Structural Elucidation of Agrochemicals and Related Derivatives Using Infrared Ion Spectroscopy

Abstract

Agrochemicals frequently undergo various chemical and metabolic transformation reactions in the environment that often result in a wide range of derivates that must be comprehensively characterized to understand their toxicity profiles and their persistence and outcome in the environment. In the development phase, this typically involves a major effort in qualitatively identifying the correct chemical isomer(s) of these derivatives from the many isomers that could potentially be formed. Liquid chromatography-mass spectrometry and nuclear magnetic resonance (NMR) spectroscopy are often used in attempts to characterize such environment transformation products. However, challenges in confidently correlating chemical structures to detected compounds in mass spectrometry data and sensitivity/selectivity limitations of NMR frequently lead to bottlenecks in identification. In this study, we use an alternative approach, infrared ion spectroscopy, to demonstrate the identification of hydroxylated derivatives of two plant protection compounds (azoxystrobin and benzovindiflupyr) contained at low levels in tomato and spinach matrices. Infrared ion spectroscopy is an orthogonal tandem mass spectrometry technique that combines the sensitivity and selectivity of mass spectrometry with structural information obtained by infrared spectroscopy. Furthermore, IR spectra can be computationally predicted for candidate molecular structures, enabling the tentative identification of agrochemical derivatives and other unknowns in the environment without using physical reference standards.

Targeted Small-Molecule Identification Using Heartcutting Liquid Chromatography–Infrared Ion Spectroscopy

“…Infrared ion spectroscopy (IRIS) − is a relatively novel approach integrating MS with infrared spectroscopy, so that an infrared spectrum, and hence direct information on chemical bonding, can be obtained for an isolated m / z -feature. Recent studies have detailed its potential for molecular structure elucidation in a variety of research fields including forensics, − environmental science, − drug development, − and clinical research. ,, IRIS is an action spectroscopy technique; IR spectra are generated by recording the photodissociation of ions after irradiation at a series of IR laser frequencies. Plotting the extent of fragmentation as a function of the IR frequency provides the IR spectrum.…”

Characterization of Solar Radiation-Induced Degradation Products of the Plant Sunscreen Sinapoyl Malate

“…38,39,42−45 Although this study focuses on SM, the presented workflow is generically applicable, and a proof-of-concept study on other agrochemical compounds has recently been published. 46 ■ CHEMICALS AND MATERIALS SM was synthesized by AgroParisTech (Paris, France) following a procedure reported previously. 47 Methanol (MeOH), water, sinapic acid ≥99%, and formic acid (FA) were obtained from Merck (Darmstadt, Germany).…”

“…The ability of modern quantum-chemical calculations to predict IR spectra with high fidelity enables us to quickly narrow down the list of candidate molecular structures for the photoproducts and achieve tentative but reasonable structural assignments. Implementing IRIS spectroscopy with quantum-chemical computational workflows facilitates a reference standard-free approach to characterize unknown (bio-)­transformation products in complex mixture samples. ,,− Although this study focuses on SM, the presented workflow is generically applicable, and a proof-of-concept study on other agrochemical compounds has recently been published …”

“… 38 , 39 , 42 − 45 Although this study focuses on SM, the presented workflow is generically applicable, and a proof-of-concept study on other agrochemical compounds has recently been published. 46 …”

Targeted small molecule identification using heartcutting liquid chromatography–infrared ion spectroscopy

“…Infrared ion spectroscopy (IRIS) [10][11][12][13][14][15][16][17] is a relatively novel approach integrating MS with infrared spectroscopy, so that an infrared spectrum, and hence direct information on chemical bonding, can be obtained for an isolated m/zfeature. Recent studies have detailed its potential for molecular structure elucidation in a variety of research fields including forensics [18][19][20][21] , environmental science [22][23][24] , drug development [25][26][27] and clinical research 25,28,29 . IRIS is an action spectroscopy technique; IR spectra are generated by recording the photodissociation of ions after irradiation at a series of IR laser frequencies.…”