METHOD FOR DETERMINATION OF VALINE IN AQUEOUS SOLUTIONS Russian patent published in 2007 - IPC G01N31/16 

FIELD: analytical chemistry of organic compounds, possibly standard analysis of sewage of production of pharmaceutical preparations such as biologically active food supplements, amino acid mixtures, vitamin complexes.

SUBSTANCE: method comprises steps of preparing aqueous solution of valine; adding to it salting out agent such as crystalline lithium sulfate in quantity 25 mass % of mass of solution; agitating and adding preliminarily prepared binary mixture of hydrophilic solvents containing 30 -40 mass % of butyl alcohol and 70 -60 mass % of ethyl acetate at relation of valine solution - binary mixture 10 : 1; extracting in vibration mixer for 5 min ( during such period inter-phase balance is achieved); after exfoliation of phases separating extract without taking aqueous layer and transferring to cell for conductometric titration for titrating by means of 0.01 mol/l solution of KOH in water free ethyl alcohol; according to results of titration plotting curve of relationship of extract electrical conductivity upon volume of consumed titrant; determining equivalent volume of titrant used for titration of valine; calculating mass of valine in organic phase according to formula: m_o = C x V x M/1000 where C -concentration of KOH in ethyl alcohol ( 0.01 mol/l); M - mol. mass of valine; determining mass of valine remained in aqueous phase after extraction by subtracting quantity of valine transferred to organic phase from initial mass of valine dissolved in water; calculating distribution factor D of valine with use of formula D = m_o/m_v and extraction degree with use of formula R =D 100/D + r where r relation of balanced volumes of aqueous and organic phases. Method allows determine valine in aqueous solutions at concentrations such as 0.05 mg/ml.

EFFECT: enhanced accuracy of determining valine in aqueous solutions with use of binary mixture of hydrophilic solvents.

2 notes, 1 tbl