Researchers developed a method to detect chromium(Ⅵ) and chromium(Ⅲ) in river water using flame atomic absorption spectrometry. They used diphenylcarbazide in acidic conditions to form a complex with chromium(Ⅵ), which was then extracted for analysis. Potassium permanganate was used to convert chromium(Ⅲ) to chromium(Ⅵ) for detection. The method had a detection limit of 0.0007 mg·L~(-1) and could accurately measure chromium concentrations in a range of 0.0007 to 1.0 mg·L~(-1). The recovery rates for chromium(Ⅵ) and chromium(Ⅲ) were between 100% to 112% and 89% to 104%, respectively.