Patrícia V. Abdelnur

Single-Shot Biodiesel Analysis: Nearly Instantaneous Typification and Quality Control Solely by Ambient Mass Spectrometry

Using a simple and easily implemented desorption/ionization mass spectrometry technique, a tiny droplet of biodiesel placed on the surface of a sheet of paper is analyzed directly and nearly instantaneously under ambient conditions. No pre-separation or sample preparation is required, and clean mass spectra are obtained with great simplicity. In the positive ion mode, easy ambient sonic-spray ionization mass spectrometry, EASI(+)-MS, provides typical profiles of the major components of biodiesel samples, that is, either methyl esters (FAME) or ethyl esters (FAEE) of the natural fatty acids and triglycerides (TAG) from residual oil or oil from adulteration. Each FAME (FAEE) or TAG molecule is detected as a single sodiated molecule, [M + Na] (+) with relative intensities that correlate well with the known fatty acid profiles of the oil. Using EASI(-)-MS, typical and complementary profiles of free fatty acids (FFA) are obtained, which are detected in their deprotonated forms [FAA - H] (-). A general, single-shot approach for biodiesel analysis is therefore described, and samples from different feedstocks, from blends with petrodiesel, or from either methanol or ethanol trans-esterification are readily typified and major parameters of quality accessed.

Fingerprinting of propolis by easy ambient sonic-spray ionization mass spectrometry.

Chemical profiles of a representative set of 49 propolis ethanolic extracts collected worldwide (North and South America, Europe, Asia and Oceania) were obtained via easy ambient sonic-spray ionization mass spectrometry (EASI-MS). This simple and easily implemented fingerprinting technique analyses directly (without any pre-separation or sample manipulation) a tiny droplet of the ethanolic extract placed on a inert surface under ambient conditions. Data acquisition took about a minute per sample with no substantial sample carry-over. Extraction of propolis with ethanol by using an ultrasonic bath method gave EASI-MS data similar to the traditional maceration method, reducing total analysis time for the crude propolis resin from a week to just ca 1h. Principal component analysis of the EASI-MS data is shown to group samples according to the plant sources of their resins, which characterizes their geographical origin.

Fabric softeners: nearly instantaneous characterization and quality control of cationic surfactants by easy ambient sonic-spray ionization mass spectrometry.

A tiny droplet of typical samples of fabric softeners from different commercial brands placed on a smooth paper surface was subjected to easy ambient sonic-spray ionization mass spectrometry (EASI-MS). With no need for sample-preparation or pre-separation procedures, EASI-MS and EASI-MS/MS identify nearly instantaneously the main surfactants and the homologous series employed in their formulations. Adulterated and low quality samples containing no or less efficient softeners are also easily recognized.

Charge-tagged N-heterocyclic carbenes

The interception, formation and characterization of the first stable, long lived charge-tagged N-heterocyclic carbenes of the general type 4x+ (x = 1–3) and analogues is reported. Via ESI(+)-MS of solutions of bromine salts of doubly, triply and quadruply charged imidazolium ion IL (3.Brn, n = 2–4), the isolated 4x+ as well as charged aggregates [3.Br(n−x)]x+ likely to be participating in the [3.Br(n−x)]x+ ⇌ 4x+ + HBr solution equilibrium could be transferred and characterized in the gas phase. Mimicking the solution equilibrium, the gaseous [3.Br(n−x)]x+ were found to dissociate nearly exclusively viaHBr loss during thermal activationvia collisions to form gaseous 4x+, which were found to add to acrolein and acetone.

Antioxidant Action of Mangrove Polyphenols against Gastric Damage Induced by Absolute Ethanol and Ischemia-Reperfusion in the Rat

Rhizophora mangle, the red mangrove, has long been known as a traditional medicine. Its bark has been used as astringent, antiseptic, hemostatic, with antifungic and antiulcerogenic properties. In this paper, we aimed to evaluate the antioxidant properties of a buthanolic fraction of the R. mangle bark extract (RM) against experimental gastric ulcer in rats. Unib-Wh rats received pretreatment of R. mangle after the induction of gastric injury with absolute ethanol and ischemia-reperfusion. Gastric tissues from both methods were prepared to the enzymatic assays, the levels of sulfhydril compounds (GSH), lipid peroxides (LPO), and the activities of glutathione reductase (GR), glutathione peroxidase (GPx), superoxide dismutase (SOD) and myeloperoxidase (MPO) were measured. The RM protected the gastric mucosa in both methods used, ethanol-induced gastric ulcer and ischemia-reperfusion, probably, by modulating the activities of the enzymes SOD, GPx, and GR and increasing or maintaining the levels of GSH; in adittion, LPO levels were reduced. The results suggest that the RM antioxidant activity leads to tissue protection; thus one of the antiulcer mechanisms present on the pharmacological effects of R. mangle is the antioxidant property.

Cyclopentadienyl and pentamethylcyclopentadienyl ruthenium complexes as catalysts for the total deoxygenation of 1,2-hexanediol and glycerol

The ruthenium aqua complexes [cp*Ru(OH2)(N–N)](OTf) (cp* = η5-pentamethylcyclopentadienyl, N–N = 2,2′-bipyridine, phen = 1,10-phenanthroline, OTf− = trifluoromethanesulfonate) and the acetonitrile complex [cpRu(CH3CN)(bipy)](OTf) (cp = η5-cyclopentadienyl) are water-, acid-, and thermally stable (>200 °C) catalysts for the hydrogenation of aldehydes and ketones in sulfolane solution. In the presence of HOTf as a co-catalyst, they effect the deoxygenation of 1,2-hexanediol to 1-hexanol and hexane. Glycerol is deoxygenated to 1-propanol in up to 18% yield and under more forcing conditions completely deoxygenated to propene. The structure of the acetonitrile pro-catalyst [cpRu(CH3CN)(bipy)](OTf) has been determined by X-ray crystallography (space groupP (a = 9.3778(10) A; b = 10.7852(10) A; c = 11.1818(13) A; α = 101.718(5)°; β = 114.717(4)°; γ = 102.712(5)°; R = 3.95%).

Easy Ambient Sonic-Spray Ionization Mass Spectrometric of Olive Oils: Quality Control and Certification of Geographical Origin

Herein, we show that easy ambient sonic spray ionization mass spectrometry in the negative ion mode [EASI(-)-MS] of water:methanol extracts of olive oil samples from 5 different countries (Portugal, Italy, Spain, Lebanon, and Greece) provides very characteristic profiles of chemotaxonomic markers, that is, free fatty acids and phenols. These EASI(-)-MS fingerprints, acquired with great speed and simplicity after minimal sample preparation, permits secure identification of the samples as olive oils via their unique profiles of fatty acids plus phenolic constituents as well the certification of geographical regions via characteristic features of the profiles of phenolic constituents.

Blends of soybean biodiesel with petrodiesel: direct quantitation via mass spectrometry

Quantitation and identification of blends of soybean biodiesel with petrodiesel were performed via mass spectrometry using two ionization techniques: electrospray ionization (ESI) and Venturi easy ambient sonic-spray ionization in its liquid mode (VL-EASI). Different soybean biodiesel/petrodiesel blends (from B0 to B100) were diluted and then directly infused and analyzed by both techniques. To investigate adulteration of Bn blends, different soybean oil/biodiesel and soybean oil/petrodiesel blends were analyzed. Analytical curves were obtained in three replicates. The two techniques were shown to provide reasonably accurate quantitation in the B1-B20 range. These techniques were also successfully used to detect contamination or adulteration of Bn blends with vegetable oils. ESI is a widely used and commercially available technique whereas a VL-EASI source can be easily mounted using common laboratory parts requiring no use of high voltages. Both techniques require no pre-separation or derivatization steps and offer, therefore, simple and fast methods for the quantitation of Bn blends. The comprehensive snapshots of the molecular composition also allow quality control and typification of the biodiesel and eventually of the vegetable oils in illegal admixtures.

Synthesis of potentially bioactive PABA-related N-(aminoalkyl)lactamic amino acids and esters via selective SNAr reactions

Potentially bioactive N-(aminoalkyl)lactamic amino acids and esters were synthesized in satisfactory to good yields by SNAr reactions of aromatic acids with N-(3-aminopropyl)lactams followed by esterification with tertiary amino alcohols. The addition–elimination SNAr mechanism was confirmed by NMR and MS measurements.Graphical Abstract

Intrinsic acidity and electrophilicity of gaseous propargyl/allenyl carbocations.

The ion/molecule chemistry of four representative propagyl/allenyl cations 1-4 of the general formula R(1)CH(+)-C[triple bond]C-R (a) <--> R(1)CH=C=C(+)-R (b), that is, the reactive C(3)H(3)(+) ions of m/z 39 from EI of propargyl chloride (H(2)C(+)-C[triple bond]C-H, 1a), isomeric C(4)H(5)(+) ions of m/z 53 from EI of 3-butyne-2-ol (2a, H(2)C(+)-C[triple bond]C-CH(3)) and 2-butyne-1-ol (CH(3)-CH(+)-C[triple bond]C-H, 3a), and Ph-C(3)H(2)(+) ions of m/z 115 from 3-phenyl-2-propyn-1-ol (H(2)C(+)-C[triple bond]C-Ph, 4a) was studied via pentaquadrupole mass spectrometry. With pyridine, proton transfer was observed as the predominant process for 1 and the sole reaction channel for the isomeric 2 and 3, whereas 4 reacted preferentially by adduct formation. These outcomes were rationalized using DFT calculations from isodesmic proton transfer reactions. Similar reaction tendencies were observed with acetonitrile and acrylonitrile, with adduct formation appearing again as a minor pathway for 1, 2 and 4, and as a major reaction channel for 4. With 1,3-dioxolane, hydride abstraction was a dominant reaction, with proton transfer and adduct formation competing as side reactions. With 2,2-dimethyl-1,3-dioxolane, an interplay of reactions including methyl anion abstraction, proton transfer, hydride abstraction and adduct formation were observed depending on the ion structure, with 4 reacting again mainly by adduct formation. Proton transfer was also observed as a dominant process in reactions with ethanol for 1, 2 and 3, with 4 being nearly unreactive whereas no adduct formation was observed for any of the carbocations studied. Limited reactivity was exhibited by these ions in cycloaddition reaction with isoprene.