United States Environmental Protection Agency	Office of Research and Development

National Exposure Research Laboratory
Research Abstract

Government Performance Results Act (GPRA) Goal #2
Annual Performance Measure #202

Significant Research Findings:

Method Development for the Determination of
Perchlorate in Drinking Water Using Ion Chromatography
With Mass Spectrometric Detection

Perchlorate (C104") is both a naturally occurring and manmade chemical. It
is used primarily as a solid oxidant in propellant products such as rockets,
pyrotechnics, air bag inflators and highway safety flares. Perchlorate was
found in drinking waters in the late 1990s and was placed in the EPA's
Unregulated Contaminant Monitoring Rule (UCMR) in 1999 to gather
nationwide occurrence data. Since that time, perchlorate has been found in
drinking waters in 34 states. Perchlorate is a known thyroid hormone
inhibitor. Thyroid hormones are critical for metabolism throughout life and
are critical for proper fetal brain development. The EPA Reference Dose
for perchlorate has not yet been determined, but the concentration of human
health concern in drinking water may be lower than what the only approved
EPA method for measuring perchlorate is capable of detecting (EPA
Method 314.0). That method uses ion chromatography to separate the
perchlorate ion from interfering ions followed by conductivity detection.
Because conductivity is a non-specific parameter, confirmation of
perchlorate is by retention time on the ion chromatography column. In
2002, the Office of Ground Water and Drinking Water (OGWDW) and the
National Exposure Research Laboratory undertook a collaborative research
effort to develop an analytical method for perchlorate with improved
selectivity and sensitivity that would be available for use in the event
perchlorate is regulated or if a second round of occurrence monitoring is
performed.

Perchlorate in drinking water was separated from potential interferences
using ion chromatography with a potassium hydroxide mobile phase. The
eluate from the chromatographic column was passed through a conductivity
suppressor to exchange the potassium ions of the mobile phase with
hydrogen so that perchlorate in a matrix of pure water could be introduced
into a mass spectrometer using an electrospray ionization interface. The
measured response in mass spectrometry, mass-to-charge ratio (m/z),

Scientific
Problem and
Policy Issues

Research
Approach


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provides specific information about perchlorate. There are two perchlorate
ions based on the 76% relative abundance of 35C1 (35C11604m/z = 99) and
the 24% relative abundance of 37C1 (37C11604m/z = 101). Using an
oxygen-18 enriched perchlorate internal standard, quantitation of
perchlorate was performed using the m/z 101 ion. Confirmation was made
by verifying the m/z 99/101 area count ratio and matching the retention
time of the labeled internal standard.

Results and	This method (U.S. EPA Method 330.0), combining ion chromatography

Impact	mass spectrometric detection, allows detection, confirmation, and

quantification of perchlorate in surface and ground waters sources, and in
finished drinking waters, at concentrations of less than 1 ng/L. The lowest
concentration minimum reporting limit of this new method is 0.1 ng/L,
whereas, the minimum reporting limit of Method 314.0 is 4 ng/L. In EPA's
preliminary risk assessment, currently under review by the National
Academy of Sciences, the concentration in drinking water protective of
human health may be as low as 1 |~ig/L. Massachusetts health officials have
adopted this level and California has set a preliminary safety standard of 6
|_ig/L . This new method for measuring perchlorate in drinking water at
0.1 |j,g/L will meet EPA's data quality objectives in the future collection of
nationwide occurrence data and support agency needs should a regulatory
determination be made.

Hedrick, E., T. Behymer, R. Slingsby and D. Munch, "U.S. EPA
Method 330.0: Determination of Perchlorate in Drinking Water by Ion
Chromatography with Suppressed Conductivity and Electrospray
Ionization Mass Spectrometry," National Exposure Research Laboratory,
Microbiological and Chemical Exposure Assessment Research Division,
Chemical Exposure Research Branch, 26 W. Martin Luther King Dr.,
Cincinnati, Ohio 45268.

Hedrick, Elizabeth and David Munch, "Measurement of perchlorate in
water by use of an 180-enriched isotopic standard and ion chromatography
with mass spectrometric detection," Journal of Chromatography A, 1039,
2004, pp. 83-88.

Hedrick, E.J., "Overview of Proposed EPA Method 330.0: Determination
of Perchlorate in Drinking Water by Suppressed Conductivity Ion
Chromatography and Mass Spectrometric Detection," Invited Speaker at
the Severn Trent 4th Annual Louisville Analytical Conference, Louisville,
KY, June 8-9, 2004.

Hedrick, E.J. and T.D. Behymer, "Development of a Better Method to
Identify and Measure Perchlorate in Drinking Water," Presented at the
EPA Science Forum 2004, Washington, DC, June 1-3, 2004.

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Hedrick, E. J., "Overview of a New EPA Method: Determination of
Perchlorate in Drinking Water by Ion Chromatography, Suppressed
Conductivity with Electrospray Ionization Mass Spectrometric Detection,"
Invited Speaker at the Texas Commission on Environmental Quality,
Environmental Trade Fair and Conference, Austin, TX, May 3-5, 2004.

Hedrick, E.J., and D.J. Munch, "Sub-ppb Quantitation and Confirmation of
Perchlorate in Drinking Waters Containing High Total Dissolved Solids
Using Ion Chromatography with Mass Spectrometric Detection,"

Presented at the American Water Works Association Water Quality
Technology Conference, Philadelphia, PA, November 2-6, 2003.

Hedrick, E.J. and D.J. Munch, "EPA Perchlorate Method Development
Activities," Invited Speaker at the Joint IDQTF/DoD EDQW Roundtable
State of the Art in Analysis of Perchlorate in Environmental Samples,
Dallas, TX, October 23, 2003

Hedrick, E.J., and D.J. Munch, "Measurement of Perchlorate in Water
Using an Oxygen-18 Enriched Isotope Standard and Ion Chromatography
Mass Spectrometric Detection," Presented at the International Ion
Chromatography Symposium, San Diego, CA, September 21-24, 2003.

Hedrick, E.J., "Methods Development to Improve Low-level Perchlorate
Detection in Drinking Water by Conductivity and Mass Spectrometry -
Issues and Impact," Invited Speaker at the Severn Trent 3rd Annual
Analytical Conference, Louisville, KY, June 17-18, 2003.

Hedrick, E.J., R. Slingsby, D.J. Munch, and D.P. Hautman, "Low-level
determination of perchlorate in drinking water using ion chromatography
mass spectrometry," Presented at: 51st ASMS Conference, Montreal,
Canada, June 8-12, 2003.

Future Research No further drinking water methods development work is required. Future

work will focus on application of the developed method to other matrices of
environmental interest such as high salinity waters and food grade
chemicals.

Questions and inquiries can be directed to:

Elizabeth Hedrick
USEPA

National Exposure Research Laboratory
26 W. Martin Luther King Dr.

Cincinnati, OH 45268-1564
Phone: (513) 569-7296
e-mail: Hedrick.elizabeth@epa.gov

Contacts for

Additional

Information


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Funding for this project was through the U.S. EPA'S Office of Research
and Development, National Exposure Research Laboratory, and the work
was conducted by the Microbiological and Chemical Exposure Assessment
Research Division.


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