New NWQL Method for Polar Pesticide Analysis--Executive Summary

Date: Sun, 19 Jul 1998 10:52:03 -0400
From: Janice R Ward <jward>
Reply-To: "Janice R Ward, Acting Chief, OWQ, Reston, VA" <jward>
Organization: USGS
To: owq@srv1rvares.er.usgs.gov,
        "A  - Division Chief and Staff"<distribution@usgs.gov>,
        "B  - Branch Chiefs and Offices"<distribution@usgs.gov>
Subject: [Fwd: New NWQL Method for Polar Pesticide Analysis--Executive Summary]

Date: Thu, 09 Jul 1998 16:26:45 -0600
From: Barbara Kemp <blkemp@cstran.cr.usgs.gov>
Reply-To: "Barbara L Kemp, Secretary (Office Automation), Denver, CO" <blkemp@cstran.cr.usgs.gov>

To: "Janice R Ward, Acting Chief, OWQ, Reston, VA" <jward>,
        wqspecs@cstran.cr.usgs.gov,
        "B  - Branch Chiefs and Offices"<distribution.b@cstran.cr.usgs.gov>,
        "DC - All District Chiefs"<distribution.dc@cstran.cr.usgs.gov>
CC: "Robert S Williams Jr., Hydrologist, Denver, CO" <bobwill@cstran.cr.usgs.gov>,
        "Robert B Green, Supervisory Chemist, Denver, CO" <rbgreen@cstran.cr.usgs.gov>,
        "Mark R Burkhardt, Chemist, Denver, CO" <mrburk@cstran.cr.usgs.gov>,
        "Jon W Raese, Tech Pubs Ed(Phy Sci)-Rep Spec, Denver, CO" <jwraese@cstran.cr.usgs.gov>,
        "Barbara L Kemp, Secretary (Office Automation), Denver, CO" <blkemp@cstran.cr.usgs.gov>
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
<http://wwwnwql.cr.usgs.gov/USGS>. 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