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Experimental setup used in the detection of different fragrance formulations using a portable quadrupole mass spectrometer coupled with the a direct membrane (DIM) probe; (a) shows the mass spectra obtained for ambient air background without any sample in the flask and (b) the schematic of the portable mass spectrometer coupled to a DIM probe with a flask placed in front of the probe.
Representative EI mass spectra of fragrant model compounds recorded using a DIM probe combined with a portable mass spectrometer. Accurate amounts of analyte were pitted into a flask and introduced into the manifold of the portable MS through a DIM probe, 5 μL, viz 10 ppb. (a) 2-methylfuran-3-thiol (Mw 114), (b) methyl butanoate (Mw 102), (c) ethyl methyl sulfide (Mw 76), and (d) 3-methylbutyl acetate (Mw 130).
The analytical performance was evaluated for all the standard fragrant model compounds studied Figure 3. Figure 3(a) shows the calibration curve for 2-methyl-3-furanthiol, and the system was linear over 4 orders of magnitude (250 to 1000 ppb) with r2 value of 0.9985, for 60 seconds sample exposure time. The LOD for the standard fragrant model compounds was determined as the concentration that produces a signal more than three times greater than the standard deviation plus the mean value of the blank, in full MS mode. For 2-methyl-3-furanthiol a limit of detection (LOD) of 2.5 pg (Table 1) was obtained when analyzed using DIM probe coupled to a portable mass spectrometer. The signal intensity ratios of the most abundant fragment peaks were found to be linear in the range from 250-10000 ppb (Figure 3).
In-situ analysis of standard model compounds in an artificial; (a) mixture of equal volumes of 10 ppm of methylbutyl acetate, 2-mehtyl-3-furanthiol, methyl butanoate, and ethyl methyl sulfide 10 ppm (v/v) using a direct membrane probe coupled to a portable mass spectrometer. Approx. 5 μL of the mixture was deposited in the flask and left for 2 hours. The headspace vapor of the mixture was detected using a portable mass spectrometer coupled to a direct membrane probe and (b) shows the mass spectrum of the real banana headspace vapor measured using DIM probe with a portable mass spectrometer.
Electron impact ionization mass spectrum for essential fragrant oils analyzed using a direct membrane probe coupled to portable mass spectrometer. (a) banana, (b) tangerine, (c) papaya, and (d) blueberry muffin. Approx. 5 μL of each was deposited in the flask and left for 2 hours forming a headspace vapor and analyzed for 2 minutes with 70 eV EI energy.
The results obtained show the capability of the portable mass spectrometer for online high-throughput rapid screening of different analyses with no sample preparation. However, the use of electron impact (EI) ionisation complicated the mass spectra of the analyte(s) studied. EI ionisation can generate ions with high internal energies (70 eV), hence in-source fragmentation is common and can complicate the interpretation and identification of the fragrant components in the mixture. To overcome this problem softer ionisation techniques (e.g., chemical ionisation (CI)) or atmospheric pressure chemical ionisation (APCI) or other ambient ionisation sources forming ions with low internal energies suppressing fragmentation can be used in unison with the portable mass spectrometer [34, 39, 74].
In this study the direct analysis of different fragrant active in complex mixtures has been demonstrated using a DIM probe coupled with a portable mass spectrometer. The results demonstrate rapid analysis allowing high throughput of different essential oil fragrant compounds of importance in the flavor and fragrance industry. The results reported that a DIM probe coupled to a portable mass spectrometer can be incorporated during in the production and the post production stages of in different flavors in the fragrance industry for quality control.
Quality control in the flavour and fragrance industry has become a global problem. Being a useful analytical tool for in-situ analysis at the source with minimal sample preparation, a DIM probe coupled with a portable mass spectrometer is proposed as the alternative analytical technique to the analysis of flavours and fragrant samples in complex matrixes such as fragrant essential oils. As demonstrated, DIM probe combined with small footprint mass spectrometer is able to detect the active components of different food flavours and fragrant essential oil with high throughput. Linear signal responses with a dynamic range of 5 orders of magnitude were obtained. The limits of detection (LOD) were 2.5 pg (absolute concentration) with good reproducibility (RSD < 10 %). The rise times of 16 to 31 seconds and fall times of 23 to 41 seconds are noteworthy providing a timely and direct analysis of different flavours and fragrants. Future work will involve optimising the membrane parameters to enhanced performance. Because no sample preparation is needed for the analysis, the duty cycle time from ambient air sampling to acquisition of results is 65 seconds or less. 2b1af7f3a8