Direct immersion dual-drop microextraction for simultaneous separation and enrichment of Cr(III) and Cr(IV) in food samples prior to graphite furnace atomic absorption spectrometry detection

•Direct immersion dual-drop microextraction (DIDDME) was firstly developed for Cr species.•Cr(III) and Cr(VI) were separated and enriched into two drops at pH 3.5, respectively.•DIDDME did not require tedious oxidation/reduction or centrifugation/filtration steps.•This method avoided risk of sample contamination and analysis errors in redox speciation strategies.•Ingenious use of DIDDME made separation of Cr(III) and Cr(VI) convenient, efficient and time-saving.