Ion chromatographic determination of hydrazine in excess ammonia for monitoring graphene oxide reduction reaction

A new ion chromatography method has been developed to study graphene oxide (GO) reduction by monitoring hydrazine concentration in the GO suspension. The method is based on ion chromatographic separation of hydrazine (from excess ammonia) and its selective determination by electrochemical detection. The developed analytical protocol overcame the significant practical challenges of atmospheric hydrazine oxidation and minimised the matrix interference in both separation and detection which result from the excess of ammonium with respect to hydrazine (up to 5.8 × 10⁴ times) in GO reduction experiments. Chromatographic separations were achieved using a high capacity IonPac CS16 cation-exchange column with a 30 mM methanesulfonic acid (MSA) eluent, within an analysis time of less than 20 min. Detection of hydrazine as hydrazinium ion using electrochemical detector was linear between 10 μM and 4 mM, with LOD and LOQ values of 3 μM and 10 μM, respectively. Standard additions confirmed 103 ± 0.8% recovery. The developed method was successfully used to determine the point of complete GO reduction with hydrazine. Reaction curves for GO reduction generated using the method were compared to results from Fourier-transform infrared spectroscopy and Raman spectroscopy to verify the utility of the approach.