Fig 1.
Structures of gentisic acid (GA) and homogentisic acid (HGA).
(a) Gentisic acid. (b) Homogentisic acid.
Fig 2.
Color changes in and absorption spectra of GA and GA analogs.
(a) Structures of acetylsalicylic acid (ASA) and salicylic acid (SA). (b) 400 mg/L ASA (I), 400 mg/L SA (II), 400 mg/L GA (III), and a mixture of GA, ASA, and SA (the final concentration of each was 400 mg/L) (IV) before and after the addition of NaOH with NaOCl·5H2O. (c) Absorption spectra of 400 mg/L ASA, 400 mg/L SA, 400 mg/L GA, and the mixture before and after the addition of NaOH with NaOCl·5H2O.
Fig 3.
Color changes in and absorption spectra of GA.
(a) Absorption spectra of GA from 50 to 800 mg/L after the addition of NaOH with NaOCl·5H2O. (b) Absorbance at 500 nm of GA from 1 to 1000 mg/L after the addition of NaOH with NaOCl·5H2O. Results are the mean ± S.D. of three experiments.
Fig 4.
Color changes in and absorption spectra of GA after the addition of different additive reagents.
(a) 400 mg/L GA after the addition of NaOH (I) or NaOH with NaOCl·5H2O (II). (b) Absorption spectra of 400 mg/L GA after the addition of NaOH or NaOH with NaOCl·5H2O.
Fig 5.
(a) MS spectrum of 400 mg/L GA. (b) MS spectrum of 400 mg/L GA after the addition of NaOH. (c) MS spectrum of 400 mg/L GA after the addition of NaOH with NaOCl·5H2O.
Fig 6.
Effects of AA on the absorption spectra of GA after the addition of NaOH with NaOCl·5H2O.
Absorption spectra of 400 mg/L GA solutions containing several concentrations of AA (10, 50, 100, 200, and 300 mg/L) after the addition of NaOH with NaOCl·5H2O.