FLOW INJECTION DETERMINATION OF ASPARAGINE AND HISTIDINE USING DIPERIODATOCUPERATE BASED ON SPECTROPHOTOMETRIC INHIBITION DETECTION IN AMINO ACID SUPPLEMENTS

A rapid and sensitive spectrophotometric method is developed for the determination of asparagine (Asn) and histidine (His) based on their inhibition effect on diperiodatocuperate (DPC) absorption intensity at 415 nm in micellar alkaline medium using a double beam spectrophotometer. The effect of different experimental parameters such as concentration of DPC, potassium hydroxide and cetyl trimethyl ammonium bromide, flow rate, sample loop volume and reaction coil length was examined. The method presented a linear range of 0.2 – 10 μg mL–1 for Asn and 0.35 – 10 μg mL–1 for His under the optimized conditions. The limits of detection (LODs) were 0.06 μg mL–1 for Asn and 0.1 μg mL–1 for His with injection throughput of 120 h –1 . The limits of quantification (LOQs) were 0.2 μg mL–1 for Asn and 0.33 μg mL–1 for His. The relative standard deviations (RSDs, n = 10) of the method were 2.9 % and 3.4% for Asn and His at 0.1 μg mL-1 concentrations level. The method was applied for the determination of Asn and His amino acid supplements. Keywords: Flow injection analysis, UV-Vis spectrophotometry, Diperiodatocuperate, Asparagine, Histidine, Amino acid supplement