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Kinetic Spectrophotometric Determination of Thiols and Ascorbic Acid

This paper describes a kinetic spectrophotometric method for the determination of L-ascorbic acid (AA) and thiols (RSH). The method is based on a redoxreaction of these compounds with an Fe(III)-phen complex at pH = 2.8. Absorbance of the Fe(II)-phen complex formed during the reaction was continuously measured by using a UV-Vis spectrophotometer with a flow cell. For determination some thiols, the catalytic effect of Cu^2+ ions was used. The rectilinear calibration graphs were obtained by plotting absorbance recorded in a fixed time interval versus concentration in the AA concentration range from 4.0 x 10^-6 to 4.0 x 10^-5 M and in the RSH concentration range from 8.0 x 10^-6 to 8.0 x 10^-5 M. The proposed method is simple and inexpensive. The applicability of the proposed method was demonstrated by determination of chosen compounds in pharmaceutical dosage forms.

kinetic determination; spectrophotometry; thiols; ascorbic acid

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