Cr(III) or Cr(VI)? For Cr(VI), complexation with diphenylcarbazide is a well-established method for UV/vis. See for example https://www.hindawi.com/archive/2016/3468635/
Chromium content in the diets used by Furukawa and Tsukahara (1966) method. Briefly, 50 to 100 mg of samples were digested using nitric acid and perchloric acid in a fume cupboard on a digestion mantle until all nitric acid expelled (When the fume stop evolving, the digested solution become golden yellow in colour if chromium is present). To the known volume of digested sample, 1 ml of diphenyl carbozide reagent was added and incubated at room temperature for 10 min. The intensity of the colour developed (bright pink) was read at 350 nm against reagent blank in UV-spectrophotometer.