Determination of Trace Ethephon in Fruit by Catalytic Methylation with (Trimethylsilyl) Diazomethane (TMSD) and Gas Chromatography-Mass Spectrometry (GC-MS)

Ethephon (ETH) is a widely used plant growth regulator in fruit production. Due to its harm to people’s health, its content is an important indicator for fruit quality control. However, due to the extremely high polarity and acidity, as well as the absence of chromophores, efficient and simple detection of ETH remains challenging. In this work, a convenient method for determining trace ETH in fruit was developed that involved a combination of catalytic methylation and gas chromatography-mass spectrometry (GC-MS) analysis. ETH in fruit was extracted with acetonitrile and derivatized with (trimethylsilyl) diazomethane (TMSD) by the catalysis of trimethylchlorosilane to generate methylated ETH (ETH-M) which was determined by GC-MS. The instrumental linear range of ETH was 10–1000 µg/L with a coefficient of determination (R 2 ) > 0.999. The limit of detection (LOD) of the method was 1.0 µg/kg. The ETH content in 12 types of fruits was determined with a reasonable recovery rate ranging from 83.20 ± 0.05% to 118.21 ± 0.01%. The ETH content in the unwashed fruits was in the range of undetectable (ND) to 111 µg/g and below the LOD in their flesh. After washing, the content was significantly reduced and even undetectable. The established method showed good efficiency, selectivity, and reproducibility, and can be used for the determination of ETH in various fruits.