introduction
In recent years, the analysis of pesticide residues has continued to develop rapidly and on a large scale. At present, the multi-residue screening analysis in food safety mostly uses a triple quadrupole mass spectrometer, but the mass spectrometry system needs to use standard materials to optimize the instrument parameters, and the number of compounds that can be simultaneously analyzed is limited, for large-scale pesticide residues. Screening has certain limitations. There is also a certain probability of false positives when analyzing complex matrix samples. This paper uses a benchtop mass spectrometer with high resolution, accurate mass (HR/AM).
Q Exactive Focus performs large-scale pesticide residue screening analysis, and the results show excellent sensitivity, precision, and analytical throughput. Screening and quantitative analysis of more than 500 pesticide residues in fruit and vegetable matrices was completed within 15 minutes of effective elution time, and through multiple methods such as accurate mass of parent ion, isotope distribution, spectral library and secondary ion database The experimental results were confirmed, which fully ensured the accuracy and reliability of the analysis results.
experimental method
Liquid chromatography
UHPLC: Thermo Scientific Ultimate 3000 RSLC
Column: Thermo Scientific Accucore aQ (150*2.1mm, 2.6μm)
Column temperature: 25 °C, flow rate: 0.4 mL/min, injection volume: 5 μL
Mobile phase: aqueous phase (W) 5 mM ammonium formate and 0.1% aqueous formic acid organic phase (M) 5 mM ammonium formate and 0.1% formic acid in methanol
Gradient elution: 
Mass spectrometry
Mass Spectrometer: Thermo Scientific Q Exactive Focus benchtop high resolution mass spectrometer. Mass spectrometry was performed using an electrospray positive ion mode. High-resolution full-scan primary mass spectrometry data and data-dependent Top1 secondary mass spectral data were acquired at 70,000 and 17,500 resolutions at FWHM@m/z 200, respectively.
Ion source condition 
Q Exactive Focus parameter settings 
Data processing method
Software: Thermo Scientific Tracefinder 3.2
Screening parameter settings: 
Sample preparation method
Refer to the method described in QuEChERS AOAC 2007.01
Experiment and discussion
In this experiment, more than 500 pesticides were analyzed in a 15-minute effective liquid phase gradient. The total ion current TIC diagram is shown in Figure 1. Under a certain Mass tolerance, the precise mass of the compound ion peak is extracted from the TIC map to obtain the extracted ion current XIC chart of the specific target compound, so the data has high throughput and traceability. Figure 2 is a XC plot of the M+H peak of Acetamiprid and the M+NH4 peak of Aldicarb. Q Exactive Focus's ultra-high resolution and good mass accuracy make the method very specific and enable highly sensitive analysis in complex matrix samples. Figure 3 is a graph showing the results of quantitative analysis. The lower left is the chromatogram of 0.1 ppb Pyridaben in the pepper matrix. As shown in Figure 3, the Pyridaben LOQ is 0.1 ppb and is in the range of 0.1 ppb to 50 ppb. Within, R2 = 0.9992 (n = 6); precision RSD < 3% (10 ppb, n = 3).
In this experiment, the data was collected by Full scan+ddms/ms. When the first-level full-scan data was obtained, the full-scale scan of the second-order ion of the specific target compound was also obtained. Figure 4 shows the second of Difenoconazole (difenoconazole). Level ion scan. In this experiment, the spectral library and fragment ion information of the standard ion scan of the standard ions were used to establish the corresponding spectral library Library and database. In the analysis of matrix-added samples, the results were confirmed by five screening indicators such as accurate mass, retention time, isotope distribution, second-level full-scan spectrum and secondary fragment ions to ensure the results of the screening. accuracy. Figure 5 shows the screening results of Difenoconazole (difenoconazole) in the pepper base.
in conclusion
Based on Orbitrap mass spectrometry, the benchtop mass spectrometry system Q Exactive Focus features high resolution, high quality accuracy, high sensitivity and wide dynamic range, and achieves high resolution and high sensitivity uniformity, while matching UHPLC scanning speed. The mass spectrometry platform with both qualitative and quantitative functions can be accurately and reliably applied to large-scale rapid screening confirmation related to food safety and high-sensitivity and high-throughput multi-residue analysis.
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