Method 608

[COFSDFML27]

I'm currently using a ECD for Method 608, my boss wants to move this analisys using a triple quad, is this acceptable by ELAP? Thank you

[James_Ball]

From our experience unless it specifies MS detector in the method most won't let you substitute. We underwent NELAC accreditation last year and were told that we had to change the way we were doing our 624 QC, we were using straight +/- 20% for CCV evaluation and they said we had to use what was in the table in the method. Funny thing is some of those pass fail limits in the table are something like 20-200% recovery, but we were forced to change our SOPs to reflect that before being accredited.

If the analytes are listed in method 625 you may be able to substitute that, but it still won't cover using the instrument in MRM mode, only single quad mode.

[Yama001]

An MS based analysis can be very nice, particularly for confirmation, but there are some matrices where the interferences will be worse (at least from a single quad perspective) than an ECD method.

[bisnettrj2]

The method allows for the use of MS, provided you can demonstrate satisfactory performance of the method on your MS. As to whether NELAP will allow you to use a triple quad over a single quad, that might be a question for them to answer. http://www.nelac-institute.org/interpret-request.php I'd do my MDL/LOD/LOQ verifications using both techniques to make sure you can meet the method requirements using both techniques.


http://water.epa.gov/scitech/methods/cw ... cs_608.pdf

Section 1.2:

"...Method 625 provides gas chromatograph/mass spectrometer
(GC/MS) conditions appropriate for the qualitative and quantitative confirmation of
results for all of the parameters listed above, using the extract produced by this method."

"12.1 Table 1 summarizes the recommended operating conditions for the gas chromatograph.
Included in this table are retention times and MDL that can be achieved under these
conditions. Examples of the separations achieved by Column 1 are shown in Figures 1
to 10. Other packed or capillary (open-tubular) columns, chromatographic conditions,
or detectors may be used if the requirements of Section 8.2 are met."