WEPAL has been providing proficiency testing for soil laboratories since 1956 to establish quality assurance and quality control standards. They produce homogenous soil samples for inter-laboratory testing through careful mixing, drying, grinding, and bulk dividing. Laboratories use WEPAL proficiency tests to validate methods, prove performance for accreditation, fine-tune activities, and maintain reliability over time. WEPAL also helps new labs build experience and supports global soil quality monitoring through the GLOSOLAN program.

1. Proficiency testing-implementing
QA/QC standards in laboratory
networks: experiences from the
WEPAL network
Winnie van Vark
WEPAL, Wageningen University

2. WEPAL
• 1956 Start Ring test with plant material
• 1988 Introduction of ring test for soil
• 1992 Organic contaminants in sediments
• 1993 Introduction of a sample dividing device
• 1996 Introduction of bulk dividing equipment
• 2000 Accreditation for organizing inter laboratory
studies
• 2010 Merge WEPAL and Quasimeme (marine)
• 2016 60th anniversary of WEPAL
> 700 participants all over the world
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3. Production of the samples
• Every laboratory analyze the same “item”
• Homogeneity is very important
• Mixing Soil and Plant (and food) materials
• Particles: difficult to mix
• Tendency to separate
• Only mixing (e.g. cement mixer) is not sufficient
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4. Drying
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5. Crushing and grinding
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6. Bulk divider
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7. Sample divider
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8. Check on homogeneity
• 10 individual pots are analysed
• P-total Average 717 mg/kg
• Expected (history) Standard deviation (σ) 47 mg/kg
• Standard deviation within pots (Sa) 41 mg/kg
• Standard deviation between pots (SS)20 mg/kg
• SS/Sigma = 0.43 (should be <0.3)
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9. Samples, Sending and Storage
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10. Member website
• Uploading results – adding and correcting results is
possible till deadline
• Method indicating codes
• Statistical evaluation by WEPAL
• Quarterly and Annual reports
• Graphical presentation of results
• Lab specific reports
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11. Use of WEPAL proficiency tests
• Performance of existing (accredited) laboratories
• Z-scores
• Supply of reference materials
• Validation of standard methods
• Set-up and training of new laboratories
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12. Validation of standards
• Within ISO/TC190, WEPAL has organized the
validation of:
• ISO 17586. Soil quality — Extraction of trace elements using dilute
nitric acid.
• ISO 20244: Soil quality — An on-site test method to quickly
determine water contents in soil using refractometry
• ISO/TS16751: Soil quality — Environmental availability of non-polar
organic compounds — Determination of the potentially bioavailable
fraction and the non-bioavailable fraction using a strong adsorbent
or complexing agent
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13. Set-up of analytical capacity
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14. Role of proficiency testing (1)
• Building and infrastructure
• Stable current
• Fume cupboards
• Instrumentation
• Sustainable
• Supplies available
• Flame photometer or ICP
• Distilled water or demi water using cartridges
• Local services available
• Staff
• Educated management
• Skilled and permanent technicians
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Awareness

15. Role of proficiency testing (2)
• Set-up of analytical methods
• Building up of experience
• Proving of experience
• Accreditation
• Maintenance of performance
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Used by the laboratory itself
to check the performance of
the new method. Large
improvements may be
necessary.
Used for fine-tuning of the
activities in the laboratory
Results of proficiency
testing are used to convince
the accreditation body Results of proficiency
testing are used to maintain
the performance of the
laboratory
Results of proficiency
testing are close to the
consensus value. The
laboratory produces
reliable results

16. WEPAL and GLOSOLAN
• WEPAL-programme in soil includes GLOSOLAN
programme
• pHwater, pHKCl, EC, OC, TN, available K, available P, CEC,
Exch Ca, Exch Mg, Exch K, Exch Na, Exch acidity, Texture
• Water retention curve asks for undisturbed samples
• Difficult to distribute
• Initiative of Wageningen University: SOPHIE
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17. SOPHIE
• Integration, Innovation and Standardization of
Measuring Soil Hydro-Physics Properties
• Side event / Kick off meeting
3rd Wageningen Soil Conference
Next meeting:
World Soil Day 2017
IBGE Brussels, 4th- 6th December
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18. Conclusions
• WEPAL Proficiency tests supply soil laboratories with
QA/QC data
• Distributed samples must be homogeneous
• Sufficient participants
• WEPAL-facilities and network can be used to validate
ISO-methods
• Starting laboratories can use WEPAL samples to build-
up experience
• WEPAL can play a role in making knowledge of WEPAL-
network available
• WEPAL includes GLOSOLAN parameters
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19. Role of WEPAL in Glosolan
• Organising Proficiency test for participating
laboratories
• Provide reports/ datasets for specific groups
• Prepare reference materials for daily routine
• Compare results laboratories using reference
materials
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20. For Discussion
Glosolan WEPAL
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INTERACTION