Amide carbon quantum dots as chemiluminescent probes for the real-time quantitative detection of the carcinogen ethylene thiourea and its homologs in vegetables

Ethylene thiourea (ETU) and propylene thiourea (PTU), the degradation products of dithiocarbamates, are carcinogenic, teratogenic, and mutagenic. In this study, we developed an ultrasensitive method for the simultaneous detection of ETU and PTU using amidated carbon quantum dots (A-CDs) as chemiluminescent probes. The distinctive chemiluminescence (CL) mechanisms of the A-CDs were elucidated using CL spectroscopy, radical trapping experiments, and mass spectrometry. ETU or PTU are oxidized by Ce(IV) resulting in the formation of sulfur-based free radicals. Then the radicals are selectively recognized by the A-CDs accompanying with CL emission. The high-performance liquid chromatography-CL method was validated by quantifying ETU and PTU in vegetables, wherein the detection limit was 0.17 μg·kg⁻¹. Comparing with previous literatures, the proposed method demonstrated advantages with lower solvent use, shorter detection time, reduced matrix effects, higher accuracy and precision. The results indicated that ETU was really detected in tomatoes, implying the potential risk of public health.