Highly sensitive spectrofluorimetric determination of l-cysteine based on inhibition of hemoglobin

A highly sensitive spectrofluorimetric method for the determination of l-cysteine based on its inhibitory action on hemoglobin (Hb) activity was developed. The optimal conditions were studied. A linear calibration graph was obtained over the range 2.00×10−7–1.50×10−6 mol l−1 for l-cysteine. The relative standard derivation was 1.30% at l-cysteine concentration of 8.00×10−7 mol l−1 (n=11). Further experimental results revealed that the inhibition of l-cysteine on this system was of the competitive type. The method was applied to determine l-cysteine in protein hydrolysate and cystine electrolyte samples with satisfactory results.