Microwave plasma torch-atomic emission spectrometry for the on-line determination of rare earth elements based on flow injection preconcentration by TiO2-graphene composite

► TiO2-graphene composite was synthesized and used for a rapid on-line pretreatment procedure coupled with MPT-AES. ► Experimental conditions were optimized to adsorb trace La, Tb, and Ho with the on-line preconcentration system. ► The on-line preconcentration system was applied to determine La, Tb, and Ho in certified reference material and high purity REE oxide samples.