Comparing levoglucosan and mannosan ratios in sediments and corresponding aerosols from recent Australian fires.

The monosaccharide anhydrides levoglucosan, mannosan, and galactosan are known as 'fire sugars' as they are powerful proxies used to trace fire events. Despite their increasing use, their application is not completely understood, especially in the context of tracing past fire events using sediment samples. There are many uncertainties about fire sugar formation, partitioning, transport, complexation, and stability along all stages of the source-to-sink pathway. While these uncertainties exist, the efficacy of fire sugars as fire tracers remains limited. This study compared high-resolution fire sugar fluxes in freshwater sediment cores to known fire records in Tasmania, Australia. Past fire events correlated with fire sugar flux increases down-core, with the magnitude of the flux inversely proportional to the distance of the fires from the study site. For the first time, fire sugar ratios (levoglucosan/mannosan, L/M) in aerosols were compared with those in sediments from the same time-period. The L/M ratio in surface sediments (1.42-2.58) were significantly lower than in corresponding aerosols (5.08-15.62). We propose two hypotheses that may explain the lower average L/M of sediments. Firstly, the degradation rate of levoglucosan is higher than mannosan in the water column, sediment-water interface, and/or sediment. Secondly, the L/M ratio of non-atmospheric emissions during fires may be lower than that of atmospheric emissions from the same fire. Due to the uncertainties about transport partitioning (atmospheric versus non-atmospheric emissions) and fire sugar degradation along all stages of the source-to-sink pathway, we advise caution when inferring vegetation type (e.g. softwood, hardwood, or grasses) based purely on fire sugar ratios in sediments (e.g. L/M ratio). Future investigations are required to increase the efficacy of fire sugars as a complimentary, or standalone, fire tracer in sediments.

A fast and simple extraction method for analysing levoglucosan and its isomers in sediments by ion chromatography tandem mass spectrometry.

The ability to trace current and past biomass burning events is important for understanding the links between human activity, fire frequency, and climate. One method of tracing biomass burning is to measure the concentrations of certain monosaccharides anhydrides (MAs), specifically levoglucosan (LEV) and its isomers, mannosan (MAN) and galactosan (GAL), which are products of cellulose and hemicellulose pyrolysis. This work presents a simple extraction method allowing for the rapid, sensitive, and selective determination of MAs in sediments. MAs detection was performed using suppressed ion chromatography with electrospray - triple-stage quadrupole tandem mass spectrometry (IC-TSQ-MS). The extraction method involves ultrasound probe sonication using water as the solvent. Extraction time, amplitude, and sonication mode were optimised. Recoveries higher than 86% for all MAs tested were achieved by applying 70% amplitude in continuous mode for 60 s. Analytical performance of the method included instrumental LODs of 0.10, 0.12 and 0.50 µg L-1 for LEV, MAN and GAL, respectively. No carryover issues, no matrix effect and no co-elution of targeted MAs with other sugars likely present in sediments samples were observed. The developed extraction method was further validated by the analysis of LEV and MAN in NIST® 1649b urban dust reference material and the resulting concentrations were in excellent agreement with previously reported values. MAs quantification in 70 lake sediment samples were carried out with concentrations found to range from 0.009 to 0.390 µg g-1 for LEV and from 0.009 to 0.194 µg g-1 for MAN. Plotting MAs concentrations versus approximate sediment age allowed the reconstruction of recent fire events impacting two locations in the Central Highlands of Tasmania, Australia.

Nanomaterial-assisted thread-based isotachophoresis with on-thread solute trapping.

This research describes a nanomaterial-assisted thread-based isotachophoresis (TB-ITP) setup for the clean-up, preconcentration, and trapping of alkaloids (coptisine, berberine, and palmatine) in biological fluids, followed by their on-thread desorption electrospray ionization mass spectrometry (DESI-MS) determination. The reusable TB-ITP setup and a DESI compatible thread holder were 3D printed. A single nylon thread was employed as the ITP substrate for solute isolation and enrichment, and a short piece of graphene oxide (GO) functionalized nylon thread was tied around the main 'separation' thread as the 'trap' for the trapping of ITP focused alkaloids. Compared to the direct DESI-MS sample analysis, the sensitivity of the proposed method for the model solutes was increased up to 10-fold, benefiting from the TB-ITP focusing and enrichment strategy. This proof-of-concept use of nanomaterial-modified threads in electrofluidic separation and concentration procedures opens up a promising avenue to explore, particularly with regard to the sensitivity and selectivity of thread-based electrofluidic separation coupled with ambient ionization MS.

Chemometric optimisation of enzymatic hydrolysis of beechwood xylan to target desired xylooligosaccharides.

Generation of specific xylooligosaccharides (XOS) is attractive to the pharmaceutical and food industries due to the importance of their structure upon their application. This study used chemometrics to develop a comprehensive computational modelling set to predict the parameters maximising the generation of the desired XOS during enzymatic hydrolysis. The evaluated parameters included pH, temperature, substrate concentration, enzyme dosage and reaction time. A Box-Behnken design was combined with response surface methodology to develop the models. High-performance anion-exchange chromatography coupled with triple-quadrupole mass spectrometry (HPAEC-QqQ-MS) allowed the identification of 22 XOS within beechwood xylan hydrolysates. These data were used to validate the developed models and demonstrated their accuracy in predicting the parameters maximising the generation of the desired XOS. The maximum yields for X2-X6 were 314.2 ± 1.2, 76.6 ± 4.5, 38.4 ± 0.4, 17.8 ± 0.7, and 5.3 ± 0.2 mg/g xylan, respectively. These values map closely to the model predicted values 311.7, 92.6, 43.0, 16.3, and 4.9 mg/g xylan, respectively.

Determination of xylooligosaccharides produced from enzymatic hydrolysis of beechwood xylan using high-performance anion-exchange chromatography tandem mass spectrometry.

High-performance anion-exchange chromatography (HPAEC) coupled with triple quadrupole mass spectrometry (HPAEC-QqQ-MS) was applied to the determination of xylooligosaccharides (XOS) derived from enzymatically hydrolysed commercial xylan from beechwood and the analytical performance and advantages of the method explored. Separation, eluent suppression, electrospray ionisation, and detection options to enhance XOS sensitivity and selectivity were evaluated, delivering a new simple, fast, selective, and sensitive solution for the characterisation of these complex compounds. The method was fully validated in terms of its analytical performance for those XOS for which standards were available, i.e., degree of polymerisation from 1 to 6. The new method was applied to the analysis of xylan hydrolysates obtained by different enzymatic hydrolysis treatments using endo-xylanase from Thermomyces lanuginosus, characterising 25 different XOS and demonstrating the method's utility for future tailoring of enzymatic hydrolysis conditions to obtain desired XOS profiles in such hydrolysates. Linear XOS and 4-O-methyl glucuronic acid (MeGluA) branched XOS were detected by direct injection of the xylan hydrolysates after a simple 10-fold sample dilution and filtration. Identification of XOS detected by HPAEC-QqQ-MS was additionally confirmed using high-resolution orbitrap mass spectrometry (HR-orbitrap-MS). Further, an ultra-sensitive and -selective method was developed by using selected reaction monitoring acquisition mode (SRM), increasing signal-to noise ratio and decreasing the limits of detection, opening future applications to low concentrated sample analysis.

Widespread phytoplankton blooms triggered by 2019-2020 Australian wildfires.

Droughts and climate-change-driven warming are leading to more frequent and intense wildfires1-3, arguably contributing to the severe 2019-2020 Australian wildfires4. The environmental and ecological impacts of the fires include loss of habitats and the emission of substantial amounts of atmospheric aerosols5-7. Aerosol emissions from wildfires can lead to the atmospheric transport of macronutrients and bio-essential trace metals such as nitrogen and iron, respectively8-10. It has been suggested that the oceanic deposition of wildfire aerosols can relieve nutrient limitations and, consequently, enhance marine productivity11,12, but direct observations are lacking. Here we use satellite and autonomous biogeochemical Argo float data to evaluate the effect of 2019-2020 Australian wildfire aerosol deposition on phytoplankton productivity. We find anomalously widespread phytoplankton blooms from December 2019 to March 2020 in the Southern Ocean downwind of Australia. Aerosol samples originating from the Australian wildfires contained a high iron content and atmospheric trajectories show that these aerosols were likely to be transported to the bloom regions, suggesting that the blooms resulted from the fertilization of the iron-limited waters of the Southern Ocean. Climate models project more frequent and severe wildfires in many regions1-3. A greater appreciation of the links between wildfires, pyrogenic aerosols13, nutrient cycling and marine photosynthesis could improve our understanding of the contemporary and glacial-interglacial cycling of atmospheric CO2 and the global climate system.

Corrigendum to "Ultra-trace determination of oxyhalides in ozonated aquacultural marine waters by direct injection ion chromatography coupled with triple-quadrupole mass spectrometry" [Heliyon 7 (4) (April 2021) e06885].

[This corrects the article DOI: 10.1016/j.heliyon.2021.e06885.].

Ultra-trace determination of oxyhalides in ozonated aquacultural marine waters by direct injection ion chromatography coupled with triple-quadrupole mass spectrometry.

A direct, robust, accurate and highly sensitive method for oxyhalide species in natural waters, including seawater, using suppressed ion chromatography coupled with mass spectrometry (IC-MS) is described. The method utilised a high capacity, high efficiency anion-exchange column (Dionex IonPac AS11-HC, 4 mm, 2 × 250 mm), with the separation achieved using an electrolytically generated potassium hydroxide gradient, delivered at 0.380 mL min-1. Applying the method, detection limits for iodate, bromate, and chlorate in seawater after direct sample injection (20 µL injection volume, samples diluted 10-fold), were 11, 30 and 13 ng L-1 (ppt), respectively. Standard addition calibrations to ozonated seawater samples were linear, in all cases R2 > 0.999 (n = 10), with intra-day repeatability of 3.7, 11.2 and 1.8 % RSD (n = 10) for a low-level standard mixture (0.30 µg L-1 of iodate, 0.15 µg L-1 of bromate, and 1.50 µg L-1 of chlorate). The method was applied to the analysis of seawater samples taken pre- and post-disinfection points within a recirculating aquacultural system. Iodate, bromate and chlorate were detected as the main oxyanionic disinfection by-products, demonstrating the practical utility of the new method as a valuable tool for monitoring changes to seawater composition following disinfection treatments.

Thread-based isoelectric focusing coupled with desorption electrospray ionization mass spectrometry.

The combination of a thread-based electrofluidic analytical device and desorption electrospray ionization mass-spectrometry (DESI-MS) was investigated for the separation and concentration of proteins. The combination delivered a low-cost novel approach for sample pretreatment and target focusing, with direct "on-thread" ambient mass spectrometry detection. For this purpose, a platform for thread-based isoelectric focusing (TB-IEF) was 3D-printed, optimised, and applied to the separation and focusing of three model proteins. Successful separation and focusing was achieved within 30 min. The TB-IEF device was coupled with DESI-MS by direct exposure of the focused solutes on the dried thread to the DESI source. As a proof-of-concept, a 10-fold increase in the DESI-MS response for insulin was achieved following the TB-IEF preconcentration, whilst simultaneously isolating the target solutes from their sample matrix.

Analysis of levoglucosan and its isomers in atmospheric samples by ion chromatography with electrospray lithium cationisation - Triple quadrupole tandem mass spectrometry.

Biomass burning (BB) emissions are a significant source of particles to the atmosphere, especially in the Southern Hemisphere, where the occurrence of anthropogenic and natural wild fires is common. These emissions can threaten human health through increased exposure, whilst simultaneously representing a significant source of trace metals and nutrients to the ocean. One well known method to track BB emissions is through monitoring the atmospheric concentration of specific monosaccharide anhydrides (MAs), specifically levoglucosan and its isomers, mannosan and galactosan. Herein, a new method for the determination of levoglucosan and its isomers in marine and terrestrial aerosol samples is presented, which delivers both high selectivity and sensitivity, through the coupling of ion chromatography and triple quadrupole tandem mass spectrometry. Optimal chromatographic conditions, providing baseline separation for target anhydrosugars in under 8 min, were obtained using a Dionex CarboPacⓇ PA-1 column with an electrolytically generated KOH gradient. To improve the ionisation efficiency for MS detection, an organic make-up solvent was fed into the IC column effluent before the ESI source, and to further increase both sensitivity and selectivity, cationisation of levoglucosan was investigated by adding salts into the make-up solvent, namely, sodium, ammonium and lithium salts. Using positive lithium cationisation with 0.5 mM lithium chloride in methanol as the make-up solvent, delivered at a flow rate of 0.02 mL min-1, the levoglucosan response was improved by factors of 100 and 10, comparing to negative ionisation and positive sodium cationisation, respectively. Detection was carried out in SRM mode for quantitation and identification, achieving an instrumental LOD of 0.10, 0.12 and 0.5 µg L-1 for levoglucosan, mannosan and galactosan, respectively. Finally, the method was applied to the analysis of 41 marine and terrestrial aerosol samples from Australia, its surrounding coastal waters and areas within the remote Southern Ocean, covering a large range of BB marker concentrations.

Recent advances in open tubular capillary liquid chromatography.

This review covers advances and applications of open tubular capillary liquid chromatography (OT-LC) over the period 2007-2018. Under the right conditions OT-LC columns have the potential to offer superior column efficiency, higher overall peak capacity, and higher column permeability compared to packed capillary and monolithic columns. However, such advantages are highly dependent upon column format and dimensions, and to date in liquid chromatography the advantages of open tubular format columns have been most widely discussed and applied in the field of proteomics. In this review we have focused on the wider variety of separation mechanisms and applications which can be achieved following the modification of the inner wall of the capillary with a thin-layer stationary phase. In particular the latest advances in stationary phase development and formation, together with new column formats and dimensions are reviewed. Detection options for OT-LC are also discussed and recent advances in this area highlighted. Finally, this review summarises existing applications of OT-LC and illustrates the future potential for this technique.

Sub-1 mL sample requirement for simultaneous determination of 17 organic and inorganic anions and cations in Antarctic ice core samples by dual capillary ion chromatography.

The significant advance of delivering high value multi-species data from sub-1 mL ice core sample volumes allows higher temporal resolution in deposition records of inorganic and low molecular weight organic anions and cations. The determination of these species is a fundamental strategic requirement in modern paleoclimate studies. Herein, for the first time, a dual capillary ion chromatography (Cap-IC) based method for the simultaneous separation of 17 organic and inorganic anions and cations in low volume Antarctic ice core samples is presented. The total amount of sample required for direct injection has been reduced to 190 µL, which is 35 times lower than the amount of sample required by standard ion chromatography methods. A dual Cap-IC system configured for the simultaneous determination of cations and anions was used throughout. A range of chromatographic parameters was optimised for both anion and cation systems to obtain baseline separations of all target analytes in a suitable run time and to minimise the amount of sample required. Baseline separation of matrix and trace 'marker' ions were achieved in less than 35 min, after injecting only 40 µL of sample in each IC system. Limits of detection (LODs) for all analytes determined were within a range similar to that achieved by previously published standard bore IC-based methods. Intra- and inter-day repeatability were evaluated, with both parameters being typically below 3% for peak area. In further validation of the method, a comparative analysis of a set of 420 ice core samples from Aurora Basin North site, Antarctica, previously analysed by standard IC, established that the proposed low sample volume technique was applicable as a routine measurement approach in ice core analysis projects.

Wall modified photonic crystal fibre capillaries as porous layer open tubular columns for in-capillary micro-extraction and capillary chromatography.

Wall modified photonic crystal fibre capillary columns for in-capillary micro-extraction and liquid chromatographic separations is presented. Columns contained 126 internal parallel 4 µm channels, each containing a wall bonded porous monolithic type polystyrene-divinylbenzene layer in open tubular column format (PLOT). Modification longitudinal homogeneity was monitored using scanning contactless conductivity detection and scanning electron microscopy. The multichannel open tubular capillary column showed channel diameter and polymer layer consistency of 4.2 ± 0.1 µm and 0.26 ± 0.02 µm respectively, and modification of 100% of the parallel channels with the monolithic polymer. The modified multi-channel capillaries were applied to the in-capillary micro-extraction of water samples. 500 µL of water samples containing single µg L(-1) levels of polyaromatic hydrocarbons were extracted at a flow rate of 10 µL min(-1), and eluted in 50 µL of acetonitrile for analysis using HPLC with fluorescence detection. HPLC LODs were 0.08, 0.02 and 0.05 µg L(-1) for acenaphthene, anthracene and pyrene, respectively, with extraction recoveries of between 77 and 103%. The modified capillaries were also investigated briefly for direct application to liquid chromatographic separations, with the retention and elution of a standard protein (cytochrome c) under isocratic conditions demonstrated, proving chromatographic potential of the new column format, with run-to-run retention time reproducibility of below 1%.