Understand the relationship
The reasoning behind the result
Two absorbances separate overlapping components
[Ca, Cb]ᵀ = K[A₁, A₂]ᵀ × DF
Absorbance from pigments can overlap at the chosen wavelengths. A two-component equation applies a coefficient matrix K to those measured values. Cross-coefficients may be negative because they subtract one component's overlapping contribution from the other.
The matrix must come from the exact method being used. Solvent, wavelength and path conventions affect coefficients; changing one while retaining another method's constants is not a valid substitution.
Convert extract concentration into recovered amount
ma,mg = Ca,mg/L × Vextract,mL/1000
The coefficient equation here must return mg/L before dilution correction. Multiply by the original-extract dilution factor once. Multiplying that concentration by extract volume in litres gives pigment mass in milligrams.
Dividing recovered pigment mass by entered sample mass gives mg per g of that stated mass basis. Fresh and dry sample masses are different bases; the calculator does not translate between them.
A negative component is a model check
A coefficient combination can produce a negative component even when both absorbances are positive. That may point to measurement, background or model compatibility issues. The signed value is retained and flagged rather than interpreted as a physical negative pigment amount.
The live contribution diagram shows the terms forming each component. Example coefficients are invented arithmetic illustrations, explicitly labelled as such; no extraction method is silently prescribed.
Follow the numbers
Follow each coefficient contribution
- With illustrative coefficients, Ca = 10 × 0.5 − 2 × 0.25 = 4.5 mg/L and Cb = −1 × 0.5 + 8 × 0.25 = 1.5 mg/L.
- In 20 mL = 0.020 L of undiluted extract, masses are 0.090 mg a and 0.030 mg b.
- For a 0.5 g measured sample, those are 0.18 mg/g a and 0.06 mg/g b; total is 0.24 mg/g.
These numbers demonstrate the entered matrix and unit conversions. They are not a recommended solvent or chlorophyll measurement protocol.
Quick guide
How to use this calculator
- Record the method and solvent and enter its exact wavelengths and coefficient convention.
- Enter corrected absorbances using the optical path expected by that method.
- Enter the original-extract dilution, volume and measured sample mass.
- Inspect each coefficient contribution and any negative model component before interpretation.
Calculation method
Calculation and interpretation
Make a chosen extraction method's wavelength coefficients explicit rather than applying a universal chlorophyll formula.
Ca = (kaa A₁ + kab A₂) × DF; Cb = (kba A₁ + kbb A₂) × DF; amount/sample mass = C × Vextract,L / msample,g
Worked example
Follow each coefficient contribution
These numbers demonstrate the entered matrix and unit conversions. They are not a recommended solvent or chlorophyll measurement protocol.
Ca = (kaa A₁ + kab A₂) × DF; Cb = (kba A₁ + kbb A₂) × DF; amount/sample mass = C × Vextract,L / msample,g
Supported inputs
Precision and limits
Experimental boundary
This workbench reconciles entered measurements or plans. It does not validate an assay, establish biological effects or replace the protocol and controls for the actual experiment.
Method supplied by the visitor
Only an entered linear two-wavelength matrix is supported. No spectral fitting, pheopigment correction, extraction-efficiency estimate, solvent preset or fresh/dry mass conversion is inferred.
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