Rapid determination of copper in diesel oil by flow injection spectrophotometry with microemulsion improving solubility

A rapid method for the determination of copper in diesel oil with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol(5-Br-PADAP) as chromogenic reagent by flow injection spectrophotometry was studied in the medium of nonionic microemulsion which was composed of OP/n-butanol/n-heptane/water.In the optimum condition,Beer's law was obeyed in the range of 0～2.0 μg/mL for copper at 558 nm and the determination frequency was 180 times/h.The proposed method need not pretreatments,such as ashing,extraction etc.It has been directly applied to the determination of copper in diesel oil with recoveries being 102.5%,103.2% and RSD of 2.91%,2.58%,respectively.