How It Works
This calculator works in 4 steps.
Enter the spike
Type the spike standard concentration and volume.
Enter the sample
Type the native concentration, or 0 for a blank, and the sample volume.
Combine
The calculator sums analyte amounts and divides by the combined volume.
Read the expected value
The calculator returns the added level, the diluted native level, and the expected total.
The Formula
The formula sums the spike and native analyte amounts and divides by the total volume.
C_exp = (C_s V_s + C_x V_x) / (V_s + V_x)C_add = C_s V_s / (V_s + V_x)%R = 100 × (C_meas − C_x,dil) / C_add- C_s / V_s:
- Spike concentration and volume
- C_x / V_x:
- Native sample concentration and volume
- C_meas:
- Measured spiked value
- C_x,dil:
- Native level after spike dilution
Adding 5 µL of 1,000 ng/mL standard to 995 µL sample at 2 ng/mL gives an added level of 5 ng/mL and an expected total of 6.99 ng/mL.
Conversion Table
The conversion table gives the added level and expected total for 6 spike designs (shared unit).
| Spike | Sample native | Added level | Expected total |
|---|---|---|---|
| 100 @ 10 µL | 0 @ 990 µL | 1 | 1 |
| 1,000 @ 5 µL | 2 @ 995 µL | 5 | 6.99 |
| 50 @ 20 µL | 5 @ 980 µL | 1 | 5.9 |
| 10 @ 100 µL | 0 @ 900 µL | 1 | 1 |
| 500 @ 2 µL | 10 @ 98 µL | 10 | 19.8 |
| 200 @ 50 µL | 1 @ 950 µL | 10 | 10.95 |
What Is the Spike-In Concentration Calculator?
The Spike-In Concentration Calculator is a tool that returns the concentration of an analyte in a sample after a known spike is added, including the sample's native level and the volume the spike adds. The result feeds spike recovery and standard addition calculations.
Spiking adds a small volume of a standard to a sample to check accuracy. The spike dilutes the sample slightly, and the sample's native analyte adds to the spike. The calculator separates the added amount from the native amount and returns the expected total for comparison with the measured value.
Common Uses
There are 5 main uses of this calculator.
Spike recovery studies
Analysts confirm accuracy at low, mid, and high levels.
Standard addition
Labs quantify analytes in complex matrices.
Method validation
Validation teams spike blank matrices.
Internal standards
Users add isotope-labeled internal standards at a set level.
Proficiency checks
QA teams prepare blind spikes.