Flow injection spectrophotometric determination of ultra trace amounts of oxalic acid

A new simple, sensitive and rapid catalytic-spectrophotometric method for t he determination of oxalic acid has been described based on its catalytic e ffect on the redox reaction between dichromate and Brilliant cresyl blue in acidic media by means of a Row injection analysis method. The color change of Brilliant cresyl blue due to its oxidation was monitored spectrophotome trically at 625 nm. The calibration graph was linear in the range of 0.020- 4.70 mu g/mL oxalic acid with a limit of detection 0.005 mu g/mL of oxalic acid. The relative standard deviation for ten replicate measurements of 0.0 20 mu g/mL and 0.900 mu g/mL was 2.2% and 1.7%, respectively. No serious in terference was identified. Oxalic acid was determined in wastewater and in spinach by the proposed method with satisfactory results.