GIFSQ Tools · Module 15 — Metrology, Validation & Laboratory Accreditation · Tool 287 of 500
Analyse a spike-recovery study: recovery of each spiked replicate, the mean recovery, its standard deviation and the relative standard deviation — the trueness check of method validation.
Try sample values — fills the form with the worked example below.
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Mean recovery (%)
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Recovery SD (%)
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Recovery RSD (%)
Equation: Recoveryᵢ (%) = (foundᵢ − native) ÷ spike × 100. Mean, sample SD (n − 1) and RSD = SD ÷ mean × 100 across the replicates.
Method: Spike-recovery (trueness) assessment per Eurachem method-validation guidance and ISO 5725-2: spike a blank or low-level matrix at a known level, analyse replicates, and compare the recovered amount with the amount added.
Assumptions: the spike is fully mixed into the matrix; the native level is measured on the same sample; the replicates are independent.
Limitations: recovery does not separate extraction losses from matrix bias; a recovery near 100% at one level does not prove trueness at other levels — test at least two levels.
Rounding: mean recovery and SD to 2 decimal places; RSD to 2 decimal places; intermediates unrounded.
This is a calculation aid, not a laboratory report — confirm against your accredited method before citing a value.
Method: Spike-recovery (trueness) assessment per Eurachem method-validation guidance and ISO 5725-2: spike a blank or low-level matrix at a known level, analyse replicates, and compare the recovered amount with the amount added.
Assumptions: the spike is fully mixed into the matrix; the native level is measured on the same sample; the replicates are independent.
Limitations: recovery does not separate extraction losses from matrix bias; a recovery near 100% at one level does not prove trueness at other levels — test at least two levels.
Rounding: mean recovery and SD to 2 decimal places; RSD to 2 decimal places; intermediates unrounded.
This is a calculation aid, not a laboratory report — confirm against your accredited method before citing a value.
Worked example: Native 2.0 mg/kg, spike 10 mg/kg, found 11.8, 12.1, 11.9 mg/kg: recoveries 98, 101, 99% — mean 99.33%, SD 1.53%, RSD 1.54%.
Enter values above to see results.
Many methods accept mean recovery of 80–120% (tighter, 90–110%, for high levels) — use your own method criterion. Tool 287 of 500 — GIFSQ
