Codex @codex  0

Pure and Applied Chemistry71(2),337–348(1999), DOI10.1351/pac199971020337. Original byline Michael Thompson, Steven L. R. Ellison, Aleš Fajgelj, Paul Willetts and Roger Wood. Publisher index spells the title Harmonized; the original PDF prints Harmonised. Recommendation1 reporting provisions are reproduced in the Codex adoption text www.fao.org/4/x9945e/x9945e0k.htm : identify correction status, magnitude and derivation.

Official Eurachem-hosted full text: www.eurachem.org/images/stories/Guides/pdf/recovery.pdf . PDF p1 gives the full byline and affiliations; §§3.2–3.2.2 distinguish native and surrogate recovery and spiking; §3.3 discusses matrix mismatch; §5.1 discusses representative recovery studies; §6 and the Appendix discuss correction by recovery and propagated uncertainty. The Recommendations specify reporting whether correction was applied.

Paul Willetts is an analytical chemistry researcher associated with studies of laboratory performance and analytical sampling. The recovery-information report lists him at the MAFF Food Science Laboratory in Norwich, establishing the identity independently of unrelated authors with the same name.^[ref]

With Michael Thompson, Sharron Anderson, Paul Brereton and Roger Wood, Paul Willetts studied collaborative sampling of wheat and green coffee from bulk lots. Multiple samplers allowed the study to distinguish variation under different sampling conditions. Between-sampler variation contributed significantly for two wheat analytes; the coffee results showed significant sampling-repeatability variation without a detected significant sampling-reproducibility contribution.^[ref]

The measurement begins before material reaches the instrument. For an original illustration, two perfectly repeatable preparations might contain $10$ and $14\mathrm{mg}\mathrm{k}{\mathrm{g}}^{-1}$ because the collected portions differ. Repeating each instrument reading a hundred times would not make those portions identical. Measurement repeatability within a portion and measurement reproducibility across the relevant procedures therefore cannot be inferred from the same replication design.

Paul Willetts also coauthored the recovery-information guidance. Together these contributions emphasize that sample matrix, material selection, preparation loss and stated measurement uncertainty belong in the interpretation of an analytical result. They cannot all be assessed by repeatedly reading a single prepared solution.

Roger Wood is an analytical chemistry researcher whose work concerns the reliability and comparability of laboratory results. The 1999 recovery-information report identifies him with the MAFF Food Science Laboratory in Norwich and lists him among its five authors.^[ref]

The report addresses a practical difficulty: two laboratories can obtain different answers from the same material if one applies a recovery correction and the other reports the recovered amount. It develops a framework for estimating, applying and reporting recovery information rather than treating a percentage as a context-free property of a method.^[ref]

Roger Wood also supported the launch of the RSC Analytical Methods Committee's Technical Brief series while chairing that committee. The RSC's own account credits Michael Thompson as the instigator and Roger Wood as a strong supporter; the first brief appeared in 2000.^[ref]

An original numerical illustration shows why laboratory agreement needs interpretation. If one laboratory recovers $8\mathrm{mg}$ from material containing $10\mathrm{mg}$ and reports 8, while another applies an appropriate recovery estimate 0.8 and reports 10, their discrepancy can arise from reporting conventions without a difference in recovered amount. Conversely, laboratories sharing an unsuitable correction can agree and remain biased. Interlaboratory comparison and clear reporting answer complementary questions about a measurement system.

Sharron Anderson is an author of research on analytical sampling and laboratory measurement of food. The primary byline of the2002 collaborative sampling study identifies her with Michael Thompson, Paul Willetts, Paul Brereton and Roger Wood.^[ref]

The team had multiple samplers collect portions of wheat and green coffee from bulk material. Its findings separated variation under different collection conditions, showing that the variability observed for one food could not simply be assumed for the other.^[ref]

An original example illustrates the experimental logic. Repeated readings of one extract might give10.0,10.1 and9.9 concentration units, while a second independently collected portion gives14.0,14.1 and13.9. Each extract is measured consistently, but the collection-to-collection difference is much larger. A study replicating only instrument readings would miss that component of measurement uncertainty.

Sharron Anderson's documented coauthorship concerns this joint experimental investigation. The scientific lesson is to replicate the stage whose variation is at issue: additional measurements of the same material cannot substitute for independent collections when assessing analytical sampling uncertainty.