METHOD OF PHOTOMETRICALLY DETERMINING UREA AND ITS DERIVATIVES Russian patent published in 1997 - IPC

FIELD: analytical methods. SUBSTANCE: determining compounds with general formula R_IHNCONHR₂ where consists in adding sulfuric acid to test sample to achieve sulfuric acid concentration 25-30 wt % in solution obtained, whereupon solution is supplemented with dimethylglyoxime and thiosemicarbazide. Colored solution is then photometered at 525-530 nm. When R₁R₂=CnH_2n+1, solution is heated for 10 min. EFFECT: increased stability of colored reaction product. 2 cl, 1 tbl