Towards the use of ion mobility mass spectrometry derived collision cross section as a screening approach for unambiguous identification of targeted pesticides in food

Abstract

Rationale Mass spectrometry (MS) is the reference method for the screening of ultra‐trace residues of pesticides in food because MS offers the required selectivity/sensitivity to gather information and enable the analyst to make informed decisions during the identification process. Here we present and discuss the use of collision cross section (CCS) values in addition to mass accuracy and retention times in a pesticide screening method that integrates all the features offered by coupling ultra‐performance liquid chromatography (UPLC) with ion mobility mass spectrometry (IMS‐MS). Methods All experiments were carried out using UHPLC coupled to a travelling wave ion mobility mass spectrometer equipped with an electrospray ionization (ESI) source working in positive mode. An in‐house library containing 200 pesticides was built using standard solutions and used as reference for a TWCCS calibration study. Matrix extracts were analyzed to evaluate the performance of different screening workflows based on TWCCS, mass accuracy and retention times. Results The results proved that TWCCS values are very consistent, as the measured values do not differ more than 1% from the in‐house reference data library and emphasized the importance of the first low m/z mobility calibration point to guarantee full independence from instrument parameters and calibrant. The screening procedure was simplified to a single step by fully exploiting the content of ion mobility without generating any false detections, either positive or negative, from spiked samples and a previous proficiency test. Conclusions The screening approach proposed in this study is unconventional and based on large mass accuracy (20 ppm) and retention time windows (0.5 min) to capture, in a first step, a maximum of detected compounds. Compounds of interest are then identified by comparing measured collision cross sections with the measured reference library collision cross sections (with relative error tolerance lower than 2%).

Ion Mobility Spectrometry in Food Analysis: Principles, Current Applications and Future Trends

“…For this reason, the use of the CCS as the information provided by IMS has been extended. Consequently, CCS databases can be created and applied to support the determination of compounds, reducing the number of false negative/positives found in classical LC–MS workflows [112], and increasing the detection rates at low concentration levels of residues [39]. In the current context of Regulation 2002/657/EC revision, it has emerged the proposal to include the CCS as IP for the identification of veterinary drugs in food [95].…”

“…However, several concerns have been raised such as the lack of CCS databases and the tolerance accepted for CCS measurements. While, until a few years ago, CCS had been barely used as verification parameter in screening approaches due to the lack of databases, this situation has now recently changed and several CCS databases for pesticides [112,113], veterinary drugs [114,115,116], mycotoxins [117] and other contaminants [108], have been reported in the last five years.…”

“…Finally, recent applications of LC–ESI–TWIMS–ToF–MS methods, which include the CCS as signal filter in data processing, report the analysis of mycotoxins in cereals [117] and pesticides in green tea powder, fresh garlic, leek, fresh herb chives and rye [112], fish feed [31], and in 20 food products (e.g., strawberries, honey, chia seed, etc.) that belong to six different commodities according to SANTE/11813/2017 [39].…”

Ion mobility mass spectrometry: Small molecule applications

“…With increased commercialization comes more routine use in many different areas, not only to study large molecule interactions and conformations, but especially in small molecule research . This is nicely illustrated in this special issue showing small molecule IMS‐MS applications in different fields, such as analysis of antibiotics, natural products, pesticides, pharmaceutical compounds, nucleic acid strands, and metabolites, on systems from four different vendors with six different instrumental designs, all providing different characteristics, advantages and disadvantages …”

“…CCS measurements also have the potential to be used as an additional qualifier next to accurate mass, fragmentation and/or retention time. Goscinny et al demonstrate the feasibility of using IMS‐MS for screening purposes of pesticides by an inter‐laboratory comparison of CCS values taking into account the importance of a sound CCS calibration procedure. Mairinger et al demonstrate on the other hand how better‐quality MS/MS data with improved dynamic range could be obtained for yeast metabolites in data‐independent acquisition (DIA) mode by aligning the drift times of dansylated metabolites with quadrupole broad band isolation.…”