A flow injection (FI) system was used to develop an efficient online sorption preconcentration system for graphite furnace atomic absorption spectrometry (GF‐AAS) and inductively coupled plasma atomic emission spectrometry (ICP‐AES). The investigated metal was preconcentrated on a microcolumn packed with 1,5‐bis(2‐pyridyl)‐3‐sulfophenyl methylene thiocarbono‐hydrazide (PSTH) immobilized on an anion‐exchange resin (Dowex 1×8‐200) and placed in the autosampler arm for GF‐AAS or in the injection valve of a FI manifold for ICP‐AES. The metal was eluted from the column using a solution of 2 M HNO3. Various parameters and chemical variables affecting the preconcentration and determination of platinum by GF‐AAS and ICP‐AES were evaluated. Under the optimum conditions, the usefulness of two different methods was studied and compared. The proposed FI‐GF-AAS method has a detection limit of 1 ng mL−1, and the precision of the method (RDS) was 1.6% at the 10 ng mL−1 level of Pt(IV); in the same way, the proposed FI‐ICP‐AES method has a detection limit of 7.4 ng mL−1, and the precision of the method (RSD) was 3.06% at the 50 ng mL−1 level of Pt(IV).