The detection wavelength was 280 nm. For EDDS analysis, EDDS in filtrate was mixed with excess FeCl3 solution (Fe3þ : EDDS molar ratio 50:1), the mobile phase was a mixed solution of methanol and formate buffer (2 mM tetrabutylammonium hydrogen sulfate and 15 mM sodium acetate, pH adjusted to 4.0 with acetic acid) (20:80, V/V).