over steam cleaning are that there is increased
detergent solutions, but would be removed by an
force available, the energy requirements are low-
acid rinse (McLaughlin and Levin 1995). Typical-
er because water does not have to be converted to
ly dilute (0.1 N) hydrochloric or nitric acid is
steam, polymeric materials are less likely to be
used. Some protocols recommend not using an
degraded, and there is less likelihood of the oper-
acid treatment on metal surfaces (Parker 1995)
ator being burned.
because it would be ineffective and because acids
Organic solvent rinses are used to remove any
corrode metal surfaces (Driscoll 1986).
residual contaminants by dissolving them. Gen-
erally, like dissolves like; i.e., polar solvents dis-
Factors affecting decontamination efficiency
solve polar contaminants, and nonpolar solvents
Parker (1995) listed several factors that would
dissolve nonpolar contaminants. Because water
affect how readily a sampling device can be de-
is a very polar solvent, nonpolar solvents are typ-
contaminated. These include the type of sam-
ically used to remove nonpolar organic contami-
pling device (e.g., pump vs. bailer), the materials
nants (e.g., oils, tars) that have not been removed
to be decontaminated, and physical characteris-
by aqueous cleaning. This is usually done either
tics of the organic contaminant, such as its aque-
by flushing the surfaces with a stream of solvent,
ous solubility, volatility, and propensity to adsorb
or circulating solvent through larger equipment.
on or absorb into materials used in the sampling
Recommended organic solvents vary with the
device. Contact time and the degree of initial con-
particular protocol but typically include acetone,
tamination on the surface are also critical factors.
hexane, or methanol. In most protocols, these sol-
Presumably removing a dilute solution will be
vents are recommended without any regard to
easier than removing neat (pure) product. Other
the type of contaminants (Parker 1995), and it
types of contaminants, such as grease and oil,
should be noted that among the three solvents
may also affect removal.
typically used only hexane is relatively nonpolar.
Several studies (Gillham and O'Hannesin
Obviously any organic solvent that is used as a
1990, Parker et al. 1990, Reynolds et al. 1990) have
rinsing agent should not be one of the target ana-
shown that less hydrophobic organic solutes
lytes or interfere with chemical analyses.
(with log octanolwater partition coefficient
There are a number of problems associated
[Kow] values less than 4) are not sorbed by non-
with using organic solvents. These can include
permeable surfaces, such as glass and stainless
steel (SS). However, sorption of more hydropho-
flammability, toxicity, disposal (although recy-
bic contaminants, such as polychlorinated biphe-
cling can reduce this problem), and possible spill-
nyls (PCBs), chlorinated pesticides, and polyaro-
age, which can cause additional contamination
matic hydrocarbons (PAHs), by SS and glass sur-
problems on site. In addition, many polymers
faces has been reported by Champion and Olsen
(e.g., the thermoplastics) are degraded by various
(1971), Ogan et al. (1978), Sharom and Solomon
organic solvents, and all polymers will sorb some
(1981), Strachan and Hess (1982), and Jones and
of these organic solvents. Sorbed contaminants
Miller (1988). Most likely these losses are due to
may subsequently desorb and thus contaminate
adsorption by these surfaces (i.e., sorption is a
water samples. Information on incompatibilities
surface phenomenon). Sharom and Solomon
between polymers and organic solvents can be
(1981) concluded that pesticides with solubilities
found in chemical resistance tables published by
in the g/L range have a tendency to be adsorbed
the Plastics Design Library (1994a, b) and in some
by glass while more soluble compounds do not.
of the scientific supply catalogs (e.g., Nalgene Co.
There has been relatively little study of desorp-
and Cole-Parmer Co.). A few decontamination
tion of organic contaminants from these surfaces.
protocols (e.g., US EPA Region IV 1991) acknowl-
Sharom and Solomon (1981) noted that the pesti-
edge that some materials are degraded by solvent
cide permethrin was much more readily des-
cleaning and eliminate this step for these materi-
orbed from glass than from polyvinyl chloride
als, although most decontamination protocols do
(PVC), polyethylene (PE), or Teflon. They were
not (Parker 1995).
able to recover up to 94% of the lost permethrin
The acid rinse is used to desorb sorbed metal
by shaking with water for one minute. Parker
ions from nonmetal (polymeric and glass) surfac-
(1995) proposed that decontamination of nonper-
es, and thus this step is usually recommended
meable surfaces, such as metals and glass, should
only if inorganics are to be analyzed. Another rea-
involve removing only surface contaminants,
son to use an acid rinse is because acid-soluble
such as any residual film (either wet or dry) that
soils are poorly removed by most mildly alkaline
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