Qualitative and Quantitative Analysis of Pesticides in Horse Feed Matrix Using Orbitrap MS

Importance of the topic

The analysis of pesticide residues in animal feed is crucial for ensuring food safety and compliance with regulatory standards. Advances in high resolution mass spectrometry enable rapid and accurate detection of trace contaminants in complex matrices such as horse feed.

Goals and overview of the study

This study evaluates the performance of a benchtop high resolution accurate mass Orbitrap mass spectrometer for qualitative and quantitative analysis of 85 common pesticides in horse feed extracts using very short UHPLC gradients.

Methods and instrumentation

Sample preparation involved QuEChERS extraction of horse feed spiked with pesticide standards at levels between 5 and 150 micrograms per kilogram. Chromatographic separation was achieved on a Thermo Scientific Accela UHPLC system with a Hypersil GOLD PFP column under a two minute water methanol gradient containing 0.1 percent formic acid at a flow rate of 800 microliters per minute and a total cycle time of five minutes. The mass spectrometer was a Thermo Scientific Exactive Plus Orbitrap equipped with an S Lens ion optics assembly, operating at a resolving power of 70000 at m/z 200 and a scan rate of 3.7 Hz. Data dependent all ion fragmentation scans were triggered via a mass inclusion list to combine full scan detection with targeted fragmentation. Data processing was performed using Thermo Scientific ExactFinder version 2.0 for both targeted screening and general unknown identification.

Used instrumentation

• UHPLC system Thermo Scientific Accela open autosampler and Accela 1250 pump with Hypersil GOLD PFP column 50 x 2.1 mm 1.9 micrometers
• Orbitrap mass spectrometer Thermo Scientific Exactive Plus with S Lens and improved electronics resolution range from 17500 to 140000 at m/z 200 and maximum scan rate of 12 Hz
• Software Thermo Scientific ExactFinder version 2.0 for qualitative and quantitative processing

Main results and discussion

• Linear calibration was achieved for nearly all pesticides across the 5 to 150 micrograms per kilogram range, demonstrating high selectivity from a 5 ppm mass extraction window and elevated resolving power
• Chromatographic peak widths of three to six seconds yielded at least ten scans per peak, supporting accurate quantitation in very short gradients
• Data dependent all ion fragmentation provided targeted fragmentation information without compromising full scan sensitivity and throughput
• Confirmation criteria including retention time, isotopic pattern matching, fragment search, and spectral library comparison ensured reliable qualitative results
• High resolution full scan separated analyte and matrix signals, preventing interferences that could cause false positives or negatives
• General unknown screening detected approximately fifteen thousand components, enabling identification of additional contaminants beyond the targeted list

Benefits and practical applications

• Combines accurate quantitative measurement with untargeted contaminant screening in a single full scan workflow
• Short UHPLC gradients increase sample throughput for routine quality control laboratories
• High selectivity and mass accuracy reduce the need for time consuming tandem mass spectrometry experiments
• Applicability to complex feed and food matrices supports regulatory compliance and safety monitoring

Future trends and opportunities

Expected developments include faster scan speeds, higher resolution, integration of ion mobility separation, advanced data independent acquisition workflows, and enhanced software for automated suspect screening and structural elucidation. These advances will broaden capabilities for multi class residue analysis, real time monitoring, and comprehensive food safety screening.

Conclusion

The Exactive Plus Orbitrap system demonstrated high sensitivity, selectivity, and throughput for pesticide residue analysis in horse feed. Ultra high resolution full scan combined with data dependent fragmentation offers a versatile solution for both quantitative and qualitative workflows in regulatory and research laboratories.

References

• Kaufmann A Butcher P Maden K Walker S Widmer M Comprehensive comparison of liquid chromatography selectivity as provided by two types of liquid chromatography detectors high resolution mass spectrometry and tandem mass spectrometry where is the crossover point Anal Chim Acta 2010 Jul 12 673(1) 60-72
• Scheibner O Damoc E Denisov E Hauschild J Lange O Czemper F Kholomeev A Makarov A Wieghaus A Bromirski M Improved analysis of biopharmaceutical samples using an MS only Orbitrap mass spectrometer presented at the 60th ASMS Conference on Mass Spectrometry and Allied Topics Vancouver Canada May 20–24 2012 ThP28 623