Simultaneous determination of the ionisation and dimerization constants and the partition and ion pair extraction coefficients for 1–8 naphtyridine derivatives

Abstract Conventional experimental studies of water/octanol partition at different pHs and concentrations were used to simultaneously evaluate (i) the true P octanol/water partition coefficient, (ii) acidity constants and (iii) extraction constants for ion pairs produced by the ions in the buffers used (phosphate ions). The studies also rejected the hypothesis that dimers are formed in the octanol phase. The method, applied to a few substituted 1,8-naphtyridine substances, used a new software whose algorithm is based on the principle of error minimisation using a simplex method. The fundamental equations used to calculate the concentration of the test species in each experimental situation (pH, concentration, phase volume ratios, counter-ions) are explained.