ABSTRACT
A new pH-metric method for determination of acid values in oilseeds without titration has been developed in the range 0.6-10 and more mg KOH/g. The method is based on a rapid (1-2 min) selective and complete extraction of free fatty acids from an oilseed test portion into a special reagent A, separation of the solution from the solid oilseed material by centrifugation or filtration, transfer of an aliquot of the solution into a pH-metric cell with reagent B for measurement of conditional pH(1)' of the formed mixture, addition of standard acid (HCl or H(2)SO(4)) and pH(2)' measurement. The reagents are non-toxic, and the method is rapid. Its metrological parameters for Soybean, Canola and Sunflower oilseeds are satisfactory for practical purposes.
ABSTRACT
The study was designed to develop an accelerated technique of air identification of trivalent chromium. The technique for alkali melting at 800-850 degrees, traditionally used for sample preparation, was replaced by acid treatment by a mixture of nitric, hydrochloric and chloric acids. Thus trivalent chromium was oxidized into hexavalent one, which was determined by means of the photocolorimetric technique by its reaction with diphenylcarbazite. The technique enabled one to lower the time for the analysis by 4 hours.
