Phaeophytin Absorbance Correction
Apply caller acid-correction convention Chl=k(Apre−Apost), phaeo=k(R·Apost−Apre); k must include method-specific acidification factors, and negative estimates are flagged rather than clamped.
Description
Acidification changes pigment absorbance and helps separate chlorophyll from its degradation products.
Acidification changes pigment absorbance and helps separate chlorophyll from its degradation products. This tool applies a caller-calibrated pre/post-acid correction convention.1
The tool returns correctedChlorophyllMicrogramsPerLiter, phaeophytinMicrogramsPerLiter, negativeEstimatePresent. The computation uses supplied observations and parameters rather than acquiring measurements.
When to use Phaeophytin Absorbance Correction
Use this for the following task: Apply caller acid-correction convention Chl=k(Apre−Apost), phaeo=k(R·Apost−Apre); k must include method-specific acidification factors, and negative estimates are flagged rather than clamped. Prepare observations and calibration parameters on the same unit and reporting basis.
How to use Phaeophytin Absorbance Correction and understand its results
- Prepare the measured quantities and supplied model parameters. Match the units and align paired lists before calculating.
- Enter beforeAcidAbsorbance, afterAcidAbsorbance, blankAbsorbance, acidificationRatio, calibratedCoefficientMgPerLiter, opticalPathCm, extractWaterVolumeRatio according to the field table, then run the tool.
- Read correctedChlorophyllMicrogramsPerLiter, phaeophytinMicrogramsPerLiter, negativeEstimatePresent. Use the calculation below to interpret the selected mean or the model’s signs, units and comparison flags.
- Review the supplied assumptions and calibration before comparing or reporting the result.
| Input field | Meaning | Value type and bounds | Requirement |
|---|---|---|---|
| beforeAcidAbsorbance | Before acid absorbance | number | Required |
| afterAcidAbsorbance | After acid absorbance | number | Required |
| blankAbsorbance | Blank absorbance | number | Required |
| acidificationRatio | Acidification ratio | number | Required |
| calibratedCoefficientMgPerLiter | Calibrated coefficient mg per liter | number | Required |
| opticalPathCm | Optical path cm | number | Required |
| extractWaterVolumeRatio | Extract water volume ratio | number | Required |
Supply nonnegative absorbances and extract-to-water ratio, positive coefficient and optical path, and an acidification ratio above one. Calculate both concentrations and flag either negative estimate.
A=before−blank; B=after−blank; k=1000×coefficient×extractWaterVolumeRatio/path; chlorophyll=k(A−B); phaeophytin=k(R×B−A) The symbols and boundary conditions refer to the supplied fields and the implementation described above.
| Output field | Meaning | Value type |
|---|---|---|
| correctedChlorophyllMicrogramsPerLiter | Corrected chlorophyll micrograms per liter | number |
| phaeophytinMicrogramsPerLiter | Phaeophytin micrograms per liter | number |
| negativeEstimatePresent | Negative estimate present | boolean |
{
"input": {
"beforeAcidAbsorbance": 0.2,
"afterAcidAbsorbance": 0.1,
"blankAbsorbance": 0.01,
"acidificationRatio": 1.7,
"calibratedCoefficientMgPerLiter": 26.7,
"opticalPathCm": 1,
"extractWaterVolumeRatio": 0.01
},
"output": {
"correctedChlorophyllMicrogramsPerLiter": 26.7,
"phaeophytinMicrogramsPerLiter": -9.878999999999994,
"negativeEstimatePresent": true
}
}Limitations and assumptions
The coefficient must include the method-specific acidification factors; it is not automatically an EPA equation constant. Negative estimates are preserved, and wavelengths, solvent effects and extraction quality are not checked.
Numerical inputs must be finite. Input-shape and calculation checks do not establish measurement quality or the validity of a supplied calibration.
Alternative or Complementary methods
Choose Chlorophyll A Extraction Concentration when you need its operation: Convert blank-corrected multiwavelength extract absorbances with caller method coefficients and path/dilution/sample-volume correction; negative estimates are retained and solvent-specific calibration is external. Choose Chlorophyll Phosphorus Regression Prediction for the complementary operation: Fit a log-power chlorophyll/phosphorus relation to caller observations with within-range median prediction; no mutable published regression or uncorrected arithmetic-mean claim.
Background reference: Method 446.0: chlorophylls and pheopigments by visible spectrophotometry.
References
-
Method 446.0: chlorophylls and pheopigments by visible spectrophotometry — Elizabeth J. Arar, U.S. Environmental Protection Agency
Similar or alternative tools
- Chlorophyll A Extraction Concentration
Convert blank-corrected multiwavelength extract absorbances with caller method coefficients and path/dilution/sample-volume correction; negative estimates are retained and solvent-specific calibration is external.
- Chlorophyll Phosphorus Regression Prediction
Fit a log-power chlorophyll/phosphorus relation to caller observations with within-range median prediction; no mutable published regression or uncorrected arithmetic-mean claim.