Multi-element determination in Brazilian honey samples by inductively coupled plasma mass spectrometry and estimation of geographic origin with data mining techniques

Multi-element analysis of honey samples was carried out with the aim of developing a reliable method of tracing the origin of honey. Forty-two chemical elements were determined (Al, Cu, Pb, Zn, Mn, Cd, Tl, Co, Ni, Rb, Ba, Be, Bi, U, V, Fe, Pt, Pd, Te, Hf, Mo, Sn, Sb, P, La, Mg, I, Sm, Tb, Dy, Sd, Th, Pr, Nd, Tm, Yb, Lu, Gd, Ho, Er, Ce, Cr) by inductively coupled plasma mass spectrometry (ICP-MS). Then, three machine learning tools for classification and two for attribute selection were applied in order to prove that it is possible to use data mining tools to find the region where honey originated. Our results clearly demonstrate the potential of Support Vector Machine (SVM), Multilayer Perceptron (MLP) and Random Forest (RF) chemometric tools for honey origin identification. Moreover, the selection tools allowed a reduction from 42 trace element concentrations to only 5. (C) 2012 Elsevier Ltd. All rights reserved.

Electrospray Ionization Mass Spectrometry Fingerprinting of Extracts of the Leaves of Arrabidaea chica

Arrabidaea chica (crajiru) is an important Amazonian plant. Its extracts are used as red pigments, antimicrobial agents and astringents. Three different varieties of this species are cultivated in the Amazon region. In this work, direct infusions of A. chica extracts from these three varieties were analyzed via electrospray ionization mass spectrometry (ESI(+)-MS) fingerprinting. Derived data from the spectra were classified by using a multivariate method (PLS-DA, partial least squares-discriminant analysis). The direct method that is herein presented relies on extraction of dry, powdered leaves with acidified methanol/water solution with no further sample preparation. The resulting supernatants were analyzed by direct infusion ESI(+)-MS, which provides characteristic fingerprints of the sample composition. 3-Deoxyanthocyanidins are important substances in A. chica, their ions were used as markers in the PLS-DA data treatment. PLS-DA was able to differentiate the three varieties. ESI(+)-MS fingerprinting works as a simple and fast method to differentiate varieties of A. chica.

Sensitive and fast determination of Sudan dyes in chilli powder by partial-filling micellar electrokinetic chromatography-tandem mass spectrometry

A fast and sensitive method for the simultaneous determination of Sudan dyes (I, II, III, and IV) in food samples was developed for the first time using partial filling micellar electrokinectic chromatography-mass spectrometry (MEKC-MS). The use of MEKC was essential to achieve the separation of these neutral analytes, while the partial filling technique was necessary to avoid the contamination of the ion source with non-volatile micelles. MEKC separation and MS detection conditions were optimized in order to achieve a fast, efficient, and sensitive separation of the four dyes. Filling 25% of the capillary with an MEKC solution containing 40 mM ammonium bicarbonate, 25 mM SDS, and 32.5% (v/v) acetonitrile, a baseline separation of the four azo-dyes was obtained in 10 min. Tandem MS was investigated in order to improve the sensitivity and selectivity of the analysis. Limits of detection (LOD) values 5, 8, 15, and 29 times better were obtained for Sudan III, I, II, and IV, respectively, using partial filling MEKC-MS/MS instead of partial filling MEKC-MS. Under optimized conditions, LOD from 0.05 to 0.2 mu g/mL were obtained. The suitability of the developed method was demonstrated through the fast and sensitive determination of Sudan I, II, III, and IV in spiked chilli powder samples. This determination could not be achieved by MEKC-UV due to the existence of several interfering compounds from the matrix.

Analysis of carvedilol enantiomers in human plasma using chiral stationary phase column and liquid chromatography with tandem mass spectrometry

Carvedilol is an antihypertensive drug available as a racemic mixture. (-)-(S)-carvedilol is responsible for the nonselective beta-blocker activity but both enantiomers present similar activity on a1-adrenergic receptor. To our knowledge, this is the first study of carvedilol enantiomers in human plasma using a chiral stationary phase column and liquid chromatography with tandem mass spectrometry. The method involves plasma extraction with diisopropyl ether using metoprolol as internal standard and direct separation of the carvedilol enantiomers on a Chirobiotic T (R) (Teicoplanin) column. Protonated ions [M + H]+ and their respective ion products were monitored at transitions of 407 > 100 for the carvedilol enantiomers and 268 > 116 for the internal standard. The quantification limit was 0.2 ng ml-1 for both enantiomers in plasma. The method was applied to study enantioselectivity in the pharmacokinetics of carvedilol administered as a single dose of 25 mg to a hypertensive patient. The results showed a higher plasma concentration of (+)-(R)-carvedilol (AUC08 205.52 vs. 82.61 (ng h) ml-1), with an enantiomer ratio of 2.48. Chirality, 2012. (C) 2012 Wiley Periodicals, Inc.

SENSITIVE METHOD FOR DETERMINATION OF PIPLARTINE, AN ALKALOID AMIDE FROM Piper SPECIES, IN RAT PLASMA SAMPLES BY LIQUID CHROMATOGRAPHY-TANDEM MASS SPECTROMETRY

Piplartine (PPTN) is an alkaloid amide found in Piper species that presents different activities. PPTN determination in rat plasma is necessary to better understand its biological effects. The aim of this study was to develop a sensitive LC-MS/MS method for the determination of PPTN in rat plasma. The performance criteria for linearity, sensitivity, precision, accuracy, recovery, and stability have been assessed and were within the recommended guidelines. The validated method proved to be suitable in a pilot study of PPTN kinetic disposition in rat plasma after a single intraperitoneal dose, and represents an appropriate tool to further pharmacokinetic studies.

Corrole isomers: intrinsic gas-phase shapes via traveling wave ion mobility mass spectrometry and dissociation chemistries via tandem mass spectrometry

Corrole and four of its isomers with subtle structural changes promoted by exchange of nitrogen and carbon atoms in the corrole ring have been studied by traveling wave ion mobility mass spectrometry and collision induced dissociation experiments. Significant differences in shapes and charge distributions for their protonated molecules were found to lead to contrasting gas phase mobilities, most particularly for corrorin, the most "confused" isomer. Accordingly, corrorin was predicted by B3LYP/6-31g(d,p) and collisional cross section calculations to display the most compact tri-dimensional structure, whereas NCC4 and corrole were found to be the most planar isomers. Better resolution between the corrole isomers was achieved using the more polarizable and massive CO2 as the drift gas. Sequential losses of HF molecules were found to dominate the dissociation chemistry of the protonated molecules of these corrole isomers, but their unique structures caused contrasting labilities towards CID, whereas NCC4 showed a peculiar and structurally diagnostic loss of NH3, allowing its prompt differentiation from the other isomers.

Mechanistic changes observed in heavy water for nitrate reduction reaction on palladium-modified Pt(hkl) electrodes

Reduction of nitrate on palladium-modified platinum single-crystal electrodes has been investigated both voltammetrically and spectroscopically in acidic media (pH = 1). Results obtained in H2O and D2O solvents are compared for the three crystallographic orientations. FTIR and differential electrochemical mass spectrometry (DEMS) results clearly indicate that the isotopic substitution of the solvent has a large effect in the mechanism of the reaction, changing the nature of the detected products. For Pt(111)/Pd and Pt(100)/Pd, N2O is detected as the main product of nitrate reduction when D2O is used as solvent, while no N2O is detected when the reaction is performed in H2O. For Pt(110)/Pd, N2O is detected in both solvents, although the use of D2O clearly favours the preferential formation of this product. The magnitude of voltammetric currents is also affected by the nature of the solvent. This has been analysed considering, in addition to the different product distribution, the existence of different transport numbers and optical constants of the solvent.

DETERMINATION OF CHLORFENVINPHOS, FIPRONIL, AND CYPERMETHRIN RESIDUES IN MEAT AND BOVINE FAT USING QUECHERS METHOD AND GAS CHROMATOGRAPHY-MASS SPECTROMETRY

Analytic methods were applied and validated to measure residues of chlorfenvinphos, fipronil, and cypermethrin in meat and bovine fat, using the QuEChERS method and gas chromatography-mass spectrometry. For the meat, 2 g of sample, 4mL of acetonitrile, 1.6 g of MgSO4, and 0.4 g of NaCl were used in the liquid-liquid partition, while 80 mg of C18, 80 mg of primary and secondary amine and 150 mg of MgSO4 were employed in the dispersive solid-phase extraction. For the fat, 1 g of sample, 5 mL of hexane, 10 mL of water, 10 mL of acetonitrile, 4 g of MgSO4, and 0.5 g of NaCl were used in the liquid-liquid partition and 50 mg of primary and secondary amine and 150 mg of MgSO4 were used in the dispersive solid-phase extraction. The recovery percentages obtained for the pesticides in meat at different concentrations ranged from 81 to 129% with relative standard deviation below 27%. The corresponding results from the fat ranged from 70 to 123% with relative standard deviation below 25%. The methods showed sensitivity, precision, and accuracy according to EPA standards and quantification limits below the maximum residue limit established by European Union, except for chlorfenvinphos in the fat.

Thermal behavior of malonylglucoside isoflavones in soybean flour analyzed by RPHPLC/DAD and eletrospray ionization mass spectrometry

Soybean (Glycine max (Merrill) L) contains high content of aglycone isoflavones, as well as glucoside and malonylconjugates. In this work, the content of isoflavones in defatted soy flour was determined by reversed-phase high-performance liquid chromatography (RPHPLC) after alcoholic extraction in methanol/water mixture in the ratio 80:20 (v/v). It was observed that the heating treatment transformed the malonylglucosides into glucoside isoflavones. After heat treatment at 121 degrees C for 30 min, nearly all malonylisoflavones were converted into glucoside, but acetylisoflavones were not detected via RPHPLC analysis. Electrospray ionization mass spectrometry confirmed the presence of malonylisoflavones in heat-treated defatted soy flour by direct infusion analysis. (c) 2012 Elsevier Ltd. All rights reserved.

Borohydride electrooxidation on Au and Pt electrodes

Direct borohydride fuel cells (DBFCs) are attractive energy generators for powering portable electronic devices, mainly due to their high energy density and number of electrons per borohydride ion. However, the lack of a highly efficient electrocatalyst for the borohydride oxidation reaction limits the performance of these devices. The most commonly studied electrocatalysts for this reaction are composed of gold and platinum. Nevertheless, for these metals, the borohydride electrooxidation reaction mechanism (BOR) is not completely understood, and the total oxidation reaction, involving eight electrons per BH4- species, competes with parallel reactions, with a lower number of exchanged electrons and/or with heterogeneous chemical hydrolysis. Considering the above-mentioned issues, this work presents recent advances in the knowledge of the BOR pathways on polycrystalline (bulk) Au and Pt electrocatalysts. It presents the studies of the BOR reaction on Au and Pt electrodes using in situ Fourier Transform Infrared Spectroscopy (FUR), and on-line Differential Electrochemical Mass Spectrometry (DEMS). The spectroscopic and spectrometric data provided physical evidence of intermediate species and the formation of H-2 in the course of the BOR as a function of the electrode potential. These results enabled to advance in the knowledge about the BOR pathways on Au and Pt electrocatalysts. (C) 2012 Elsevier Ltd. All rights reserved.

New Approaches for the Ethanol Oxidation Reaction of Pt/C on Carbon Cloth Using ATR-FTIR

This work describes the study of the ethanol oxidation reaction of a Pt/C Etek electrocatalyst that was supported on different substrates, such as gold, glassy carbon and carbon cloth treated with PTFE. In the ethanol oxidation reaction, the activity varies with the substrate, as well as the pathways for ethanol oxidation, as studied by an ATR-FTIR in situ setup using the carbon cloth as the electrocatalyst support. The electrocatalyst Pt/C supported on gold starts acetaldehyde production from ethanol oxidation at an onset potential of 0.1 V less than that observed for the same process on Teflon-treated carbon cloth. The Pt/C supported on the carbon cloth starts its CO2 production for the same oxidation process at 0.2 V less than on the Pt/C supported on gold substrate. The differences in catalytic activity for the ethanol oxidation reaction depend not only on the electrocatalyst but also on various electrode factors, such as the substrate, the roughness of the electrode and the charge transfer resistance.

An environmentally friendly analytical procedure for nickel determination by atomic and molecular spectrometry after cloud point extraction in different samples

Cloud point extraction (CPE) was employed for separation and preconcentration prior to the determination of nickel by graphite furnace atomic absorption spectrometry (GFAAS), flame atomic absorption spectrometry (FAAS) or UV-Vis spectrophotometry. Di-2-pyridyl ketone salicyloylhydrazone (DPKSH) was used for the first time as a complexing agent in CPE. The nickel complex was extracted from the aqueous phase using the Triton X-114 surfactant. Under optimized conditions, limits of detection obtained with GFAAS, FAAS and UV-Vis spectrophotometry were 0.14, 0.76 and 1.5 mu g L-1, respectively. The extraction was quantitative and the enrichment factor was estimated to be 27. The method was applied to natural waters, hemodialysis concentrates, urine and honey samples. Accuracy was evaluated by analysis of the NIST 1643e Water standard reference material.

Measurement of airborne gunshot particles in a ballistics laboratory by sector field inductively coupled plasma mass spectrometry

The present study aimed determines lead (Pb), antimony (Sb) and barium (Ba) as the major elements present in GSR in the environmental air of the Ballistics Laboratory of the Sao Paulo Criminalistics Institute (I.C.-S.P.), Sao Paulo, SP, Brazil. Micro environmental monitors (mini samplers) were located at selected places. The PM2.5 fraction of this airborne was collected in, previously weighted filters, and analyzed by sector field inductively coupled plasma mass spectrometer (SF-HR-ICP-MS). The higher values of the airborne lead, antimony and barium, were found at the firing range (lead (Pb): 58.9 mu g/m(3); barium (Ba): 6.9 mu g/m(3); antimony (Sb): 7.3 mu g/m(3)). The mean value of the airborne in this room during 6 monitored days was Pb: 23.1 mu g/m(3); Ba: 2.2 mu g/m(3); Sb: 1.5 mu g/m(3). In the water tank room, the air did not show levels above the limits of concern. In general the airborne lead changed from day to day, but the barium and antimony remained constant. Despite of that, the obtained values suggest that the workers may be exposed to airborne lead concentration that can result in an unhealthy environment and could increase the risk of chronic intoxication. (C) 2011 Elsevier Ireland Ltd. All rights reserved.

FTIR and SEM analysis of CO2 laser irradiated human enamel

Objectives: Considering the enamel chemical structure, especially carbonate band, which has a major role in the caries prevention, the objective of the present study was to assess the chemical alterations on the enamel irradiated with CO2 laser by means of FTIR spectroscopy and SEM analysis. Design: The enamel surfaces were analysed on a spectrometer for acquisition of the absorption spectrum relative to the chemical composition of the control sample. The irradiation was conducted with a 10.6-mu m CO2 laser (0.55 W, 660 W/cm(2)). The carbonate absorption band at 1600-1291 cm(-1) as well as the water absorption band at 3793-2652 cm(-1) was measured in each sample after the irradiation. The water band was measured again 24-h after the irradiation. The band area of each chemical compound was delimited, the background was subtracted, and the area under each band was integrated. Each area was normalized by the phosphate band (1190-702 cm(-1)). Results: There was a statistically significant decrease (p < 0.05) in the water content after irradiation (control: 0.184 +/- 0.04; irradiated: 0.078 +/- 0.026), which increased again after rehydration (0.145 +/- 0.038). The carbonate/phosphate ratio was measured initially (0.112 +/- 0.029) and its reduction after irradiation indicated the carbonate loss (0.088 +/- 0.014) (p < 0.05). Conclusion: The 10.6-mu m CO2 laser irradiation diminishes the carbonate and water contents in the enamel after irradiation. (C) 2012 Elsevier Ltd. All rights reserved.

STUDY BY MASS SPECTROMETRY OF SOLUTIONS OF [HYDROXY(TOSYLOXY)IODO]BENZENE: PROPOSED DISPROPORTIONATION MECHANISMS

STUDY BY MASS SPECTROMETRY OF SOLUTIONS OF [HYDROXY(TOSYLOXY)IODO]BENZENE: PROPOSED DISPROPORTIONATION MECHANISMS. Solutions of [hydroxy(tosyloxy)iodo]benzene (HTIB or Koser's reagent) in acetonitrile were analyzed using high resolution electrospray ionization mass spectrometry (ESI-MS) and electrospray ionization tandem mass spectrometry (ESI-MS/MS) under different conditions. Several species were characterized in these analyses. Based on these data, mechanisms were proposed for the disproportionation of the iodine(III) compounds in iodine(V) and iodine(I) species.