Milk and milk products — Determination of copper content — Photometric reference method

Applies to milk, skimmed milk, whey, buttermilk, evaporated milk, sweetened condensed milk, dried whole and skimmed milk, cream and butter, butterfat, ice-cream, hard, semi-hard and soft cheese of various ages and processed cheese, caseins, caseinates and coprecipitates. The principle of determination consists in digesting the organic material with a mixture of nitric and sulfuric acids and neutralizing with ammonium hydroxide solution followed by complexing the copper as a salt of diethyldithiocarbamic acid.