Rapid discrimination of bergamot essential oil by paper spray mass spectrometry and chemometric analysis

Aqueous chemistry of nalidixic acid and its complexes with biological relevant cations: A combination of potentiometric, UV spectrophotometric, MS and MS/MS study

Nalidixic acid (NAL) is a broad-spectrum antimicrobial widely used for urinary tract infections. As demonstrated, complexation of NAL with Zn2+, Mn2+ and Cu2+ was often used to get new formulations with an enhanced efficiency and potency. Therefore, the elucidation of behavior of NAL in solution and of its interaction with metal cations are crucial to better understand the influence of complexation on NAL efficiency and to find the optimal conditions to propose novel formulations. As a preliminary study, spectrophotometric titrations were carried out on NAL to determine the values of the protonation constants and to define its acid-base behavior. Then, the interaction with the three metal cations Zn2+, Mn2+ and Cu2+ was investigated by potentiometric and spectrophotometric titrations, varying the conditions of temperature, ionic strength and metal-ligand ratio, thus allowing to get the most robust speciation model and to determine the formation constants with Zn2+, Mn2+, and Cu2+ under different conditions, the sequestering ability of NAL towards metal cations, the formation enthalpic and entropic changes. A simulation under serum conditions was reported to show the relevance of the investigated species. Finally, LD-MS (laser desorption ionization mass spectrometry) and MS/MS analyses highlighted for all systems the formation of the complex species between Zn2+, Mn2+ and Cu2+ with NAL. MS/MS investigations assigned the sites of coordination of the ligand with the metal cation. More precisely, deprotonated NAL coordinates the metal cation via the oxygens of the carboxylate and the carbonyl groups.

Paper Spray Tandem Mass Spectrometry for Assessing Oleic, Linoleic and Linolenic Acid Content in Edible Vegetable Oils

Oleic, linoleic and linolenic acids exert several beneficial effects on human health, some of which are also certified by recent European and U.S. regulations. The goal of the presented work was to develop an innovative methodology to evaluate their content in edible vegetable oils, in order to increase the value of oils from a nutraceutical perspective. The protocol is based on the use of paper spray ionization coupled with tandem mass spectrometry experiments, which allowed the recording of data very quickly and with high specificity. All investigated compounds gained a good linear relation (r2 higher than 0.98). Accuracy values are near 100% for all concentration levels examined, and the repeatability and reproducibility data result lower than 15%, highlighting the consistence of the methodology. The developed approach was successfully applied for the analysis of different real samples, and its robustness was confirmed by comparing the results obtained with those coming from the classical and official methodology.

High-throughput determination of vitamin E in extra virgin olive oil by paper spray tandem mass spectrometry

Extra virgin olive oil provides an important intake of α-tocopherol, which is part of vitamin E complex. A fast analytical method for its quantification, based on paper spray mass spectrometry, has been developed. The methodology possesses the ability to record mass spectra without sample preparation or preseparation steps. The experiments were performed in Multiple Reaction Monitoring scan mode; in particular, the transitions m/z 429 → m/z 163 for α-tocopherol and m/z 435 → m/z 169 for the labeled internal standard were monitored, in order to obtain the greatest specificity and the best sensitivity. The accuracy of the method was tested analyzing spiked samples prepared at concentrations within the dynamic range of the calibration curve, which returned values near 100%. Furthermore, good values of LOQ and LOD were obtained, demonstrating that this approach can be applied for a rapid screening of tocopherols in different vegetable oils. The results were compared with analyses performed by traditional chromatographic methods. Graphical abstract.

In Vitro Anti-Inflammatory and Radical Scavenging Properties of Chinotto (Citrus myrtifolia Raf.) Essential Oils

Chinotto (Citrus myrtifolia Raf.) is a widely diffused plant native from China and its fruits have a wide-spread use in confectionary and drinks. Remarkably, only little has been reported thus far on its bioactive properties, in contrast to those of the taxonomically related bergamot (Citrus bergamia Risso). The present study aimed to investigate potential in vitro anti-inflammatory and radical scavenging properties of chinotto essential oils (CEOs) and to establish to what extent their composition and bioactivities are dependent on maturation. Essential oil from half ripe chinotto (CEO2) reduced the production of nitric oxide (NO) and the expression of inflammatory genes, cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS), cytokines, including interleukin-1β (IL-1β) and interleukin-6 (IL-6), and chemokine monocyte chemotactic protein-1 (MCP-1) by lipopolysaccharide (LPS)-stimulated RAW264,7 macrophages. Limonene, linalool, linalyl acetate, and γ-terpinene were found to be the main components in CEO2. Moreover, CEO2 showed high radical scavenging activity measured as Trolox equivalents (TE) against both 2,2′-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS). These findings show that chinotto essential oil represents a valuable part of this fruit and warrants further in vivo studies to validate its anti-inflammatory potential.

Discrimination of constructed air samples using multivariate analysis of full scan membrane introduction mass spectrometry (MIMS) data

RATIONALE

Volatile and semi-volatile organic compounds (S/VOCs) are important atmospheric pollutants affecting both human and environmental health. They are directly measured as an unresolved mixture using membrane introduction mass spectrometry (MIMS). We apply chemometric techniques to discriminate, classify, and apportion air samples from a variety of sources.

METHODS

Full scan mass spectra of lab-constructed air samples were obtained using a polydimethylsiloxane membrane interface and an electron ionization ion trap mass spectrometer. Normalized full scan spectra were analyzed using principal component analysis (PCA), cluster analysis, and k-nearest neighbours (kNN) for sample discrimination and classification. Multivariate curve resolution (MCR) was used to extract pure component contributions. Similar techniques were applied to VOC mixtures sampled from different woodsmoke emissions and from the headspace above aqueous hydrocarbon solutions.

RESULTS

PCA successfully discriminated 32 constructed VOC mixtures from nearly 300 air samples, with cluster analysis showing similar results. Further, kNN classification (k = 1) correctly classified all but one test set sample, and MCR successfully identified the pure compounds used to construct the VOC mixtures. Real-world samples resulting from the combustion of different wood species and those associated with water contaminated with different commercial hydrocarbon products were similarly discriminated by PCA.

CONCLUSIONS

Chemometric techniques have been evaluated using full scan MIMS spectra with a series of VOC mixtures of known composition containing known compounds, and successfully applied to samples with known sources, but unknown molecular composition. These techniques have application to source identification and apportionment in real-world environmental samples impacted by atmospheric pollutants.

Novel Selectivity-Based Forensic Toxicological Validation of a Paper Spray Mass Spectrometry Method for the Quantitative Determination of Eight Amphetamines in Whole Blood

Paper spray tandem mass spectrometry is used to identify and quantify eight individual amphetamines in whole blood in 1.3 min. The method has been optimized and fully validated according to forensic toxicology guidelines, for the quantification of amphetamine, methamphetamine, 3,4-methylenedioxyamphetamine (MDA), 3,4-methylenedioxy-N-methylamphetamine (MDMA), 3,4-methylenedioxy-N-ethylamphetamine (MDEA), para-methoxyamphetamine (PMA), para-methoxymethamphetamine (PMMA), and 4-fluoroamphetamine (4-FA). Additionally, a new concept of intrinsic and application-based selectivity is discussed, featuring increased confidence in the power to discriminate the amphetamines from other chemically similar compounds when applying an ambient mass spectrometric method without chromatographic separation. Accuracy was within ±15% and average precision was better than 15%, and better than 20% at the LLOQ. Detection limits between 15 and 50 ng/mL were obtained using only 12 μL of whole blood. Graphical abstract ᅟ.

Paper Spray Mass Spectrometry for the Forensic Analysis of Black Ballpoint Pen Inks

This article describes the use of paper spray mass spectrometry (PS-MS) for the direct analysis of black ink writings made with ballpoint pens. The novel approach was developed in a forensic context by first performing the classification of commercially available ballpoint pens according to their brands. Six of the most commonly worldwide utilized brands (Bic, Paper Mate, Faber Castell, Pentel, Compactor, and Pilot) were differentiated according to their characteristic chemical patterns obtained by PS-MS. MS on the negative ion mode at a mass range of m/z 100-1000 allowed prompt discrimination just by visual inspection. On the other hand, the concept of relative ion intensity (RII) and the analysis at other mass ranges were necessary for the differentiation using the positive ion mode. PS-MS combined with partial least squares (PLS) was utilized to monitor changes on the ink chemical composition after light exposure (artificial aging studies). The PLS model was optimized by variable selection, which allowed the identification of the most influencing ions on the degradation process. The feasibility of the method on forensic investigations was also demonstrated in three different applications: (1) analysis of overlapped fresh ink lines, (2) analysis of old inks from archived documents, and (3) detection of alterations (simulated forgeries) performed on archived documents. Graphical Abstract ᅟ.