"Concentration of gamma-aminobutyric acid {CAS 56-12-2} per unit volume of the water body [particulate >0.2um phase] by filtration, ortho-phthalaldehyde reaction and high performance liquid chromatography (HPLC)"@en . . "SDN:P01::FA15HPP5" . "ortho-phthalaldehyde reaction/ reverse phase HPLC (GF/F filtered)"@en . .