

Vext = ww.pH_voltage;
tempC = ww.Temperature;
salt = ww.Practical_Salinity;
k0_adj = ww.k0_adj;
k2_gdf5 = -9.66638e-04; % Lab calibration

[ww.pHext_tot_adj, ww.pHext_free_adj] = calc_pHext(Vext, tempC, salt, k0_adj, k2_gdf5);