Convert a spectrophotometer reading into concentration using a linear standard curve.
| Concentration x | – |
Use this calculator after you fit absorbance versus standards: you have slope and intercept and a sample signal, and this inverts the line.
The calculation is x = (signal − intercept) / slope. The result uses the same concentration unit as your standards. If the intercept is nearly zero you can leave it at 0. The slope cannot be zero.
This inverts a straight line. It does not weight points, reject outliers, or report uncertainty.
Slope m: Slope of the line, signal per concentration unit, for example 0.042 AU per mg/L.
Intercept b: Y-intercept of that line, often near 0. Use 0 if you forced the fit through the origin.
Signal y: Sample reading in the same units as the y-axis of the curve, usually absorbance.
Concentration x: Unknown concentration on the standard-curve scale.
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