Rapid Identification of Adulteration in Extra Virgin Olive Oil via Dynamic Headspace Sampling and High-Pressure Photoionization Time-of-Flight Mass Spectrometry

Abstract

High-pressure photoionization time-of-flight mass spectrometry (HPPI-TOFMS) combined with dynamic headspace sampling was developed for rapid identification of adulteration in extra virgin olive oil (EVOO). The volatile organic compound (VOC) fingerprints of EVOO, refined rapeseed oil (r-RO), peanut oil (PO), corn oil (CO), fragrant rapeseed oil (f-RO), and sunflower oil (SO) were obtained in just 1.5 min, which enabled satisfactory classification of different edible oils. 1,4-Bis­(methylene)­cyclohexane and dimethyl disulfide were unique VOCs in r-RO and f-RO, respectively, while 2,5-dimethylpyrazine and 2-methylpyrazine were distinctive VOCs in PO. Percentages as low as 3% r-RO, 1% PO, and 1% f-RO in r-RO–EVOO, PO–EVOO, and f-RO–EVOO mixtures, respectively, were successfully identified based on the characteristic VOCs. Linear regression equations of these VOCs were established and utilized for predicting the adulteration proportions. The good agreements between the actual adulteration proportions and the predicted ones demonstrated that HPPI-TOFMS was reliable for the quantification of EVOO adulteration.

Discriminating extra virgin olive oils from common edible oils: Comparable performance of PLS‐DA models trained on low‐field and high‐field 1H NMR data

“…15 Recent work has focused on sampling the volatile headspace of samples using gas chromatography-mass spectrometry, but these approaches require experienced analysts to operate and maintain the instrument. 16,17 Spectroscopic techniques, including 1 H NMR, are attractive alternatives for authenticating samples and detecting adulteration in olive oil samples. 1,10,18 High-field (HF) NMR (> 300 MHz) spectroscopy is a powerful analytical technique, but has large upfront and recurring costs, and requires a large specialised space for the instrument, frequent maintenance, and experienced staff for operation.…”

Rapid Determination of Ethyl Carbamate in Chinese Liquor via a Direct Injection Mass Spectrometry with Time-Resolved Flash-Thermal-Vaporization and Acetone-Assisted High-Pressure Photoionization Strategy

“…A soft ionization technique is characterized by its high molecular ion [M] + or quasimolecular ion [M + H] + yield and low degree of fragmentation, which makes it easier for mass spectral interpretation of analytes especially in the complicated matrix. In recent years, a number of DIMS methods with different soft ionization sources, e.g., electrospray ionization (ESI), proton transfer reaction (PTR), single photon ionization (SPI), and highpressure photoionization (HPPI), have been developed for rapid analysis of trace targeted components among complicated matrices, such as breath gas, 22,23 urines, 24 seawater samples, 25 foods and beverages, 26,27 and so on, 28,29 while avoiding the inherent shortcomings in chromatographic separation and sample pretreatment methods. DIMS coupled with an ESI source has been developed and successfully applied for analysis of EC in sugarcane spirit and foods with an analysis time of only 2 min.…”

“…A soft ionization technique is characterized by its high molecular ion [M] + or quasi-molecular ion [M + H] + yield and low degree of fragmentation, which makes it easier for mass spectral interpretation of analytes especially in the complicated matrix. In recent years, a number of DIMS methods with different soft ionization sources, e.g., electrospray ionization (ESI), proton transfer reaction (PTR), single photon ionization (SPI), and high-pressure photoionization (HPPI), have been developed for rapid analysis of trace targeted components among complicated matrices, such as breath gas, , urines, seawater samples, foods and beverages, , and so on, , while avoiding the inherent shortcomings in chromatographic separation and sample pretreatment methods. DIMS coupled with an ESI source has been developed and successfully applied for analysis of EC in sugarcane spirit and foods with an analysis time of only 2 min. , Recently, Li et al developed a new soft ionization technique, dopant-assisted photoionization (DAPI), based on a vacuum ultraviolet (VUV) lamp for online and real-time analyses of explosives and illegal drugs by ion mobility spectrometry and mass spectrometry. − However, as no chromatographic preseparation process is included, DIMS is susceptible to matrix effects such as competitive ionization and mass peak overlapping interference when dealing with samples with a complex matrix, ,, especially Chinese liquor, which contains more than 99% of ethanol and water, and other flavor components. − Generally, the ethanol accounts for 30–60% of the Chinese liquor.…”

Hydrogen-Assisted Photoionization and Its Use in Promoting Mass Spectrometry Analysis of VOCs

“…Currently, PI is often employed as an internal source in various miniature MS systems, ,− due to its compact structure and high tolerance to operating pressure. ,,, Locating the PI source inside the vacuum provides several benefits for small instruments, including simplifying the instrument structure and reducing ion losses during transport. However, the ion yield is limited under low operating pressure, and improving ionization efficiency and ion utilization becomes crucial to enhancing the sensitivity of miniature PI-MS instruments.…”

“…So far, many techniques have been developed to enhance ion yields in VUV-PI. At first, researchers improve the light intensity of the VUV beam by developing high-power VUV lamps. , Second, since PI is initiated by collisions between photons and gas analyte molecules, increasing the source pressure can also promote analyte ionization through more frequent photon–molecule collisions. − Another way to enhance PI efficiency is to introduce a dopant to the source to induce the dopant-assisted chemical ionization. ,, For this strategy, the dopant molecules absorb the photons and form sufficient reagent ions that can further react with the analyte molecules to induce their ionization. Volatile compounds such as benzene, toluene, hydrogen sulfide, and CH 2 Cl 2 are commonly used dopants. ,, Despite being effective in enhancing ion yields, these solvents are not suitable for widespread use as they may cause some health and environmental issues. − Some green dopants such as O 2 have also been developed for PI analysis.…”