Spectrophotometric Determination of Cysteine by Complexation With Iron (Iii) Using Reversed Flow Injection Analysis (R-Fia)

Fakhr Eldin O. Suliman, Salama B. Salama*, Taqiya Al-Abri and Salma M. Z. Al-Kindy

Sultan Qaboos Universtiy, College of Science, Department of Chemistry, Al-Khod 123 (Sultanate of Oman)

A simple spectrophotometric flow injection analysis (FIA) method has been developed for the assay of cysteine. In this method a purple colored complex of cysteine and iron (III) was monitored at a wavelength of 545 nm. The optimum operating conditions for the quantitative assays of cysteine were, pH 9.7, flow rate, 2.6 ml/min; coil length, 50 cm; and sample loop size, 85μL. Beer's law was obeyed for the range 500-2500 ppm with a correlation coefficient of 0.9996 . The maximum relative standard deviation was 1.73% (n = 10). Other amino acids tested show minimum or no interference when analyzed in mixtures with cysteine.

Amino acids; flow injection analysis; iron(III); spectrophotometry