10 Replies Latest reply on Oct 3, 2018 3:14 PM by mkpbphd

    Passing a 525.3 DFTPP Tune Check on GC-QQQ

    mkpbphd

      We are currently working on running EPA 525.3 (and 625/8270) on our GC-QQQ. Our accrediting organization has said that they will consider it acceptable, as long as we meet all of the QC in the methods. Unfortunately, this includes passing a DFTPP tune check in scan, even though we will be running MRM. While the EPA 625 criteria are not compatible with the autotune results, the EPA 525 criteria are much broader (as they are intended for targeted analysis) and using autotune, the DFTPP check passes about a third of the time.

       

      I've reached out to a couple of the environmental experts at Agilent, but I figured I'd ask the community as well and see if anyone here has any ideas. We only need to be able to pass the tune check on Q1, and it's very close. When it fails, it's only one ion ratio, and only barely, 443 rel to 442 (~26%, limit 15-24%).


      One person suggested increasing the threshold in acquisition. I tried everything from 50 to 100000, but it didn't seem to have any effect.

       

      Does anyone know if there is something I can do within Custom/Advanced/Manual tune to improve just that ion ratio? I'm not comfortable enough with the function within advanced or manual to want to start playing around.

        • Re: Passing a 525.3 DFTPP Tune Check on GC-QQQ
          ron_tackett

          Since this has not been tested, have you tried lowering the 414 ratio in tune and see what happens with 442 and 443?

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            • Re: Passing a 525.3 DFTPP Tune Check on GC-QQQ
              mkpbphd

              I spent the last couple days playing around with the ratios and I think I've succeeded! Thanks Ron!

               

              Here's what I ended up doing, for anyone else that might be trying the same thing. First, I will say these conditions only work with the 5 ppm DFTPP solution specified by 525.3 and not the 50 ppm DFTPP solution specified by 625. Luckily, 625.1 also allows the use of less concentrated solutions. (However, to pass the new tailing requirements, Benzidine and Pentachlorophenol seem to need to be more concentrated than 5 ppm).

               

              To get a tune that passed DFTPP without sacrificing my sensitivity, I looked at my autotune report (see attached) and recalculated the ratios as if 219 was 100% (as the custom tune does not allow you to enter values >100). I then entered these values into the custom tune and started adjusting the 414 and 502 values. I found that it works best if I drop both of them together rather than just the 414. I was able to pass the DFTPP check by setting them both at 8%, but over several runs the result fluctuated between 23.5 and 24, which is too close to failing for my taste. I prefer to have a little wiggle room so that I hopefully won't have to re-tune and calibrate every day. With both set at 6%, I'm averaging 22% on my tune check, which is a bit more comfortable. (As you can see in the attached custom tune result, the actual ratio is closer to 8%.)

               

              In an unexpected bonus, I'm actually seeing increased responses for most of my compounds (organochlorine pesticides). The responses were highest when I had the custom tune set for 7 and 8%, but even with 6%, I'm seeing increased responses relative to the autotune conditions.

               

              Autotune.jpgCustom Tune.jpg

            • Re: Passing a 525.3 DFTPP Tune Check on GC-QQQ
              timstrutt

              Hi,

               

              You mentioned 8270. The method 8270E has been recently updated  (Promulgated in July:  https://www.epa.gov/sites/production/files/2017-04/documents/method_8260d_update_vi_final_03-13-2017_0.pdf  ) Appendix A lists 65 changes from 8270D and the method is more amenable for GC-MS/MS equipment (sections 1.3 and 1.5).

               

              For MS/MS SRM In section 6.1.3.3 "When analysis is performed using product ions for quantitation, it is not an appropriate verification of the system to perform DFTPP analysis and meet the criteria outlined in Sec.. 11.3.1 ." Section 11.3.1 is particularly helpful.

               

              "11.3.1.2 Use the DFTPP mass intensity criteria in the manufacturer's instructions as primary tuning acceptance criteria or those in Table 3 as default tuning acceptance criteria if the primary tuning criteria are not available. Alternatively, other documented tuning criteria may be used (e.g., CLP or Method 625)),, provided that method performance is not adversely affected. The analyst is always free to choose criteria that are more stringent than those included in this method or to use other documented criteria provided they are used consistently throughout the ICAL, calibration verification, an d sample analyses."

               

              For Table 3 "The criteria are taken from Reference 11 (Method 525.3 )"

               

              Regards,

              Tim

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                • Re: Passing a 525.3 DFTPP Tune Check on GC-QQQ
                  mkpbphd

                  Hi Tim!

                   

                  Yes, I'm aware of 8270E but we have not updated to it yet, as to the best of my knowledge is had not been officially promulgated. Do you know where the response to comments from the comment period (which closed in June 2017) is located? I can't find it.

                   

                  Unfortunately, ultimately, it is not relevant to my issue, as most of our analysis is going to be by 625 or 525 (wastewater for discharge permits and drinking water for our aquifer injection project). We will be using 8270 but only for a limited set of projects (TCLP extracts).

                   

                  While 625.1 mentions that GC/MS/MS is a technique that is great for matrix interferences and allows the use of it as a primary or confirmation analysis technique, there are no exceptions to the QC requirements (such as DFTPP) given in the remainder of the method text.

                   

                  Sec. 3.4: "The use of CI or MRM mass spectrometry may be utilized to support electron ionization (EI) mass spectrometry or as a primary method for identification and quantification. While the use of these enhanced techniques is encouraged, it is not required."

                   

                  It does, however, include an exception similar to that in 8270D allowing the use of alternative manufacturer or documented criteria. However, 525.3 has no such exception, as the criteria in 525.3 were broadened specifically to be more applicable to target analysis (the original DFTPP criteria were developed primarily for unknowns analysis, so that individual lab and library results would match). And as these additions to methods are very new, Agilent has not yet established/published alternative manufacturer criteria for the triple quad.

                   

                  As a result, in order for our analysis to proceed and to obtain accreditation for these methods, it was necessary for me to find a way to pass a DFTPP tune check by 525.3 criteria (525.3 specifies that you must run it in full scan, even if using SIM analysis). As you can see from my results above, I was able to do that.

                   

                  Thank you for your help, and if you have a link to the response to comments, I would love to see it. I wish that more of the methods were as updated to new technology as 8270E, since we all know that running a DFTPP tune check for MRM work is pointless (and 625.1 increased the frequency to every 12 hours). Unfortunately the methods are what they are, and for accreditation purposes, we have to work within the restrictions they give us.

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