Spike Recovery Calculator

What is spike recovery?

Spike recovery checks how much of a known amount of analyte, added deliberately to a real sample, is found again by the method. Because the spike travels through the same matrix, extraction and instrument response as the sample itself, it measures accuracy under working conditions rather than in clean standard solution.

Spike recovery formula

Recovery % = (spiked result − unspiked result) / amount added × 100

How to calculate spike recovery

1. Analyse the sample as received and record the unspiked result.
2. Add a known amount of analyte and analyse the spiked sample the same way.
3. Subtract the unspiked result from the spiked result to get the measured increase.
4. Divide that increase by the amount added and multiply by 100.

Spike recovery example

A waste-water sample reads 1.20 mg/L of an analyte. After spiking to add 5.00 mg/L, the spiked sample reads 6.05 mg/L. The measured increase is 6.05 − 1.20 = 4.85 mg/L, so recovery is 4.85 / 5.00 × 100 = 97.0 %.

Percent recovery vs spike recovery

Percent recovery compares a measured result with a known, expected value — measured / expected × 100 — and suits reference materials or a known amount carried through a procedure. Spike recovery subtracts the analyte the sample already contained, so it is the correct form whenever the matrix has a background level. Both tabs above are available on this page.

Whichever form you use, all values must share one unit and one basis. Acceptance windows for recovery come from your own method, not from this calculator.

Related recovery work

• Convert a spike level between mass and trace units with the ppm / ppb conversion calculator.
• Work out a spiking stock strength with the percent solutions calculator.
• Prepare the spiking solution itself with the dilution calculator or the solution preparation calculator.