Detection Methods Of Amino Acids Based On Derivatization And Potentiometric Sensor

Amino acids are widely distributed in biological fluids and involved in various biological processes.The contents and kinds of amino acids in biological fluids and tissue are important indicators for diagnostic metabolic disease.Meanwhile,The contents and kinds of amino acids in foods can also affect the tastes?aroma and nutritive value.Amino acids detection are attracting more and more researchers,the current detection methods have some drawbacks,such as cost?test speed and detection limit.So,development a new method for detec tion amino acids is impending.Based on the molecular characteristic of amino acids,we develop two methods based on derivatization and potentiometric sensor for detection of amino acids,the specific contents are as follow.?1?Owing to most amino acids without ultraviolet absorption,so derivatization is necessary under ultraviolet detection mode.Phenylisothiocyanate is used as the derivative reagent to derivate amino acids,study the influence of the types of chromatographic column?the mobile phase constituents and the detection wavelength on amino acids derivatives separation.The results indicate that amino acids derivatives can be fully separated under 254nm using acetonitrile and 0.1 mol/L sodium acetate as mobile phase and C18 column as separation column.Methodology validation indicate that the correlation coefficients between the peaks areas of amino acids derivatives and the amino acids concentrations was above0.999?inter-day and intra-day precision ranged from 1.26%to 6.66%and the recoveries of amino acids was between 80.14%and 111.85%.The developed method was used to detect the contents of amino acids in Lycium Barbarum.The contents of 11 detected amino acids in Lycium Barbarum ranged from 11.9%to 23.4%.?2?Phenylisothiocyanate is used as the derivative reagent to derivate free amino acids,study the influence of extraction temperature?extraction solvent and solid-liquid ratio on the extract content of free amino acids in Lycium Barbarum.The res ults indicate that free amino acids can yield maximum extract contents under 95?using water as extraction solvent and the liquid-solid ratio was 10:1.The developed method was used to detect the contents of free amino acids in Lycium Barbarum.The contents of 11 detected free amino acids in Lycium Barbarum ranged from 3.1%to 9.4%.?3?Amino acids can chelate with copper ions,which lead to reducing the concentration of copper ions,the changed concentrations can be evaluated by potential.Amino acids were detected directly by C u²⁺-selective-electrode,study the influence of the concentration of inner filling solution?concentration of buffer salts?the percent of organic phase on the chelating of amino acids with copper ions.The results indicate that there were no obvious influence on the chelating of amino acids with copper ions when using 0.01 mol/L C uC l₂ as inner filling solution?0.00001 mol/L ammonium acetate as buffer and the percent of acetonitrile below30%.The correlation coefficients between the potential drop and the amino acids concentration was above 0.991,indicate that this method can be used to detect amino acids accurately.In addition,derivatization is not necessary for this method and the cost is low,especially suitable for fields testing.