An element’s light signature.
Electrons in atoms occupy quantised energy states. A downward transition emits a photon matching the energy gap; an upward transition absorbs matching energy. Distinct allowed gaps give each element characteristic spectral lines. Models of atoms were refined by evidence such as scattering and spectroscopy.
Atomic absorption spectroscopy measures how much characteristic light is absorbed by free atoms. Known standards establish a calibration relationship. An unknown within the calibrated range can be estimated by interpolation, allowing for dilution and measurement uncertainty.
Absorption calibration
Explore the relationship
Ideal linear calibration through a blank-corrected origin. Real standards require uncertainty and linearity checks.
Tap or focus a plotted point to read its values.
View plotted data as a table
| Series | Concentration / mg L⁻¹ | Absorbance |
|---|---|---|
| Absorbance | 0 | 0 |
| Absorbance | 0.0833333 | 0.00833333 |
| Absorbance | 0.166667 | 0.0166667 |
| Absorbance | 0.25 | 0.025 |
| Absorbance | 0.333333 | 0.0333333 |
| Absorbance | 0.416667 | 0.0416667 |
| Absorbance | 0.5 | 0.05 |
| Absorbance | 0.583333 | 0.0583333 |
| Absorbance | 0.666667 | 0.0666667 |
| Absorbance | 0.75 | 0.075 |
| Absorbance | 0.833333 | 0.0833333 |
| Absorbance | 0.916667 | 0.0916667 |
| Absorbance | 1 | 0.1 |
| Absorbance | 1.08333 | 0.108333 |
| Absorbance | 1.16667 | 0.116667 |
| Absorbance | 1.25 | 0.125 |
| Absorbance | 1.33333 | 0.133333 |
| Absorbance | 1.41667 | 0.141667 |
| Absorbance | 1.5 | 0.15 |
| Absorbance | 1.58333 | 0.158333 |
| Absorbance | 1.66667 | 0.166667 |
| Absorbance | 1.75 | 0.175 |
| Absorbance | 1.83333 | 0.183333 |
| Absorbance | 1.91667 | 0.191667 |
| Absorbance | 2 | 0.2 |
| Absorbance | 2.08333 | 0.208333 |
| Absorbance | 2.16667 | 0.216667 |
| Absorbance | 2.25 | 0.225 |
| Absorbance | 2.33333 | 0.233333 |
| Absorbance | 2.41667 | 0.241667 |
| Absorbance | 2.5 | 0.25 |
| Absorbance | 2.58333 | 0.258333 |
| Absorbance | 2.66667 | 0.266667 |
| Absorbance | 2.75 | 0.275 |
| Absorbance | 2.83333 | 0.283333 |
| Absorbance | 2.91667 | 0.291667 |
| Absorbance | 3 | 0.3 |
| Absorbance | 3.08333 | 0.308333 |
| Absorbance | 3.16667 | 0.316667 |
| Absorbance | 3.25 | 0.325 |
| Absorbance | 3.33333 | 0.333333 |
| Absorbance | 3.41667 | 0.341667 |
| Absorbance | 3.5 | 0.35 |
| Absorbance | 3.58333 | 0.358333 |
| Absorbance | 3.66667 | 0.366667 |
| Absorbance | 3.75 | 0.375 |
| Absorbance | 3.83333 | 0.383333 |
| Absorbance | 3.91667 | 0.391667 |
| Absorbance | 4 | 0.4 |
| Absorbance | 4.08333 | 0.408333 |
| Absorbance | 4.16667 | 0.416667 |
| Absorbance | 4.25 | 0.425 |
| Absorbance | 4.33333 | 0.433333 |
| Absorbance | 4.41667 | 0.441667 |
| Absorbance | 4.5 | 0.45 |
| Absorbance | 4.58333 | 0.458333 |
| Absorbance | 4.66667 | 0.466667 |
| Absorbance | 4.75 | 0.475 |
| Absorbance | 4.83333 | 0.483333 |
| Absorbance | 4.91667 | 0.491667 |
| Absorbance | 5 | 0.5 |
Explore: Change calibration sensitivity and compare the concentration inferred from a given absorbance.
A calibration gives absorbance 0.20 at 2 mg and 0.40 at 4 mg .
- Under the linear calibration, absorbance 0.30 corresponds to 3 mg .
- A fivefold-diluted sample would originally contain 15 mg .
Assumed knowledge
Reading a straight-line graph.
Learning checkpoints & source
YOUR LEARNING CHECKPOINT- Relate electron transitions to line spectra.
- Use calibration data to infer concentration.