Method validation, storage stability and field trial for residues of florasulam and pyroxsulam in cereal by liquid chromatography with tandem mass spectrometry

ABSTRACT

A QuEChERS method with liquid chromatography-tandem mass spectrometry (LC-MS/MS) was modified and validated for the determination of florasulam and pyroxsulam residues in wheat grain and straw. The validated method was applied to cereals including oat, millet, corn and rice. Average recoveries were 76-113% with RSDs 2-15%. The limits of quantitation (LOQ) were 0.005 mg/kg for wheat grain and 0.01 mg/kg for wheat straw and four cereals. Ion suppression for florasulam (−28% to −76%) was observed in all the matrices except corn, whereas ion enhancement were shown for pyroxsulam (44% to 83%). Degradation rates of florasulam and pyroxsulam were 6% and 23%, respectively, in wheat grain and straw after eight-week storage at −20°C. The ultimate residues in field trials in ten regions were all ≤0.05 mg/kg, and long term dietary risk assessment indicated that hazard quotients were 0.02% and 0.001% for florasulam and pyroxsulam, respectively, which shows that it is safe to spray the two herbicides on wheat.

KEYWORDS:

• Cereals
• pesticides
• QuEChERS
• florasulam
• pyroxsulam

Article highlights

• QuEChERS method was modified for analysis of florasulam and pyroxsulam in wheat and other four cereal matrices (oat, millet, corn and rice).

• Matrix effects were investigated and cereal matrices that have similar matrix effects (difference less than 20%) were grouped.

• Residues were stable in wheat grain and straw after 8-week storage at −20°C.

• Dietary risk assessment indicated that it is safe to spray the two herbicides on wheat.

Disclosure statement

The authors have no conflicts of interest to declare.

Ethical approval

This article does not contain any studies with human participants or animals performed by any of the authors.

Informed consent

Informed consent was obtained from all individual participants included in the study.

Supplementary material

Supplemental data for this article can be accessed on the publisher’s website.

Additional information

Funding

The current study was funded by National Key R&D Program of China, grant number [2016YFD0200206].