Headspace mass spectrometry methodology: application to oil spill identification in soils

In the present work we report the results obtained with a methodology based on direct coupling of a headspace generator to a mass spectrometer for the identification of different types of petroleum crudes in polluted soils. With no prior treatment, the samples are subjected to the headspace generation process and the volatiles generated are introduced directly into the mass spectrometer, thereby obtaining a fingerprint of volatiles in the sample analysed. The mass spectrum corresponding to the mass/charge ratios (m/z) contains the information related to the composition of the headspace and is used as the analytical signal for the characterization of the samples. The signals obtained for the different samples were treated by chemometric techniques to obtain the desired information. The main advantage of the proposed methodology is that no prior chromatographic separation and no sample manipulation are required. The method is rapid, simple and, in view of the results, highly promising for the implementation of a new approach for oil spill identification in soils. Figure PCA score plots illustrate clear discrimination of types of crude oil in polluted soil samples (e.g. results are shown for vertisol)     

Amplification of noble gas ion lines in the afterglow of a pulsed hollow cathode discharge and possible benefit for analytical glow discharge mass spectrometry

A high-current pulsed hollow cathode discharge was used to study the role of atomic and ionic metastables involved in ionization plasma processes. We observed the enhancement of the spectral emission lines of noble gas ions in the afterglow. A study of the processes that involve atomic and ionic metastables is of great interest since it should lead to a better understanding of and enhanced control over the ionization mechanisms crucial to analytical glow discharge mass spectrometry (GDMS) analysis. Figure Time profile of Ti, Ti⁺, and Ne⁺ spectral lines     

Fourier transform ion cyclotron resonance mass spectrometry of covalent adducts of proteins and 4-hydroxy-2-nonenal, a reactive end-product of lipid peroxidation

Covalent adduction of the model protein apomyoglobin by 4-hydroxy-2-nonenal, a reactive end-product of lipid peroxidation, was characterized by nanoelectrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (FTICR). The high mass resolving power and mass measurement accuracy of the instrument facilitated a detailed compositional analysis of the complex reaction product without the need for deconvolution and transformation to clearly show the pattern of adduction and component molecular weights. Our study has also demonstrated the value of electron capture dissociation over collision-induced dissociation for the tandem mass spectrometric determination of site modification for the 4-hydroxy-2-nonenal adduct of oxidized insulin B chain as an example. Figure FTICR allowed characterization of 4-hydroxy-2-nonenal (HNE)-modified apomyoglobin (an expanded spectrum of the +15 charge state is shown)     

The photochemical behaviour of five household pyrethroid insecticides and a synergist as studied by photo-solid-phase microextraction

In the present study, solid-phase microextraction in photochemical studies was used to investigate UV light induced photodegradation of five pyrethroids (empenthrin, transfluthrin, allethrin, phenothrin and cyphenothrin) and a synergist (piperonyl butoxide), which are common ingredients of household insecticides. Gas chromatography coupled with mass spectrometry was used to separate and tentatively identify the parent compounds and their corresponding photoproducts generated in the same polydimethylsiloxane fibre. Kinetics curves were obtained and apparent first-order rate constants and half-lives were estimated. Twenty-six photoproducts were tentatively identified and photodegradation pathways for the compounds investigated were proposed. It is a matter of some concern that three of the photoproducts identified [(3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylic acid, 3-phenoxybenzaldehyde and (3-phenoxyphenyl)methanol] have been reported to be endocrine disruptors. There is no record of previous studies of cyphenothrin and empenthrin photodegradation, and therefore the present study represents the first attempt to elucidate the photochemical behaviour of these compounds. Figure Photo-SPME for Pyrethroids     

Nuclear magnetic resonance of mass-limited samples using small RF coils

Figure Schematic diagram of a typical arrangement used for hyphenating chemical microseparations (e.g. capillary HPLC, CE, or CEC) with microcoil NMR detection     

Determination of glucosinolates in traditional Chinese herbs by high-performance liquid chromatography and electrospray ionization mass spectrometry

A reversed-phase HPLC method has been developed for determination of twelve intact glucosinolates—glucoiberin, glucocheirolin, progoitrin, sinigrin, epiprogoitrin, glucoraphenin, sinalbin, gluconapin, glucosibarin, glucotropaeolin, glucoerucin, and gluconasturtiin—in ten traditional Chinese plants. The samples were extracted with methanol and the extracts were cleaned on an activated Florisil column. A mobile phase gradient prepared from methanol and 30 mmol L⁻¹ ammonium acetate at pH 5.0 enabled baseline separation of the glucosinolates. Glucosinolate detection was confirmed by quadrupole time-of-flight tandem mass spectrometric analysis in negative-ionization mode. Detection limits ranged from 0.06 to 0.36 μg g⁻¹ when 5 g of dried plant was analyzed. Recoveries of the glucosinolates were better than 85% and precision (relative standard derivation, n = 3) ranged from 5.3 to 14.6%. Analysis of the glucosinolates provided scientific evidence enabling differentiation of three pairs of easily confused plants. Figure Glucosinolates Analysis for the Differentiation of Easily-Confusing Herbs     

Inorganic mass spectrometry as a tool for characterisation at the nanoscale

Inorganic mass spectrometry techniques may offer great potential for the characterisation at the nanoscale, because they provide unique elemental information of great value for a better understanding of processes occurring at nanometre-length dimensions. Two main groups of techniques are reviewed: those allowing direct solid analysis with spatial resolution capabilities, i.e. lateral (imaging) and/or in-depth profile, and those for the analysis of liquids containing colloids. In this context, the present capabilities of widespread elemental mass spectrometry techniques such as laser ablation coupled with inductively coupled plasma mass spectrometry (ICP-MS), glow discharge mass spectrometry and secondary ion/neutral mass spectrometry are described and compared through selected examples from various scientific fields. On the other hand, approaches for the characterisation (i.e. size, composition, presence of impurities, etc.) of colloidal solutions containing nanoparticles by the well-established ICP-MS technique are described. In this latter case, the capabilities derived from the on-line coupling of separation techniques such as field-flow fractionation and liquid chromatography with ICP-MS are also assessed. Finally, appealing trends using ICP-MS for bioassays with biomolecules labelled with nanoparticles are delineated.      

Electrospray mass spectrometry analysis of dendritic branches bearing peripheral fullerene subunits

The electrospray mass spectrometric characterization of neutral dendrons with a carboxylic acid function or a t-butyl ester moiety at the central point and up to eight peripheral C₆₀ subunits has been performed and is described in detail. Molecules bearing a carboxylic acid group at the center turned out to be preferentially ionized by deprotonation, whereas those with a t-butyl ester head group were ionized by reduction of the C₆₀ units in the infusion capillary of the electrospray source. Electronic supplementary material Supplementary material is available for this article at and is accessible for authorized users.     

Determination of IGF-I in horse plasma by LC electrospray ionisation mass spectrometry

The insulin-like-growth factor (IGF-I) peptide is considered to be the main indirect marker for growth hormone administration (GH) in a horse. Further to a previous investigation on measurement of IGF-I in plasma samples by mass spectrometry, this study focuses on quantitative and qualitative analysis of intact IGF-I in horse plasma. First, protein-transposing software has been developed for IGF-I to facilitate its quantification by HPLC–electrospray–ion-trap mass spectrometry. Second, product-ion scan experiments on IGF-I have been conducted on standard samples, non-fortified equine plasma samples, fortified plasma samples, and equine GH post-administration samples. This “top-down” approach method enables characterisation of fragment ions corresponding to the carboxy terminal end, which can be useful for the confirmation of the presence of IGF-I in plasma samples. Figure Structure of IGF-I and amino acid sequences of IGF-I and R3 IGF-I. Deconvolution mass spectra of the IGF-I and R3 IGF-I mixture     

Determination of antimicrobial residues and metabolites in the aquatic environment by liquid chromatography tandem mass spectrometry

Antimicrobials are used in large quantities in human and veterinary medicine. Their environmental occurrence is of particular concern due to the potential spread and maintenance of bacterial resistance. After intake by the organisms, the unchanged drug and its metabolized forms are excreted and enter wastewater treatment plants where they are mostly incompletely eliminated, and are therefore eventually released into the aquatic environment. The reliable detection of several antimicrobials in different environmental aqueous compartments is the result of great improvements achieved in analytical chemistry. This article provides an overview of the more outstanding analytical methods based on liquid chromatography tandem mass spectrometry, developed and applied to determine antimicrobial residues and metabolites present in surface, waste, and ground waters.      

Determination of polychlorinated biphenyls in ambient air by gas chromatography coupled to triple quadrupole tandem mass spectrometry

A multiresidue method for determining 22 polychlorinated biphenyls (PCBs) in air has been developed and validated by gas chromatography (GC) coupled to tandem mass spectrometry (MS/MS) using a triple quadrupole analyzer (QqQ). The method was validated in terms of both steps of sampling and analysis. The sampling method, which is based on active sampling using polyurethane foam (PUF) as adsorbent, was validated by generating standard atmospheres. The retention capacity of this sampling sorbent allows up to 5 m³ of air to be sampled without any breakthrough for most compounds. Two solvent extraction methods were compared: sonication and Soxhlet extraction with a mixture of n-hexane:diethyl ether (95:5 v/v). Both extraction methods yielded similar results, but the first one required less solvent and time. The method exhibited good accuracy (80.3–99.8%), precision (2.2–15.2%) and lower limits that allowed quantification and confirmation at levels as low as 0.008 ng/m³. Finally, the method was applied to the analysis of PCBs in the air in areas near to a municipal solid-waste landfill and directly above the refuse in the landfill, where it indicatedd the presence of some of the target compounds. Figure General chemical structure of polychlorinated biphenyls     

Assessment of metastable atom bombardment (MAB) ionization mass spectrometry for the fast determination of heterocyclic aromatic amines in cooked meat

An investigation of metastable atom bombardment (MAB) ionization mass spectrometry for the fast characterization of mutagenic/carcinogenic heterocyclic aromatic amines (HAAs) formed during heating processes of meats is presented. The aim of our study was to use the selective ionization of MAB to develop a detection method for HAAs in non-purified meat extracts, thus avoiding purification and concentration steps and reducing analysis time. Sample introduction into the MAB ion source was achieved by pyrolysis, allowing the direct and fast insertion of complex food extracts into the mass spectrometer. Analysis conditions were optimized on standard HAAs by using different ionization gases for the MAB process. Metastable nitrogen was selected as the best MAB gas for the analysis of HAAs. Ionization selectivity is shown by the detection of heterocyclic amines in non-purified chicken meat extracts spiked with HAAs. A quantitative approach is also presented by using pyrograms as chromatograms for quantification purposes. HAAs determination using Py-MAB-ToF was finally performed on cooked chicken breast extracts and compared to an LC-APCI-MS/MS method. Although Py-MAB-ToF sensitivity remains to be improved in the present state of development of our prototype device, only 2 h from the cooking were required to obtain quantitative results in good agreement with HAAs concentrations measured by LC-MS/MS in 36 h. Figure Experimental set-up for pyrolysis-MAB-ToF mass spectrometry experiments.     

Laser desorption/ionization mass spectrometry analysis of monolayer-protected gold nanoparticles

Monolayer-protected gold nanoparticles (AuNPs) feature unique surface properties that enable numerous applications. Thus, there is a need for simple, rapid, and accurate methods to confirm the surface structures of these materials. Here, we describe how laser desorption/ionization mass spectrometry (LDI-MS) can be used to characterize AuNPs with neutral, positively, and negatively charged surface functional groups. LDI readily desorbs and ionizes the gold-bound ligands to produce both free thiols and disulfide ions in pure and complex samples. We also find that LDI-MS can provide a semi-quantitative measure of the ligand composition of mixed-monolayer AuNPs by monitoring mixed disulfide ions that are formed. Overall, the LDI-MS approach requires very little sample, provides an accurate measure of the surface ligands, and can be used to monitor AuNPs in complex mixtures.      

Comparison of planar SDS-PAGE,CGE-on-a-chip,and MALDI-TOF mass spectrometry for analysis of the enzymatic de-<Emphasis Type="Italic">N</Emphasis>-glycosylation of antithrombin III and coagulation factor IX with PNGase F

Three different analytical techniques (planar SDS-PAGE, CGE-on-a-chip and MALDI-TOF-MS) applied for determination of the molecular weight of intact and partly and completely de-N-glycosylated human serum glycoproteins (antithrombin III and coagulation factor IX) have been compared. N-Glycans were removed from the protein backbone of both complex glycoproteins using PNGase F, which cleaves all types of asparagine-attached N-glycan provided the oligosaccharide has at least the length of a chitobiose core unit. Two of the applied techniques were based on gel electrophoretic separation in the liquid phase while the third technique was the gas-phase technique mass spectrometry. It was demonstrated that the enzymatic de-N-glycosylation generally worked well (completely or partially) with both glycoproteins (one containing only N-glycans and the second N- and O-glycans). All three methods were suitable for monitoring the de-N-glycosylation progress. While the molecular weights determined with MALDI-TOF-MS were most accurate, both gel electrophoretic methods provided molecular weights that were too high because of the attached glycan structures. Figure CGE-on-a-chip, SDS-PAGE and MALDI mass spectrometric pattern obtained from therapeutic glycoprotein     

Aptamers as molecular recognition elements for electrical nanobiosensors

Recent advances in nanotechnology have enabled the development of nanoscale sensors that outperform conventional biosensors. This review summarizes the nanoscale biosensors that use aptamers as molecular recognition elements. The advantages of aptamers over antibodies as sensors are highlighted. These advantages are especially apparent with electrical sensors such as electrochemical sensors or those using field-effect transistors. Figure Feeling proteins with aptamer-functionalized carbon nanotubes     

Laser ablation inductively coupled plasma mass spectrometry for direct analysis of the spatial distribution of trace elements in metallurgical-grade silicon

The spatial distribution and concentration of impurities in metallurgical-grade silicon (MG-Si) samples (97–99% w/w Si) were investigated by use of laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The spatial resolution (120 μm) and low limits of detection (mg kg⁻¹) for quality assurance of such materials were studied in detail. The volume-dependent precision and accuracy of non-matrix-matched calibration for quantification of minor elements, using NIST SRM 610 (silicate standard), indicates that LA-ICP-MS is well suited to rapid process control of such materials. Quantitative results from LA-ICP-MS were compared with previously reported literature data obtained by use of ICP-OES and rf-GD-OES. In particular, the distribution of element impurities and their relationship to their different segregation coefficients in silicon is demonstrated. Dedicated to Professor Klaus G. Heumann     

Modifying argon glow discharges by hydrogen addition: effects on analytical characteristics of optical emission and mass spectrometry detection modes

An overview of the effects produced by the presence of hydrogen in a glow discharge (GD), generated either in argon or in neon, is given. Extensive work related to the addition of hydrogen to GDs, coupled with optical emission spectrometry (OES) and mass spectrometry (MS), has been published in the last few years in an attempt to explain the processes involved in the discharge of mixed gases. Although numerous experimental results have already been explained theoretically, a complete understanding of the effects brought about by mixing hydrogen with argon (or another discharge inert gas) has not been reported yet. The use of theoretical models implemented using a computer has allowed the importance of some collisional and radiative processes in the inert gas plasma when hydrogen is present to be evaluated. This review shows, however, that both experimental work and theoretical work are still needed. The influence of small quantities of hydrogen on discharge parameters, such as electrical current or dc bias voltage, on crater shapes and on sputtering rates is thoroughly reviewed along with the effect on the analytical signals measured by OES and MS. Also, hydrogen-effect corrections needed to carry out proper calibrations for direct solid quantitative analyses are discussed. Figure Hydrogen induced changes in the Ar glow discharge reactions.     

Coupled thermogravimetry, mass spectrometry, and infrared spectroscopy for quantification of surface functionality on single-walled carbon nanotubes

We have successfully applied coupled thermogravimetry, mass spectrometry, and infrared spectroscopy to the quantification of surface functional groups on single-walled carbon nanotubes. A high-purity single-walled carbon nanotube sample was subjected to a rapid functionalization reaction that attached butyric acid moieties to the nanotube sidewalls. This sample was then subjected to thermal analysis under inert desorption conditions. Resultant infrared and mass spectrometric data were easily utilized to identify the desorption of the butyric acid groups across a narrow temperature range and we were able to calculate the degree of substitution of the attached acid groups within the nanotube backbone as 1.7 carbon atoms per hundred, in very good agreement with independent analytical measurements made by inductively coupled plasma optical emission spectrometry (ICP-OES). The thermal analysis technique was also able to discern the presence of secondary functional moieties on the nanotube samples that were not accessible by ICP-OES. This work demonstrates the potential of this technique for assessing the presence of multiple and diverse functional addends on the nanotube sidewalls, beyond just the principal groups targeted by the specific functionalization reaction.      

HPLC-ICP-MS and HPLC-ES-MS/MS characterization of synthetic seleno-arsenic compounds

Various toxicological and metabolic interactions have been reported to exist between arsenic and selenium. In the present study, synthetic seleno-arsenic compounds, potentially suitable for probing metabolic interactions between these two elements, were prepared and tentatively characterized by using high-performance liquid chromatography (HPLC)–electrospray tandem mass spectrometry and HPLC–inductively coupled plasma mass spectrometry. In analogy to the recently identified thio-arsenic species, which can be prepared from their corresponding oxo-arsenic species via reaction with H₂S, the seleno-arsenic compounds were also derived from oxo-arsenic compounds via reaction with H₂Se. Figure H₂Se bubbled into solutions containing oxo‐arsenosugars converts them into their seleno‐arsenosugar analogues.     

Simultaneous quantification of cilostazol and its primary metabolite 3,4-dehydrocilostazol in human plasma by rapid liquid chromatography/tandem mass spectrometry

A simple, rapid, sensitive and selective liquid chromatography/electrospray tandem mass spectrometry method was developed and validated for the simultaneous quantification of cilostazol and its primary metabolite 3,4-dehydrocilostazol in human plasma using mosapride as an internal standard. The method involves a simple one-step liquid-liquid extraction with a diethyl ether and dichloromethane mixture (7:3). The analytes were chromatographed using an isocratic mobile phase on a reversed-phase C₁₈ column and analyzed by mass spectrometry in the multiple reaction monitoring mode using the respective [M+H]⁺ ions, m/z 370/288 for cilostazol, m/z 368/286 for 3,4-dehydrocilostazol and m/z 422/198 for the internal standard. The assay exhibited a linear dynamic range of 5–2,000 ng/mL for cilostazol and 5–400 ng/mL for 3,4-dehydrocilostazol in human plasma. The lower limit of quantitation was 5 ng/mL for both cilostazol and its metabolite. Acceptable precision and accuracy were obtained for concentrations over the standard curve ranges. A run time of 2.5 min for each sample made it possible to analyze more than 400 human plasma samples per day. The validated method has been successfully used to analyze human plasma samples for application in pharmacokinetics, bioavailability or bioequivalence studies.