Table 1.
The parameters of the function εtotal = [εacid + εbase × 10–(pKa–pH))/(1 + 10–(pKa–pH)] fitted to molar absorption at 340 and 400nm as a function of pH
| Wavelength (nm) | εacid (M–1 cm–1) | εbase (M–1 cm–1) | pK a |
|---|---|---|---|
| 340 | 23155.7±207.8 | 5626.7±267.1 | 8.09±0.039 |
| 400 | 495.8±108.4 | 35634.7±138.2 | 8.07±0.010 |
Data are presented in Supplementary Fig. S2. The function was derived from the expression of the acid constant, the mass balance, and the law of Lambert-Beers and describes the pH dependence of coniferyl aldehyde with respect to the pKa of the phenol group. εacid and εbase are the molar absorption coefficients of the protonated (phenol-form) and the unprotonated (phenolate form) of coniferyl aldehyde, respectively. The molar absorption coefficient to any pH needed can be calculated using the formula and the constants.