Selective and Sensitive Quantification of Acetochlor and S-Metolachlor in Maize and Soybean Plant Samples by Gas Chromatography-Tandem Mass Spectrometry

Irina Gabriela Cara,Gerard Jitareanu,Anca Elena Calistru,Lucian Raus,Denis Topa,Feodor Filipov

doi:10.3390/agriculture11040283

Abstract

Herbicide residue analysis has gained importance worldwide, mainly for food quality control to minimize potentially adverse impacts on human health. A Gas chromatography-tandem mass spectrometry (GC-MS) method for quantitative analysis of acetochlor and s-metolachlor in maize and soybean straw has been developed, validated and applied to analyze the residues of anilide herbicides. Straw material was dried, homogenized and extracted with a mixture of n-hexane and acetone by an accelerated solvent extraction method. Chromatographic separation of the target analytes was performed on an Agilent 7832 GC equipped with a mass spectrometer detector, a split-splitless injector and an HP-5 MS (5% phenylmethyl siloxane) capillary column (30 m × 0.25 mm × 0.25 µm). Under these parameters, the limit of detection (LOD) values were 0.2 ng g−1 for acetochlor and 0.07 ng g−1 for s-metolachlor, with average recoveries between 86% and 119.7%. The method was validated for acetochlor and s-metolachlor in maize and soybean straw at 0.5 and 0.01 mg kg −1. Furthermore, the final residues of the two herbicides in maize and soybean straw were below the maximum residue limit (MRL) at harvest time. The proposed method is suitable for routine analysis.

Highlights

Maize (Zea Mays L.) and soybean (Glycine hispida L.) crops are valuable resources that meet the requirements for human consumption and animal feed as well as for energy production [1]
To obtain the expected yield, the losses related to pests, insects and disease are managed using chemicals pesticides, which inevitably leads to residues in the environment [2]
Drying and homogenization followed by accelerate solvent extraction using a low polarity solvent has proven to be an efficient, reproducible and simple extractive method for acetochlor and s-metolachlor

Summary

Introduction

Maize (Zea Mays L.) and soybean (Glycine hispida L.) crops are valuable resources that meet the requirements for human consumption and animal feed as well as for energy production [1]. Acetochlor and s-metolachlor are highly efficient and long-lasting pre-emergent herbicides applied to maize or soybean crops to control a wide range of annual grasses and broadleaf weeds [3,4]. Both are systemic herbicides absorbed mainly by shoots and roots of germinating weeds and translocated to the foliage. The mode of action of these herbicides is via inhibition of cell division and elongation in plants due to the interference with a number of enzymes [4] Because of their strong herbicidal activities, there are already 654 types of commercially available acetochlor products and approximately 4.2% of the global s-metolachlor herbicide usage is in Europe [5,6]. Acetochlor and s-metolachlor are endocrine-disrupting chemicals and potential human carcinogens, which can induce endocrine disruption, oxidative stress, and immune-toxicity in nontarget organisms [13]

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