Rapid analysis of phosphoamino acids from phosvitin by near‐infrared cyanine 1‐(ε‐succinimydyl‐hexanoate)‐1′‐methyl‐3,3,3′,3′‐tetramethyl‐indocarbocyanine‐5,5′‐disulfonate potassium derivatization and polyacrylamide‐coated CE with LIF detection

Abstract

A polyacrylamide-coated CE method with LIF detection was developed for analyzing three phosphoamino acids including phosphotyrosine (p-Tyr), phosphothreonine (p-Thr), and phosphoserine (p-Ser). A near-infrared dye, 1-(ε-succinimydyl-hexanoate)-1'-methyl-3,3,3',3'-tetramethyl-indocarbocyanine-5,5'-disulfonate potassium (MeCy5-OSu) was employed for derivatization of these phosphoamino acids. Results indicated that the complete baseline resolution of each phosphoamino acid was obtained within 6.1 min, using 10 mmol/L phosphate buffer (pH 4.0) containing 60 mmol/L SDS as running buffer. The highest derivatization efficiency was achieved in 0.2 mol/L borate buffer (pH 8.8) for 30 min at 30 °C. Linearity of response was found in the range of 0.05-1 μmol/L. The correlation coefficients for these phosphoamino acids were from 0.9940 to 0.9976. The LODs for phosphotyrosine, phosphothreonine, and phosphoserine were about 6, 8, and 8 nmol/L, respectively. The proposed method has been successfully applied to the determination of phosphoamino acids in the hydrolysis sample of a phosphorylated phosvitin. Average recoveries for phosvitin sample were in the range of 94.0-98.0% and coefficients of variation ranged from 2.7 to 4.8%.