Influence of the ageing phenomenon on the low-frequency electrical impedance behavior of naphazoline hydrochloride solutions and paracetamol syrup.

The influence of the ageing process on the low frequency behavior of some electrical parameters of naphazoline hydrochloride solutions at 0.5% and 1% in concentration and of 2% paracetamol syrup, is studied. The impedance measurements were performed, in the range between 200 Hz and 1 MHz, using an impedance analyzer and a cell for liquids with plane parallel electrodes whose separation can be changed by using a set of spacers, provided by the manufacturer, in order to get better control of the influence of electrodes polarization effect. The ageing state was artificially generated by dilution and/or heating separated procedures. The results show that this dielectric technique can be used as a good quality complementary control technique.