Various theoretical approaches based on capture collision theory have been developed to compute the rate coefficients of ion-molecule reactions in the gas phase. These theoretical methods require the electric dipole moment and polarizability of the neutral molecule as input parameters for accurate rate coefficient calculations. Given the energetic environment inside the CI-MS drift tube, rates…
These computed molecular parameters, including dipole moment, polarizability, proton affinity, and ionization energy of volatile organic compounds (VOCs), are crucial for the identification and quantification of VOCs in chemical ionization mass spectrometry. These parameters are determined using Density Functional Theory (DFT) methods implemented in software such as Gaussian and Quantum ESPRESSO. The electric dipole moment…
SIFT-MS Analytic Method These Direct Injection Mass Spectrometry (DIMS) techniques rely on calibrating instruments using standards with known concentrations and protonated ion signals. Although the most accurate analysis requires calibrating the instrument for each volatile organic compound (VOC) in a complex gas mixture, this process is both labor-intensive and time-consuming. In practice, obtaining precise standards…
Soft chemical ionization is a powerful analytical technique employed in Selected Ion Flow Tube Mass Spectrometry (SIFT-MS) for the precise detection and quantification of trace gases, particularly volatile organic compounds (VOCs), present in ambient air samples. This method hinges on the interaction of selected reagent ions with VOCs within a controlled environment, allowing for rapid…
Chemical ionization mass spectrometry Chemical ionization mass spectrometry (CI-MS) is a technique used to analyze chemical compounds by ionizing them in the gas phase using chemical reactions rather than electron impact ionization, which is commonly used in electron ionization mass spectrometry (EI-MS). In CI-MS, the sample molecules are ionized by reacting them with reagent ions…
Volatile organic compounds (VOCs) are found in many food and flavor products, and their presence can affect the flavor, aroma, and quality of the product. VOCs are used to analyze food and flavor products to determine their quality, as well as to identify potential contaminants. Common VOCs found in food and flavor products include ethanol,…
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