Schiff base was synthesized by deep eutectic solvent and applied to the rapid detection of glutamic acid, aspartic acid, arginine and ascorbic acid

Glutamic acid (Glu), aspartic acid (Asp), arginine (Arg) and ascorbic acid (AA) play an important role in the body’s protein anabolism, promoting tissue healing, improving disease resistance, as well as promoting bone growth, improving malnutrition, antioxidant and so on. Therefore, rapid detection of Glu, Asp, Arg and AA is of great significance. 2-methoxy-4-(((5-phenyl-1,3,4-thiadiazol-2-yl)imino)methyl)phenol (Probe A) was synthesized with deep eutectic solvent as catalyst under mild conditions. The Probe A was applied to the detection of Glu, Asp, Arg and AA, and the results showed that Probe A could well identify Glu, Asp, Arg and AA. Glu, Arg and AA are well recognized at pH = 6–12. Asp is well recognized at pH = 7–12. The binding ratios between Probe A and Glu, Asp, Arg, AA were 2:3, 2:3, 1:2 and 2:3, respectively. The association constants were 9.59 × 10 3  M −1 , 7.34 × 10 3  M −1 , 4.46 × 10 4  M −1 , 1.69 × 10 4  M −1 , respectively. The detection limits were 3.33 × 10 –5  M, 1.62 × 10 –5  M, 2.22 × 10 –4  M, and 1.69 × 10 –5  M, respectively. The probe solution quickly became colorless after adding Glu, Asp and AA, and orange-red after adding Arg. The identification mechanism of Probe A with Glu, Asp, Arg and AA was obtained by infrared titration and nuclear magnetic titration. This method provides an important way for rapid detection of Glu, Asp, Arg and AA.