Two D-π-A Schiff-Base-Functionalized Silica Gel Adsorbents for Preconcentration of Copper Ions in Foods and Water for Detection

Copper is an essential element in many biological processes and plays an important role in carbohydrate and lipid metabolism. Excess or deficiency of Cu ions can cause disturbances in cellular homeostasis and damage the central nervous system. Here, for the first time, two functionalized silica gel( SG-A and SG-B) adsorbents were prepared and tested for copper detection via the reactions of chlorinated silica gelwith two novel D-π-A Schiff basecompounds: 2-amino-3-(quinolin-2-ylmethyleneamino)maleonitrile (A) and 2-(4-(diethylamino)-2-hydroxybenzylideneamino)-3-aminomaleonitrile (B) in the thionyl chloridesolution, respectively. SG-A and SG-B as adsorbents filled in a microcolumn were used to enrich trace Cu ions in foods and water with the detection of flame atomic absorption spectrometry. Because of the strong coordination between two D-π-A Schiff basecompounds and Cu2+ ions, the stable heterocyclic Cu2+- SG-A/B complex is formed. For a sample volume of 30 mL, detection limits of 0.09 μg L–1 and 0.15...