Abstract
A novel heart-cutting two-dimensional liquid chromatography coupled with tandem mass spectrometry (2D-LC-MS/MS) was developed for the qualitative and quantitative analysis of methomyl residue in tobacco. Compared to traditional methodologies, fairly high sensitivity and stability were achieved, and the sample procedure was simplified in the two-dimensional liquid chromatography (2D-LC) method. Although methomyl had poor retention performance in most of the reversed-phase liquid chromatography (RPLC) columns, an effective RP/RP strategy was successfully facilitated. An XB-Phenyl column was employed in the first dimension to effectively remove thousands of interference compounds in the matrix. In the second dimension, an ADME column was applied for further separation. After optimization of the separation conditions, a six-way valve was utilized for direct transformation of the target fraction from the 1st column to the 2nd column. A dynamic range of 2.5 ng/mL to 500 ng/mL was achieved with correlation coefficient (r2) greater than 0.9995. The limit of detection and limit of quantification were determined to be 0.69 and 2.30 ng/mL, respectively. The 2D-LC method shows high sensitivity, good reproducibility, and recovery for methomyl in tobacco samples. Therefore, the new method was quite suitable for routine analysis.
Highlights
Methomyl (S-methyl-1-N-[(methylcarbamoyl)oxy]thioacetimidate) is a systemic broad-spectrum carbamate pesticide, which is widely used in agriculture [1]
For tobacco samples, matrix interferences were still serious after QuEChERS in the LC-MS/MS method, which affect ionization efficiency of methomyl
During determination of methomyl in tobacco by the conventional LC-MS/MS, matrix interference was the major problem which seriously inhibits the signals of the target compound
Summary
Methomyl (S-methyl-1-N-[(methylcarbamoyl)oxy]thioacetimidate) is a systemic broad-spectrum carbamate pesticide, which is widely used in agriculture [1]. Based on acetylcholinesterase inhibition, methomyl was toxic and hazardous to the environment and human beings [2, 3]. It was classified as a high hazardous compound by the World Health Organization (WHO) [4]. Erefore, it is important to develop an efficient and sensitive analytical method for trace amount of methomyl residue in complex samples such as tobacco and tobacco products. There was a serious complex matrix effect during detection of tobacco samples. For tobacco samples, matrix interferences were still serious after QuEChERS in the LC-MS/MS method, which affect ionization efficiency of methomyl. Every 15–20 injections would show a visible decrease in intensity of MS
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