A rapid and automated flow injection spectrophotometric determination method for pioglitazone/metformin hydrochloride in pharmaceutical preparation and to confirmation of its reaction principle using PCX column

Abstract Based on the flow injection analysis (FIA) and the gold nanoparticles (AuNPs) optical probe, a rapid and precise automation method was developed and was used for the determination of the pioglitazone HCl (PIO) and metformin HCl (MET) hydrochloride in diabetes pharmaceuticals. The synthesis of AuNPs was to utilize the classical Frens’ method, which realized the stable store for 35 days. The method principle is that under the acidic condition, the protonated PIO and MET rapidly induce the aggregation of the negative-charge AuNPs probe to cause its color change. To confirm this reaction, an online continuous monitoring system with a PCX column was first designed and used, in which we found that the key factor inducing the AuNPs agglomeration is the electrostatic attraction. Additionally, the use of the nature that PIO can be slightly dissolved in water and solid-liquid extraction technique, the MET in the pharmaceuticals was separated. By means of this combined strategy, the two matters in the pharmaceutical preparations were successfully determined in the ranges of 0.5 to 10 mg L−1 for PIO and 10 to 100 mg L−1 for MET, with the recoveries of 96 to 106% for PIO and 98 to 108% for MET. This method not only achieved the purpose of using one AuNPs optical probe to synchronously quantify PIO and MET, but it also showed such merits of high automation degree, fast analysis speed (24 samples h−1), high precision and good repeatability (RSD = 1.09% PIO, 0.48% MET).