First NENALAB Meeting, 9-11 June 2020 (online)

1. QA/QC in the Lab
Rob De Hayr
Science Leader Chemistry Centre, Qld, Aus
Vice Chair GLOSOLAN
Co-Chair Pillar 5 Pacific Soil Partnership
Queensland Representative ASPAC Executive Committee

3. Poeple
• Knowledge
• Experience
• Training
• Ownership

4. • Temperature
• Water and Air Quality
• Lab design
• Hygiene
• Tidiness
Environment

5. • Standard Operating Procedures
• Safe Work Practices
• QC (reference samples, blanks, repeats,
control charts, ring tests etc.)
Processes

6. • QA
• Quality Documentation ISO17025
• Expectation of how you operate and deal with analytical
issues
• LIMS
Systems

7. • Fit for purpose
• Training
• Maintenance
Equipment

8. Internal Quality Control
Rob De Hayr

9. The Quality Management System (QMS) is
the over arching system that a laboratory (or
other business) puts in place.
Quality Assurance (QA) is the planned and
systematic implementation of that QMS.
Quality Control (QC) checks the lab methods
are performing as expected.
Laboratory QA/QC definitions

10. Laboratory QA/QC
Standardised Methods
Quality Control Samples & Charts
Equipment Maintenance
Competent Trained Staff
Corrective & Preventive Actions
Customer Complaint System
Unambiguous Reporting of Results
Quality

11. Quality
Inter-laboratory Proficiency Testing
Method Validation/Verification
Auditing
Data Management (LIMS)
Root Cause Analysis
Reference Materials
Equipment Calibrations & Checks
Laboratory QA/QC

12. Quality Control
• QC is applied to the specific tests performed by the
laboratory, on an ongoing basis.
• QC tools normally used in agricultural testing
Laboratories are:
• Run blanks
• In house QC samples
• Replicate analyses
• Certified Reference Materials (CRM’s)
• Inter laboratory Comparison Programmes ILCP’s)
• Sample Exchanges

13. • Best made from purchased 1,000 ppm
solutions
• If not pure chemicals
• Marked with a ‘use by’ date
• New ones always compared with old (even if
out-of-date)
Standard solutions

14. • Always have method blanks (should go through
the entire process)
• Likely different to standard blank or zero
standard
• Do two at least per run
• When the blank is significant (>2 X PQL) blank
correction may be necessary
• If same, use mean
• If different use low one
Blanks

15. • Duplicates selected from the same run and/or
Repeats from a previous run
• Suggest at least 2 samples duplicated per 40
samples
• Essential if no control sample available
• Possible acceptance criteria:
• Same run – use 0.7 times Uncertainty estimate.
• Different run – use 1.4 times Uncertainty
Duplicates & Repeats

16. Relationship between Reproducibility Value (R)
and Uncertainty (U)
• R can be defined as equal to 2√2 X reproducibility
standard deviation.
• U is calculated from 2 X the reproducibility
standard deviation,
• Therefore R = √2 X U = 1.4 X U.
Duplicates & Repeats

17. • Usually every 20 solutions/samples – depends on
method or instrument
• Suggest if drift exceeds 5% relative - recalibrate
Drift check standard

18. • Depends on method
• Not often used in soil and plant analysis
• More useful for analyses near detection limit.
Recovery spikes

19. • Certified Reference Material (can be very costly)
• Secondary Reference Material (can also be
costly)
• In-house Reference Material
• Run with every batch of samples and chart results
Reference Materials

20. Reference Materials (CRMs, SRMs)
• May or may not be Certified. Certified means it
is metrologically traceable back to primary
standards.
• Sourced from a certified external provider.
• Come with stated Consensus or Certified analyte
levels, usually with Uncertainty Limits.
• An excellent external check on the laboratory
performance (accuracy).

21. In-house QC samples
• Bulk samples usually prepared in-house
• From relatively uniform sampling area
• Thoroughly mixed
• Packed in manageable containers (e.g.500 mL)
• Establish Warning and Control Limits
• Run with every batch of samples.
• Monitoring long-term stability.

22. • Normally, two different QC samples per batch.
• Replicated at least every 20 - 40 samples
• Results compared with acceptability criteria
• May also be at the end of the run to monitor any
drift
In-house QC samples (cont.)

23. Some acceptance criteria for verification checks
Chemistry Centre, Qld, Australia
Check Acceptance Criteria
Instrument QC ICPOES
- two monthly repeatability check
- two monthly limit of quantitation
check
- fortnightly check of sensitivity
- %RSD < 5%
- <50% change from month to
month
- if >30% change in sensitivity
of any one analyte
investigate causes.
Ion chromatograph
- repeatability check
- monitoring of system pressure, total
conductivity & retention time
- %RSD < 5%
- Retention Time ± 1 min
Calibration of
Instrument
Most instruments R2 > 0.99
Old vs new
standards
Normal concentration
Ultra-trace concentrations
< 3% at mid-range (25%-70% of
calibration range)
< 10% at mid-range (25%-70% of
calibration range)
Blanks < 2 times PQL
Duplicates (of
full method)
Minimum frequency = 1 in 20 - Difference < uncertainty (same run)
- Difference < 1.4 times x uncertainty
(different runs)
Recovery Spikes %Recovery at ultra-trace concentrations
= [Spiked Conc–Sample Conc] x 100
Spiked Conc
100% ± 20%

24. Thanks for your attention
Guidelines for Quality Management in Soil and Plant Laboratories.
(FAO Soils Bulletin - 74)
ISO 17025:2017 General requirements for the competence of
testing and calibration laboratories