Protocols for Cleaning a Teflon Cone Splitter to Produce Contaminant-Free Subsamples for Subsequent Determinations of Trace Elements
In Reply Refer To: February 7, 1997
Mail Stop 412
OFFICE OF WATER QUALITY TECHNICAL MEMORANDUM 97.03
Subject: Protocols for Cleaning a Teflon Cone Splitter to Produce
Contaminant-Free Subsamples for Subsequent Determinations
of Trace Elements
SYNOPSIS
This memorandum describes laboratory and field protocols for cleaning a
Teflon cone splitter to collect a contaminant-free subsample for
subsequent determination of trace elements. Also described is the testing
that was done to determine if these protocols allow production of
contaminant-free (at the microgram-per-liter level) trace-element data
from filtered surface-water samples. The laboratory-cleaning
("laboratory") protocol is adapted from methods developed and tested by
the Office of Water Quality (OWQ) and the National Water Quality
Assessment (NAWQA) Program. The field-cleaning ("field") protocol is
supported by data from tests performed by the Upper Colorado River Basin
Study Unit (UCOL) of the NAWQA.
Results of tests for the field protocol, and an evaluation of information
available for the laboratory protocol, show that these protocols can be
used to clean a Teflon cone splitter to produce contaminant-free
subsamples for analysis of trace elements. These protocols do not address
the use of methanol and the additional cleaning steps that may be
required when splitting samples to be analyzed for organic constituents.
Because the possibility of unpredictable and erratic contamination always
exists, adequate quality-control measures are required (Horowitz and
others, 1994).
BACKGROUND
The Water Resources Division Instrument Committee (ICOM) funded a series
of tests to develop nationally consistent guidelines for selecting,
cleaning, and using the cone splitter and the
U.S. Geological Survey (USGS) churn splitter. One component of these
tests focuses on cleaning a Teflon cone splitter to produce
contaminant-free subsamples for subsequent analysis of trace elements. To
this end, the Office of Water Quality, in cooperation with the NAWQA,
developed two protocols: a laboratory-cleaning protocol adapted from a
procedure described by Shelton (1994, p.13) and Horowitz and others
(1994, pp. 41-44) and a field-cleaning protocol based on a procedure for
cleaning a USGS churn splitter described by Horowitz and others (1994,
pp. 52-56).
The efficacy of the laboratory protocol is supported by unpublished data
collected under the NAWQA program. The field protocol was tested by the
NAWQA UCOL under the guidance of Bob Boulger (Grand Junction, Colorado)
at six surface-water sites affected by acid-mine drainage. Principal
differences between the laboratory and field protocols are:
1. The laboratory protocol entails complete disassembly of the
cone splitter, whereas the field protocol does not require
complete disassembly except after obtaining subsamples of
water that is very turbid or is suspected of being highly
contaminated. If that condition exists, the laboratory
protocol is required.
2. The laboratory protocol includes a detergent
soak-and-scrubbing step, whereas no detergent is used to
clean the cone splitter in the field protocol.
3. The laboratory protocol includes a 30-minute acid soak,
whereas a single acid rinse is used in the field protocol.
PROTOCOLS FOR CLEANING A TEFLON CONE SPLITTER FOR TRACE ELEMENTS
A. LABORATORY CLEANING PROTOCOL
The laboratory cleaning is required for new or previously used equipment.
It may be done in a laboratory or another suitable location, such as a
motel room. This procedure also should be followed when the splitter has
been used at a site with known or suspected high concentrations of trace
elements. (NOTE: this procedure can only be done outside of the
laboratory if the 5-percent hydrochloric acid (HCl) used is initially
prepared in a laboratory):
1. Fully disassemble the cone splitter, carefully safeguarding
all of the small parts.
2. Soak the splitter parts and Teflon tubing for 30 minutes in a
2-percent or less solution of phosphate-free detergent. The
amount of detergent used depends on the hardness of the tap
water. Wearing disposable gloves, scrub with a nonmetallic
brush. A metal-free swab such as those designed for cleaning
video cassette recorders can be used to clean the small
splitter parts.
3. Change gloves and rinse thoroughly with warm tap water to
remove all soap residue.
4. Soak non-metal parts for 30 minutes in a 5-percent, by
volume, solution of HCl. Carefully swirl the acid solution
several times during the 30-minutes soak to enhance
desorption of trace elements not removed during the detergent
washing process. The used acid/water solution should be
placed in a neutralization container for proper disposal
(Horowitz and others, 1994, p. 12).
5. Change gloves and rinse three times with 1-liter aliquots of
deionized water. Reassemble the cone splitter.
NOTE: This cleaning protocol is approved only for trace-element
samples. If organic samples are collected, a methanol rinse is
needed (see Shelton, 1994).
6. Place the cone splitter in a new plastic bag and seal; store
in a plastic storage container or a second plastic bag for
transport.
Validation of Laboratory Protocol:
The laboratory protocol, adapted from a procedure developed by the OWQ
and the NAWQA (Shelton, 1994, p. 13), is supported by data collected
operationally by the NAWQA. Although very little data was collected to
validate the laboratory protocol, its efficacy can be inferred from that
fact that its requirements (disassembly, detergent rinse, and a 30-minute
acid soak) are more stringent than those for the field cleaning protocol,
which provided acceptable results. In combination, this information has
led to the laboratory protocol's Division-wide acceptance.
B. FIELD CLEANING PROTOCOL
The field-cleaning protocol is used if the splitter is to be used at
another site during the same sampling trip. (The laboratory protocol is
required if the splitter has been allowed to dry before being cleaned or
if the splitter was used at a site with known or suspected high
concentrations of trace elements.) After processing an environmental
sample and before leaving a field site, clean the Teflon cone splitter as
follows:
1. Inspect the cone splitter. If it appears dirty, is suspected
of being contaminated, or has been allowed to dry, then it
should be fully disassembled and cleaned using the laboratory
cleaning protocol described above. Otherwise, proceed as
outlined below.
2. Discard any used plastic bags from storing cone splitter.
3. Rinse the splitter thoroughly with deionized water.
4. Wearing disposable gloves, rinse by passing one liter of
5-percent by volume HCL through the cone splitter. The used
acid/water solution should be placed in a neutralization
container for proper disposal (Horowitz and others, 1994,
p. 12).
NOTE: This cleaning protocol is approved only for trace-element
samples. If organic samples are collected, a methanol rinse is
needed (see Shelton, 1994).
5. Change gloves and rinse the cone splitter with at least three
1-liter aliquots of deionized water.
6. Pack the cone splitter in a new plastic bag and seal; store
in a plastic storage container or a second plastic bag for
transport to the next site.
Field Protocol Test Procedure:
Two Teflon cone splitters of standard design manufactured by Geotech
Environmental Equipment, Inc., were used in the tests. Although Teflon
screens in the cylindrical reservoir normally are used to prevent larger
detritus from passing through the cone splitter and into subsamples, no
screens were available for use in these tests. The tests were performed
with the cone splitter enclosed in a plastic bag chamber to minimize the
potential for introducing air-borne contaminants.
At each of six sites during a regularly scheduled field trip,
environmental samples of water affected by acid mine drainage were
processed through the cone splitter. After the environmental sample was
processed at the first site, the wet cone splitter was placed in double
plastic bags, returned to a motel room, cleaned using the laboratory
protocol, and reassembled, placed in a clean set of plastic bags, and
transported to the second site. At the second, and each of four
subsequent sites, an environmental sample was processed through the cone
splitter and the splitter was cleaned using the field protocol. After
each field cleaning, field-blank subsamples were obtained, and the
splitter was placed in clean, double plastic bags and then in the field
vehicle for transport to the next site.
Blank samples were analyzed for trace elements and other ions (schedule
172) at the National Water-Quality Laboratory (NWQL). Environmental
samples were analyzed at the NWQL using NAWQA schedule 2703. The
constituents analyzed were aluminum, antimony, barium, beryllium,
cadmium, chromium, cobalt, copper, iron, lead, manganese, molybdenum,
nickel, silver, uranium, and zinc (table 1).
Detailed information on the test procedure and results can be found in
Bob Boulger's unpublished report, "Test of Field Cleaning of Teflon Cone
Splitter for Trace metals Sample Processing." Instructions for obtaining
an electronic copy of this document are provided at the end of this
memorandum.
Validation of Field Protocol:
Table 1 shows analytical results from blank and environmental samples
collected by the UCOL at six sites in October 1995. Of the five trace
elements detected in the field blanks, only two -- copper and zinc --
were detected in blanks obtained after cleaning equipment at each of two
or more sites. Detectable trace-element concentrations in the blanks were
less than about twice the environmental-sample (schedule 2703) method
detection limit. In two cases, zinc was detected in field blanks (0.7 &
0.6 micrograms/liter) taken after cleaning a cone splitter exposed to a
high environmental concentration (3,100 & 1,400 micrograms/Liter,
respectively). Also, the iron concentration in one field blank
(6 micrograms/Liter) was found to exceed that of the environmental sample
(4 micrograms/Liter).
The type, frequency, and low concentrations detected in blank samples
were considered typical of random detections characteristic of such
quality-control testing. Furthermore, when cross-contamination does
occur, it is insignificant with respect to the associated concentrations
in the previously processed environmental sample, and (or) is random in
nature. Overall, the results support the conclusion that the field
protocol can be used to clean a Teflon cone splitter sufficiently to
minimize cross-contamination of trace-element samples.
EQUIPMENT AND FIELD BLANKS
Equipment and field blanks should be processed in accordance with the
procedures described in Horowitz and others (1994) and Shelton (1994).
Equipment blanks are to be processed at least once a year for each set of
sampling equipment. The number of field blanks required depends on
individual project's data-quality objectives.
CONCLUSIONS
The tests described in this memo show that Teflon cone splitter can be
cleaned sufficiently using the previously described protocols to produce
contaminant-free subsamples for subsequent analysis of trace elements.
These protocols do not address the additional cleaning steps that are
required when splitting samples to be analyzed for organic constituents.
Because the possibility of unpredictable, erratic contamination always
exists, adequate quality-control measures are required (Horowitz and
others, 1994).
REFERENCES
Horowitz, A.J., Demas, C.R., Fitzgerald, K.K., Miller, T.L., and
Rickert, D.R., 1994, U.S. Geological Survey protocol of the collection
and processing of surface-water samples for the subsequent
determination of inorganic constituents in filtered water: Open-File
Report 94-539, 57 p.
Shelton, L.R., 1994, Field guide for collecting and processing
stream-water samples of the National Water Quality Assessment Program:
Open-File Report 94-455, 42 p.
INSTRUCTIONS FOR OBTAINING FIELD PROTOCOL TEST INFORMATION
Bob Boulger's unpublished report, "Test of Field Cleaning of Teflon Cone
Splitter for Trace metals Sample Processing." Instructions for obtaining
an electronic copy of this document in FrameMaker4 format via the file
transfer protocol follow:
type: ftp 136.177.10.10
at login prompt, type: anonymous
at id prompt, type: anonymous
type: cd pub/conesplitter/
type: binary
type: get tcs.experiment.report/
David A. Rickert /S/
Chief, Office of Water Quality
Attachment
This memorandum does not supercede any existing memoranda.
Distribution: A, B, S, FO, PO
District Water-Quality Specialists
Regional Water-Quality Specialists NR, SR, CR, WR
Attachment
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Constituent concentrations in environmental1 and blank subsamples from a Teflon cone splitter for six surface-water sites, October 1995.
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| Constituent Concentrations
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| | Site 1 | Site 2 | Site 3 | Site 4 | Site 5 | Site 6 |
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| Constituent| Method | Envirom | Equip- | Envirom | Field | Envirom | Field | Envirom | Field | Environ | Field | Envirom | Field |
| in ug/L | Detection| ental | ment | ental | Blank | ental | Blank | ental | Blank | mental | Blank | ental | Blank |
| | Level | Sample | Blank2 | Sample | | Sample | | Sample | | Sample | | Sample | |
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| Aluminum | 0.3 | 4 | <0.3 | 21,0003 | <0.3 | 600 | <0.3 | 30 | 0.4 | 10 | <0.3 | 5.0 | <0.3 |
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| Antimony | 0.2 | <1 | <0.2 | <1 | <0.2 | <1 | <0.2 | <1 | <0.2 | <1 | <0.2 | <1 | <0.2 |
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| Barium | 0.2 | 443 | <0.2 | 19 | <0.2 | 43 | <0.2 | 43 | <0.2 | 24 | <0.2 | 39 | <0.2 |
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| Beryllium | 0.2 | <1 | <0.2 | <1 | <0.2 | <1 | <0.2 | <1 | <0.2 | <1 | <0.2 | <1 | <0.2 |
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| Cadmium | 0.3 | <1 | <0.3 | 5 | <0.3 | 2 | <0.3 | <1 | <0.3 | 73 | <0.3 | 4 | <0.3 |
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| Chromium | 0.2 | <1 | <0.02 | 43 | <0.02 | <1 | <0.2 | <1 | <0.2 | <1 | <0.2 | <1 | 0.3 |
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| Cobalt | 0.2 | <1 | <0.2 | 3603 | <0.2 | 11 | <0.2 | 7 | <0.2 | <1 | <0.2 | <1 | <0.2 |
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| Copper | 0.2 | 2 | <0.2 | 8703 | 0.2 | 170 | <0.2 | 5 | <0.2 | 1 | 0.4 | <1 | 0.3 |
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| Iron | 3.0 | <3 | <3 | 12,0003 | <3 | 190 | <3 | 4 | 6 | 13 | <3 | 8 | <3 |
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| Lead | 0.3 | <1 | <0.3 | 393 | <0.3 | 1 | <0.3 | <1 | <0.3 | 7 | <0.3 | 2 | <0.3 |
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| Manganese | 0.1 | 36 | <0.1 | 1,7003 | <0.1 | 480 | <0.1 | 370 | <0.1 | 26 | <0.1 | 15 | <0.1 |
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| Molybdenum | 0.2 | 43 | <0.2 | <1 | <0.2 | <1 | <0.2 | 2 | <0.2 | <1 | <0.2 | <1 | <0.2 |
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| Nickel | 0.5 | 2 | <0.5 | 293 | <0.5 | 10 | <0.5 | 8 | <0.5 | 2 | <0.5 | 1 | <0.5 |
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| Silver | 0.2 | <1 | <0.2 | <1 | <0.2 | <1 | <0.2 | <1 | <0.2 | <1 | <0.2 | <1 | <0.2 |
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| Uranium | 0.2 | <1 | <0.2 | <1 | <0.2 | <1 | <0.2 | <1 | <0.2 | <1 | <0.2 | <1 | <0.2 |
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| Zinc | 0.5 | 170 | <0.5 | 1,300 | <0.5 | 430 | <0.5 | 120 | <0.5 | 3,1003 | 0.7 | 1,400 | 0.6 |
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| 1Minimum reporting level for all environmental samples is 1.0 micrograms/Liter. |
| |
| 2The acid-rinse cleaning step for the equipment blank was preceded by soaking a disassembled cone splitter in phosphate-free |
| detergent for 30 minutes, followed by 3 DIW rinses before reassembly. |
| |
| 3Maximum constituent concentration in the six environmental sample. |
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