spiked sample

**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.