Structure elucidation of a novel analogue of pesticide from express post parcel by HRMS
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An express post parcel was confiscated due to the stuff was not equal to the named stuff. HPLC coupled with high resolution mass spectrometry (HRMS) was applied to separate and elucidate the unknown by the combination of the accurate molecular weight, isotope ratio, and fragments. Nuclear magnetic resonance spectroscopy was performed for further confirmation. A new derivative of pesticide chlorantraniliprole was found and first reported. The pesticide analogue named 3-Bromo-1-(3-chloro-2-pyridinyl)-N-[2,4- dichloro-6-(isopropylcarbamoyl) henyl]-1H-pyrazole- 5-carboxamide. The derivative of chlorantraniliprole was not able to be detected by any routine pesticide residue analysis. It could be illegally used in claimed organic food or any natural vegetable. Besides, the dishonest people import illegal chemical through express post parcel without registering to any authority, made hazardous chemical transportation management very hard, as well the prevention of the entry of chemicals into food chain.
KeywordsUnknown compound High resolution mass spectrometry Chlorantraniliprole derivative Orbitrap
An express post parcel was confiscated by customs due to the stuff was in fact not the equal of the named stuff and not met the actual needs of the regulation. The parcel was identified as unknown powder and previously sent to analytical labs for routine pesticide and drug screening. However, the reports all answered not detected. In this study, Orbitrap MS coupled with liquid chromatography was applied for the analysis of unknown compound in matrix with purification. The unknown compound structural elucidation was done by the combination of the accurate molecular weight, isotope ratio, and fragments of the unknown. A rare pesticide was identified and reported in this paper. The “new” pesticide was actually a derivative of a registered pesticide.
2 Materials and methods
2.2 Separation and detection
An UltiMate 3000 Standard LC system (Thermo Fisher Scientific Inc. Waltham, MA, USA), an Acquity UPLC HSS T3 column (2.1 × 100 mm, 1.8 μm), and the eluent consisted of 0.1% formic acid water solution (A) and acetonitrile with 0.1% formic acid (B) was utilized. The linear gradient programed as following: 0–1 min, 10% B; 1–11 min, 10–100% B; 11–19 min, 100% B; 19–20 min, 100–10% B; 20–25 min, 10% B. The flow rate was 250 µL/min. Orbitrap MS was Q Exactive Plus Hybrid Quadruple-Orbitrap Mass Spectrometer (Thermo Fisher Scientific Inc.). The heater and capillary temperature was set to 250 °C and 240 °C, respectively. The capillary of the ESI interface was set to 3.8 kV. Sheath gas and auxiliary gas were set to 50 and 5 units, respectively. Scan range was m/z = 100–1000 and resolution was 140 k (defined at m/z = 200 and was set at full width at half maximum). C-trap was set to allow 1 × 106 charges and the maximum injection time was 100 ms. For product ion scan, the HCD (higher-energy collisional dissociation) was set to 30 eV and 60 eV with precursor ion window 1.7 Da. The resolution was set to be 35 k.
The purified unknown powder was prepared in deuterated chloroform in a Wilman 528-PP 5 mm NMR tube. NMR spectra were acquired on a Bruker FT-NMR (400 MHz, Bruker, Billerica, MA, USA), equipped with a 5 mm PABBO BB probe. Chemical shift δ values were cited in parts per million (ppm) in reference to tetramethylsilane as zero ppm. The multiplicity abbreviations used to describe NMR signals are s = singlet, d = doublet, m = multiplet, and j = j coupling.
3 Results and discussion
3.1 Unknown powder structural elucidation
Possible element composition of the unknown (M + H)
3-Bromo-1-(3-chloro-2-pyridinyl)-N-[2,4-dichloro-6-(isopropylcarbamoyl)phenyl]-1H-pyrazole-5-carboxamide is an pesticide analogue and discovered in illegal import. The newly synthesized pesticide derivative is not possible to be detected by any routine pesticide residue analysis. The illegal import of harmful chemical to use in food production sure will harm people and the environment. There have been reports that more and more unapproved analogues found in foods, such as structurally modified analogues of phosphodiesterase type-5 (PDE-5) inhibitor drugs and new psychoactive substances (NPS) [3, 4]. Our finding of a novel pesticide analogue should get the governmental authorities to pay attention to chemical and pesticide managements. The provided mass spectrum is a good tool for scientists on the compound detection and the data library establishment. High resolution Orbitrap mass spectrometry is successfully applied in the structure elucidation of unknowns assisted with HPLC offers fast detection with simple purification and other instrumentation.
Compliance with ethical standards
Conflict of interest
The authors declare no conflicts of interest.