scholarly journals N<sub>2</sub>O isotopocule measurements using laser spectroscopy: analyzer characterization and intercomparison

2020 ◽  
Vol 13 (5) ◽  
pp. 2797-2831 ◽  
Author(s):  
Stephen J. Harris ◽  
Jesper Liisberg ◽  
Longlong Xia ◽  
Jing Wei ◽  
Kerstin Zeyer ◽  
...  
Keyword(s):  
Mole Fraction ◽  
Matrix Effects ◽  
Matrix Composition ◽  
Trace Gas ◽  
N2o Production ◽  
Spectral Interferences ◽  
Isotopic Species ◽  
Accuracy And Repeatability ◽  
Detection Schemes ◽  
Specific Correction

Abstract. For the past two decades, the measurement of nitrous oxide (N2O) isotopocules – isotopically substituted molecules 14N15N16O, 15N14N16O and 14N14N18O of the main isotopic species 14N14N16O – has been a promising technique for understanding N2O production and consumption pathways. The coupling of non-cryogenic and tuneable light sources with different detection schemes, such as direct absorption quantum cascade laser absorption spectroscopy (QCLAS), cavity ring-down spectroscopy (CRDS) and off-axis integrated cavity output spectroscopy (OA-ICOS), has enabled the production of commercially available and field-deployable N2O isotopic analyzers. In contrast to traditional isotope-ratio mass spectrometry (IRMS), these instruments are inherently selective for position-specific 15N substitution and provide real-time data, with minimal or no sample pretreatment, which is highly attractive for process studies. Here, we compared the performance of N2O isotope laser spectrometers with the three most common detection schemes: OA-ICOS (N2OIA-30e-EP, ABB – Los Gatos Research Inc.), CRDS (G5131-i, Picarro Inc.) and QCLAS (dual QCLAS and preconcentration, trace gas extractor (TREX)-mini QCLAS, Aerodyne Research Inc.). For each instrument, the precision, drift and repeatability of N2O mole fraction [N2O] and isotope data were tested. The analyzers were then characterized for their dependence on [N2O], gas matrix composition (O2, Ar) and spectral interferences caused by H2O, CO2, CH4 and CO to develop analyzer-specific correction functions. Subsequently, a simulated two-end-member mixing experiment was used to compare the accuracy and repeatability of corrected and calibrated isotope measurements that could be acquired using the different laser spectrometers. Our results show that N2O isotope laser spectrometer performance is governed by an interplay between instrumental precision, drift, matrix effects and spectral interferences. To retrieve compatible and accurate results, it is necessary to include appropriate reference materials following the identical treatment (IT) principle during every measurement. Remaining differences between sample and reference gas compositions have to be corrected by applying analyzer-specific correction algorithms. These matrix and trace gas correction equations vary considerably according to N2O mole fraction, complicating the procedure further. Thus, researchers should strive to minimize differences in composition between sample and reference gases. In closing, we provide a calibration workflow to guide researchers in the operation of N2O isotope laser spectrometers in order to acquire accurate N2O isotope analyses. We anticipate that this workflow will assist in applications where matrix and trace gas compositions vary considerably (e.g., laboratory incubations, N2O liberated from wastewater or groundwater), as well as extend to future analyzer models and instruments focusing on isotopic species of other molecules.

scholarly journals N<sub>2</sub>O isotopocule measurements using laser spectroscopy: analyzer characterization and intercomparison

2019 ◽  
Author(s):  
Stephen J. Harris ◽  
Jesper Liisberg ◽  
Longlong Xia ◽  
Jing Wei ◽  
Kerstin Zeyer ◽  
...  
Keyword(s):  
Mole Fraction ◽  
Matrix Effects ◽  
Matrix Composition ◽  
Trace Gas ◽  
N2o Production ◽  
Spectral Interferences ◽  
Isotopic Species ◽  
Accuracy And Repeatability ◽  
Detection Schemes ◽  
Specific Correction

Abstract. For the past two decades, the measurement of N2O isotopocules – isotopically substituted molecules 14N15N16O, 15N14N16O and 14N14N18O of the main isotopic species 14N14N16O – has been a promising technique for understanding N2O production and consumption pathways. The coupling of non-cryogenic and tuneable light sources with different detection schemes, such as direct absorption quantum cascade laser absorption spectroscopy (QCLAS), cavity ring-down spectroscopy (CRDS) and off-axis integrated cavity output spectroscopy (OA-ICOS), has enabled the production of commercially-available and field-deployable N2O isotopic analyzers. In contrast to traditional isotope-ratio mass-spectrometry (IRMS), these instruments are inherently selective for position-specific 15N substitution and provide real-time data, with minimal or no sample pretreatment, which is highly attractive for process studies. Here, we compared the performance of N2O isotope laser spectrometers with the three most common detection schemes: OA-ICOS (N2OIA-30e-EP, ABB-Los Gatos Research Inc.), CRDS (G5131-i, Picarro Inc.) and QCLAS (dual QCLAS and preconcentration (TREX)–mini QCLAS, Aerodyne Research Inc.). For each instrument, the precision, drift and repeatability of N2O mole fraction [N2O] and isotope data were tested. The analyzers were then characterized for their dependence on [N2O], gas matrix composition (O2, Ar) and spectral interferences caused by H2O, CO2, CH4 and CO to develop analyzer-specific correction functions. Subsequently, a simulated two end-member mixing experiment was used to compare the accuracy and repeatability of corrected and calibrated isotope measurements that could be acquired using the different laser spectrometers. Our results show that N2O isotope laser spectrometer performance is governed by an interplay between instrumental precision, drift, matrix effects and spectral interferences. To retrieve compatible and accurate results, it is necessary to include appropriate reference materials following the identical treatment (IT) principle during every measurement. Remaining differences between sample and reference gas compositions have to be corrected by applying analyzer-specific correction algorithms. These matrix and trace gas correction equations vary considerably according to N2O mole fraction, complicating the procedure further. Thus, researchers should strive to minimize differences in composition between sample and reference gases. In closing, we provide a calibration workflow to guide researchers in the operation of N2O isotope laser spectrometers in order to acquire accurate N2O isotope analyses. We anticipate that this workflow will assist in applications where matrix and trace gas compositions vary considerably (e.g. laboratory incubations, N2O liberated from wastewater or groundwater), as well as extending to future analyzer models and instruments focusing on isotopic species of other molecules.

A practical approach to non-spectral interferences elimination in inductively coupled plasma optical emission spectrometry

2016 ◽  
Vol 70 (6) ◽  
Author(s):  
Anna Krejčová ◽  
Tomáš Černohorský ◽  
Lenka Bendakovská
Keyword(s):  
Inductively Coupled Plasma ◽  
Matrix Effects ◽  
Optical Emission ◽  
Optical Emission Spectrometry ◽  
Emission Spectrometry ◽  
Spectral Interferences ◽  
Inductively Coupled ◽  
The Matrix ◽  
Plasma Optical Emission Spectrometry ◽  
Matrix Concentration

AbstractMatrix effects and practical possibilities of reducing accompanying non-spectral interferences in inductively coupled plasma optical emission spectrometry (ICP-OES) were studied for microconcentric Micromist, concentric and V-groove nebulizers (VGN) coupled with two cyclonic spray chambers of different sizes. The effect of a wide scale of interferents and mixtures thereof in the concentration range of up to 2 mass % (Na, Ca, Ba, La, urea) or up to 20 vol. % (nitric acid) on the analysis of Cd, Cu, K, Mg, Mn, Pb and Zn was investigated in terms of their analytical recovery and Mg(II) 280.27 nm/Mg(I) 285.29 nm line intensity ratio. Recoveries of ionic lines were lower than those of atomic lines (37–102 %) depending on the matrix concentration. The Mg(II)/Mg(I) ratios were found to be 12–15 and they slightly decreased as the matrix load increased. Exceptional behavior of pure La matrix, steeply lowering the recoveries and Mg(II)/Mg(I) ratios was observed. A Micromist nebulizer coupled with a small inner volume spray chamber provided the highest recoveries (94–102 %), lowest matrix effects across the matrix loads and, compared to others, the least significant dependence without worsening of the analytical characteristics (recoveries, signal background ratios and the Mg(II)/Mg(I) ratios) across the studied matrices.

Study of matrix effects and spectral interferences in the determination of lead in sediments, sludges and soils by SR-ETAAS using slurry sampling

Talanta ◽  
2010 ◽  
Vol 82 (2) ◽  
pp. 523-527 ◽  
Author(s):  
Marianela Savio ◽  
Soledad Cerutti ◽  
Luis D. Martinez ◽  
Patricia Smichowski ◽  
Raúl A. Gil
Keyword(s):  
Matrix Effects ◽  
Slurry Sampling ◽  
Spectral Interferences

scholarly journals Decadal variability of soil CO<sub>2</sub>, NO, N<sub>2</sub>O, and CH<sub>4</sub> fluxes at the Höglwald Forest, Germany

2012 ◽  
Vol 9 (5) ◽  
pp. 1741-1763 ◽  
Author(s):  
G. J. Luo ◽  
N. Brüggemann ◽  
B. Wolf ◽  
R. Gasche ◽  
R. Grote ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Soil Temperature ◽  
Trace Gases ◽  
Trace Gas ◽  
High Temporal Resolution ◽  
N2o Production ◽  
Field Station ◽  
Freeze Thaw ◽  
Gas Fluxes ◽  
Trace Gas Fluxes

Abstract. Besides agricultural soils, temperate forest soils have been identified as significant sources of or sinks for important atmospheric trace gases (N2O, NO, CH4, and CO2). Although the number of studies for this ecosystem type increased more than tenfold during the last decade, studies covering an entire year and spanning more than 1–2 years remained scarce. This study reports the results of continuous measurements of soil-atmosphere C- and N-gas exchange with high temporal resolution carried out since 1994 at the Höglwald Forest spruce site, an experimental field station in Southern Germany. Annual soil N2O, NO and CO2 emissions and CH4 uptake (1994–2010) varied in a range of 0.2–3.0 kg N2O-N ha−1yr−1, 6.4–11.4 kg NO-N ha−1yr−1, 7.0–9.2 t CO2-C ha−1yr−1, and 0.9–3.5 kg CH4-C ha−1yr−1, respectively. The observed high fluxes of N-trace gases are most likely a consequence of high rates of atmospheric nitrogen deposition (>20 kg N ha−1yr−1) of NH3 and NOx to our site. For N2O, cumulative annual emissions were ≥ 0.8 kg N2O-N ha−1yr−1 in years with freeze-thaw events (5 out 14 of years). This shows that long-term, multi-year measurements are needed to obtain reliable estimates of N2O fluxes for a given ecosystem. Cumulative values of soil respiratory CO2 fluxes tended to be highest in years with prolonged freezing periods, i.e. years with below average annual mean soil temperatures and high N2O emissions (e.g. the years 1996 and 2006). Furthermore, based on our unique database on trace gas fluxes we analyzed if soil temperature, soil moisture measurements can be used to approximate trace gas fluxes at daily, weekly, monthly, or annual scale. Our analysis shows that simple-to-measure environmental drivers such as soil temperature or soil moisture are suitable to approximate fluxes of NO and CO2 at weekly and monthly resolution reasonably well (accounting for up to 59 % of the variance). However, for CH4 we so far failed to find meaningful correlations, and also for N2O the predictive power is rather low. This is most likely due to the complexity of involved processes and counteracting effects of soil moisture and temperature, specifically with regard to N2O production and consumption by denitrification and microbial community dynamics. At monthly scale, including information on gross primary production (CO2, NO), and N deposition (N2O), increased significantly the explanatory power of the obtained empirical regressions (CO2: r2 =0.8; NO: r2 = 0.67; N2O, all data: r2 = 0.5; N2O, with exclusion of freeze-thaw periods: r2 = 0.65).

Application of Stable Isotope Dilution and Liquid Chromatography Tandem Mass Spectrometry for Multi-Mycotoxin Analysis in Edible Oils

2019 ◽  
Vol 102 (6) ◽  
pp. 1651-1656
Author(s):  
Kai Zhang ◽  
David Xu
Keyword(s):  
Stable Isotope ◽  
Isotope Dilution ◽  
Corn Oil ◽  
Edible Oils ◽  
Matrix Effects ◽  
Safety Issue ◽  
Response Factors ◽  
Calibration Standards ◽  
Stable Isotope Dilution ◽  
Accuracy And Repeatability

Background: Mycotoxin contamination in oils remains an important food safety issue. To monitor the occurrence of mycotoxins in edible oils, it is important to develop analytical methods that can determine multiple mycotoxins in oil products. A stable isotope dilution LC-tandem MS (LC-MS/MS) method for the simultaneous determination of 12 mycotoxins in five edible oil matrixes (canola, corn, olive, peanut, and soybean oil) was developed and validated. Methods: Prior to extraction, the oil samples were fortified with ¹³C uniformly labeled internal standards (¹³C-IS) for 12 target mycotoxins, followed by extraction and LC-MS/MS analysis. Quantitation was achieved using solvent-only calibration standards, relative response factors of ¹³C-IS, and target mycotoxins. Results: The majority of recoveries in oil for ochratoxin A and aflatoxins B1, B2, G1, and G2 fortified at 1, 10, and 100 ng/g as well as deoxynivalenol; fumonisins B1, B2, and B3; T-2 toxin; HT-2 toxin; and zearalenone fortified at 10, 100, and 1000 ng/g ranged from 80 to 120% with RSDs of <20%. The method LOQs ranged from 0.1 ng/g (aflatoxin B1) to 6.4 ng/g (zearalenone). Among 16 U.S. market samples, zearalenone was detected in three corn oil samples at 37, 185, and 317 ng/g, respectively. T-2 toxin was found in two corn oil samples at 7 and 10 ng/g, respectively. Conclusions: The method provides sufficient selectivity, sensitivity, accuracy, and repeatability to screen edible oils for regulated mycotoxins such as aflatoxins at low nanogram per gram concentrations without using conventional standard addition or matrix-matched calibration standards to correct for matrix effects.

scholarly journals Quantifying the Impact of the COVID-19 Pandemic Restrictions on CO, CO2, and CH4 in Downtown Toronto Using Open-Path Fourier Transform Spectroscopy

Atmosphere ◽  
2021 ◽  
Vol 12 (7) ◽  
pp. 848
Author(s):  
Yuan You ◽  
Brendan Byrne ◽  
Orfeo Colebatch ◽  
Richard L. Mittermeier ◽  
Felix Vogel ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Mole Fraction ◽  
Urban Areas ◽  
Trace Gas ◽  
Reference Period ◽  
Mean Values ◽  
Percentage Decrease ◽  
Open Path ◽  
The Impact ◽  
At Home

During the global COVID-19 pandemic, anthropogenic emissions of air pollutants and greenhouse gases (GHGs), especially traffic emissions in urban areas, have declined. Long-term measurements of trace gas concentrations in urban areas can be used to quantify the impact of emission reductions on GHG mole fractions. Open-path Fourier transform infrared (OP-FTIR) spectroscopy is a non-intrusive technique that can be used to simultaneously measure multiple atmospheric trace gases in the boundary layer. This study investigates the reduction of mole fractions and mole fraction enhancements above background for surface CO, CO2, and CH4 in downtown Toronto, Canada (the fourth largest city in North America) during the 2020 and 2021 COVID-19 stay-at-home periods. Mean values obtained from these periods were compared with mean values from a reference period prior to the 2020 restrictions. Mean CO mole fraction enhancement declined by 51 ± 23% and 42 ± 24% during the 2020 and 2021 stay-at-home periods, respectively. The mean afternoon CO2 mole fraction enhancement declined by 3.9 ± 2.6 ppm (36 ± 24%) and 3.5 ± 2.8 ppm (33 ± 26%) during the stay-at-home periods in 2020 and 2021. In contrast, CH4 mole fraction enhancement did not show any significant decrease. Diurnal variation in CO during the stay-at-home period in 2020 was also significantly reduced relative to the reference period in 2020. These reductions in trace gas mole fraction enhancements coincide with the decline of local traffic during the stay-at-home periods, with an estimated reduction in CO and CO2 enhancements of 0.74 ± 0.15 ppb and 0.18 ± 0.05 ppm per percentage decrease in traffic, respectively.

scholarly journals Activity of Moxifloxacin Against Biofilms Formed by Clinical Isolates of Staphylococcus aureus Differing by Their Resistant or Persister Character to Fluoroquinolones

2021 ◽  
Vol 12 ◽  
Author(s):  
Tiep K. Nguyen ◽  
Frédéric Peyrusson ◽  
Wafi Siala ◽  
Nhung H. Pham ◽  
Hoang A. Nguyen ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Matrix Effects ◽  
Extracellular Dna ◽  
Clinical Isolates ◽  
Matrix Composition ◽  
Local Concentration ◽  
Response Curves ◽  
Stationary Phase Culture ◽  
Microtiter Plates ◽  
The Difference

Staphylococcus aureus biofilms are poorly responsive to antibiotics. Underlying reasons include a matrix effect preventing drug access to embedded bacteria, or the presence of dormant bacteria with reduced growth rate. Using 18 clinical isolates previously characterized for their moxifloxacin-resistant and moxifloxacin-persister character in stationary-phase culture, we studied their biofilm production and matrix composition and the anti-biofilm activity of moxifloxacin. Biofilms were grown in microtiter plates and their abundance quantified by crystal violet staining and colony counting; their content in polysaccharides, extracellular DNA and proteins was measured. Moxifloxacin activity was assessed after 24 h of incubation with a broad range of concentrations to establish full concentration-response curves. All clinical isolates produced more biofilm biomass than the reference strain ATCC 25923, the difference being more important for those with high relative persister fractions to moxifloxacin, most of which being also resistant. High biofilm producers expressed icaA to higher levels, enriching the matrix in polysaccharides. Moxifloxacin was less potent against biofilms from clinical isolates than from ATCC 25923, especially against moxifloxacin-resistant isolates with high persister fractions, which was ascribed to a lower concentration of moxifloxacin in these biofilms. Time-kill curves in biofilms revealed the presence of a moxifloxacin-tolerant subpopulation, with low multiplication capacity, whatever the persister character of the isolate. Thus, moxifloxacin activity depends on its local concentration in biofilm, which is reduced in most isolates with high-relative persister fractions due to matrix effects, and insufficient to kill resistant isolates due to their high MIC.

X-Ray Fluorescence Determination of Trace Elements in Complicated Matrices

1986 ◽  
Vol 30 ◽  
pp. 309-314 ◽  
Author(s):  
Liu Yawen ◽  
Fan Qinmin ◽  
Li Daolun
Keyword(s):  
Trace Elements ◽  
Matrix Effects ◽  
Light Element ◽  
Direct Determination ◽  
Matrix Composition ◽  
Single Element ◽  
X Rays ◽  
Fluorescence Determination ◽  
Relative Errors

AbstractA method for the direct determination of trace elements in light element matrices is described. The intensity of Compton scatter of the incident X-rays from the specimen was used to evaluate the apparent absorption factor for the direct correction for matrix effects. This permits the use of single element standards for samples of varied and complicated matrix composition. Relative errors of approximately 5% were obtained for results in the concentration range of 10-200 ppm.

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