Analysis of amino acids in blood by combining zeolitic imidazolate framework-8-based solid phase extraction and capillary electrophoresis.

Detection of amino acids (AAs) in blood is helpful to diagnose some diseases. In this work, a method is developed for determination of trace amounts of AAs in bovine blood by combining solid phase extraction (SPE) and capillary electrophoresis (CE). Zeolitic imidazolate framework-8 (ZIF-8) nanoparticles are prepared and used as adsorbents to simultaneously extract three AAs (tryptophan, tyrosine, phenylalanine). Under the optimum extraction conditions, the extraction efficiencies of ZIF-8 for AAs are 95.1% (tryptophan), 91.1% (tyrosine), and 90.1% (phenylalanine), respectively. Interestingly, ZIF-8 demonstrates good extraction ability for AAs in high concentration of acetonitrile (ACN) aqueous solutions. Thus, they can be directly used to extract AAs from the deproteinized blood sample using ACN. An α-cyclodextrin-mediated cation selective exhaustive injection-sweeping CE method is developed for analysis of the extracted AAs. The detection limits for AAs range from 0.13 to 0.37 μg mL using the SPE/CE method. Standard addition method is used to evaluate the feasibility of the method in bovine blood samples. The standard addition curves demonstrate good linearity with determination coefficient > 0.9912.