METHOD FOR DETERMINING ALANINE IN AQUEOUS SOLUTION

FIELD: analytical chemistry of organic compounds, possibly alanine content control method in protein mixtures and biologically active supplements. ^ SUBSTANCE: method comprises steps of preparing aqueous solution of alanine; adding to it lithium sulfate in quantity 20 - 25 mass% in relation to mass of solution; agitating and adding triple mixture of hydrophilic solvents containing 30 mass % of isopropyl alcohol, 30 mass of ethyl acetate and 40 mass % of acetone at volume relation of aqueous- salt solution - triple mixture of solvent 10 : 1; extracting in vibration mixer for 5 min for achieving inter-phase equilibrium; curing for 1 - 2 min for exfoliation of phases; separating extract and transferring to cell for potentiometric titration; determining alanine content in extract due to plotting according to EMF measurement results differential titration curve (relationship of EMF change depending upon volume of used titrant); with use of respective maximum of curve determining equivalent volume of titrant( KOH solution in water free ethyl alcohol) consumed for titration of alanine solution; calculating according to formula m0 = C x V x M/1000 where C - concentration of KOH solution in ethyl alcohol (0.01 mol/l), M -mol. mass of alanine; the determining mass of alanine remained in aqueous -salt solution by subtracting quantity of alanine transferred to organic phase from initial mass of alanine; calculating distribution factor D of alanine according to formula D = mo/mB; determining extraction degree R = D - 100/D + r where D -distribution factor of alanine between triple mixture of hydrophilic solvents and aqueous -salt solution, r - relation of equilibrium volumes of aqueous and organic phases. Method provides determination of alanine in aqueous solution at concentration such as 0.01 mg/ml. ^ EFFECT: enhanced accuracy of determination of alanine in aqueous solution with use of salting out agent and tripe mixture of hydrophilic solvents. ^ 2 notes, 1 tbl