METHOD OF DETERMINING NITRATE, REDUCING AGENT AND A METHOD OF PREPARATION THEREOF Russian patent published in 2003 - IPC

FIELD: analytical methods. SUBSTANCE: determination of nitrate involves reducing the latter into nitrite with the aid of vanadium(III) salt in presence of two compounds able to be diazotized, one of them being added to analytical sample before addition of reducing agent and reacts with nitrite and other nitrosation agents present in sample. The other of the two compounds, preferably sulfanilamide, is added to reaction mixture after all amount of nitrite present in sample is consumed. Nitrite arising upon reduction of nitrate reacts with both compounds able to be nitrosed. Azo dye formed during combination of the second compounds able to be nitrosed with substituted naphthylamine, in particular N¹,N¹- diethyl-N²-naphthylethylenediamine, is determined colorimetrically. Amount of dye formed depends on reduction time and vanadium(III) concentration. Concentration of nitrate in the sample is found from calibration graph plotted with standard samples. Method is well suited at high nitrite concentrations decreasing sensitivity in known methods. Reducing agent, which is vanadium salt mixture, is prepared by treating acid solution of vanadium salt with magnesium metal (independent claims). EFFECT: increased sensitivity and selectivity of analysis and enhanced availability of reducing agent. 9 cl, 15 ex