A fish scale-like magnetic nanomaterial as a highly efficient sorbent for monitoring the changes of auxins level under cadmium stress

Sorbents with high surface utilization and good dispersibility are of great importance for extraction performance of magnetic solid phase extraction (MSPE). In this study, a fish scale-like magnetic nanomaterial (Co@Co3O4/OCN) was synthesized, which can be used as a highly efficient MSPE sorbent due to its strong magnetism, special morphology, doping of N elements, numerous micro-mesopores cavities and organic functional groups (hydroxyl, carboxyl). Further, a Co@Co3O4/OCN-based MSPE method for monitoring the changes of three auxins (indole-3-acetic acid, indole-3-propionic acid and 3-indole butyric acid) level was successfully established. Wide linear ranges (1.0-1000.0 pg mL-1) with good correlation coefficients (R > 0.9992), low limits of detection (LODs, 0.2-4.0 pg mL-1) and satisfactory repeatability (RSD ≤ 5.9%, n = 3) were obtained. Using the developed method, various growth parts and different growth periods of plants under Cd stress were monitored. The results showed auxins in various parts of plants had differential response under Cd stress, and there was a threshold for the changes of auxins levels against Cd stress. This indicates that the developed fish scale-like Co@Co3O4/OCN nanomaterial has a good application prospect for enriching small molecular targets containing hydroxyl and carboxyl groups.