Lab Matters Winter 2020 - Page 16

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 LAB MATTERS Winter 2020 PublicHealthLabs @APHL