Trace-Element Contamination--Findings of Study on the Cleaning of Sampler Caps, Nozzles, Bottles, and Bags for Trace-Element Work at the Part-Per-Billion Level
In Reply Refer To: February 19, 1993
Mail Stop 412
OFFICE OF WATER QUALITY TECHNICAL MEMORANDUM 93.06
Subject: Trace-Element Contamination--Findings of Study on the
Cleaning of Sampler Caps, Nozzles, Bottles, and Bags
for Trace-Element Work at the Part-Per-Billion Level
SYNOPSIS
As part of the development of a new part-per-billion (ppb)
protocol for collecting and processing samples for analysis of
dissolved trace elements, the Office of Water Quality (OWQ)
conducted a study on the effectiveness of cleaning plastic and
Teflon 1/ D-77 sampler components (caps, nozzles, bottles, and
bags) to reduce contamination. Procedures for both laboratory and
field cleaning were tested. Nitric (HNO3) and hydrochloric (HCl)
acids were compared for their effectiveness in cleaning, and tests
were included to determine the amount of rinsing with deionized
water (DIW) required to prevent carryover of nitrate, chloride,
and methanol, or trace elements from methanol (a final methanol
rinse is required on equipment when both trace elements and
organics are collected). To determine the success of the cleaning
procedures, test results were compared to values of one-half the
target reporting level (RL) specified for each trace element for
the ppb procedure. The major findings of the study were:
1. DIW blanks processed through equipment in an "initial
condition" (before any cleaning) contained trace elements above
one-half the target RL.
2. Dilute HNO3 and HCl solutions (approximately 5 percent by
volume) were equally effective for cleaning both plastic and
Teflon D-77 sampler caps, nozzles, bottles, and bags.
3. Carryover of chloride and nitrate from the use of HCl and
HNO3, respectively, was not evident for either the laboratory or
field cleaning procedure.
4. Both plastic and Teflon components are acceptable for trace-
element sampling because the laboratory cleaning procedure reduced
trace-element contamination well below the target RLs.
5. Both old and new plastic and Teflon components are acceptable
because they were adequately cleaned by the laboratory procedure.
____________________
1/ Any use of trade, product, or firm names is for descriptive
purposes only and does not imply endorsement by the
U.S. Government.
6. The field cleaning procedure was effective in reducing trace-
element contamination for both plastic and Teflon sampler
components to levels below one-half the target RLs for all
constituents except beryllium (Be). Based on the test results,
the OWQ has revised the field cleaning procedure.
7. Based on this study, in the D-77 bag sampler, Teflon bags are
preferred and Reynolds Oven Bags are acceptable for use with the
ppb protocol.
8. A laboratory cleaning procedure for plastic and Teflon bags
was effective except for manganese (Mn) and zinc (Zn). Projects
using bags should produce adequate equipment blanks to insure bag
trace-element contamination is under control (less than one-half
RLs).
INTRODUCTION
One of the key elements in developing a new ppb protocol for
collecting and processing samples for dissolved trace elements is
an adequate cleaning procedure. Cleaning procedures for both
laboratory and field cleaning of sampler caps, nozzles, bottles,
and bags were developed.
In April 1992, the OWQ conducted a study on the effectiveness of
newly developed laboratory and field procedures for cleaning
plastic and Teflon sampler components used in D-77 samplers. This
memo describes the major findings of the study.
OBJECTIVES
The objectives of the study were to:
1. Establish the efficacy of the proposed laboratory cleaning
procedure (detergent scrubbing and soak, tap water rinse, dilute
HCl soak, and copious DIW rinses) for precleaning those parts of
surface-water samplers--for both plastic and Teflon components--
that come into direct contact with water-sediment samples.
2. Determine if the laboratory cleaning procedure is effective
for both new and old sampler components.
3. Determine if HNO3 (a possible alternative cleaning agent) is
better, equivalent, or worse than HCl (the cleaning agent selected
for the procedure) for precleaning sampler components and bags.
4. Determine the amount of DIW rinsing required to prevent
carryover of chloride, nitrate, and methanol or trace elements
from methanol.
5. Establish the efficacy of the field cleaning procedure (dilute
HCl rinses and copious DIW rinses) which is intended to be used
between sampling sites to prevent trace-element carryover.
STUDY COMPONENTS
The study, designed by John Zogorski (OWQ), was conducted
April 1-16, 1992, at the Central Region Branch of Regional
Research facilities in Boulder, Colorado. Kathy Fitzgerald (OWQ),
Bob Boulger (Colo.), and Dave Johncox (Colo.) conducted the study,
which consisted of the following components:
1. Equipment blanks were collected from a series of plastic and
Teflon bottles and bags (identified below) to assess their initial
condition prior to cleaning.
2. Equipment was cleaned using the laboratory procedure, and
equipment blanks were collected after various levels of DIW
rinsing to determine:
(a) if both new and old equipment could be adequately
cleaned,
(b) if plastic and Teflon equipment could be adequately
cleaned, and
(c) the amount of DIW rinsing needed.
3. Equipment was exposed to a solution containing a high trace-
element concentration and was subsequently recleaned using the
laboratory procedure; equipment blanks were collected after
various levels of DIW rinsing to determine the efficacy of the
laboratory cleaning procedure.
4. Equipment was exposed to a solution containing a high trace-
element concentration and was subsequently cleaned using the
field procedure; equipment blanks were collected after various
levels of DIW rinsing to determine the efficacy of the field
cleaning procedure.
5. Some of the equipment was cleaned with HCl and some with HNO3.
SAMPLER COMPONENTS AND BAGS EVALUATED
The following D-77 sampler components and bags were evaluated:
Plastic (polypropylene) 1 new (OWQ)
components
6 old (WA (2), CO, CA, KS (2))
Teflon components 1 new (KY)
5 old (NWQL 1/, CA, KY, MA, WA)
Small plastic bags Glad brand 2 bags
Reynolds Oven Bag 2 bags
Large plastic bags Reynolds Oven Bag 2 bags
(from Charlie Demas)
Jensen Inert Tedlar 2 bags
Small Teflon bags Corps of Engineers 2 bags
(Vicksburg, MS)
American Durafilm 2 bags
Large Teflon bags American Durafilm 2 bags
Jensen Inert 2 bags
______________________________________________________________
1/NWQL = National Water Quality Laboratory.
Three-liter sampler bottles were shipped to the Colorado District
from the Districts listed in column 2 above. All bags, except for
the oven bags from Charlie Demas, were purchased specifically for
this study. The Glad and Reynolds bags were purchased at local
grocery stores.
CONSTITUENTS ANALYZED
Most trace elements were analyzed with inductively coupled plasma
mass spectrometry by the Methods Research and Development Program,
NWQL, with a detection level of 0.2 ug/L. Constituents included
aluminum (Al), arsenic (As), barium (Ba), beryllium (Be), cadmium
(Cd), chromium (Cr), cobalt (Co), copper (Cu), lead (Pb), manganese
(Mn), molybdenum (Mo), nickel (Ni), silver (Ag), thallium (Tl),
thorium (Th), uranium (U), and zinc (Zn). Five other elements
including iron (Fe), lithium (Li), selenium (Se), strontium (Sr),
and vanadium (V) were analyzed by the Inorganic Program, NWQL.
Selected equipment blanks were also analyzed for major elements and
nutrients at the NWQL.
DATA INTERPRETATION
To determine the efficacy of the two cleaning procedures,
equipment blank results were compared to the levels representing
one-half the respective target reporting levels specified for the
new trace-element protocol. These values were reported earlier in
OWQ Technical Memorandum 92.12 and are given in table 1.
Table 1.--Reporting limits of selected elements for NASQAN, 1991,
and the new part-per-billion (ppb) protocol
_________________________________________________________________
One-half target
1991 Target reporting
NASQAN reporting limit limit for
reporting limit 1/ for ppb protocol ppb protocol 2/
Element (ug/L) (ug/L) (ug/L)
_________________________________________________________________
Al 10 10 5.0
Ba 2 2 1
Be 0.5 0.5 0.25
Cd 1 1 0.5
Co 3 1 0.5
Cr 1 1 0.5
Cu 1 1 0.5
Fe 3 3 1.5
Pb 1 1 0.5
Mn 1 1 0.5
Mo 10 1 0.5
Ni 1 1 0.5
Ag 1 0.2 0.1
Zn 3 3 1.5
_________________________________________________________________
1/For samples in which specific conductance < 2,000 uS/cm.
2/Maximum limit set from all sources of contamination in the ppb
protocol.
The analytical data from this study are not presented in this
memo, but are available for review. Contact the Chief, Office of
Water Quality, for additional information.
MAJOR FINDINGS
1. Many of the "initial condition" blanks (DIW blanks processed
before any cleaning) contained trace-element concentrations in
excess of one-half the target RL, especially Al, Cu, and Zn. This
finding supports the need for a rigorous cleaning, beyond rinsing
only with DIW.
2. Dilute HNO3 and HCl solutions (approximately 5 percent by
volume) were equally effective for cleaning both plastic and
Teflon D-77 sampler caps, nozzles, bottles, and bags.
3. Carryover of chloride and nitrate from the use of HCl and HNO3,
respectively, was not evident for either the laboratory or field
cleaning procedure.
4. The laboratory cleaning procedure (detergent scrubbing and
soak, tap water rinse, dilute HCl soak, and copious DIW rinses)
was effective in reducing trace-element contamination to levels
well below one-half the target RLs for both plastic and Teflon
sampler components. Therefore, either plastic or Teflon
components can be used with the D-77 sampler for trace-element
sampling at the ppb level.
5. Both new and old plastic and Teflon D-77 components were
adequately cleaned by the laboratory cleaning procedure.
Therefore, both new and old components may be used with the new
ppb protocol.
6. The field cleaning procedure (dilute HCl rinses and copious DIW
rinses) was effective in reducing trace-element contamination for
both plastic and Teflon sampler components to levels below one-
half the target RLs for all constituents except Be. Blanks from
both the plastic and Teflon components were found to contain Be at
levels slightly above one-half the target RL (0.25 ug/L). Low-
level hits of Cu were also consistently found for both plastic and
Teflon components; however, detected levels were consistently
below one-half of the target RL (0.5 ug/L). Based on the test
results, the OWQ has revised the field cleaning procedure.
7. The following types of bags were evaluated: Teflon (Jensen
Inert and American Durafilm), and plastic (Glad and Reynolds Oven
brands). After a futile attempt to detergent wash Glad plastic
bags and Reynolds oven bags, the study team decided that this step
should be eliminated from the laboratory cleaning procedure (it is
possible to wash the thicker Teflon bags). Laboratory cleaning of
plastic and Teflon bags thus consisted of an acid (HCl) soak and
copious DIW rinses. Because plastic and oven bags are
inexpensive, they can be disposed of after use, which eliminates
the need for field cleaning. The field cleaning procedure was
effectively used on the Teflon bags. One of the plastic Glad bags
developed holes during the laboratory cleaning and rinsing
process; because oven bags are sturdier, they are the preferred
choice for non-Teflon bags. Based on this study, for use in D-77
bag samplers, Teflon bags are preferred, Reynolds Oven Bags are
acceptable, and the other tested bags are unacceptable for use
with the ppb protocol.
8. The laboratory cleaning procedure for plastic and Teflon bags
was effective in consistently reducing trace-element contamination
to levels below one-half of the target RLs for all constituents
except manganese (Mn) and zinc (Zn). Two of the 10 equipment
blanks for plastic bags contained Mn above one-half the target RL
(0.50 ug/L) (small plastic bag = 0.61 ug/L; large plastic bag =
0.50 ug/L). One of the 21 equipment blanks for plastic and Teflon
bags contained Zn above one-half the target RL (1.50 ug/L) (small
Teflon bag = 1.50 ug/L), although approximately 50 percent of all
blanks contained detectable levels of Zn. Based on these results,
acid soaking with copious DIW rinses is effective for cleaning
plastic and Teflon bags for all constituents except possibly Mn
and Zn. Projects that choose to use plastic and Teflon bags
should incorporate more than the normal percentage of equipment
blanks into their quality control plan to determine if
contamination from the sampler bag actually occurs.
SUMMARY
Previous studies have shown that the D-77 and DH-81 samplers are
the least contaminating samplers for dissolved trace-element
sample collection. This study was conducted to test the
effectiveness of procedures for cleaning the plastic and Teflon
components of these samplers. Only 3-liter D-77 bottles were
tested, but the results should apply to any size bottle made of
the same materials.
The study showed that (a) cleaning beyond DIW rinsing is
necessary, (b) the laboratory cleaning procedure is effective for
ppb-level work for both plastic and Teflon, and for both new and
old equipment, (c) the field cleaning procedure is not completely
effective and needed to be modified, (d) plastic bags can be
cleaned with acid (HCl) soaks and DIW rinsing prior to use, but
should be disposed of after use, and (e) Teflon bags can be
cleaned and reused.
Art Horowitz will be conducting training sessions in each of the
Regions on the new cleaning procedures beginning in April 1993.
Following training, side-by-side comparisons of the new and old
procedures will be done in at least one District in each Region.
The results will be evaluated, modifications will be made if
necessary, and additional training will then be completed. Full
implementation of the ppb sampling procedure is scheduled for
October 1993.
David A. Rickert
Chief, Office of Water Quality
This memorandum refers to Office of Water Quality Technical
Memorandum 92.12.
Key Words: Contamination, samplers, trace element
Distribution: A, B, S, FO, PO