Calculator Input
Formula Used
The corrected signal is calculated first:
Corrected intensity = Smoothed intensity - Baseline intensity
The main area uses the trapezoidal rule unless another method is selected:
Area = Σ ((yᵢ + yᵢ₊₁) / 2) × (tᵢ₊₁ - tᵢ)
Estimated amount is calculated as:
Amount = Normalized area × Calibration factor × Dilution factor ÷ Recovery fraction
If an internal standard area is entered, normalized area becomes:
Normalized area = Corrected area ÷ (Internal standard area × Response factor)
How to Use This Calculator
- Paste retention time and intensity pairs into the data box.
- Choose the peak start and end time.
- Select the baseline and integration method.
- Enter noise, calibration, dilution, recovery, and standard values if needed.
- Press the calculate button.
- Review the graph and peak statistics.
- Download the CSV or PDF report.
Example Data Table
| Retention Time | Intensity | Comment |
|---|---|---|
| 0.30 | 150 | Peak window starts |
| 0.50 | 480 | Signal rising |
| 0.70 | 1280 | Apex region |
| 0.90 | 760 | Signal falling |
| 1.20 | 160 | Peak window ends |
Area Under an Extracted Ion Chromatogram
Why Peak Area Matters
An extracted ion chromatogram shows signal for one selected ion or mass range. It is often used in mass spectrometry. The curve can confirm retention time, peak shape, and approximate response. Area under the curve is important because it links signal strength with analyte quantity.
How the Calculation Works
This calculator accepts retention time and intensity pairs. It sorts the points and selects the chosen time window. It can smooth the signal with a moving average. It can subtract a baseline. The baseline may be zero, constant, linear, or minimum based. After correction, the tool integrates the remaining peak.
The trapezoidal rule is the safest default for real chromatograms. Real data often have uneven spacing. The method divides the curve into small trapezoids. Each trapezoid uses two neighboring intensities and the time gap between them. Simpson integration can be useful when spacing is even. Rectangle integration is included for quick checks.
Baseline and Quality Checks
Baseline choice matters. A high baseline can reduce the final area. A low baseline can overstate abundance. Use a narrow peak window when nearby peaks overlap. Use linear baseline when the signal slopes across the peak. Use constant baseline when the noise floor is steady. Use zero baseline only for already corrected data.
Signal quality should also be reviewed. The calculator reports apex time, peak height, centroid, width at half height, and signal to noise. These values help identify poor integration. A broad width may suggest coelution. A low signal to noise value may indicate unreliable quantitation. The concentration estimate uses calibration factor, dilution, recovery, internal standard area, and response factor when supplied.
Good Reporting Practice
Always inspect the graph before using results. Check that the integrated window includes the whole peak. Check that the baseline follows the real background. Compare exported values with instrument software when method validation is required. This tool supports learning, method development, and transparent reporting.
For best precision, export the CSV after each run. Store the method settings with the sample name. This makes reviews easier. It also helps when a peak must be reintegrated later. Small changes in window limits can change results. Document every setting for repeatable analytical work. Use consistent units across every calculation and final report when possible.
FAQs
What is an extracted ion chromatogram?
It is a chromatogram made from a selected ion, mass, or mass range. It helps isolate one analyte signal from full scan data.
Which integration method should I use?
The trapezoidal method is best for most real data. It handles uneven time spacing better than Simpson integration.
Why does baseline correction change area?
Baseline correction removes background signal. This leaves the peak response that is more closely linked with the analyte.
When should I use a linear baseline?
Use it when the background signal rises or falls across the peak. It connects the first and last selected intensities.
What does signal to noise mean?
It compares corrected peak height with noise level. Higher values usually mean a more reliable detected peak.
Can this replace instrument software?
No. It is useful for checks, teaching, and transparent calculations. Validated laboratory reporting should follow approved software and methods.
What units are used for area?
Area units depend on your input units. If time is minutes and intensity is counts, area is count minutes.
Why enter an internal standard area?
Internal standard normalization can reduce variation from injection volume, matrix effects, and instrument response changes.