Accurate selected ion flow tube mass spectrometry quantification of ethylene oxide contamination in the presence of acetaldehyde

The reaction mechanisms of ethylene oxide and propylene oxide with food Simulants: Based on experiments and computational analysis

Ethylene oxide (EO) and propylene oxide (PO) are widely used as sterilizing agents in the food industry. However, their residues in food packaging can migrate into food and react with it, affecting the accuracy of residue detection in food. This study aims to explore the reaction mechanisms between EO and PO and aqueous food simulants using both experimental and computational methods. Especially to investigate the effects of temperature, pH and material structure on these reactions. Experimentally, the stability of EO and PO in different types of aqueous food simulants at 20 °C, 40 °C and 70 °C was observed. It was found that at 20 °C, EO and PO reacted rapidly in 4 % EtOH, which 90 % has reacted in 72 h, and only 10 %-20 % reacted in other types of food simulants. All reactions accelerated with increasing temperature. At 70 °C, all reactions have been completed except for 50 % EtOH, which 80 % has reacted in 72 h. Gas chromatography-mass spectrometry (GC-MS) analysis revealed that EO and PO can form diols or glycol ethers. Computationally, Density Functional Theory (DFT) and Transition State Theory (TST) was used to calculate the energy barriers of the reaction processes. The results showed that the energy barrier for the reaction of EO and PO with water is about 125 kJ/mol. The energy barrier can be reduced by about 40 kJ/mol with acid catalysis. Reactivity at the binding sites was analyzed through the Fukui function (FF), average local ionization energy (ALIE), and electrostatic potential (ESP) analysis. According to the results, the f + value at C7 in PO is 0.041 higher than it at C5. The ESP value of EO is 0.15 kcal/mol higher than that of PO and the ALIE value of EO is also 0.11 eV higher. The experimental results show the impact of temperature, and calculation results highlight the effects of pH and material structure on reaction mechanism. These results can help guide the development of safer packaging materials and provide theoretical support for more accurate detection of residues in food.

Basics of utilizing NH4+ ions for accurate phthalate ester quantification via selected ion flow tube mass spectrometry in food

Phthalate esters, frequently used as plasticizers in consumer products, raise concerns because of potential health effects. Using density functional theory (DFT) with B3LYP and 6-311++G(d, p) basis sets, their properties, such as dipole moment, polarizability, proton affinity and ionization energy of phthalate esters are obtained. Reaction kinetics and thermodynamics of popular reagent ions like H3O+ , NH4 + , NO+ and O2 + ∙ are computed to know the feasibility of the reactions with such ions. Proton affinity and ionization energy indicate high susceptibility to proton and charge transfer reactions. High dipole moments contribute to elevated rate coefficients in proton transfer reaction mass spectrometry (PTR-MS) and selected ion flow tube mass spectrometry (SIFT-MS). PTR-MS rates are influenced by drift tube conditions, supported by high center-of-mass collisional energy of Ecm = 0.28 eV. SIFT-MS rates diminish with rising temperature. The high kinetic energy data of H3O+ , NO+ and O2 + ∙ suggests that simple proton transfer and charge transfer reactions are overruled due to very high internal energy which could lead to extensive fragmentation of phthalate esters. The energetic profile of NH4 + ions indicates their suitability for quantifying phthalate esters using NH4 + -CI-MS techniques.

Improved volatiles analysis workflows using automated selected ion flow tube mass spectrometry (SIFT-MS)

Selected ion flow tube mass spectrometry (SIFT-MS) is a recent addition to the routine analysis and research laboratory toolkit, primarily as a quantitative tool. SIFT-MS employs ultra-soft chemical ionisation to directly analyse volatile organic compounds (VOCs) in air and headspace in real-time with high specificity and sensitivity. Coupling SIFT-MS with conventional laboratory automation equipment (i.e., that used with chromatography systems) has proved straightforward and enables unattended operation, processing up to 230 samples per day per SIFT-MS instrument. Automated SIFT-MS systems have been applied to analysis of headspace (static, continuous, multiple headspace extraction, and standard additions), sample bags, and thermal desorption tubes. Applications using these approaches include consumer and drug product testing for volatile impurities (such as benzene, formaldehyde, and nitrosamines), environmental samples, clinical research, and materials testing. The stability of the SIFT-MS technique, coupled with its ability to analyse diverse VOCs in a single run, removes the need for system configuration changes and hence reduces calibration demand and streamlines workflows, reducing the time to report the first results in a sequence schedule and increasing sample throughput compared to chromatographic systems. This article reviews the development of the automated-SIFT-MS approach using a variety of application examples and recommends hardware and software improvements that could further enhance its adoption.

Integrating density functional theory and chemical ionization mass spectrometry techniques to assess benzophenone derivatives in food packaging: implications for enhancing food quality and safety

Benzophenone and related derivatives are widely used as photoinitiators for food packaging to cure inks or lacquers with ultraviolet (UV) light on cardboard and paper. However, there are concerns about the potential health risks of their migration into food. Knowing the physical and chemical properties of benzophenone and its derivatives could play a significant role in their quantification and analysis using chemical ionization mass spectrometry (CI-MS) methods. These parameters are evaluated using B3LYP/6-311++** density functional theory (DFT) implemented on Gaussian code. Ion-molecule chemistry through the selection of reagent ions, reaction energetics and kinetics, thermodynamic stability, and reactivity of molecules deemed to foster VOC identification and quantification via CI-MS techniques. The VOCs under study are expected to undergo exothermic reactions from H3 O+ , NH4 + , NO+ , and O2 + ions, except endothermic proton transfer from NH4 + to 2-hydroxy-4-methoxybenzophenone and 2,3,4-trihydroxy benzophenone. These compounds possess less proton affinities than NH3 and are least stable in their protonated forms. The DFT computed properties provide the basis for developing reliable and accurate methods to detect and measure the presence of benzophenone and its derivatives in packaging materials and food products.

Robust Automated SIFT-MS Quantitation of Volatile Compounds in Air Using a Multicomponent Gas Standard

Selected ion flow tube mass spectrometry, SIFT-MS, has been widely used in industry and research since its introduction in the mid-1990s. Previously described quantitation methods have been advanced to include a gas standard for a more robust and repeatable analytical performance. The details of this approach to calculate the concentrations from ion-molecule reaction kinetics based on reaction times and instrument calibration functions determined from known concentrations in the standard mix are discussed. Important practical issues such as the overlap of product ions are outlined, and best-practice approaches are presented to enable them to be addressed during method development. This review provides a fundamental basis for a plethora of studies in broad application areas that are possible with SIFT-MS instruments.