Physiology of Finfish and Shellfish (2+1)

Procedure

25ml of water sample is taken in a conical flask and 1mlof citrate solution is added. Now 1ml of phenol-nitroprusside and 1ml of NaOCl or 3ml of bleaching powder solution is added. The contents are mixed well and the flask is covered with aluminium foil. The flask is then kept in dark for about 2 hours. If the colour develops within 5 minutes, the analysis is repeated with fresh sample. After 2 hours the sample is taken to the spectrophotometer for concentration determination by measuring optical density(OD).

Again after 30 minutes of introduction of fish, the water sample can be taken to spectrophotometer after adding reagents for the estimation of NH₃^-N.