Development of dye-sensitized solar cells using pigment extracts produced by Talaromyces atroroseus GH2.

The identification of more efficient, clean, secure, and competitive energy supply is necessary to align with the needs of sustainable devices. For this reason, a study for developing innovative dye-sensitized solar cells (DSSCs) based on microbial pigments is reported starting from Talaromyces atroroseus GH2. The fungus was cultivated by fermentation and the extracellular pigment extract was characterized by HPLC-DAD-ESI-MS analyses. The most abundant compound among the 22 azaphilone-type pigments identified was represented by PP-O. The device's behavior was investigated in relation to electrolyte and pH for verifying the stability on time and the photovoltaic performance. Devices obtained were characterized by UV-vis measurements to verify the absorbance intensity and transmittance percentage. Moreover, photovoltaic parameters through photo-electrochemical measurements (I-V curves) and impedance characteristics by Electrochemical Impedance Spectroscopy (EIS) were determined. The best microbial device showed a short-circuit current density (Jsc) of 0.69 mA/cm2, an open-circuit photo-voltage (Voc) of 0.27 V and a Fill Factor (FF) of 0.60. Furthermore, the power conversion efficiency (PCE) of the device was 0.11%. Thus, the present study demonstrated the potential of microbial origin pigments for developing DSSCs.

Determination of mineral oil hydrocarbon contamination in Citrus essential oils by using on-line liquid-gas chromatography: critical aspects.

The present manuscript reports and discusses critical issues related to the determination of mineral oil hydrocarbon contamination in Citrus essential oils (EOs); an on-line liquid-gas chromatography system equipped with a Y-interface was used (with no additional off-line step for pre-concentration). In total, eighteen samples were analyzed, specifically eleven cold-pressed (CP) and seven distilled EOs. With regard to the CP EOs, various degrees of mineral oil saturated hydrocarbon (MOSH) contamination were detected, ranging between 10.7 and 338.4 mg kg-1 (only one sample was MOSH-free); different MOSH sub-fractions were determined, with the > C25- ≤ C35 sub-fraction always present, with an average concentration of 74.5 mg kg-1. Based on the EO composition, different sample amounts were injected to avoid the overloading of the LC column and consequently the GC one, thus leading to different limits of quantification (LoQ), which were either 2 mg kg-1 (for bergamot EO) or 5 mg kg-1 (for all the other investigated samples). For all samples, the mineral oil aromatic hydrocarbon level was always lower than the LoQ.

Rapid evaporative ionization mass spectrometry: A survey through 15 years of applications.

Rapid evaporative ionization mass spectrometry (REIMS) is a relatively recent MS technique explored in many application fields, demonstrating high versatility in the detection of a wide range of chemicals, from small molecules (phenols, amino acids, di- and tripeptides, organic acids, and sugars) to larger biomolecules, that is, phospholipids and triacylglycerols. Different sampling devices were used depending on the analyzed matrix (liquid or solid), resulting in distinct performances in terms of automation, reproducibility, and sensitivity. The absence of laborious and time-consuming sample preparation procedures and chromatographic separations was highlighted as a major advantage compared to chromatographic methods. REIMS was successfully used to achieve a comprehensive sample profiling according to a metabolomics untargeted analysis. Moreover, when a multitude of samples were available, the combination with chemometrics allowed rapid sample differentiation and the identification of discriminant features. The present review aims to provide a survey of literature reports based on the use of such analytical technology, highlighting its mode of operation in different application areas, ranging from clinical research, mostly focused on cancer diagnosis for the accurate identification of tumor margins, to the agri-food sector aiming at the safeguard of food quality and security.

Contribution of Phenolic Compounds to the Antioxidant Activity of Leaf and Flower Extracts of Sinapis pubescens L. subsp. pubescens (Brassicaceae).

Within a study focused on Sinapis pubescens subsp. pubescens wild from Sicily (Italy), an edible species still unexplored, our earlier published work has demonstrated good in vitro antioxidant properties for the flower and leaf hydroalcoholic extracts, exhibiting quite different qualitative-quantitative phenolic profiles. Herein, further research was designed to elucidate the role played by phenolic compounds in the different antioxidant mechanisms highlighted for the extracts. To achieve this goal, the crude extracts were subjected to liquid-liquid partitioning with solvents of increasing polarity; then, the fractions were investigated for their antioxidant properties using different in vitro assays. For both flowers and leaves, the ethyl acetate fractions exhibited the best activity in DPPH and reducing power assays, followed by n-butanol. The total phenolic content determination indicated these fractions as the phenolic-rich ones, which were characterized by HPLC-PDA/ESI-MS analysis. Conversely, the phenolic-rich fractions did not show any chelating activity, which was highlighted for the more hydrophobic ones.

Potential of GC-Combustion-MS as a Powerful and Versatile Nitrogen-Selective Detector in Gas Chromatography.

Here, we show the potential and applicability of the novel GC-combustion-MS approach as a nitrogen-selective GC detector. Operating requirements to achieve reproducible and compound-independent formation of volatile NO species as a selective N-signal during the combustion step are described. Specifically, high temperatures (≥1000 °C) and post-column O2 flows (0.4 mL min-1 of 0.3% O2 in He) turned out to be necessary when using a vertical oven without makeup flow (prototype #1). In contrast, the use of a horizontal oven with 1.7 mL min-1 He as an additional makeup flow (prototype #2) required milder conditions (850 °C and 0.2 mL min-1). A detection limit of 0.02 pg of N injected was achieved, which is by far the lowest ever reported for any GC detector. Equimolarity, linearity, and peak shape were also adequate. Validation of the approach was performed by the analysis of a certified reference material obtaining accurate (2% error) and precise (2% RSD) results. Robustness was tested with the analysis of two complex samples with different matrices (diesel and biomass pyrolysis oil) and N concentration levels. Total N determined after the integration of the whole chromatograms (524 ± 22 and 11,140 ± 330 µg N g-1, respectively) was in good agreement with the reference values (497 ± 10 and 11,000 ± 1200 µg N g-1, respectively). In contrast, GC-NCD results were lower for the diesel sample (394 ± 42 µg N g-1). Quantitative values for the individual and families of N species identified in the real samples by parallel GC-MS and additional GC × GC-MS analyses were also obtained using a single generic internal standard.

A method for the determination of 70 pesticides in extra virgin olive oil based on a limited-volume solvent extraction step prior to comprehensive two-dimensional gas chromatography-tandem mass spectrometry.

The goal of the present research was to develop a method based on a miniaturized solvent extraction step (using only 500 µL of acetonitrile, with no further clean-up or concentration processes) prior to cryogenic-modulation comprehensive two-dimensional gas chromatography-tandem mass spectrometry for the determination of seventy pesticides in extra virgin olive oil, exploiting the enhanced specificity and sensitivity of this technique. Limits of quantification were always below European legislation residue limits, intra-day precision was between 0.3 and 4.9% (at the 50 and 100 µg kg-1 concentration levels), inter-day precision was between 1.6 and 6.1% (at the 100 µg kg-1 concentration level), recovery (at the 20, 50, and 100 µg kg-1 concentration levels) was in the 14-120% range, accuracy at the initial stage of the work (within repeatability conditions) was between 79 and 110%, while accuracy after 3 months (within intermediate precision conditions) was between 91 and 121% (at the 50 and 100 µg kg-1 concentration levels). Finally, the matrix effect was always positive, between 16 and 197%. The method was applied to the investigation of twenty samples, and eleven of these were found to be contaminated.

A miniaturized comprehensive approach for total lipidome analysis and vitamin D metabolite quantification in human serum.

The balance between the different lipid molecules present in biological fluids accurately reflects the health state of the organism and can be used by medical personnel to finely tune therapy to a single patient, a process known as precision medicine. In this work, we developed a miniaturized workflow for the analysis of different lipid classes at the intact level, as well as their fatty acid constituents, starting from human serum. Fatty acids were identified by using flow-modulated comprehensive gas chromatography coupled to mass spectrometry (FM-GC × GC-MS), and their relative amount as well as the ratio of specific FA classes was determined by using FM-GC × GC with a flame ionization detector. Ultra-high-performance liquid chromatography coupled to tandem mass spectrometry was used for the simultaneous quantification of vitamin D metabolites and assessment of different intact lipid classes. An MRM method was developed for the quantification of five vitamin D metabolites (vitamin D2, vitamin D3, 25-hydroxyvitamin D2, 25-hydroxyvitamin D3, 24R,25-dihydroxyvitamin D3), and validated in terms of LoD, LoQ, accuracy, and precision, also using a certified reference material. At the same time, a combination of SCAN, precursor ion scan, and neutral loss scan, in both positive and negative modes, was used for the identification of 81 intact lipid species, such as phospholipids, cholesteryl esters, and triacylglycerols, in less than 25 min. In order to easily monitor the lipid composition and speed up the identification process, a two-dimensional map of the lipidome was generated, by plotting the molecular weight of the identified molecules versus their retention time. Moreover, a relative quantification was performed within each lipid class identified. The combination of untargeted and targeted data could provide useful information about the pathophysiological condition of the organism and evaluate, in a tailored manner, an efficient action.

Determination of the polyphenolic content of berry juices using focusing-modulated comprehensive two-dimensional liquid chromatography coupled to mass spectrometry detection.

In this work, a comprehensive two-dimensional liquid chromatography system, comprised of a ZIC-HILIC and C18 columns in the first and second dimensions, respectively, was tuned and employed for attaining high resolution profiles of the polyphenolic pattern in seven commercial berry juices. The developed HILIC × RP-LC method was validated in terms of linearity range, correlation coefficients, limit of detection, limit of quantification, precision (intra- and inter-day), and recovery. A total of 104 polyphenolic compounds belonging to different chemical classes (hydroxybenzoic and cinnamic acid derivatives, flavone glycosides, flavonols, flavonol glycosides, dihydroflavonols, and anthocyanin glycosides) have been characterized and quantified in the juices investigated. Despite the constituents being similar, a notable quantitative variation among the analyzed berry species was observed. Elderberry contained the highest amount of polyphenols (918 ± 1.10 mg 100 mL-1), followed by chokeberry (516 ± 0.08 mg 100 mL-1). On the other hand, raspberry contained the lowest amount (104 ± 1.21 mg 100 mL-1). Further, total phenolic, flavonoid, and anthocyanin contents were determined spectrophotometrically, yielding consistent results. The free-radical scavenging activity (DPPH test) and reducing power of the juices, expressed as IC50 (µL mL-1) and mg ASE mL-1, varied from 2.79 ± 0.03 (honeyberry) to 31.66 ± 0.02 (blueberry) and from 1.71 ± 0.01 (blueberry) to 8.89 ± 0.12 (chokeberry), respectively. Such a ZIC-HILIC × C18 platform based on focusing modulation, never employed so far for berry juices, showed a remarkable separation capability with high values of corrected peak capacity (up to 1372) and orthogonality (Ao up to 0.80), thus providing a great applicability to be advantageously employed for other complex food samples.

Solid-phase microextraction Arrow combined with comprehensive two-dimensional gas chromatography-mass spectrometry for the elucidation of the volatile composition of honey samples.

In this work, a solid-phase microextraction (SPME) Arrow method combined with comprehensive two-dimensional gas chromatography-mass spectrometry (GC × GC-MS) was developed for the elucidation of the volatile composition of honey samples. The sample preparation protocol was optimized to ensure high extraction efficiency of the volatile organic compounds (VOCs) which are directly associated with the organoleptic properties of honey and its acceptance by the consumers. Following its optimization, SPME Arrow was compared to conventional SPME in terms of sensitivity, precision, and number of extracted VOCs. The utilization of SPME Arrow fibers enabled the determination of 203, 147, and 149 compounds in honeydew honey, flower honey, and pine honey, respectively, while a significantly lower number of compounds (124, 94, and 111 for honeydew honey, flower honey, and pine honey, respectively) was determined using conventional SPME. At the same time, the utilization of SPME Arrow resulted in enhanced sensitivity and precision. All things considered, SPME Arrow and GC × GC-MS can be considered as highly suitable for the elucidation of the volatile composition of complex food samples resulting in high sensitivity and separation efficiency.

Hidden threat lurking in extensive hand hygiene during the Covid-19 pandemic: investigation of sensitizing molecules in gel products by hyphenated chromatography techniques.

During the Covid-19 pandemic, health agencies worldwide have recommended frequent handwashing and sanitizing. A variety of hand gel products were made available on the market, often with fragrances added to curtail the strong smell of alcohol. Commonly used Citrus fragrances contain volatile aroma constituents and non-volatile oxygen heterocyclic compounds (OHCs), consisting mostly of polymethoxyflavones, coumarins, and furocoumarins. The latter have long been investigated for their phototoxic properties, and their safety as cosmetic product ingredients has been debated recurrently. To this concern, twelve commercial Citrus-scented products were investigated in this study. An extraction method was optimized for thirty-seven OHC compounds, obtaining absolute mean recovery values in the 73.5-116% range with only few milliliters of solvent consumption. Analysis by ultra-high-pressure liquid chromatography with tandem mass spectrometry detection evidenced that three samples did not conform to the labeling requirements for fragrance allergens (coumarin) laid down by the European Union Regulation on Cosmetic Products. The total furocoumarin (FC) content of the samples investigated was in the 0.003-3.7ppm range, with some noteworthy exceptions. Specifically, in two samples, the total FCs were quantified as 89 and 219 ppm, thus exceeding the safe limits recommended up to a factor of 15. Finally, the consistency of the volatile fingerprint attained by gas chromatography allowed drawing conclusions on the authenticity of the Citrus fragrances labeled, and several products did not conform to the information reported on the label concerning the presence of essential oils. Besides the issue of product authenticity, analytical tools and regulatory actions for widespread testing of hand hygiene products are urgent, to protect consumers' health and safety.

Listeria monocytogenes exposed to antimicrobial peptides displays differential regulation of lipids and proteins associated to stress response.

With the onset of Listeria monocytogenes resistance to the bacteriocin nisin, the search for alternative antimicrobial treatments is of fundamental importance. In this work, we set out to investigate proteins and lipids involved in the resistance mechanisms of L. monocytogenes against the antimicrobial peptides (AMPs) nisin and fengycin. The effect of sub-lethal concentrations of nisin and lipopeptide fengycin secreted by Bacillus velezensis P34 on L. monocytogenes was investigated by mass spectrometry-based lipidomics and proteomics. Both AMPs caused a differential regulation of biofilm formation, confirming the promotion of cell attachment and biofilm assembling after treatment with nisin, whereas growth inhibition was observed after fengycin treatment. Anteiso branched-chain fatty acids were detected in higher amounts in fengycin-treated samples (46.6%) as compared to nisin-treated and control samples (39.4% and 43.4%, respectively). In addition, a higher relative abundance of 30:0, 31:0 and 32:0 phosphatidylglycerol species was detected in fengycin-treated samples. The lipidomics data suggest the inhibition of biofilm formation by the fengycin treatment, while the proteomics data revealed downregulation of important cell wall proteins involved in the building of biofilms, such as the lipoteichoic acid backbone synthesis (Lmo0927) and the flagella-related (Lmo0718) proteins among others. Together, these results provide new insights into the modification of lipid and protein profiles and biofilm formation in L. monocytogenes upon exposure to antimicrobial peptides.

A dilute-and-inject low-pressure gas chromatography-tandem mass spectrometry method for phthalate determination in extra virgin olive oil.

The goal of this study was to develop a method for the determination of nine phthalic acid esters in extra virgin olive oils using low-pressure gas chromatography-triple-quadrupole mass spectrometry. Sample preparation was simple, environmental friendly, and rapid inasmuch that it involved only dilution (< 1 mL of hexane). The low-pressure gas chromatography analyses were performed by using a 5 m wide-bore column. The limit of quantification for the phthalates ranged from 0.06 to 1.14 mg kg-1 . Both intra- and interday precisions were measured, with coefficient of variation values ranging from 0.2% to 11.7%. The trueness of the method was measured by evaluating accuracy at the initial stage of the work and after 2 months, with values ranging between -8.7% and 12.1%. Moreover, blind accuracy was comprised between -11.6% and 14.2%. The method involves the use of simplified instrumentation and reduced analysis times (nearly two times faster) compared to a previously published comprehensive two-dimensional gas chromatography-triple-quadrupole mass spectrometry method, leading to a reduction of energy and helium consumption. The approaches were compared in analytical terms and for the environmental impact. In total, 23 olive oil samples were analyzed, with at least one phthalate detected in all but one sample.

Preparative three-dimensional GC and nuclear magnetic resonance for the isolation and identification of two sesquiterpene ethers from Dictyota Dichotoma.

Separation science plays a crucial role in the isolation of novel compounds contained in complex matrices. Yet their rationale employment needs preliminary structure elucidation, which usually requires sufficient aliquots of grade substances to characterize the molecule by nuclear magnetic resonance experiments. In this study, two peculiar oxa-tricycloundecane ethers were isolated by means of preparative multidimensional gas chromatography from the brown alga species Dictyota dichotoma (Huds.) Lam., aiming to assign their 3D structures. Density functional theory simulations were carried out to select the correct configurational species matching the experimental NMR data (in terms of enantiomeric couples). In this case, the theoretical approach was crucial as the protonic signal overlap and spectral overcrowding were preventing any other unambiguous structural information. Just after the identification through the density functional theory data matching of the correct relative configuration it was possible to verify an enhanced self-consistency with the experimental data, confirming the stereochemistry. The results obtained further pave the way toward structure elucidation of highly asymmetric molecules, whose configuration cannot be inferred by other means or strategies.

Comparative Study on Phenolic Profile and Biological Activities of the Aerial Parts of Sinapis pubescens L. subsp. pubescens (Brassicaceae) Wild from Sicily (Italy).

This work aimed to investigate Sinapis pubescens subsp. pubescens spontaneously grown in Sicily (Italy) as new potential source of active metabolites; specifically, a comparative study on leaf, flower, and stem hydroalcoholic extracts was performed. Polyphenols were quantitatively determined by spectrophotometric methods and characterized by HPLC-PDA/ESI-MS; a total of 55 polyphenolic compounds were identified, highlighting considerably different qualitative-quantitative profiles. The extracts showed antioxidant activity, evaluated by in vitro assays; particularly, the leaf extract displayed the best radical scavenging activity (DPPH test) and reducing power, while the flower extract showed the greatest chelating activity. The antimicrobial properties of the extracts were investigated against bacteria and yeasts by standard methods; no antimicrobial activity was found against the strains tested. The extracts resulted to be non-toxic after preliminary toxicity evaluation by the Artemia salina lethality bioassay. The aerial parts of S. pubescens subsp. pubescens proved to be valuable sources of antioxidants for pharmaceutical and nutraceutical applications.

Chemical Profile, Antioxidant and Cytotoxic Activity of a Phenolic-Rich Fraction from the Leaves of Brassica fruticulosa subsp. fruticulosa (Brassicaceae) Growing Wild in Sicily (Italy).

Recently, our research team has started a study on Brassica fruticulosa subsp. fruticulosa, an edible plant traditionally used to treat various ailments, little investigated to date. Good in vitro antioxidant properties were highlighted for the leaf hydroalcoholic extract, with the secondary higher than the primary ones. In continuation of the ongoing research, this work was designed to elucidate the antioxidant properties of the phenolic compounds contained in the extract. For this purpose, a phenolic-rich ethyl acetate fraction (Bff-EAF) was obtained from the crude extract by liquid-liquid extraction. The phenolic composition was characterized by HPLC-PDA/ESI-MS analysis and the antioxidant potential was investigated by different in vitro methods. Furthermore, the cytotoxic properties were evaluated by MTT, LDH and ROS determinations on human colorectal epithelial adenocarcinoma cells (CaCo-2) and human normal fibroblasts (HFF-1). Twenty phenolic compounds (flavonoid and phenolic acid derivatives) were identified in Bff-EAF. The fraction exhibited good radical scavenging activity in the DPPH test (IC50 = 0.81 ± 0.02 mg/mL), and moderate reducing power (ASE/mL = 13.10 ± 0.94) and chelating properties (IC50 = 2.27 ± 0.18 mg/mL), contrary to what previously observed for the crude extract. Bff-EAF reduced in a dose-dependent manner CaCo-2 cell proliferation after 72 h of treatment. This effect was accompanied by the destabilization of the cellular redox state due to the antioxidant and pro-oxidant activities displayed by the fraction at lower and higher concentrations. No cytotoxic effect was observed on HFF-1 fibroblasts, used as control cell line.

Direct analysis in real time of high-quality extra virgin olive oils for the rapid and automatic identification of origin trademark.

BACKGROUND: Following our previous research on the differentiation of Italian extra virgin olive oils (EVOOs) by rapid evaporative ionization mass spectrometry coupled to a tandem high resolution mass analyser, the present study deals with the evaluation of another direct mass spectrometry (direct-MS) approach for the rapid and automatic discrimination of EVOOs. In particular, direct analysis in real time (DART-MS) was explored as an ambient MS (AMS) source for the building of a top-quality Italian EVOOs database and fast identification of unknown samples. A single quadrupole detector (QDa) was coupled with DART, taking advantage of a cost-saving, user-friendly and less sophisticated instrumental setup. Particularly, quickstrip cards, located on a moving rail holder, were employed, allowing for the direct analysis of 12 EVOO spots in a total analysis time of 6 min. The aim was to develop a reliable statistical model by applying principal component and linear discriminant analyses to clusterize and classify EVOOs according to geographical origin and cultivar, as main factors determining their nutritional and sensory profiles. RESULTS: Satisfactory results were achieved in terms of identification reliability of unknown EVOOs, as well as false positive risk, thus confirming that the use of AMS combined with chemometrics is a powerful tool against fraudulent activities, without the need for mass accuracy data, which would increase the analysis cost. CONCLUSION: A DART ionization source with a compact and reliable QDa MS analyser allowed for rapid fingerprinting analysis. Furthermore, MS spectra provided quali-quantitative information successfully related to EVOO differentiation. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Flow-modulated comprehensive two-dimensional gas chromatography combined with time-of-flight mass spectrometry: use of hydrogen as a more sustainable alternative to helium.

The present research is focused on the use and evaluation of hydrogen, as a more sustainable alternative to helium, within the context of fast flow modulation comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry. In such a respect, a comparison was made between the two mobile phases in terms of speed and overall chromatography performance. All experiments were carried out by using the following column set: low polarity with dimensions 10 m × 0.25 mm ID × 0.25 µm df and medium polarity with dimensions 2 m × 0.10 mm ID × 0.10 µm df. Fundamental gas chromatography parameters (efficiency, resolution) were measured under different experimental conditions, using the two carrier gases. Efficiency was measured in both the first and second dimensions, using a probe compound under isothermal conditions; after defining the optimum carrier gas conditions, a mixture containing 20 pesticides was analyzed to measure resolution, again in the first and second dimensions, using a temperature program. It was found (as expected) that a similar chromatography performance could be attained when using hydrogen, albeit with a circa 25% reduction in analysis time. Signal-to-noise ratios of the pesticides were calculated, using both carrier gases, with such values generally reduced (on average by 14%) when using hydrogen. Finally, a comparison was made between mass spectral profiles obtained analyzing the pesticides and fatty acid methyl esters using the two mobile phases. Even though mass spectral differences were observed, the ion profiles could be considered generally similar.

Non-psychoactive cannabinoids identification by linear retention index approach applied to a hand-portable capillary liquid chromatography platform.

The aim of the present research was the application of the linear retention index (LRI) system for the identification of non-psychoactive cannabinoids using a portable LC instrument. The miniaturization, viz. the use of very low quantities of mobile phase, enabled the development of a compact mobile system to be used for in situ analysis, also according to a green and cost-saving approach. In particular, new capillary LC (cap-LC) methods coupled with UV detection were developed for the analysis of extracts of Cannabis sativa L. Two setups were explored to achieve the efficient separation of twenty-four cannabinoids: a single column setup which exploited a sub-2 µm packing to increase the chromatographic resolution, and a dual-column setup based on the serial connection of two different stationary phases, each coupled to an UV detector. The latter allowed the determination of two LRI values for each analyte, thus increasing the identification power. Moreover, since two different wavelengths were used on the LED-based UV detectors, the ratio of the absorbances measured on each chromatographic trace represented a third identification criterion, thus fulfilling the recommendations of the Scientific Working Group for The Analysis of Seized Drugs (SWDRUG) about the categories of analytical techniques to be used and the minimum number of parameters required for the unambiguous identification of drugs. The obtained results could be used for the development of a novel analytical method for fast and automatic in situ forensic investigations and hemp breeding programs, also minimizing the consumption of both sample and solvent.

The online coupling of liquid chromatography to Fourier transform infrared spectroscopy using a solute-deposition interface: A proof of concept.

Hyphenated techniques combining chromatographic and spectroscopic methods are the gold standard to effectively handle the emerging challenges in the analysis of unknown chemical components in mixtures, and in this regard the coupling of liquid chromatography to Fourier transform infrared spectroscopy (LC-FTIR) is no exception. While earlier attempts to couple LC to IR spectroscopy relied almost entirely on offline techniques, clear motivations for implementing online LC-FTIR instrumentation emerged from the need for shorter analysis time, a higher degree of automation and sample throughput, better reproducibility, and reduced contamination. Most recent designs of LC-FTIR concepts have aimed to combine the advantages of both approaches by means of a solvent-elimination interface. The hyphenated instrumentation and method presented in this research are based on a pneumatically assisted LC-FTIR interface, relying on a small-scale self-regulating spray dryer to attain desolvation of the LC eluent stream while retaining the spatial and temporal resolution of the dissolved substrates. Focused deposition of the dried analytes occurs onto a ZnSe disc for continuous transmission mid-IR analysis at a resolution of 4 cm-1. The optimization of the LC-FTIR technique is discussed in terms of interface parameters, limits of detection, and limits of quantification for a pair of furanocoumarin isomers differing in the position (linear or angular type) of the furan ring fused to coumarin. Finally, confident discrimination between the two closely related molecules was attained by matching the experimental FTIR spectra in a dedicated library. The quality match factors obtained were higher than 99% for both molecules. The limit of identification (LOI) was determined experimentally as the minimum amount of substance yielding a library-searchable IR spectrum (affording a quality match factor higher than 90%). Specifically, LOI of 0.6 µg and 1.25 µg was determined for psoralen and angelicin, respectively.

Supercritical fluid chromatography-tandem mass spectrometry of oxygen heterocyclic compounds in Citrus essential oils.

Oxygen heterocyclic compounds are secondary metabolites mainly present in the non-volatile fraction of cold-pressed Citrus essential oils. Under this denomination are included coumarins, furocoumarins, and polymethoxyflavones. These compounds possess numerous beneficial properties for human health, but the ingestion of large amounts of coumarins is often related to toxic effects, whereas the phototoxicity caused by furocoumarins and UVA exposure has been well known for a long time. This research has been aimed at the validation of an analytical approach, based on supercritical fluid chromatography coupled to tandem mass spectrometry, for the analysis of OHCs in Citrus essential oils. Among eight columns tested, packed with different stationary phases, the pentafluorophenyl allowed the best baseline separation in 8 min and by using less than 10% of methanol. Calibration curves of twenty-eight standards (coumarins, furocoumarins, polymethoxyflavones) were constructed on spiked lemon distilled essential oil and the method was validated according to the EURACHEM guidelines, by calculating linearity, limit of detection (LoD), limit of quantification (LoQ), accuracy, intra-day, and inter-day precision. Specifically, recoveries were in the 80.0-118.6% range, regression coefficients were between 0.9904 and 0.9998, the LoDs were in the 0.0004-0.0470 mg kg-1 range, the LoQs were in the 0.0014-0.1536 mg kg-1 range, and coefficients of variation were between 0.3 and 2.6% (intra-day) and 1.1 and 7.4% (inter-day). The quantitative profiles of thirteen cold-pressed Citrus essential oils were determined.