Abstract
Chlorophenoxy acid herbicides (CAHs), which are widely used on cereal crops, have become an important pollution source in grains. In this work, a highly hydrophobic poly (octadecyl methacrylate-co-trimethylolpropane trimethacrylate) [poly (OMA-co-TRIM)] monolithic column has been specially prepared for hydrophobic in-tube solid-phase microextraction (SPME) of CAHs in rice grains. Due to the hydrophobicity of CAHs in acid conditions, trace CAHs could be efficiently extracted by the prepared monolith with strong hydrophobic interaction. Several factors for online hydrophobic in-tube SPME, including the length of the monolithic column, ACN and trifluoroacetic acid percentage in the sampling solution, elution volume, and elution flow rate, were investigated with respect to the extraction efficiencies of CAHs. Under the optimized conditions, the limits of detection of the four CAHs fell in the range of 0.9–2.1 μg/kg. The calibration curves provided a wide linear range of 5–600 μg/kg and showed good linearity. The recoveries of this method ranged from 87.3% to 111.6%, with relative standard deviations less than 7.3%. Using this novel, highly hydrophobic poly (OMA-co-TRIM) monolith as sorbent, a simple and sensitive online in-tube SPME-HPLC method was proposed for analysis of CAHs residue in practical samples of rice grains.
Highlights
In order to fulfill the world’s growing demand for food, herbicide application to cereal crops is imperative
The results indicated that the sufficient extraction of chlorophenoxy acid herbicides (CAHs) could be obtained with 12 cm of keeping other parameters constant, the extraction efficiencies of the analytes increased with the the poly (OMA-co-TRIM) monolithic column
The residual contents of 2,2-CPPA, 2,3-CPPA, 2,4-D, and 2,4-DP detected by the proposed online hydrophobic in-tube solid-phase microextraction (SPME)-high performance liquid chromatography (HPLC) method were 19.8 μg/kg, 21.4 μg/kg, 29.3 μg/kg, and 34.6 μg/kg, respectively, while the values detected by the standard method of LC-MS were 22.3 μg/kg, 20.1 μg/kg, 29.4 μg/kg, and 38.4 μg/kg, respectively
Summary
In order to fulfill the world’s growing demand for food, herbicide application to cereal crops is imperative. Because of their low cost, high weeding effectiveness and little effect on cereal crops, chlorophenoxy acid herbicides (CAHs), represented by 2,4-dichlorophenoxyacetic acid (2,4-D), are extensively used on cereal crops for the selective control of most broadleaf weeds [1]. For the high absorption of CAHs by crops, CAHs have become an important pollution source in cereal grains, which cause potential pollution to food with further potential toxicity against humans. It has become important work to detect and monitor the residual level of CAHs in cereal grains by developing reliable analytical methods that are simple, highly sensitive, and cost-effective
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