Proficiency testing WEPAL-QUASIMEME

Wageningen University & Research has advanced facilities for proficiency testing and reference material covered within WEPAL-QUASIMEME. Routine laboratory performance studies are organised by WEPAL-QUASIMEME and provide the basis of external quality assurance for institutes that make regular chemical measurements in the terrestrial, aquatic and/or marine environment. In total, nine accredited proficiency testing programmes are offered to laboratories worldwide.

Proficiency tests

Reference materials

Catalogue 2025

What is Proficiency testing?

Proficiency testing determines the performance of individual laboratories for specific tests or measurements and is used to monitor laboratories’ continuing performance. Proficiency testing is also called interlaboratory comparison. Proficiency testing compares the measuring results obtained by the participating laboratories.

About

WEPAL-QUASIMEME is part of Wageningen Research, the Netherlands (Chamber of Commerce no. 09098104) and offers accredited proficiency testing programmes in environmental matrices for laboratories world-wide.
Accreditation is according to ISO17043 and granted by the Dutch Accreditation Council RvA a co-signatory to the ILAC and IAF Multilateral Agreements.

Declaration of accreditation

RvA Scope R002

WEPAL-QUASIMEME Proficiency tests

FAQ

Who is WEPAL-QUASIMEME?

WEPAL-QUASIMEME is an organiser for proficiency tests in environmental matrices with global participation. WEPAL-QUASIMEME offers proficiency tests related to the terrestrial environment (soil, plants, manure, compost and biomass), the freshwater environment (freshwater, wastewater and sediment), the marine environment (seawater, marine sediment, biota and shellfish toxins).

WEPAL-QUASIMEME is more than a proficiency testing scheme. The routine laboratory performance studies of WEPAL-QUASIMEME provide the basis of external quality assurance for institutes that make regular chemical measurements in the terrestrial, aquatic and marine enviroment. Most studies have two or four rounds per annum with per round a minimum of two test materials containing the analytes at different concentrations.

What does WEPAL-QUASIMEME offer?

WEPAL-QUASIMEME offers worldwide accredited proficiency testing programmes (ISO17043) and samples from the proficiency test schemes are available as reference material in our webshop.

Soil	International Soil-analytical Exchange Programme	ISE
Freshwater Sediment	International Sediment Exchange for tests on Organic Contaminants	SETOC
Marine Sediment	Marine Sediment Exchange Programme	MS
Seawater	Marine Aquatic Exchange Programmes	AQ
Fresh- and wastewater	Fresh- and wastewater Exchange Programmes	FW
Plants	International Plant-analytical Exchange Programme	IPE
Biota	Marine Biota Exchange Programmes	BT
Shellfish Toxins	Marine Shellfish toxins Exchange Programmes	BT
Manure & Compost	Manure and Refuse Exchange Programme	MARSEP
Biomass	Biomass Exchange Programme	BIMEP
Special excercises	Development excercises	DE

Why should I participate in Proficiency testing

Participation in WEPAL-QUASIMEME Proficiency tests allows your laboratory to compare your performance to those of other, similar laboratories. Proficiency testing is an essential element of laboratory quality assurance. The presence of systematic errors and/or random errors will be revealed, which allows your laboratory to take - if it feels necessary - corrective actions to improve the performance. Each laboratory gets a performance score (z’-score) for each reported test result. This score will prove the laboratory's good performance. Proof which can be used to convince your staff, your clients and your National Accreditation Body.

Validate internal laboratory Quality Assurance.
Beneficial for method development and improvement.
Support accreditation (e.g. ISO17025).
Support QA of environmental monitoring data.
Provide data for national or international programmes.

Do I need Proficiency testing?

Yes, if your laboratory wants to comply with international standards (ISO) and (inter)national legislation regular participation in Proficiency testing is mandatory. Proficiency tests are a basis for the integrity and trust of the customer, accreditation body, and management. Regular participation to Proficiency tests is prescribed in the ISO17025. National accreditation bodies (NAB) will audit whether your laboratory participates in relevant schemes and how the evaluation of the results is implemented in your quality system.

What are my benefits of routine Proficiency testing

Validate internal laboratory Quality Assurance.
Beneficial for method development and improvement.
Support accreditation (e.g. ISO17025).
Support QA of environmental monitoring data.
Provide data for national or international programmes.

Perhaps as importantly for the technical performance of the laboratory, regular Proficiency testing provides independent feedback on the quality of analytical results, enabling your laboratory to monitor and improve performance over time.

Why should I choose for WEPAL-QUASIMEME?

WEPAL-QUASIMEME has over 65 (!) years of experience in Proficiency testing.
Participation is open to all laboratories involved in the offered matrices.
The vast number of determinands to choose from range from elements, chemical pollutants, toxins, and nutritional values to microplastics and human and animal pathogens.
WEPAL-QUASIMEME Proficiency tests are recognised by the National Accreditation Bodies. The organisation is compliant to ISO17043 and accredited by the Dutch Accreditation Council RvA.
All received samples are guaranteed homogeneous and stable for the objective of the test.
Track trace information of shipped packages is available.
WEPAL-QUASIMEME offers competitive fees.
Participants in WEPAL-QUASIMEME programmes are entitled to discounts for multiple orders e.g. Proficiency testing programmes, available reference materials and other services.
Determinands can be added to a program free of charge when possible.
Reports are strictly confidential and published within four weeks after the submission deadline.
With regular questionnaires WEPAL-QUASIMEME investigates your needs to improve the quality of the services provided.

What to expect from WEPAL-QUASIMEME?

Natural test materials of relevant matrices with determinands at realistic concentrations.
Test materials with full evidence of homogeneity and stability for the duration of the test.
Clear protocols how to handle the test materials.
Full performance assessment based on robust statistics, performance summary sheets and exercise reports.
Confidential information on own laboratory performance and anonymised results from all participants.
Method information about the methods used by participants.
Workshops for discussion and improvement in methodology.
A Helpdesk, which is supported by experts in the field.
News, workshops and conferences.

How does my participation work?

In WEPAL-QUASIMEME Proficiency tests the participating laboratories receive at least two samples per program/period. Each laboratory analyses the samples according to the method used in their normal routine and reports its results to WEPAL-QUASIMEME. The analytical results reported by each laboratory are compared to the reference value for that measurand. The reference value (consensus value) for WEPAL-QUASIMEME is determined using robust statistics.

What is the added value of my participation?

After receiving a Proficiency test report, the scores can be assessed on performance. In the event of poor performance, you are able to take corrective measures to properly guarantee the quality of your laboratory. Internally, the obtained Proficiency test material and/or the results of the Proficiency test can also be used for other daily quality assurance purposes, such as specific validations or harmonization of new analysis methods or sampling techniques. An example of this is the determination of the precision and correctness in varying matrices and parameters.

How do I subscribe to a WEPAL-QUASIMEME interlaboratory study?

Fill in the application form here
Select the programmes and rounds you wish to subscribe to.
It is strongly advised to join each round organised for a selected exercise in a specific year. Nevertheless, it is also possible to join a single round or a selection of different rounds.
When your laboratory needs a proforma invoice first, you can request a quotation in the application process.

What are the rules for testing a Proficiency test sample

A PT sample should be treated and tested exactly like any other sample that is tested by the participating laboratory, which is a requirement from ISO17025 and ISO17043. It should not receive any special treatment or attention. Excessive testing is not allowed. Only when the laboratory performs a test in duplicate routinely, the PT sample may also be tested in duplicate. No extra QC, nor extra calibration may be done that is deviating from the routine procedure that is used for regular samples to be tested. Also it is not allowed to contact other participating laboratories about the test results on the PT sample before the final PT report is published.

What are the terms of participation?

Terms & Conditions WEPAL-QUASIMEME

Can I report my results electronically?

Yes. Subscribe to one of the WEPAL-QUASIMEME Proficiency tests gives you admittance to the members website. Here you can submit your analytical data. Your data are stored directly in the WEPAL-QUASIMEME database, including a data check. Adding and changing the data is possible until the deadline of the current period.

How is my confidentiality guaranteed?

WEPAL-QUASIMEME is designed to support the quality systems of laboratories. The information provided can be used by the laboratory for accreditation and for submission of data to monitoring, research or contracted organizations. It is the full responsibility of the laboratory to disclose information on its participation in WEPAL-QUASIMEME and its performance.
While WEPAL-QUASIMEME gives full support to each laboratory's quality system, it is not in itself part of that system. In setting this standard of confidentiality WEPAL-QUASIMEME maintains a position of impartiality. Support can be given to a laboratory which may requests assistance to improve performance in a particular study, for instance using the network to enable a participant to contact an experienced laboratory who can provide guidance and specific information. The laboratory itself decides when, if and to whom it makes information on its methods and performance available.
The following statements refer to data and information.

WEPAL-QUASIMEME complies with the European General Data Protection Regulation (Directive 95/46/EC).
All reports and information on the performance of individual participants will remain confidential within the WEPAL-QUASIMEME team. WEPAL-QUASIMEME will not convey any information on data generated by a specific participant in the laboratory performance study to any third party without permission of the participant. This also includes the transfer of information from one participant to another within the proficiency testing studies
All individual sets of data generated by a participant in the WEPAL-QUASIMEME studies including information on the assessment of performance of the laboratory such as Z-scores or comments on laboratory performance shall remain the property of the laboratory submitting these data.
WEPAL-QUASIMEME is allowed to use data of laboratories for studies and publications when the data are made anonymous and cannot be traced back to the laboratory. Examples of such studies include papers on statistics or evaluations of performance criteria.
Participants may use data and information extracted from WEPAL-QUASIMEME reports after written permission from WEPAL-QUASIMEME with due acknowledgement to WEPAL-QUASIMEME.
All general comments made by the WEPAL-QUASIMEME assessors on any study, where there is no specific reference to any identifiable laboratory, shall remain the property of WEPAL-QUASIMEME and be available for publication.
WEPAL-QUASIMEME strongly recommends each participant to make full use of their own study performance results in support of their Quality System for chemical measurements.

What are the deadlines for submission of results?

Each round runs for approximately three months (January-March, April-June, July-September and October-December). Participants can send in results during the entire period of each round. Deadlines for each round are presented in the table below.

Programme	R1	R2	R3	R4
Soil (ISE)	31/3	30/6	30/9	31/12
Plants (IPE)	31/3	30/6	30/9	31/12
Freshwater S.	31/3	30/6	30/9	31/12
Marine S.	30/6	31/1
Seawater (SQ)	30/6	31/1
Biota (BT	30/6	31/1
Shellfish T.	30/6	31/1
Manure & C.	31/3	30/6	30/9	31/12
Biomass		30/6		31/12

Can I purchase extra samples?

Yes. If you participate for many determinands, it is possible the supplied amount of material is less than needed, in that case you can ask for additional samples against a reduced price.

What type of report will I receive?

When participating in a WEPAL-QUASIMEME proficiency test programme, you may receive three types of reports during the annual cycle.

The individual evaluating report of your performance (Z-scores) in a round of a proficiency test programme presented as .pdf and as .csv file, that can be imported directly into your quality system
A periodic report with the testing results of all participating laboratories in a certain round
An annual report summarizing the overall testing results of the proficiency test programmes from WEPAL on soil, plant, freshwater sediment, biomass and manure & compost.

The results of your determinations are processed at WEPAL-QUASIMEME and published under confidential code names.

Content

The WEPAL-QUASIMEME reports contain:

all individual data with information about the method used (MIC)
a statistical evaluation
for QUASIMEME a table with ranked performance
a summary of the results for each sample
z'-score plots based on consensus values per determinand/matrix combination using robust statistics showing the deviation from the reference value (see graph).
other graphical information (ranked results and histograms)

Click here to get a glimpse of what to expect in a report.

Method Indicating Code (MIC)

WEPAL-QUASIMEME provides all reported results with a Method Indicating Code (MIC). The code indicates the critical steps in the procedure of analysis that can affect the results. This offers all participants the possibility to compare the results of their analytical procedures more specifically with the results of other participants.

Can I purchase reference materials?

Yes. Samples from previous Proficiency tests are being sold as reference materials and can be used for method development or as reference samples for internal quality control. The samples are accompanied by a “Certificate of Analysis” providing information gathered from the results of the WEPAL-QUASIMEME PT schemes, such as:

the consensus value: the mean value of the dataset obtained from the PT, calculated with robust statistics
the standard deviation and coefficient of variation
number of results used to calculate the consensus value
median and MAD (Median of Absolute Deviation)

An overview of the reference materials and more information about how to order can be found in the WEPAL-QUASIMEME webshop.

Which additional services does WEPAL-QUASIMEME offer?

Option for ordering certified samples used in our regular proficiency testing scheme.
Preparation of internal reference materials from material collected and offered by your own laboratory, with or without consensus values.
Organisation of proficiency tests for a selected group of laboratories.
Organisation of proficiency tests within your laboratory, to compare results from several colleagues.
Organisation of development exercises on new emerging pollutants or difficult compounds to analyse.
On behalf of the International Organization for Standardization (ISO) WEPAL-QUASIMEME also organises international laboratory-evaluating programmes for environmental and agricultural laboratories.

For more information see our services on request

Proficiency testing WEPAL-QUASIMEME

What is Proficiency testing?

About

WEPAL-QUASIMEME Proficiency tests

Soil - ISE

Freshwater sediment - SETOC

Marine Sediment

Freshwater and wastewater

Seawater

Plants - IPE

Biota

Shellfish toxins

Manure & Compost - MARSEP

Biomass - BIMEP

Special excercises

Services on request - WEPAL-QUASIMEME

The WEPAL-QUASIMEME 2026 catalogue is now available

Highlight: AQ-8 Triazines and Pesticides in Seawater

Participants Call for Next Round of Microplastics Proficiency Testing

WEPAL-QUASIMEME Reaches Record Customer Loyalty in 2025

Subscription Open – Proficiency Test on CECs in Marine Samples