Direct Analysis Of Complex Mixtures Research Articles

Novel Ion Trap Scan Modes to Develop Criteria for On-Site Detection of Sulfonamide Antibiotics.

Advances in ambient ionization techniques have facilitated the direct analysis of complex mixtures without sample preparation. Significant attention has been given to innovating ionization methods so that multiple options are now available, allowing for ready selection of the best methods for particular analyte classes. These ambient techniques are commonly implemented on benchtop systems, but their potential application with miniature mass spectrometers for in situ measurements is even more powerful. These applications require that attention be paid to tailoring the mass spectrometric methodology for the on-site operation. In this study, combinations of scan modes are employed to efficiently determine what tandem mass spectrometry (MS/MS) operations are most useful for detecting sulfonamides using a miniature ion trap after ionization. First, mixtures of representative sulfonamide antibiotics were interrogated using a 2D MS/MS scan on a benchtop ion trap in order to determine which class-specific fragments (ionic or neutral) are shared between the sulfonamides and thus have diagnostic value. Then, three less-used combination scans were recorded: (i) a simultaneous precursor ion scan was used to detect both analytes and an internal standard in a single ion injection event to optimize quantitative performance; (ii) a simultaneous precursor/neutral loss scan was used to improve detection limits; and finally, (iii) the simultaneous precursor/neutral loss scan was implemented in a miniature mass spectrometer and representative sulfonamides were detected at concentrations as low as 100 ng/mL by nano-electrospray and 0.5 ng absolute by paper spray ionization, although improvements in the stability of the home-built instrumentation are needed to further optimize performance.

Direct analysis of complex mixtures by mass spectrometry

Mixture analysis can provide information on individual components if the sample is first subjected to chromatographic separation. Two critical capabilities, soft ionization and the ability to mass-select and then dissociate ions of a particular m/z, coalesced in 1975, allowing direct analysis of complex mixtures by mass spectrometry. Chemical ionization was used as the soft ionization method and mass-analysis used the ion kinetic energy spectrometer (MIKES). Soft molecular ionization produces a set of ions that are structural surrogates of the neutral molecules; they can be mass-selected and allowed to spontaneously dissociate (i.e. as metastable ions) or fragmented upon energy transfer e.g. in the course of collision-induced dissociation (CID). The second stage of mass analysis provides information about the atomic connectivity in the precursor ion and by implication in the original molecule. This review focuses on the development of complex mixture analysis by mass spectrometry and allied topics. Discussion of the activation techniques associated with (collision-induced dissociation, surface-induced dissociation and metastable ion dissociation) emphasizes the importance of energy transfer phenomena and the internal energies distributions of ions to explain the observed mass spectra. The translational to internal energy transfer in collisions is readily accessed in the MIKES where the second stage mass analyzer is a kinetic energy/charge analyzer. Collisions in the keV range can also be used to change ion the charge state via the processes of charge exchange, electron stripping, or charge inversion. New ionization sources for analysis of non-volatile compounds that were introduced during the time period (1975–1990) of this review included secondary ion mass spectrometry, plasma desorption and field ionization and they are briefly discussed. Several types of scans were developed to rapidly access information of the individual components, including chemically specific scans (e.g. neutral loss scans of mass 30 for nitro compounds).

New approach to complex organic compounds mixtures analysis based on gas chromatography–atmospheric pressure photoionization–mass-spectrometry

The mass-spectra of a number of different hydrocarbons were obtained using atmospheric pressure photoionization (APPhI) and photochemical ionization (APPhCI) mass-spectrometry. The respective mass-spectra consisted mainly of molecular (M+) or quasimolecular (MH+) ion peaks or both. The composition of aromatic hydrocarbons in straight-run gasoline was investigated using standard PIONA method, based on capillary GC and retention time indexes, and GC/MS (APPhI). 56 aromatic hydrocarbons were identified using GC/MS (APPhI) and 43-using standard PIONA method. The opportunities of MS (APPHCI) for determination of impurities in pure hydrocarbons and for direct analysis of complex mixtures without separation were demonstrated when MS (APPhCI) analysis for GC standards of benzene and toluene was carried out (main component vapor was reagent gas). The targeted PAHs and phtalates were registered selectively in 44 component model mixture of semivolatiles with partial or without separation of the components, using GC/MS (APPhI).

Direct analysis of polyols using 3-nitrophenylboronic acid in capillary electrophoresis: thermodynamic and electrokinetic principles of molecular recognition

The design of boronic acid sensors for photometric detection of carbohydrates has relied on exploiting differences in the thermodynamic stability of complex formation for molecular recognition. Herein, we introduce a direct method for analysis of sugar alcohols using 3-nitrophenylboronic acid (NPBA) as an electrokinetic probe in capillary electrophoresis (CE). Dynamic complexation of neutral polyols by NPBA during electromigration allows for their simultaneous resolution and UV detection based on formation of an anionic ternary boronate ester complex in phosphate buffer. Unlike conventional boronic acid sensors, thermodynamic and electrokinetic processes in CE allow for improved selectivity for the resolution of sugar alcohol stereoisomers having different vicinal polyol chain lengths even in cases when binding affinity is similar due to differences in their complex mobility. Three complementary approaches were investigated to compare the thermodynamics of polyol chelation with NPBA, namely direct binding assays by CE, UV absorbance spectroscopy and an indirect pK (a) depression method. Overall, CE offers a convenient platform for characterization of reversible arylboronic acid interactions in free solution while allowing for direct analysis of complex mixtures of neutral/UV-transparent polyols without complicated sample handling.

Paper Spray for Direct Analysis of Complex Mixtures Using Mass Spectrometry

Paper Spray for Direct Analysis of Complex Mixtures Using Mass Spectrometry

Paper Spray for Direct Analysis of Complex Mixtures Using Mass Spectrometry

Complex mixtures can be ionized directly from paper for quantitative mass spectrometric analysis of trace components. Prior separations are an option.

Probing proteins on functionalized silicon surfaces using matrix-assisted laser desorption/ionization mass spectrometry

Flat H-terminated Si(1 1 1) substrates modified with alkyl monolayers terminated with hydrophobic and hydrophilic functional groups were prepared using known surface functionalization methods and characterized by FTIR, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The surfaces were then used for the study of non-specific binding of proteins from complex mixtures (using standard mixture of proteins with average molecular weight ∼6–66 kDa) by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). Protein adsorption on these surfaces (following on-probe fractionation of the mixture) was found to be dependent on the nature of surface functional groups, and nature and pH of rinsing solutions used. The results obtained in this work demonstrate that simple silicon-based surface modifications can be effective for direct analysis of complex mixtures by MALDI-MS. Preliminary results obtained using similarly functionalized porous silicon substrates proved that such substrates are (due to their increased surface areas) better performing than flat silicon.

Separation of complex fructo-oligosaccharides (FOS) and inulin mixtures by HPTLC-AMD

A first attempt at the separation of fructo-oligosaccharides (FOS) and inulin mixtures is presented. Preliminary results obtained by automated multiple development (AMD) of diol layers with an acetonitrile-acetone-water polarity gradient are reported. The method is very promising and highly suitable for simple, direct analysis of complex mixtures of fructo-oligosaccharides (FOS) and inulin in samples of natural origin.

Tandem Mass Spectrometry (MS/MS) for Analysis of Additives in a Rubber Vulcanizate

Abstract MS/MS appears to have considerable potential as a means for improved direct mass spectral characterization of organic additives in rubber compounds. In this report, we have shown how daughter-ion, parent-ion, and neutral-loss scans can improve the specificity for identification of organic additive components in rubber vulcanizates. The use of MS/MS to reduce the “chemical noise” in the direct analysis of complex mixtures is demonstrated. MS/MS should not be viewed as a technique that will replace other mass spectral methods in rubber applications. For example, desorption ionization methods, GC/MS, LC/MS and high-resolution mass measurements will still have important roles. MS/MS can serve as a supplemental tool for direct mixture analysis that is both rapid and powerful.

Structural identifications of straight-chain fatty acids and esters in coal extracts by linked scanning mass spectrometry

Structural identifications of geochemically significant straight-chain fatty acids and esters in coal extracts were carried out by linked scanning mass spectrometry together with field desorption mass spectrometry. The results obtained demonstrate the usefulness of the technique for direct analysis of complex mixtures to elucidate detailed molecular structures of individual constituents. The extracts of lignites contain straight-chain fatty acids with C 24 to C 34 and long-chain fatty esters with C 48 to C 64, the latter being missing from subbituminous coals and neither is found in those of bituminous coals. The free fatty acids, the acyl and the alkoxyl groups of esters all extend from C 24 to C 34 and are qualitatively similar to each other in carbon-number distribution indicating that they were probably derived from common precursor compounds. The presence and/or absence of fatty acids and fatty esters parallels the rank of coals and may be connected with chemical changes brought about during maturation, such as hydrolysis of the esters, conversions of the acids into paraffins, etc.

Multiple reaction monitoring in mass spectrometry/mass spectrometry for direct analysis of complex mixtures

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMultiple reaction monitoring in mass spectrometry/mass spectrometry for direct analysis of complex mixturesR. W. Kondrat, G. A. McClusky, and R. G. CooksCite this: Anal. Chem. 1978, 50, 14, 2017–2021Publication Date (Print):December 1, 1978Publication History Published online1 May 2002Published inissue 1 December 1978https://doi.org/10.1021/ac50036a020RIGHTS & PERMISSIONSArticle Views1574Altmetric-Citations138LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (518 KB) Get e-Alerts Get e-Alerts

Mass Spectral Confirmation of Aflatoxins

Abstract Two methods for mass spectral (MS) confirmation of aflatoxins in agricultural products and in physiological fluids are described. In the first method, electron ionization (EI) mass spectra are obtained following isolation by thin layer chromatography (TLC) and compared with available reference mass spectra to provide structural confirmation. Extensive sample cleanup is required for confirmation at the 10—1000 ppb level and minimum sample size is 10—50 ng aflatoxin isolated by TLC. The second method restricts the MS scanning to particular ions which are characteristic of the suspected aflatoxins and requires spectrometer resolution above 5000. The latter method, called high resolution selected ion monitoring (HRSIM), has a sensitivity below 0.0001 μg for aflatoxin B1 and makes possible direct analysis of complex mixtures. Employing HRSIM analysis on complex mixtures lowers the detection limit for aflatoxins M1 and B1 by 100-fold or more below the limit for highly purified samples. We attribute this dramatic sensitivity enhancement to a reduction in surface bonding between the aflatoxins and the glass sample containers used to introduce the samples. The HRSIM is generally applicable to compounds that cannot be separated by gas chromatography prior to MS analysis.