis, temperature
for short-term projects, you might consider bring-
swings of 5 or 10 degrees over the course of the
ing your own cylinders. In any case, always have
working day can have an effect on identification
extra in case of purity problems or leaks.
and quantitation results. For this reason stable cli-
mate control is a necessity. Any operations that
Sample storage
must be performed outside should take place in a
To avoid compromise, samples and standard
sheltered area away from the prevailing wind and
solutions should be stored separately. If a reliable,
direct sunlight. Small, portable folding tables can
continuous power supply is available, small re-
improve working conditions dramatically.
frigerators or freezers are ideal. Another choice is
8
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