Visual detection of Cu2+ in high-copper feed based on a fluorescent derivative of rhodamine B

In this work, a reversible "turn on-off" fluorescent probe (RE) was designed and synthesized using rhodamine B spirolactam and 3-Ethoxysalicylaldehyde as raw materials. Experimental results showed that the probe has high sensitivity and selectivity to realize "naked eye" recognition for Cu2+ in EtOH-PBS buffer solution (1:2) at pH 7.4 with the detection limit of 27 nM (1.73 × 10−3 mg/kg). The recognition process was reversible for 4 times, and the recognition mechanism has been verified by 1H NMR and HRMS. The probe was used to detect the Cu2+ content quickly in high-copper feed when the copper ion exceeds from the standard limits. The accuracy of fluorescent probe method was verified by comparing it with atomic absorption spectrometry and recovery percentage of spiked samples. Furthermore, the copper content was accurately detected by probe in pig manure, urine, serum, pork, and portable test strips which were employed for visual detection of copper content.