Chemical Modification and Quantification of 1-Methylcyclopropene in Supramolecular Complex with Cucurbit[6]Uril by High-Performance Liquid Chromatography

The highly unstable 1-methylcyclopropene (1-MCP) is used as an agrochemical in the form of supramolecular complexes with various receptors to extend the shelf life of fruits and vegetables. To control the content of 1-MCP in the complex with cucurbit[6]uril, a new analytical method involving the release of 1-MCP from the complex, its chemical transformation into a more stable derivative, and subsequent HPLC analysis of the latter was developed in this study. The reaction of 1-MCP with dimethyl acetylenedicarboxylate leading to the formation of dimethyl 2-(2-methylcycloprop-2en-1-yl)maleate was adopted from the literature, but the reaction conditions were significantly improved, making it suitable for routine analyses. To make this reaction suitable for the quantitative determination of 1-MCP in complex with cucurbit[6]uril, a multistep procedure was developed that allows the release of the gas from the complex upon dissolution, extraction and derivatization of 1-MCP in a suitable organic solvent, separation, evaporation and drying of the organic layer, and analysis of the residue (crude dimethyl 2-(2-methylcycloprop-2en-1-yl)maleate) by high-performance liquid chromatography (HPLC). The elaborated methodology allows reliable quantitative determination of 1-MCP in a supramolecular complex with cucurbit[6]uril, involving a relatively simple synthesis procedure using commercially available reagents and subsequent HPLC analysis of the derivative, which is non-volatile and stable for at least 10 days under normal storage conditions.