Viorica Lopez-Avila

Fast and robust direct immersion solid phase microextraction coupled with gas chromatography-time-of-flight mass spectrometry method employing a matrix compatible fiber for determination of triazole fungicides in fruits.

A fast and robust method was developed for the determination of ten triazole fungicides in fruit samples using direct immersion solid-phase microextraction coupled to gas chromatography with time-of-flight mass spectrometry detection (DI-SPME-GC-ToFMS). In this work, a newly developed concept of solid-phase microextraction (SPME) sorbent, which allows for direct immersion extraction in complex food matrices, has been applied in the analysis of 10 triazole fungicides in grapes and strawberries pulps. Potential factors affecting the extraction efficiency were investigated and optimized, including extraction temperature, sample pH, and ionic strength, agitation speed, extraction and desorption times. Under optimized conditions, the method was linear for over 4 orders of magnitude in concentration, with linear regression coefficients (R(2)) greater than 0.99 for all test compounds in both matrices. Method reproducibility, as determined by analysis of spiked grapes and strawberries, was better than ±20%. The limits of quantitation objective (LOQs) ranged from 0.25 to 5 ng g(-1) for both matrices, well below the maximum residues levels allowed for those compounds in both matrices. The method was successfully applied in the analysis of commercial samples of grapes and strawberries. Finally, the new SPME method was compared to a modified version of t QuEChERS AOAC method: the limits of quantitation reached by SPME were at least one order of magnitude lower than those achieved by the QuEChERS method, whereas precision and accuracy were comparable for both methods.

Separation of haloacetic acids in water by capillary zone electrophoresis with direct UV detection and contactless conductivity detection

The separation of haloacetic acids (HAAs) in water by capillary zone electrophoresis with direct UV and contactless conductivity detection was investigated using phosphate, citrate, and borate buffers, and the experimental data were compared to simulation data predicted by a computational program known as PeakMaster. Good agreement between the experimental data and simulation data predicted by PeakMaster was found. Using the phosphate buffer or the citrate buffer and electrokinetic injection it was possible to quantitate HAAs at 0.1 ppm levels in water.

Urine Peptidomic and Targeted Plasma Protein Analyses in the Diagnosis and Monitoring of Systemic Juvenile Idiopathic Arthritis

PurposeSystemic juvenile idiopathic arthritis is a chronic pediatric disease. The initial clinical presentation can mimic other pediatric inflammatory conditions, which often leads to significant delays in diagnosis and appropriate therapy. SJIA biomarker development is an unmet diagnostic/prognostic need to prevent disease complications.Experimental DesignWe profiled the urine peptidome to analyze a set of 102 urine samples, from patients with SJIA, Kawasaki disease (KD), febrile illnesses (FI), and healthy controls. A set of 91 plasma samples, from SJIA flare and quiescent patients, were profiled using a customized antibody array against 43 proteins known to be involved in inflammatory and protein catabolic processes.ResultsWe identified a 17-urine-peptide biomarker panel that could effectively discriminate SJIA patients at active, quiescent, and remission disease states, and patients with active SJIA from confounding conditions including KD and FI. Targeted sequencing of these peptides revealed that they fall into several tight clusters from seven different proteins, suggesting disease-specific proteolytic activities. The antibody array plasma profiling identified an SJIA plasma flare signature consisting of tissue inhibitor of metalloproteinase-1 (TIMP1), interleukin (IL)-18, regulated upon activation, normal T cell expressed and secreted (RANTES), P-Selectin, MMP9, and L-Selectin.Conclusions and Clinical RelevanceThe urine peptidomic and plasma protein analyses have the potential to improve SJIA care and suggest that SJIA urine peptide biomarkers may be an outcome of inflammation-driven effects on catabolic pathways operating at multiple sites.

Determination of stimulants using gas chromatography/high-resolution time-of-flight mass spectrometry and a soft ionization source

RATIONALE The aim of this study was to investigate the mass spectral fragmentation of a small set of stimulants in a high-resolution time-of-flight mass spectrometer equipped with a soft ionization source using vacuum ultraviolet (VUV) photons emitted from different plasma gases. It was postulated that the use of a plasma gas such as Xe, which emits photons at a lower energy than Kr or Ar, would lead to softer ionization of the test compounds, and thus to less fragmentation. METHODS A set of nine stimulants: cocaine, codeine, nicotine, methadone, phenmetrazine, pentylenetetrazole, niketamide, fencamfamine, and caffeine, was analyzed by gas chromatography/time-of-flight mass spectrometry (GC/TOFMS) in positive ion mode with this soft ionization source, using either Xe, Kr, or Ar as plasma gases. Working solutions of the test compounds at 0.1 to 100 ng/μL were used to establish instrument sensitivity and linearity. RESULTS All test compounds, except methadone and pentylenetetrazole, exhibited strong molecular ions and no fragmentation with Xe-microplasma photoionization (MPPI). Methadone exhibited significant fragmentation not only with Xe, but also with Kr and Ar, and pentylenetetrazole could not be ionized with Xe, probably because its ionization energy is above 8.44 eV. The Kr- and Ar-MPPI mass spectra of the test compounds showed that the relative intensity of the molecular ion decreased as the photon energy increased. CONCLUSIONS When coupled to a TOF mass spectrometer this soft ionization source has demonstrated signal-to-noise (S/N) ratios from 7 to 730 at 100 pg per injection (depending on the compound), and a dynamic range of three orders of magnitude (100 pg to 100 ng) for some of the test compounds.

Identification of methylhexaneamine by GC high-resolution TOFMS and soft ionization

UNLABELLED Methylhexaneamine (MHA) is a stimulant that is added to dietary supplements and its safety is an on-going debate, prompting the World Anti-Doping Agency to add it to the 2010 prohibited list. Gas chromatography-low resolution mass spectrometry (GC-MS) with electron ionization (EI) requires derivatization to convert MHA into a less volatile compound, and a 2-3 min solvent delay to prevent filament damage. Without derivatization, the EI mass spectrum of MHA, which exhibits an abundant immonium ion at m/z 44 and no other fragment ions with relative intensity >10%, is very similar to the EI mass spectra of 2-aminoheptane, 1,4-dimethylamylamine, and n-hexylmethylamine. When using derivatization with trifluoroacetic anhydride (TFAA) and GC-high resolution time-of-flight mass spectrometry with soft ionization, the derivatized MHA diastereoisomers can be distinguished from the trifluoroacetyl-derivatives of 1-aminoheptane, 2-aminoheptane, 1,4-dimethylamylamine (1,4-DMAA) and n-hexylmethylamine. Several nutritional supplements were analysed for MHA by this technique and the results of the measurements are presented here. KEYWORDS GC high-resolution TOFMS; Soft-ionization; Methylhexaneamine; Nutritional supplements.

Identification of Compounds in Commercial Kava Extracts by Gas Chromatography with Electron Ionization High-Resolution Mass Spectrometry

This paper discusses the identification of kava lactones and related compounds by gas chromatography (GC) and quadrupole time-of-flight mass spectrometry (QTOFMS) with an electron ionization source. Three herbal preparations from different sources were analyzed by both GC-low-resolution MS and GC-high-resolution MS. The exact mass measurements generated with a research QTOFMS with mass accuracies in the low ppm range were combined with the isotope abundance ratios to confirm the presence of kava lactones and to identify additional compounds present in the Kava extracts. Although the availability of standards is of upmost importance to unequivocally confirm compound identities, the combination of accurate mass ( 10,000) and literature information on the approximate composition of the herbal extracts provides a powerful analytical tool to help identify organic compounds in herbal extracts.

Mass Spectral Fragmentation Studies of Coumarin-Type Compounds Using GC High-Resolution MS

The present study was undertaken to investigate fragmentation of a set of thirteen coumarins that bear amino-, alkylamino-, alkyl-, fluoroalkyl-groups, and heterocyclic rings, in a high-resolution (>10,000) quadrupole time-of-flight mass spectrometer equipped with an the electron ionization source and interfaced to a gas chromatograph. We have demonstrated how our data processing software is used to generate molecular formulas from high-resolution accurate mass measurements and isotope ratios, and have shown that only with a high-resolution MS can one distinguish between the loss of CO, C2H4, or CH2N. EI mass spectra are shown for all coumarins tested here, and proposed fragmentation pathways based on the high-resolution MS data are proposed for two coumarins.

Environmental Applications of Soft Ionization with GC–TOFMS and GC–QTOFMS

Abstract Soft ionization used with gas chromatography time-of-flight mass spectrometry (GC–TOFMS) allows for the selective ionization of aliphatic hydrocarbons and polycyclic aromatic sulfur heterocycles in certified standard reference oil (NIST SRM2721) and coal tar (NIST SRM1597a). Soft ionization is accomplished by photoionization from vacuum ultraviolet resonance lines produced by Xe, Kr, and Ar microplasmas. Molecular ion fragmentation of an aliphatic hydrocarbon C 24 H 50 in a TOF mass spectrometer and a QTOF mass spectrometer using Ar and Kr are compared. The advantage of using soft ionization, as compared with the more commonly used electron ionization, lies in the enhancement of the relative intensity of molecular ions, which can be controlled by the choice of plasma gas. Furthermore, the enhanced selectivity provided by the ability to select the ionization wavelength is demonstrated through the qualitative analysis of a series of polycyclic aromatic sulfur heterocycles including dibenzothiophene, naphthothiophene, benzonaphthothiophene, and various methylated derivatives of these compounds.

Determination of Chlorophenoxy Acid Methyl Esters and Other Chlorinated Herbicides by GC High-resolution QTOFMS and Soft lonization

Gas chromatography with quadrupole time-of-flight mass spectrometry (GC-QTOFMS) and soft ionization generated by a rare-gas plasma is described here for the determination of various chlorophenoxy acid methyl esters and a few chlorinated herbicides. This plasma-based, wavelength-selectable ionization source, which can use Xe, Kr, Ar, Ne, or He as the plasma gas, enables ionization of GC-amenable compounds with ionization energies below 8.4, 10, 11.6, 16.5, or 22.4 eV, respectively. The advantages of soft ionization include enhanced molecular ions, reduced fragmentation, and reduced background noise as compared to electron ionization. In the study presented here for two plasma gases, we demonstrate that Kr plasma, which is softer than Ar plasma, yields molecular ions with a relative intensity >60% for 11 of the 16 test compounds. When using this “tunable” plasma to ionize the analytes, there is the possibility for selective ionization and less fragmentation, which may lead to increased sensitivity and may help structure elucidation, especially when using high-resolution mass spectrometry that generates accurate masses within a few parts per million (ppm) mass errors. Data generated with the Ar plasma and real matrices such as a peppermint extract, a plum extract, and an orange peel extract, spiked with 16 test compounds, indicate that the test compounds can be detected at 1–10 pg/μL of extract, and compounds such as menthone, limonene, eucalyptol, pinene, caryophylene, and other C15H24 isomers, which are present in the peppermint and the orange peel extracts at ppm to percent levels, do not appear to interfere with the determination of the chlorophenoxy acid methyl esters or the chlorinated herbicides, although there were matrix effects when the test compounds were spiked at 1–10 pg/μL of extract.

Methods for Detection of Matrix Metalloproteinases as Biomarkers in Cardiovascular Disease

Matrix metalloproteinases (MMPs) are a family of zinc-dependent proteolytic enzymes that degrade extracellular matrix (ECM) components like collagen, fibronectin, and laminin. While this activity is important for normal development, morphogenesis, and wound healing, deregulation of MMP activity has been implicated in a number of cardiovascular diseases, including congenital heart defects, atherosclerosis, myocardial infarction, and congestive heart failure. MMPs are good potential diagnostic indicators of cardiovascular disease, but current detection methods are time consuming and quite laborious. This review will discuss MMP biology, current methods for detection of MMPs from patient samples, and potential new developments in multiplexed analysis of MMPs.