CASE STUDY 2: Qualitative Pesticide Screening and Binary Comparison of a Spinach Sample Using HRMS

Importance of the Topic

Multi-residue screening is critical for ensuring food safety and regulatory compliance. Complex matrices such as spinach require methods capable of detecting both known and unknown pesticide residues. High-resolution mass spectrometry combined with advanced data workflows can address the expanding list of analytes and uncover unexpected contaminants in a single analysis.

Objectives and Study Overview

This case study aims to demonstrate a rapid and consistent workflow for qualitative screening of pesticide residues in a spinach extract using non-targeted HDMSE data. The goals were to identify target compounds from a predefined list and to discover unknown residues through comparative analysis against a blank sample.

Methodology and Instrumentation

A spinach extract prepared by the QuEChERS protocol (0.5 g/mL in 50% acetonitrile) was analyzed with a 5 µL injection on UPLC coupled to HRMS. Employed instrumentation included:

• ACQUITY UPLC I-Class system
• ACQUITY UPLC BEH C18 column
• Xevo G2-S QTof and Xevo G2-XS QTof mass spectrometers
• SYNAPT G2-Si HDMS module
• UNIFI Scientific Information System with Pesticide Screening Application Solution

Data were acquired in non-targeted MSE/HDMSE mode, processed via data componentization, and reviewed using customized filters, binary comparison, halogen matching, and batch elucidation tools.

Main Results and Discussion

• All nine spiked target pesticides were detected at the expected levels.
• Five additional non-target pesticides (ametoctradin, bixafen, penflufen, pyriofenone, and valifenalate) were discovered via binary compare and halogen match filters.
• The UNIFI discovery tool provided accurate elemental compositions and matched spectral fragments against ChemSpider libraries, confirming the identity of unknown residues.

Benefits and Practical Applications of the Method

• Sensitivity: Unbiased MSE data enable detection of precursors and fragments below regulatory limits.
• Speed: Fast duty cycles capture full chromatographic peaks for simultaneous qualitative and quantitative review in a single run.
• Selectivity: Apex3D peak picking and componentization discriminate co-eluting compounds in complex matrices.
• Workflow Efficiency: Integrated filters and views reduce review time and support consistent data interpretation.

Future Trends and Potential Applications

Advancements in HRMS instrumentation and software will expand non-targeted screening capabilities, enabling:

• Higher throughput analysis with automated unknown identification.
• Integration of multivariate and machine learning–based data mining approaches.
• Real-time monitoring of emerging contaminants in food and environmental samples.

Conclusions

The combined use of HDMSE acquisition, data componentization, and an integrated scientific information system provides a robust, sensitive, and efficient approach for simultaneous targeted and non-targeted pesticide screening in complex food matrices. This workflow streamlines the path from sample injection to actionable results.

Reference

• Cleland G, Graham K, Rosnack K, Burgess J. Simple HRMS data review using workflows, views, and filters within a novel integrated scientific information system. Waters Technical Note 720005436EN, July 2015.
• Cleland G, Graham K, Rosnack K, Burgess J. Qualitative pesticide screening of a dried cherry sample using HRMS. Waters Application Note 720005437EN, July 2015.
• Waters Corporation. Overview of the principles of MSE. White Paper 720004036EN, October 2011.
• ChemSpider Database. Royal Society of Chemistry. Accessed July 2015.