Proficiency Testing (PT)

Laboratories are required to participate in at least one single-concentration proficiency testing study per certification or registration period for each analyte or analyte group identified by the department. For aqueous and solid matrices, laboratories shall analyze aqueous matrix (WP) proficiency testing samples for each combination of technique and analyte or analyte group in a laboratory’s fields of accreditation. For the drinking water matrix, laboratories shall analyze (WS) proficiency testing samples for each combination of method and analyte or analyte group in a laboratory’s fields of certification.

Which analytes require a PT?

'WS' PTs Only Allowed for Drinking Water
'WP' PTs Only Allowed for Aqueous/Solid Matrices

Use Only Approved Methodologies for PTs
PTs Must be Analyzed by Appropriate Technology
QCS vs. PT

"Solid" Matrix PTs Are Not Acceptable

graphic barring solid matrix PTs.
Wisconsin DNR does not accept solid matrix PTs.

Please note that solid-matrix (or 'real-world' sample) PTs are not acceptable to obtain/maintain accreditations under the Solid matrix. "WP" PT samples are required to satisfy PT requirements for any Solid matrix- technology-analyte combinations. If a lab is accredited for a given technology - analyte combination under both the Aqueous and Solid matrices, successful analysis of one WP PT for that analyte-technology combination will count towards both the Aqueous and Solid matrices.

Key PT-Related Dates

Wisconsin has several specific PT sample date requirements, which are described below.

'Date'= 'Study Close Date'. The study close date for the results submitted with applications must be no older than 6 months prior to the date the application is received by the WDNR.
Renewal PT Deadline= August 15. PTs required for annual accreditation renewal must be received by the Department on or before August 15 of each calendar year.
Application-related PTs must be < 6 months 'old'. For any initial or revised applications, any PT results required as part of the application must not be more than six (6) months (180 days) from the date which the application is received. For this determination, the 'Study Close Date' is used. Please plan accordingly.

'WS' PTs are only acceptable for Drinking Water matrix

Some parameters are available in both Water Supply (WS, Drinking Water) and Water Pollution (WP, Non-Potable Water) studies. The concentration ranges in these studies are different. More importantly, the acceptance criteria used to evaluate WS PT studies is defined by federal and state rule and differs from evaluation criteria used for WP studies. Therefore we only accept WS PT results for method-analyte combinations in the drinking water matrix.

'WP' PTs are only acceptable for Aqueous/Solid matrices

For the same reasons why WS PTs are only allowed for the drinking water matrix, only WP studies are acceptable for technology - analyte combinations under the aqueous and solid matrices.

PTs must be analyzed/reported using an approved method

Results reported from unapproved methods will not be accepted. Please note that in March 2007, the EPA promulgated a major final rule which made sweeping changes to approved methods for testing performed in support of the Clean Water Act (CWA) and Safe Drinking Water Act (SDWA). This effectively eliminated most of the old '200' series of methods for Flame and Graphite Furnace AA.

Another example is for BOD testing. The EPA finally eliminated its method 405.1 for BOD determinations. Actually, all method 405.1 ever did was instruct users to follow the Standard Methods procedure (5210 B) for BOD. Subsequently, any PT results submitted with the method code or method identifier of 405.1 will not be acceptable for meeting either application or accreditation renewal PT requirements

Download a list of "deleted" methods.

PT analytical technology must match your accreditation

Another problem that cropped up during the recent accreditation renewal was that labs analyzed PTs, but analyzed them using a technology different from the technology for which the lab was actually accredited. A number of labs were initially (9/1/08) accredited for various pesticides by both GC and GC/MS, but only submitted PT data analyzed using one of the technologies.

If Acme Labs reports PT results for lead using Standard Methods method 3111B (a FLAA technique) but the ACME lab is actually certified for lead only by GFAA, then the PT will not be valid for renewal of ACME Lab's accreditation. In fact, PTs are not even required for metals by FLAA. ACME would have to do (purchase and) analyze another PT, and use GFAA this time. This happened to a number of labs who routinely analyze alkalinity using colorimetric technology, yet the labs were certified only for alkalinity by titrimetry.

Check your Scope of Accreditation before (analyzing) reporting PT results and make sure you have all technologies covered for a given analyte before submitting your results to the PT Provider.
Remember: you can report results from several different technologies for any given PT. The only limitation is the volume of PT sample available for analysis. This happens frequently with wet chemistry.

A cross-reference list of technologies based on common wet chemistry methods is provided on our website.

Last Revised: Wednesday June 16 2010