Time-resolved thermal desorption miniature ion trap mass spectrometry for rapid and simultaneous quantification of multiple cooling agents in complex matrices

Miniaturized mass spectrometry has emerged as a powerful analytical technique characterized by its portability, rapid analysis capability, and operational simplicity, making it particularly suitable for on-site detection across various fields. However, the accurate quantitative determination of multiple compounds in complex matrices remains challenging due to factors such as competitive ionization and limited ion storage capacity. In this study, a time-resolved thermal desorption continuous atmospheric pressure interface ion trap mass spectrometer (TRTD-CAPI-ITMS) coupled with an acetone-assisted photoionization source was developed for simultaneous detection of multiple cooling agents for ensuring product safety and quality control. To evaluate the performance of the system, time-resolved thermal desorption curves of cooling agent mixtures with varying boiling points and concentrations were systematically investigated. The prominent signals of all the cooling agents could be observed simultaneously at a thermal desorption time of 2.0 seconds. However, a key challenge was identified during simultaneous quantitation: non-linear concentration-dependent signal responses were observed with increasing cooling agent concentrations. Competitive ionization between the target cooling agents was confirmed as the primary cause of this phenomenon. To address this issue, two critical parameter adjustments were implemented: (1) reducing the sample load to decrease the number of competing analyte components in the ionization region, and (2) elevating the concentration of acetone dimer reagent ions to ensure sufficient reagent ions for effective ionization of the target cooling agents. As a result, competitive ionization was eliminated, and good linear calibration curves were obtained for all four cooling agents, with all linear correlation coefficients (<i>R</i>²) exceeding 0.99. Finally, the TRTD-CAPI-ITMS was applied to the quantitative determination of cooling agents in commercial dentifrice samples, with whole detection time less than 4 minutes, demonstrating the potential of TRTD-CAPI-ITMS as a powerful tool for field detection of cooling agents in complex matrices, with broad applicability in quality control and safety assessment across relevant industries.