The determination method of Cr (VI) using diphenylcarbazide is a spectrophotometric method. You need to measure the absorbance of samples after the formation of colored compounds. Then read the corresponding concentration on the calibration curve.

Acidify 10 ml Cr (VI) solution with 0.5 ml !:! HCl and add 1ml of 0.1 ml of Diphenyl Carbazide dissolved in acetone. Stay for 15 min and measure the absorbance at 540 nm. Quantify using standard solution using same method.

Thank you Cristian & Supriya

At first you have to acidify with dilute sulfuric acid (shake), and then immediately add the reagent solution (shake), preferably in acetone. If there are any organic compounds present in the sample solution, keep exact timing and prove the result by recovery.

You should also prove that CrVI is stable during the extraction procedure. The reaction itself was interfered only by excess Vanadium. Organics usually react at pH< 6.

I preferred to work in 50 ml volumetric flasks. Mixing is easy; colour development needs longer, but it is stable for a longer time.