"Absorbance of electromagnetic radiation (493nm wavelength) {light absorbance} by the suspended particulate material >GF/F [pigment phase] by filtration and spectrophotometry on residue before and after methanol pigment extraction and differencing of the measurements"@en . . "SDN:P01::PIGA493A" . "Diff. of spectrophotometric spectra on GF/F filterered material pre and post methanol extraction"@en . .