New NWQL Method for Polar Pesticide Analysis--Executive Summary Date: Sun, 19 Jul 1998 10:52:03 -0400 From: Janice R Ward Reply-To: "Janice R Ward, Acting Chief, OWQ, Reston, VA" Organization: USGS To: owq@srv1rvares.er.usgs.gov, "A - Division Chief and Staff", "B - Branch Chiefs and Offices" Subject: [Fwd: New NWQL Method for Polar Pesticide Analysis--Executive Summary] Date: Thu, 09 Jul 1998 16:26:45 -0600 From: Barbara Kemp Reply-To: "Barbara L Kemp, Secretary (Office Automation), Denver, CO" To: "Janice R Ward, Acting Chief, OWQ, Reston, VA" , wqspecs@cstran.cr.usgs.gov, "B - Branch Chiefs and Offices", "DC - All District Chiefs" CC: "Robert S Williams Jr., Hydrologist, Denver, CO" , "Robert B Green, Supervisory Chemist, Denver, CO" , "Mark R Burkhardt, Chemist, Denver, CO" , "Jon W Raese, Tech Pubs Ed(Phy Sci)-Rep Spec, Denver, CO" , "Barbara L Kemp, Secretary (Office Automation), Denver, CO" Subject: New NWQL Method for Polar Pesticide Analysis--Executive Summary In Reply Refer To: Mail Stop 407 MEMORANDUM July 9, 1998 To: Office of Water Quality District Water Quality Specialists Regional Water Quality Specialists "B" Distribution "DC" Distribution From: Robert S. Williams, Jr., Chief National Water Quality Laboratory Branch of Analytical Services Subject: New NWQL Method for Polar Pesticide Analysis--Executive Summary At the recent Water-Quality Specialists' meeting in Las Vegas, it was requested that the NWQL provide more information regarding method development, Laboratory activities that might be of interest throughout the Water Resources Division, and planned changes in customer services. Our colleagues and customers want to be better informed regarding NWQL policies and procedures. To do a better job of providing news about NWQL activities, we plan to improve our communication through increased use of electronic mail, technical memos, the NWQL Newsletter, the usgs.labnews Discussion Group on the Internet, and continuing improvement of our Web site Home Page at . The NWQL also will use various forums, such as seminars and discussion groups, to provide information about our Laboratory. The attached documents were prepared in response to the request from the Water-Quality Specialists. Similar information will now be included in future NWQL Newsletters and in other communications from the NWQL. The attached Executive Summary contains the type of information that will be placed in the NWQL Newsletter. The full memorandum was originally sent to Schedule 2060 Review Team members. We invite our readers and customers to let us know how they regard our efforts and to offer suggestions for improvement as we strive to strengthen our operation. 2 Attachments: Executive Summary--New method being developed for determining polar organic pesticides Burkhardt Memorandum--Polar pesticide analysis by LC/MS: An update ATTACHMENT 1 - EXECUTIVE SUMMARY New Method Being Developed for Determining Polar Organic Pesticides A new liquid chromatography/mass spectrometry (LC/MS) method for determining polar organic pesticides and pesticide metabolites in water samples is expected to be available by spring 1999 from the National Water Quality Laboratory (NWQL). This new method is designed to replace the existing Schedule 2050, but to ensure consistent data quality, Schedule 2050 will remain available until the new method is fully developed and successfully implemented. The NWQL Methods Research and Development Program is designing this new method with knowledge gained from efforts to incrementally improve Schedule 2050. Mark Burkhardt, co-lead chemist on the project, said that the efforts in developing an interim method over the past 18 months have resulted in the following improvements: 1. A polymer-based solid-phase extraction cartridge demonstrates higher extraction efficiencies of selected compounds than the graphitized carbon cartridges used in Schedule 2050. 2. The use of acidified acetone instead of acidified methylene chloride/methanol as the elution solvent improves the recovery of selected compounds. It also reduces concentration-step time by about 25 minutes. 3. A mass spectrometer successfully resolves small concentrations of selected compounds from background interference caused by dissolved organic compounds (DOCs), which was not possible with the photodiode-array detection system used in the present method. Burkhardt said that in addition to these technical improvements, the extraction process will be automated and several new compounds will be added to the schedule. The new method is expected to be more rugged, accurate, and precise than the method it will replace. The new design is being drafted and will be reviewed by a joint team from NWQL and the National Water-Quality Assessment Program (NAWQA) prior to final approval. ATTACHMENT 2 - BURKHARDT MEMORANDUM Polar Pesticide Analysis by LC/MS: An Update MEMORANDUM April 20, 1998 To: Schedule 2060 Review Team Members From: Mark R. Burkhardt Chemist, Methods Research and Development Program National Water Quality Laboratory Subject: Polar Pesticide Analysis by LC/MS Update As part of the National Water Quality Laboratory's (NWQL's) continuing commitment to improve the accuracy and precision of all analytical methods, Schedule 2050 was jointly reviewed last August. Representatives from the National Water-Quality Assessment Program (NAWQA), Branch of Quality Systems, and the Office of Water Quality participated. At this meeting, we discussed a plan that would eventually lead to using a liquid chromatography/mass spectrometry (LC/MS) method for Schedule 2050 analytes and several additional compounds. The methodology, method comparability, data transfer, and potential impact on data quality and NWQL's customers were part of this discussion. In the meantime, the development of Schedule 2060 was judged to be the best approach to provide incremental improvements to Schedule 2050 until a LC/MS method was ready. In March of this year, when it became apparent that river-water samples with large concentrations of dissolved organic compounds (DOCs) interfered with the determination of small concentrations of target analytes, several alternatives were considered. During a progress review on March 16, Jeff Martin, Mark Burkhardt, Ron Brenton, Merle Shockey, and Bob Green agreed to stop further development of Schedule 2060 because of a technical limitation of the photodiode-array detection system. Development will be shifted entirely to a LC/MS method for pesticides in water rather than investing additional resources in Schedule 2060. The selectivity provided by mass spectrometric detection should eliminate the DOC interference. Schedule 2050 will remain on-line ensuring consistent data quality until a LC/MS method has been developed and implemented. The planning, optimization, and development processes for the LC/MS method have begun. The tentative date for availability of a LC/MS method for polar pesticides in water samples (based on the target analytes in Schedule 2050) is early next year. The following paragraphs summarize the history of Schedule 2060 development and provide additional details, including the recent decision to end further work. Background: The Methods Research and Development Program (MRDP) undertook the development of Schedule 2060 to add several analytes and provide a bridge between Schedule 2050 and a proposed LC/MS based method. Schedule 2060 was intended to provide incremental improvements over Schedule 2050 in 1997 and 1998 until a LC/MS method could be brought on-line in 1999 or 2000. The expected incremental improvements included automating the extraction process, using a solid-phase extraction cartridge that removed target analytes from environmental water samples more efficiently, and developing a single LC gradient for the separation of the target analytes. Initial success was achieved by replacing the graphitized carbon SPE cartridge with a polymer-based SPE cartridge. However, when the method was transferred to the Organic Chemistry Program in 1997, the analyte recoveries dropped from 80 to 90 percent to 20 to 40 percent. It was ultimately determined that the SPE cartridge manufacturer had changed the manufacturing procedure, thus altering the physical properties of the SPE cartridges. Once this problem was identified, additional testing was done to determine if a replacement SPE cartridge could be found or if a different elution solvent could be used with the polymer-based SPE cartridge. When the elution solvent was changed from methylene chloride/methanol to acidified acetone, the polymer-based SPE cartridge outperformed all other SPE cartridges tested for recovery and relative standard deviation. The acidified acetone removed the target analytes from the SPE cartridge without damaging the cartridge material. Recoveries in reagent-water and ground-water samples again ranged from 80 to 90 percent, and the transfer of the method to the Organic Chemistry Program resumed. Technical Limitation: During the week of March 8, 1998, a more important obstacle became apparent when analyzing river-water samples. It was demonstrated that small concentrations of target analytes in the presence of DOCs were not resolved by the photodiode-array detection system. The presence of DOCs masks the ultraviolet (UV) absorption spectra of small concentrations of the target analytes, making it impossible to qualify and quantify them with the detector. Rationale for Stopping Schedule 2060 Development: Unforeseen problems have resulted in a greatly increased development time for Schedule 2060. With the requirement for higher selectivity, the rapid maturation of the LC/MS technology and the likelihood of circumventing interferences with LC/MS, there are no longer any clear reasons for developing an interim method. Lessons Learned: Several important pieces of information have been gathered over the last 18 months during the development of Schedule 2060: 1. The polymer-based solid-phase extraction (SPE) cartridge has demonstrated higher extraction efficiencies of target analytes from water samples than the graphitized carbon cartridges used in Schedule 2050. 2. The use of acidified acetone instead of acidified methylene chloride/methanol as the elution solvent improves the recovery of the target analytes from the SPE cartridges. Using acidified acetone as the elution solvent has reduced the concentration-step time by about 25 minutes because it can be removed more easily than the methylene chloride/methanol mixture. 3. Small concentrations of target analytes in the presence of DOC interferences cannot be adequately quantified with a photodiode-array detection system, but can be resolved from the background DOC concentrations using a mass spectrometer. 4. The drafting of an implementation plan and the resulting verification process has been a useful exercise. An implementation plan for the LC/MS method will be drafted and reviewed by a NWQL/NAWQA team using a process similar to the one developed for the Schedule 2060 method. The plan will be used to transfer the method from MRDP to the Organic Chemistry Program in Production and provide data to relate Schedule 2050 to the new Schedule. The experience gained in developing Schedule 2060 will greatly reduce the effort required to develop and verify a LC/MS method. In effect, the methodology prior to the detection step in Schedule 2060 will be used in the new LC/MS method. The recent experience of the MRDP with LC/MS technology in developing other methods along with the separation plan developed for Schedule 2060 should lead to a rugged, accurate, and precise method to determine polar organic pesticides and pesticide metabolites. If you have additional questions or concerns, please contact me at mrburk@usgs.gov or (303) 467-8093. My thanks to everyone for their insight and helpful advice. cc: Chief, NWQL, MS 407 NWQL Senior Staff Janice Ward, OWQ, MS 412 Tim Miller, NAWQA, MS 413