NATIONAL WATER QUALITY LABORATORY
TECHNICAL MEMORANDUM 95-10
September 13, 1995
To: Assistant Chief Hydrologist for Technical Support
Regional Hydrologists
Chief, Office of Water Quality
Assistant Chief, Office of Water Quality
Acting Chief, NAWQA
Area Hydrologists
District Chiefs
Regional Water-Quality Specialists
Assistant Regional Hydrologists for NAWQA
District Water-Quality Specialists
Chiefs, NAWQA Study-Units
Administrative Officer, NWQL
Chief, Ocala Project Office
Chief, Yucca Mountain Project Office
QA Manager, Yucca Mountain Project
Chief, Branch of Technical Development & Quality Systems
Employees, National Water Quality Laboratory
From: Peter F. Rogerson, Chief
National Water Quality Laboratory
Branch of Analytical Services
Subject: Overview of the QA/QC plan for the Radchem/Stable Isotope contracts
at the NWQL
Author: Ann H. Mullin, Supervisory Radchem Unit Chemist, (303) 467-8235
(AHMULLIN)
Revision: None
SCOPE
The Districts are frequently asked by cooperators to submit a quality
assurance/quality control (QA/QC) plan for the analytical work listed in the
proposals. The purpose of this memo is to describe QA procedures and
standards in place at the National Water Quality Laboratory (NWQL) to monitor
the performance of the contract laboratories. This information may be useful
to the Districts in preparation of their QA/QC plans.
The NWQL has agreements with the Reston Stable Isotope Laboratory (RSIL) for
determining D/H, O-18/O-16, and S-34/S-32 and with the Menlo Park Isotope
Laboratory (MPIL) for determining tritium. The Reston lab also analyzes
O-18/O-16 and C-13/C-12 in samples of calcite and CO . The NWQL has
commercial contracts for determination of N-15/N-14 with Global Geochemistry
in California; C-14 and C-13/C-12 with the University of Waterloo in Ontario,
Canada; low-level tritium with the University of Miami in Florida; and
radiochemical constituents excluding C-14 and H-3 which are covered in other
contracts and excluding the in-house work gross alpha, gross beta, radon, and
laser uranium--with Quanterra-Richland in Washington.
A comprehensive QA/QC program is maintained by the NWQL for samples submitted
to the laboratories listed above. Blind QC samples are included in each batch
of samples analyzed by the RSIL--a minimum of 2 percent for 0-18/0-16 and D/H
and a minimum of 5 percent for S-34/S-32. In addition, all of the oxygen and
deuterium samples are analyzed in duplicate on different days.
Double-blind QC samples are submitted with each batch sent to MPIL and the
commercial laboratories. Duplicate samples for radiochemical analyses (which
includes tritium) must be within 2 sigma of one another. Spiked samples for
radiochemical analyses (which includes tritium) must be within 2 sigma of the
known value. For stable isotopes, the precision requirements are 1 sigma, as
follows:
0-18/0-16 within 0.15 permil*
Deuterium within 1.5 permil
C-13/C-12 within 0.15 permil
S-34/S-32 within 0.2 permil
N-15/N-14 within 0.2 permil
*Permil is parts per thousand
The contract labs run internal standards, duplicates, and blinds with each
batch of USGS samples. If these internal QC samples indicate a bias or
problem, corrective action is taken by the lab before data are reported. If
there is sufficient sample, the samples are re-run. If not, the samples
are reported "ruined during analysis."
If a District requests a rerun and the second value is not within 2 sigma of
the original value, a third run would be requested, providing that there is
sufficient sample. If there is not sufficient sample, the District will be
notified.
For radiochemical analyses at the contract lab, in addition to assessing the
data from the blind samples, the Radchem Unit at the NWQL also reviews (1) the
quarterly report from Quanterra listing data for all duplicate, blank, and
spiked samples that are analyzed with USGS samples; (2) Quanterra's results
for the U.S. Department of Energy Quality Assurance Program; and (3)
Quanterra's results for the U.S. Environmental Protection Agency Performance
Evaluation
Study (EPA) to ensure that Quanterra is within acceptable limits and is
maintaining EPA certification.
The NWQL does not have standards for solid samples for radiochemical or stable
isotope analysis. Also, no method is available for accurately spiking a
suspended sample. For these types of samples, the NWQL relies on duplicates
submitted by the Districts. These duplicates check the precision of the
methods.
On occasion, District personnel will contact the NWQL with concerns about
possible interferences with samples for specific radiochemical analyses. In
these cases, the NWQL will submit duplicate samples to check the precision and
will spike some of the duplicates to check recoveries and the method accuracy.
The duplicates and spiked samples are considered part of the NWQL QC plan and
costs are built into the District charges for the analytical work.
Districts with large radiochemical or stable isotope projects sometimes
contact the Radchem Unit requesting permission to submit some of their samples
in duplicate to be used as part of the NWQL QC plan. Such requests are
accommodated on a limited basis at no charge to the Districts. Because the
samples are analyzed in outside labs, the integrity of the results to be used
as part of the Districts' QC plans is not compromised.
There are advantages when the Districts to submit their radiochemical and
stable isotope samples through the NWQL. National programs such as National
Water Quality Assessment require use of the NWQL to ensure consistency. Other
WRD programs, such as Yucca Mountain, are required to use laboratories that
are on the USGS Branch of Technical Development & Quality Systems approved
list. The NWQL in-house and contract operations are on this approved list.
However, on the basis of QA/QC, there are two main advantages. First, QC
samples with known values are not always readily available to the Districts.
Radiochemical standards, when available, usually require a nuclear license
with the NRC. Thus the Districts typically have to rely on blanks and
duplicate samples that check only the precision, not the accuracy, of the
method. As previously noted, the NWQL adds blind QC samples to shipments,
thereby enabling Districts to also evaluate method accuracy. Second, costs
for QC sample analysis and interpretation are covered by the Radchem Unit.
The costs for these QC activities would have to be covered by the District
projects if they were to submit samples directly.
All QA/QC data produced by contract labs (both commerical and USGS) are
validated by the NWQL and are available to the Districts on request.
References: Prescribed Procedures for Measurement of Radioactivity in
Drinking Water EPA-600/4-80-032, August 1980
Impact on Database: None
Supercedes: None
Key Words: isotope, blind samples, radiochemical, permil, QA/QC
Distribution: See above plus the continua USGS.labnews, .waterquality &
.radchem; WRD Secretaries; Field and Project Offices