Water-soluble tunable ionic liquid probes for the sensitive detection of glyphosate by fluorescence turn-off-on

Evaluation of glyphosate content in tea products is a food safety topic worthy of social attention due to most glyphosate is dissolved in water as well during tea brewing. So it requires that the probe can not only realize the sensitive detection of glyphosate, but also has good water solubility to realize the practical detection of glyphosate in water-based samples such as tea infusions. To better suit the demands of practical applications, a water-soluble quinoline fluorescent ionic liquid probe (EHQCA) was synthesized for the sensitive detection of glyphosate by fluorescence “turn-off-on”. Interestingly, the introduction of the imidazolium cation module easily achieved the switchable water solubility of the fluorophore without complex group modification. According to the different competitive coordination ability, EHQCA-Cu 2+ with fluorescence-off was first constructed, and then Cu 2+ was captured by glyphosate to restore fluorescence. The probe behaved a sensitive (detection limit of 2.2 × 10 −8  M), rapid (less than 5 s) and selective response (among 20 interferences) to glyphosate. Meaningfully, satisfactory recovery (98–103 %) and low RSD (< 1.27 %) were obtained in 12 green tea infusions from different varieties and origins. Therefore, the ionic liquid-based fluorescent probes offers strong technical support for the detection of pesticides in foods such as tea, and have broad prospects in the field of food safety monitoring and evaluation.