GC-TQMS application: Stability in quantitative analysis of residual agricultural chemicals in food by GC-MS/MS - Stability verification of pesticides in spinach extract -

  • Summary

MSTips No.262

As "food safety" is recognized as an increasingly important issue on a global scale, many nations have their own regulations on residual agricultural chemicals in food. In Japan, the positive list system, which was enforced at the end of May 2006, stipulates a uniform standard of 10 ppb as a quantity that is considered safe for human health. Under the positive list system, more agricultural chemicals need to be examined, and as a result, techniques capable of accurately and collectively analyzing residual agricultural chemicals in food are in increasing demand. While mass spectrometry (MS) is known for its high detection sensitivity, MS/MS is becoming the mainstream of pesticide analysis for its superior sensitivity and selectivity.
The JMS-TQ4000GC, JEOL’s latest GC-MS/MS, has a unique ion storage/ejection mechanism within the MS/MS collision cell and incorporates new firmware to support MS/MS analysis with up to 36,000 transitions. In this work, we report the stability of 8 pesticides that were added to spinach extract.

Sample and Method

For the sample, 15 g of spinach was processed by using AOAC 2007.01 extraction method, and the resulting extraction solution was mixed with an 8 component 100 ppb standard solution at 9:1. Table 1 shows the measuring conditions used for the analysis.



Table1 Measurement conditions

[GC-TQMS condition]

System JMS-TQ4000GC (JEOL)
Ionization mode EI+: 70eV, 50µA
GC column VF-5ms(Agilent), 30m × 0.25mm, 0.25µm
Oven temp. 50°C (1min) → 25°C/min → 125°C → 10°C/min → 300°C
Inlet temp. 250°C
Inlet mode Splitless, 2µL
He flow 1.0mL/min (Constant Flow)
MS/MS mode Peak Dependent SRM

Results and Discussion

Fig. 1 shows the reproducibility (n = 50) of the SRM chromatographic peak area of the 8 pesticides (10 ppb) added to the spinach extract. And Fig.2 shows overlaid SRM chromatogram for all 50 injections. The peak area reproducibility for each pesticide was less than CV10%, thus showing strong measurement stability. These results confirmed that the JMS-TQ4000GC shows highly reproducible results for agricultural chemicals.

Fig.1 SRM chromatograms,upper: Spinach extract solution only, lower: 10ppb pesticides in the spinach extract solution
Compound SRM peak area ave. CV (%)
Fenarimol 1168018 1.7
Oxadiazon 1047475 7.1
Difenoconazole 1 2558083 3.4
Difenoconazole 2 3047319 3.2
Etofenprox 5045185 1.9
Fenothiocarb 938218 4.3
Dicofol 1247254 4.6
Picolinafen 1547959 3.8

Fig.1 Reproducibility of SRM chromatographic peak area for the 8 pesticides in spinach extract solution

Fig.2 Overwriting for the 50 SRM chromatograms in spinach extract solution

Fig.2 Overlaid of the 50 SRM chromatograms in spinach extract solution

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