Chlorinated paraffin analysis by gas chromatography Orbitrap high-resolution mass spectrometry: Method performance, investigation of possible interferences and analysis of fish samples.

For decades, high quantities of short-chain chlorinated paraffins (SCCP) and medium-chain chlorinated paraffins (MCCP) have been widely used, for instance as plasticizers or flame retardants, leading to global pollution due to unintentional emissions from products or waste. Due to the high complexity of chlorinated paraffins with several thousand congeners there is no consensus on an analytical procedure for SCCPs and MCCPs in food samples. Amongst the multitude of methods currently in use, high-resolution mass spectrometry is particularly valuable for in-depth studies of homologue patterns. Here we analyse SCCPs and MCCPs with gas chromatography coupled to high-resolution Orbitrap mass spectrometry (GC-Orbitrap-HRMS) operated in full-scan acquisition in electron capture negative ion (ECNI) mode at 60,000 and 120,000 resolution (FWHM, m/z 200, equals roughly 30,000 and 60,000 at 5% peak height). Linear dynamic range, selectivity and sensitivity tests confirmed an excellent linearity in a concentration range of 25-15,000 pg/µL with very low limits of detection (LODs) in the low pg/µL range. Spiking experiments with high levels of native mono- and di-ortho-polychlorinated biphenyls (PCBs) and mixtures of MCCP and SCCP standards did not have a negative impact on isotope ratios of the examined homologues. Besides the [M-Cl]- fragment ions used for quantification, the mass spectra of homologues also featured [M-HCl]- ions whose abundance increased with decreasing chlorination degree. In addition, [M-HCl-Cl]- ions were detected with a relative abundance of 5-10%. Three salmon (Salmo salar) samples farmed in Norway showed a consistent CP homologue pattern which differed both from the CP pattern in a sample from Scottish aquaculture and a wild salmon sample. These measurements produce evidence that discretely different CP patterns may exist in different areas of origin. Our results demonstrate that GC/ECNI-Orbitrap-HRMS is well-suited for the analysis of CPs by overcoming a range of mass interference problems and due to its thus far unmatched sensitivity.

A novel targeted/untargeted GC-Orbitrap metabolomics methodology applied to Candida albicans and Staphylococcus aureus biofilms.

INTRODUCTION: Combined infections from Candida albicans and Staphylococcus aureus are a leading cause of death in the developed world. Evidence suggests that Candida enhances the virulence of Staphylococcus-hyphae penetrate through tissue barriers, while S. aureus tightly associates with the hyphae to obtain entry to the host organism. Indeed, in a biofilm state, C. albicans enhances the antimicrobial resistance characteristics of S. aureus. The association of these microorganisms is also associated with significantly increased morbidity and mortality. Due to this tight association we hypothesised that metabolic effects were also in evidence. OBJECTIVES: To explore the interaction, we used a novel GC-Orbitrap-based mass spectrometer, the Q Exactive GC, which combines the high peak capacity and chromatographic resolution of gas chromatography with the sub-ppm mass accuracy of an Orbitrap system. This allows the capability to leverage the widely available electron ionisation libraries for untargeted applications, along with expanding accurate mass libraries and targeted matches based around authentic standards. METHODS: Optimised C. albicans and S. aureus mono- and co-cultured biofilms were analysed using the new instrument in addition to the fresh and spent bacterial growth media. RESULTS: The targeted analysis experiment was based around 36 sugars and sugar phosphates, 22 amino acids and five organic acids. Untargeted analysis resulted in the detection of 465 features from fresh and spent medium and 405 from biofilm samples. Three significantly changing compounds that matched to high scoring library fragment patterns were chosen for validation. CONCLUSION: Evaluation of the results demonstrates that the Q Exactive GC is suitable for metabolomics analysis using a targeted/untargeted methodology. Many of the results were as expected: e.g. rapid consumption of glucose and fructose from the medium regardless of the cell type. Modulation of sugar-phosphate levels also suggest that the pentose phosphate pathway could be enhanced in the cells from co-cultured biofilms. Untargeted metabolomics results suggested significant production of cell-wall biosynthesis components and the consumption of non-proteinaceous amino-acids.

Applicability of gas chromatography/quadrupole-Orbitrap mass spectrometry in support of pharmaceutical research and development.

RATIONALE: Gas chromatography/mass spectrometry (GC/MS) is a fundamental tool used to identify impurities throughout the active pharmaceutical ingredients development process. The coupling of Orbitrap mass spectrometry with GC marks an exciting advance in capability for GC/MS, offering a significant step change in resolving power, mass accuracy, sensitivity and linear range. METHODS: A range of pharmaceutically relevant samples representing typical starting materials has been investigated with particular reference to impurity identification. The mass accuracy in Electron Ionisation (EI) and Chemical Ionisation (CI) was investigated for impurity identification. The linearity and mass accuracy over a wide dynamic range were evaluated. The number of scans obtained across chromatographic peaks was assessed at various resolution settings from 15,000 to 120,000 (full width at half maximum (FWHM) at m/z 200). RESULTS: All the accurate mass measurements for impurities were within <1 ppm of the theoretical m/z value. The scan speed at the highest resolution produced 11 scans across the peak, and the mass accuracy for all scans was consistently <1 ppm - sufficient for impurity investigations and quantitative analysis. Linearity was demonstrated for N,N,N'-trimethylethylenediamine over a concentration range of 0.0001 to 0.1250 µg/mL (w/v) with a correlation coefficient R(2) = 0.9996 and mass accuracy across all concentrations at <1.1 ppm. CONCLUSIONS: GC/Orbitrap MS has been evaluated for both qualitative and quantitative analysis of typical pharmaceutical precursors and impurities. Accurate mass measurement across a wide dynamic range, linearity and the ability to identify impurities in EI and CI illustrate that this instrument is a powerful tool of great benefit to pharmaceutical analysis.

Characterization of iodinated disinfection by-products in chlorinated and chloraminated waters using Orbitrap based gas chromatography-mass spectrometry.

Recent developments in gas chromatography (GC)-mass spectrometry (MS) have opened up the possibility to use the high resolution-accurate mass (HRAM) Orbitrap mass analyzer to further characterize the volatile and semivolatile fractions of environmental samples. This work describes the utilization of GC Orbitrap MS technology to characterize iodine-containing disinfection by-products (iodo-DBPs) in chlorinated and chloraminated DBP mixture concentrates. These DBP mixtures were generated in lab-scale disinfection reactions using Llobregat river water and solutions containing Nordic Lake natural organic matter (NOM). The DBPs generated were concentrated using XAD resins, and extracts obtained were analyzed in full scan mode with the GC Orbitrap MS. Integration of high resolution accurate mass information and fragment rationalization allowed the characterization of up to 11 different iodo-DBPs in the water extracts analyzed, including one new iodo-DBP reported for the first time. Overall, formation of iodo-DBPs was enhanced during chloramination reactions. As expected, NOM characteristics and iodide and bromide content of the tested waters affected the amount and type of iodo-DBPs generated.

Meeting the European Commission performance criteria for the use of triple quadrupole GC-MS/MS as a confirmatory method for PCDD/Fs and dl-PCBs in food and feed samples.

Until recently, European Union (EU) legislation required the use of high-resolution gas chromatography coupled to high-resolution mass spectrometry (HRGC-HRMS) based on magnetic sector analyzers as a standard approach for confirmatory analysis of dioxins (PCDDs) and furans (PCDFs) in feed and food. However, recent technological advances in MS instruments enabled other alternative analytical techniques to meet the same analytical criteria as those requested for HRGC-HRMS. In this sense, triple quadrupoles (GC-MS/MS) can be a realistic alternative for the analysis of dioxins. In this work, the performance of GC-MS/MS technology was evaluated against the criteria demanded by the EU for confirmatory analysis of dioxins and PCBs in food and feed. Thus, the study comprises a number of parameters including chromatographic separation, limit of quantification, linearity, repeatability, and ion ratio precision. Analyses of solvent standards as well as sample extracts (inter-calibration extracts and certified reference materials) were also considered within the scope of this study. Additionally, direct comparisons of the results obtained by GC-MS/MS with those from GC-HRMS were made. The results of this work suggested that GC-MS/MS was highly sensitive and selective for confirmatory analysis of PCDD/Fs and related compounds in food and feed samples and meets all the criteria requested by the European Commission.

Isoprene synthesis protects transgenic tobacco plants from oxidative stress.

Isoprene emission represents a significant loss of carbon to those plant species that synthesize this highly volatile and reactive compound. As a tool for studying the role of isoprene in plant physiology and biochemistry, we developed transgenic tobacco plants capable of emitting isoprene in a similar manner to and at rates comparable to a naturally emitting species. Thermotolerance of photosynthesis against transient high-temperature episodes could only be observed in lines emitting high levels of isoprene; the effect was very mild and could only be identified over repetitive stress events. However, isoprene-emitting plants were highly resistant to ozone-induced oxidative damage compared with their non-emitting azygous controls. In ozone-treated plants, accumulation of toxic reactive oxygen species (ROS) was inhibited, and antioxidant levels were higher. Isoprene-emitting plants showed remarkably decreased foliar damage and higher rates of photosynthesis compared to non-emitting plants immediately following oxidative stress events. An inhibition of hydrogen peroxide accumulation in isoprene-emitting plants may stall the programmed cell death response which would otherwise lead to foliar necrosis. These results demonstrate that endogenously produced isoprene provides protection from oxidative damage.

Transient release of oxygenated volatile organic compounds during light-dark transitions in Grey poplar leaves.

In this study, we investigated the prompt release of acetaldehyde and other oxygenated volatile organic compounds (VOCs) from leaves of Grey poplar [Populus x canescens (Aiton) Smith] following light-dark transitions. Mass scans utilizing the extremely fast and sensitive proton transfer reaction-mass spectrometry technique revealed the following temporal pattern after light-dark transitions: hexenal was emitted first, followed by acetaldehyde and other C(6)-VOCs. Under anoxic conditions, acetaldehyde was the only compound released after switching off the light. This clearly indicated that hexenal and other C(6)-VOCs were released from the lipoxygenase reaction taking place during light-dark transitions under aerobic conditions. Experiments with enzyme inhibitors that artificially increased cytosolic pyruvate demonstrated that the acetaldehyde burst after light-dark transition could not be explained by the recently suggested pyruvate overflow mechanism. The simulation of light fleck situations in the canopy by exposing leaves to alternating light-dark and dark-light transitions or fast changes from high to low photosynthetic photon flux density showed that this process is of minor importance for acetaldehyde emission into the Earth's atmosphere.

Correlation of short-chained carbonyls emitted from Picea abies with physiological and environmental parameters.

• The spectrum and diurnal course of carbonyl exchange of mature Norway spruce (Picea abies) was analysed in a temperate forest and under controlled conditions. In parallel, plant physiological and meteorological parameters were determined. • Spruce emitted acetaldehyde, formaldehyde and acetone under field and laboratory conditions. • Carbonyl emissions were highest at midday, for acetaldehyde amounting up to 100 nmol m-2  min-1 . During darkness uptake was also observed. Fumigation of spruce seedlings with acetaldehyde indicated a compensation point of c. 6 ppb. The exchange rates were strongly correlated with temperature and mass flow of ethanol in the xylem sap. The studies further indicated that the height of a twig on the tree affects its carbonyl emission rates. • The present findings support the view that acetaldehyde emission by spruce is related to mass flow of ethanol in the xylem sap, as previously shown for tree seedlings under controlled conditions. The basis of formaldehyde and acetone emissions by spruce is still not clear and remains to be studied in further experiments.

Elevated atmospheric CO2 causes seasonal changes in carbonyl emissions from Quercus ilex.

• The effect of elevated atmospheric CO2 on the carbonyl emissions of leaves from two Mediterranean oak species (Quercus ilex and Q. pubescens) was analyzed under field conditions. • Physiological and meteorological parameters were determined in parallel with measurements of carbonyl emissions. Gas exchange was quantified in dynamic cuvettes combined with an infrared gas analyzer. • Acetaldehyde and acetone emissions from leaves of Q. ilex were enhanced by elevated CO2 in the autumn (from 14-40 nmol m-2  min-1 and from 2-8 nmol m-2  min-1 , respectively), but not in the summer. No significant effects were found for leaves of Q. pubescens. The effects of CO2 on Q. ilex were mainly a result of decreased emissions by control trees under ambient CO2 concentrations in the autumn; emissions from trees exposed to elevated CO2 remained at a high level. • Elevated atmospheric CO2 causes autumnal changes in carbonyl emissions from Quercus ilex. These effects suggest that the production of acetaldehyde and acetone depend on developmental factors. It is not yet clear whether the altered carbonyl emissions are a unique feature of Q. ilex.