Spiked Sample is a sample to which a known quantity of the analyte has been deliberately added — used to evaluate measurement recovery (the ability to accurately measure a known addition) and to detect matrix effects that might cause the measurement to read high or low.

Spiking Protocol

• Base Sample: Start with a real sample matrix — containing the natural level of the analyte.
• Spike Addition: Add a known, accurately measured quantity of the analyte — at a level that produces a measurable increase.
• Measurement: Measure both the unspiked and spiked samples — calculate recovery.
• Recovery: $\%Recovery = frac{C_{spiked} - C_{unspiked}}{C_{added}} imes 100\%$ — ideal = 100%.

Why It Matters

• Matrix Effects: The sample matrix (other chemicals present) can interfere with the measurement — spiked samples detect this.
• Method Validation: Recovery testing is a standard method validation requirement — demonstrates the method works in real samples.
• Semiconductor: Contamination monitoring (ICP-MS for metals, TXRF) uses spiked samples to verify recovery in different sample types.

Spiked Sample is the known addition test — adding a known quantity of analyte to verify that the measurement method recovers the correct amount from real samples.