A flexible ion chromatography column-switching system with a switching time window (STW) calibration program for the determination of myo-inositol in infant formula by pulsed amperometric detection

This study introduces a flexible ion chromatographic column-switching technique for the direct analysis of myo-inositol in infant formula samples by pulsed amperometric detection. The system, based on two pumps, two columns and three six-pore valves, allowed for free automatic switching between the switching time window (STW) calibration mode and analysis mode. Chromatographic parameters, including chromatographic columns, mobile phases, elution gradient, column-switching parameters, detector waveform parameters, etc., were optimized systematically for the analysis of myo-inositol in infant formula. In this method, both the pretreatment column and analytical column were arranged to be activated and regenerated during their idle time by optimizing the switching program of the three valves, thus increasing the efficiency of the method. The detection potential, E1, of the quadruple-potential waveform was also optimized and it was set to 0.027 V, which offered both excellent sensitivity and a stable baseline. By applying this optimized method to real samples, the determination of myo-inositol in infant formula was achieved in only 20 minutes, with a linear dynamic range from 0.05 μg mL−1 to 120 μg mL−1, and a limit of detection (LOD) (S/N = 3) of 2.5 μg g−1. The results demonstrate the feasibility of this method for routine analysis of myo-inositol in infant formula with the advantages of automation, simple pretreatment, low cost, good stability, and no use of organic reagents.