ENVIRONMENTAL HEALTH
Maine Proposes New Drinking Water Testing Method
Using LRN-C Equipment
By Jim Eaton, chemist, Maine State Health and Environmental Testing Laboratory and Stephanie Mathias, chemist, Maine State Health and
Environmental Testing Laboratory
Under US Environmental Protection
Agency (EPA) method 531.2, regular
monitoring for methylcarbamoyloximes
and N-methylcarbamates in drinking
water supplies is an important public
health requirement. The Maine State
Health and Environmental Testing
Laboratory (MEHETL) is the only laboratory
certified in the state to conduct EPA
Method 531.2. Approximately 100 public
water systems are reliant on MEHETL for
this critical testing. In November 2018,
the laboratory experienced instrumental
problems with its fluorescence detector
and post-column derivatization system
that resulted in prolonged offsite repair
and overhaul. As a result, the laboratory’s
certification for method 531.2 lapsed for
four months, customer samples were
untested and the laboratory’s license was
in jeopardy.
MEHETL recognized the value of
developing a robust alternate method
for these analytes. The triple quadrupole
mass spectrometer (triple quad)
normally used for Laboratory Response
Network for Chemical Threats (LRN-C)
activity was identified as a potential
replacement platform for the current
method. After researching alternatives,
MEHETL decided on a Restek carbamate
pesticides publication, which provided the
parameters needed to develop a viable
triple quad method. MEHETL applied this
method and produced data that indicated
it could be a good alternative to the
current EPA method.
Multipurposing in the Laboratory
Recognizing a potential efficiency and
flexibility for laboratories, MEHETL
investigated how this method could
be used for compliance purposes. The
state compliance officer could not
use this method for state-determined
SDWA compliance methods because
it was not EPA-approved. MEHETL
ultimately submitted this method to
EPA’s Alternative Test Procedure process
through the Office of Water’s Standards
and Risk Management Division’s Technical
Support Center in Cincinnati to determine
equivalence with method 531.2. The
Technical Support Center responded
quickly with approval to proceed, and
MEHETL developed a method and a
validation plan. At the time, there was
only one EPA-approved SDWA triple quad
method.
This new method has three main benefits.
First, the post column derivatization step
is eliminated which eliminates analyst
exposure to and disposal of methyl amine,
a hazardous substance. Second, an LC-MS/
MS analysis reduces analyst run time
from forty-five minutes to twelve minutes.
Third, LC-MS/MS analysis improves
throughput. In the current method, only
compound retention time is used for
identification. Mass spectrometry provides
an additional certainty by associating
specific mass fragments to a target
compound, allowing more confidence in
the customer’s results.
Getting the Word Out
In April 2019, MEHETL presented this
work to the Berkeley, CA LRN-C meeting
to recruit other labs to participate in the
EPA-outlined method validation study.
Utah, Alabama and Michigan agreed to
participate. The validation plan called
for the three labs to run seven replicates
in tap and deionized water at 1 ppb, 2
ppb and 15 ppb spiking levels. Maine
ran two additional matrices, a high salt
and a high total organic carbon matrix.
MEHETL provided these labs with the
method parameters and quality control
requirements, and shipped empty treated
sample bottles to run replicates.
MEHETL Chemist Stephanie Mathias analyzes for methylcarbamoyloximes and N-methylcarbamates in drinking water using a Sciex
triple quadrupole mass spectrometer. Photo: Jim Eaton
14
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