Introducing the new 2D-liquid chromatograph and high-resolution mass spectrometer in the Chemical Advanced Resolution Methods (ChARM) core facility at Michigan Tech

A Thermo Scientific Orbitrap Elite Mass Spectrometer (high-resolution Orbitrap Elite MS) and a Dionex UltiMate 3000 two-dimensional liquid chromatographic (2d LC) system were recently acquired. The Orbitrap Elite MS is a hybrid instrument, which includes a dual pressure linear ion trap MS and a compact high-field Orbitrap MS. The instrument design enables high-quality, fast MSn characterization with ultrahigh resolution measurements (R = 240,000 at m/z 400) for mass measurements with less than 1 ppm mass error. Therefore, the instrument has the qualitative capability to identify molecular formulas and structure and, when paired with modern chromatography, provides quantitative assessment of analytes. Quantitative measurements of trace molecules in complex mixtures require advanced chromatography methods, which can be developed with the new high-end 2-D LC. The combination of 2-D LC and Orbitrap Elite MS allows for separation, detection and quantification of a wide range of sample analytes for studies involving metabolomics, environmental and atmospheric samples to proteomic applications.https://digitalcommons.mtu.edu/techtalks/1010/thumbnail.jp

Molecular and physical characteristics of aerosol at a remote free troposphere site: Implications for atmospheric aging

Aerosol properties are transformed by atmospheric processes during long-range transport and play a key role in the Earth\u27s radiative balance. To understand the molecular and physical characteristics of free tropospheric aerosol, we studied samples collected at the Pico Mountain Observatory in the North Atlantic. The observatory is located in the marine free troposphere at 2225m above sea level, on Pico Island in the Azores archipelago. The site is ideal for the study of long-range-transported free tropospheric aerosol with minimal local influence. Three aerosol samples with elevated organic carbon concentrations were selected for detailed analysis. FLEXPART retroplumes indicated that two of the samples were influenced by North American wildfire emissions transported in the free troposphere and one by North American outflow mainly transported within the marine boundary layer. Ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry was used to determine the detailed molecular composition of the samples. Thousands of molecular formulas were assigned to each of the individual samples. On average  ∼ 60% of the molecular formulas contained only carbon, hydrogen, and oxygen atoms (CHO),  ∼ 30% contained nitrogen (CHNO), and  ∼ 10% contained sulfur (CHOS). The molecular formula compositions of the two wildfire-influenced aerosol samples transported mainly in the free troposphere had relatively low average O∕C ratios (0.48±0.13 and 0.45±0.11) despite the 7–10 days of transport time according to FLEXPART. In contrast, the molecular composition of the North American outflow transported mainly in the boundary layer had a higher average O∕C ratio (0.57±0.17) with 3 days of transport time. To better understand the difference between free tropospheric transport and boundary layer transport, the meteorological conditions along the FLEXPART simulated transport pathways were extracted from the Global Forecast System analysis for the model grids. We used the extracted meteorological conditions and the observed molecular chemistry to predict the relative-humidity-dependent glass transition temperatures (Tg) of the aerosol components. Comparisons of the Tg to the ambient temperature indicated that a majority of the organic aerosol components transported in the free troposphere were more viscous and therefore less susceptible to oxidation than the organic aerosol components transported in the boundary layer. Although the number of observations is limited, the results suggest that biomass burning organic aerosol injected into the free troposphere is more persistent than organic aerosol in the boundary layer having broader implications for aerosol aging

Atmospheric organic matter in clouds: exact masses and molecular formula identification using ultrahigh-resolution FT-ICR mass spectrometry

Clouds alter the composition of atmospheric aerosol by acting as a medium for interactions between gas- and particulate-phase substances. To determine the cloud water atmospheric organic matter (AOM) composition and study the cloud processing of aerosols, two samples of supercooled clouds were collected at the Storm Peak Laboratory near Steamboat Springs, Colorado (3220 m a.s.l.). Approximately 3000 molecular formulas were assigned to ultrahigh-resolution mass spectra of the samples after using a reversed-phase extraction procedure to isolate the AOM components from the cloud water. Nitrogen-containing compounds (CHNO compounds), sulfur-containing compounds (CHOS and CHNOS compounds) and other oxygen-containing compounds (CHO compounds) with molecular weights up to 700 Da were observed. Average oxygen-to-carbon ratios of ∼0.6 indicate a slightly more oxidized composition than most water-soluble organic carbon identified in aerosol studies, which may result from aqueous oxidation in the clouds. The AOM composition indicates significant influences from biogenic secondary organic aerosol (SOA) and residential wood combustion. We observed 60% of the cloud water CHO molecular formulas to be identical to SOA samples of α-pinene, β-pinene, d-limonene, and β-caryophyllene ozonolysis. CHNO compounds had the highest number frequency and relative abundances and are associated with residential wood combustion and NOxoxidation. Multiple nitrogen atoms in the assigned molecular formulas for the nighttime cloud sample composite were observed, indicating the significance of nitrate radical reactions on the AOM composition. Several CHOS and CHNOS compounds with reduced sulfur (in addition to the commonly observed oxidized sulfur-containing compounds) were also observed; however further investigation is needed to determine the origin of the reduced sulfur-containing compounds. Overall, the molecular composition determined using ultrahigh-resolution Fourier-transform ion cyclotron resonance (FT-ICR) mass spectrometry provides an unambiguous identification of the cloud water organic anion composition in the Rocky Mountain area that could help to improve the understanding of aqueous-phase processes

Data representing two separate LC-MS methods for detection and quantification of water-soluble and fat-soluble vitamins in tears and blood serum

Tears serve as a viable diagnostic fluid with advantages including less invasive sample to collect and less complex to prepare for analysis. Several water-soluble and fat-soluble vitamins were detected and quantified in human tears and compared with blood serum levels. Samples from 15 family pairs, each pair consisting of a four-month-old infant and one parent were analyzed; vitamin concentrations were compared between tears and blood serum for individual subjects, between infants and parents, and against self-reported dietary intakes. Water-soluble vitamins B1, B2, B3 (nicotinamide), B5, B9 and fat-soluble vitamin E (α-tocopherol) were routinely detected in tears and blood serum while fat-soluble vitamin A (retinol) was detected only in blood serum. Water-soluble vitamin concentrations measured in tears and blood serum of single subjects were comparable, while higher concentrations were measured in infants compared to their parents. Fat-soluble vitamin E concentrations were lower in tears than blood serum with no significant difference between infants and parents. Serum vitamin A concentrations were higher in parents than infants. Population trends were compiled and quantified using a cross correlation factor. Strong positive correlations were found between tear and blood serum concentrations of vitamin E from infants and parents and vitamin B3 concentrations from parents, while slight positive correlations were detected for infants B3 and parents B1 and B2 concentrations. Correlations between infants and parents were found for the concentrations of B1, B2, B3, and E in tears, and the concentrations of B2, A, and E in blood serum. Stronger vitamin concentration correlations were found between infants and parents for the breast-fed infants, while no significant difference was observed between breast-fed and bottle-fed infants. This work is the first to demonstrate simultaneous vitamin A, B, and E detection and to quantify correlations between vitamin concentrations in tears and blood serum. Our results suggest that tears are a viable biofluid to monitor nutritional health because they sufficiently mirror blood serum data and may enhance the speed of deficiency diagnoses

Molecular insights on aging and aqueous-phase processing from ambient biomass burning emissions-influenced Po Valley fog and aerosol

To study the influence of regional biomass burning emissions and secondary processes, ambient samples of fog and aerosol were collected in the Po Valley (Italy) during the 2013 Supersito field campaign. After the extent of fresh vs. aged biomass burning influence was estimated from proton nuclear magnetic resonance (1H NMR) and high-resolution time-of-flight aerosol mass spectrometry (HR-ToF-AMS), two samples of fog water and two samples of PM1 aerosol were selected for ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) analysis. Molecular compositions indicated that the water-soluble organic matter was largely non-polymeric without clearly repeating units. The selected samples had an atypically large frequency of molecular formulas containing nitrogen and sulfur (not evident in the NMR composition) attributed to multifunctional organonitrates and organosulfates. Higher numbers of organonitrates were observed in aerosol, and higher numbers of organosulfates were observed in fog water. Consistent with the observation of an enhanced aromatic proton signature in the 1H-NMR analysis, the average molecular formula double-bond equivalents and carbon numbers were higher in the fresh biomass-burning-influenced samples. The average O:C and H:C values from FT-ICR MS were higher in the samples with an aged influence (O:C = 0.50–0.58, and H:C = 1.31–1.37) compared to those with fresh influence (O:C = 0.43–0.48, and H:C = 1.13–1.30). The aged fog had a large set of unique highly oxygenated CHO fragments in the HR-ToF-AMS, which reflects an enrichment of carboxylic acids and other compounds carrying acyl groups, highlighted by the NMR analysis. Fog compositions were more oxidized and SOA (secondary organic aerosol)-like than aerosols as indicated by their NMR measured acyl-to-alkoxyl ratios and the observed molecular formula similarity between the aged aerosol and fresh fog, implying that fog nuclei must be somewhat aged. Overall, functionalization with nitrate and sulfate moieties, in addition to aqueous oxidation, triggers an increase in the molecular complexity in this environment, which is apparent in the FT-ICR MS results. This study demonstrates the significance of the aqueous phase in transforming the molecular chemistry of atmospheric organic matter and contributing to secondary organic aerosol

Climatology and Atmospheric Chemistry of Non-Methane Hydrocarbon Emissions over the North Atlantic.

European Geosciences Union (EGU), General Assembly. Viena, Austria, 07 - 12 April 2013.Non-methane hydrocarbons (NMHC) covering the C2 to C7 volatility range have been monitored at the Pico Mountain Observatory, Pico Island, Azores, Portugal, since 2004. The Observatory is located at 2225 m a.s.l. in the caldera of the Pico Mountain volcano, and during most times receives lower free tropospheric air that has been transported across the North Atlantic. The 7-year NMHC record has been analyzed for seasonal behavior of photochemical processing, atmospheric transport time, and source region using ratios of NMHC species as indicators of photochemical aging and HYSPLIT model outputs. Transport conditions resulting in elevated and low NMHC conditions were specifically studied to investigate seasonal pollution transport in the North Atlantic region

High molecular weight SOA formation during limonene ozonolysis: insights from ultrahigh-resolution FT-ICR mass spectrometry characterization

The detailed molecular composition of laboratory generated limonene ozonolysis secondary organic aerosol (SOA) was studied using ultrahigh-resolution Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry. Approximately 1200 molecular formulas were identified in the SOA over the mass range of 140 to 850 Da. Four characteristic groups of high relative abundance species were observed; they indicate an array of accretion products that retain a large fraction of the limonene skeleton. The identified molecular formulas of each of the groups are related to one another by CH2, O and CH2O homologous series. The CH2 and O homologous series of the low molecular weight (MW) SOA (m/z \u3c 300) are explained with a combination of functionalization and fragmentation of radical intermediates and reactive uptake of gas-phase carbonyls. They include isomerization and elimination reactions of Criegee radicals, reactions between alkyl peroxy radicals, and scission of alkoxy radicals resulting from the Criegee radicals. The presence of compounds with 10–15 carbon atoms in the first group (e.g. C11H18O6) provides evidence for SOA formation by the reactive uptake of gas-phase carbonyls during limonene ozonolysis. The high MW compounds (m/z \u3e 300) were found to constitute a significant number fraction of the identified SOA components. The formation of high MW compounds was evaluated by molecular formula trends, fragmentation analysis of select high MW compounds and a comprehensive reaction matrix including the identified low MW SOA, hydroperoxides and Criegee radicals as building blocks. Although the formation of high MW SOA may occur via a variety of radical and non-radical reaction channels, the combined approach indicates a greater importance of the non-condensation reactions over aldol and ester condensation reaction channels. Among these hemi-acetal reactions appear to be most dominant followed by hydroperoxide and Criegee reaction channels

A laboratory facility to study gas-aerosol-cloud interactions in a turbulent environment: The Π Chamber

A detailed understanding of interactions of aerosols, cloud droplets/ice crystals, and trace gases within the atmosphere is of prime importance for an accurate understanding of Earth’s weather and climate. One aspect that remains especially vexing is that clouds are ubiquitously turbulent, and therefore thermodynamic and compositional variables, such as water vapor supersaturation, fluctuate in space and time. With these problems in mind, a multiphase, turbulent reaction chamber—called the Π chamber because of the internal volume of 3.14 m3 with the cylindrical insert installed—has been developed. It is capable of pressures ranging from 1,000 to –60 hPa and can sustain temperatures of –55° to 55°C, thereby spanning much of the range of tropospheric clouds. To control the relative humidity in the chamber, it can be operated with a stable, unstable, or neutral temperature difference between the top and bottom surfaces, with or without expansion. A negative temperature difference induces turbulent Rayleigh–Bénard convection and associated supersaturation generation through isobaric mixing. Supporting instrumentation includes a suite of aerosol generation and characterization techniques; temperature, pressure, and humidity sensors; and a phase Doppler interferometer. Initial characterization experiments demonstrate the ability to sustain steady-state turbulent cloud conditions for times greater than 1 day, with droplet diameters typically in the range of 5–40 µm. Typical turbulence has root-mean-square velocity fluctuations on the order of 10 cm s–1 and kinetic energy dissipation rates of 1 × 10–3 W kg–1

Measurement of Free Tropospheric Aerosols in the North Atlantic at the Pico Mountain Observatory.

AAAR 31st Annual Conference. Minneapolis, Minnesota, October 8-12, 2012.The Pico Mountain Observatory is located at 2225 m amsl on an inactive volcano at Pico Island in the Azores archipelago in the North Atlantic ~3900 km east and downwind of North America (38º28'15''N; 28º24’'14''W). The unique location of the Observatory enables sampling of free tropospheric air transported over long, intercontinental distances and is rarely affected by local emissions. The Observatory is affected mainly by North American outflow after its trans-Atlantic transport. Therefore, its location is ideal for observations of long-range transported pollutants emitted from anthropogenic and biogenic continental sources. The composition of continental pollution outflow is altered during transport by mixing, chemical reactions, phase changes, and removal processes. Thus, the properties of aerosol and trace gases in downwind regions are impacted by the outflow of pollutants, their chemical transformation, and sinks. In previous work, the sampled air-mass measurements (including CO, O3, NOx, NOy, NMHC, black carbon and aerosol optical size) and the simulations of their dispersion indicated outflow of North American tropospheric ozone and its precursors. Although the measurements have been crucial in explaining the evolution of North American gaseous pollution, little is known regarding the nature of the aged aerosol. New work is currently underway at the Observatory to provide chemical characterization of the intercepted free tropospheric aerosols. Here, we show the preliminary results of the free tropospheric aerosol composition and its physical properties. Samples were collected using high-volume filter samplers with quartz filters and analyzed for organic and elemental carbon (OC and EC, respectively). We compare the observed OC and EC values to the collocated measurements of gas- and particle-phase species, meteorological parameters and to the values found in current literature. We highlight the future work in which we will select filter samples based on the arrival of highly polluted air masses from anthropological or biomass burning emissions for further detailed analysis

The Morphology of Atmospheric Aerosol and Some Implications

The morphology of individual atmospheric particles, including their mixing state, shape and internal structure, can have important atmospheric implications. Understanding the mechanisms leading to specific morphologies, the role of morphology in different atmospheric processes, and accounting for these details in models present considerable challenges. Several approaches are currently underway to make progress toward the resolution of these difficulties; for example, development and deployment of improved single particle analytical and observational tools, use of accurate electromagnetic models to quantitatively predict the interactions of solar radiation with single complex particles, and particle resolved models. In this presentation we will present single particle analyses of samples collected during several field campaigns. Implications of these results on the effects upon aerosol optical properties will be discussed