Quantitative analysis of methacycline hydrochloride by direct potentiometry using the internal solid contact sensor.

An internal solid contact sensor (ISCS) for the determination of methacycline hydrochloride (MC.Cl), Pt/PPy/PVC(MC-PT), is described, based on the use of conducting poly(pyrrole) (PPy) as solid contact material and MC-phosphotungstate (PT) as the ion exchanger and dibutyl phthalate (DBP) as the plasticizer. A direct potentiometric method for the quantitative analysis of MC.Cl is also described. Under the condition of pH 2.7, the linear concentration range, slope (25 degrees C) and detection limit of the sensor are 6.4 x 1.0(-6) - 3.0 x 1.0(-3) M, 52.4 +/- 0.2 mV/decade and 4.4 x 1.0(-6) M, respectively. The response time is <5 s. The determinations of MC.Cl in tablets were carried out by direct potentiometry. The average recovery and relative standard deviation are 100.1 and 0.7% (n = 4), respectively.