Ozone Interference Research Articles

Ozone as Redox Bioregulator in Preventive Medicine: The Molecular and Pharmacological Basis of the Low-Dose Ozone Concept-A Review.

The best form of prevention against human infection through bacteria, viruses, and other parasites is ozone disinfection of wastewater and drinking water as a highly effective, well-known method. Various preclinical studies showed promising results, which are being revisited and reconsidered in times of pandemics and led to interesting results in recent clinical trials and reports, as presented by the example of protective measures against COVID-19 in particularly vulnerable clinical personnel. The application of ozone in the form of the low-dose concept induces its regulation by interference of ozone or its peroxides into the redox equilibrium of the biological system, which finally results in the restoration of the glutathione equilibrium. The antioxidant system is activated, the immune system is modulated, and thus the defense mechanisms are improved. In patients with rheumatoid arthritis, repeated ozone treatments have led to new findings in "immunomodulation" through ozone. The more effective immune response is discussed as the response of innate immune memory and opens interesting aspects for complementary treatment of autoimmune diseases.

Detection of Trace Explosives Using a Novel Sample Introduction and Ionization Method.

A novel sample introduction and ionization method for trace explosives detection is proposed and investigated herein, taking into consideration real-world application requirements. A thermal desorption sampling method and dielectric barrier discharge ionization (DBDI) source, with air as the discharge gas, were developed. The counter flow method was adopted firstly into the DBDI source to remove the interference of ozone and other reactive nitrogen oxides. A separated reaction region with an ion guiding electric field was developed for ionization of the sample molecules. Coupled with a homemade miniature digital linear ion trap mass spectrometer, this compact and robust design, with further optimization, has the advantages of soft ionization, a low detection limit, is free of reagent and consumable gas, and is an easy sample introduction. A range of common nitro-based explosives including TNT, 2,4-DNT, NG, RDX, PETN, and HMX has been studied. A linear response in the range of two orders of magnitude with a limit of detection (LOD) of 0.01 ng for TNT has been demonstrated. Application to the detection of real explosives and simulated mixed samples has also been explored. The work paves the path to developing next generation mass spectrometry (MS) based explosive trace detectors (ETDs).

Simultaneous measurement of local densities of atomic oxygen and ozone in pure oxygen pulsed barrier discharge under atmospheric pressure

Atomic oxygen and ozone are essential reactive species in plasma oxidation processes. Pure oxygen discharge is preferable to produce atomic oxygen and ozone while a difficulty in measuring their local densities exists. The ozone density is typically measured by UV absorption, but its resolution is insufficient for measuring the local ozone density in filamentary discharges. The atomic oxygen density can be measured by two-photon absorption laser-induced fluorescence (TALIF) method. However, ozone interference from the in situ atomic oxygen production due to ozone fragmentation by the incident UV light disturbs the TALIF measurement of the discharge-originated atomic oxygen. Therefore, compensation for ozone interference is necessary in atomic oxygen measurements. In this study, we propose a method to separate ozone interference from the discharge-originated atomic oxygen signal by focusing on different TALIF signal dependence on the laser intensity between atomic oxygen density and ozone density. By changing the laser intensity in the TALIF measurement, we separate the signal of atomic oxygen density from that of ozone interference. Under a short-gapped pulsed barrier discharge at a 3.1 mJ discharge energy, the gas temperature and the local densities of the atomic oxygen and ozone in the observed volume are estimated to be approximately 380 K, 3.8–11.3 , and 3.4 , respectively. This estimated atomic oxygen density is consistent with the absolute atomic oxygen density calibrated by the Xe-TALIF measurement. This consistency indicates that our method is applicable for absolute density measurements of atomic oxygen using ozone as the calibration reference.

Low-cost sensors and microscale land use regression: Data fusion to resolve air quality variations with high spatial and temporal resolution

AbstractThe strong temporal and spatial gradients in NO2 concentrations frequently observed in urban microenvironments are very difficult to measure and model accurately. Recent developments in low-cost air quality instruments have led to improvement in the spatial coverage of time-resolved measurement, however interpolation is still needed to map pollutant concentrations and connect time-as well as space-dependent variations to urban design features. Here we propose a novel approach that uses a previously-described microscale land use regression (LUR) model to spatially interpolate data from a well-calibrated network of low-cost air quality instruments. We use a semiconducting oxide-based ozone sensor to provide a robust correction of the output of an electrochemical NO2 sensor for ozone interference. We characterise signal noise probably associated with meniscus fluctuations as a significant error source, that can be handled with appropriate signal averaging. The LUR model is used to provide high spatial resolution in the data set, whilst correlation with sensor measurements provides a time-dependent estimate associated with different land use types. Observations from the network of instruments showed marked variability in NO2 concentrations over short distances (on the scale of 100 m), with highest concentrations reached near bus stops, intersections and under shop awnings. This approach connects the complex time- and space-dependent variations to urban design features and is a promising way forward as a basis for objective spatial mapping of time-dependent mean concentration fields and local population exposure estimates.

Technical note: A simple theoretical model framework to describe plant stomatal “sluggishness” in response to elevated ozone concentrations

Abstract. Elevated levels of tropospheric ozone, O3, cause damage to terrestrial vegetation, affecting leaf stomatal functioning and reducing photosynthesis. Climatic impacts under future raised atmospheric greenhouse gas (GHG) concentrations will also impact on the net primary productivity (NPP) of vegetation, which might for instance alter viability of some crops. Together, ozone damage and climate change may adjust the current ability of terrestrial vegetation to offset a significant fraction of carbon dioxide (CO2) emissions. Climate impacts on the land surface are well studied, but arguably large-scale modelling of raised surface level O3 effects is less advanced. To date most models representing ozone damage use either O3 concentration or, more recently, flux-uptake-related reduction of stomatal opening, estimating suppressed land–atmosphere water and CO2 fluxes. However there is evidence that, for some species, O3 damage can also cause an inertial “sluggishness” of stomatal response to changing surface meteorological conditions. In some circumstances (e.g. droughts), this loss of stomata control can cause them to be more open than without ozone interference. To both aid model development and provide empiricists with a system on to which measurements can be mapped, we present a parameter-sparse framework specifically designed to capture sluggishness. This contains a single time-delay parameter τO3, characterizing the timescale for stomata to catch up with the level of opening they would have without damage. The larger the value of this parameter, the more sluggish the modelled stomatal response. Through variation of τO3, we find it is possible to have qualitatively similar responses to factorial experiments with and without raised O3, when comparing to reported measurement time series presented in the literature. This low-parameter approach lends itself to the inclusion of ozone-induced inertial effects being incorporated in the terrestrial vegetation component of Earth system models (ESMs).

Performance of the Radiello® diffusive sampler for formaldehyde measurement: the influence of exposure conditions and ozone interference

The radial diffusive standard sampler Radiello® filled with Florisil impregnated with 2,4-dinitrophenylhydrazine (DNPH) was evaluated with the goal of survey monitoring the formaldehyde concentration in indoor air for a 4.5 day sampling time.

Solid-phase supported profluorescent nitroxide probe for the determination of aerosol-borne reactive oxygen species

Reactive oxygen species (ROS) and free radicals play important roles in the chemical transformation and adverse health effects of environmental aerosols. This work presents a simple and sensitive method for sampling and analysis of ROS using a packed column coated with a profluorescent nitroxide scavenger, proxyl fluorescamine (PF). Quantification was performed by extraction and analysis using HPLC with fluorescence detection. For comparison, the conventional method of collecting aerosols into dichlorofluorescin (DCFH) aqueous solution was used as a reference. The method was successfully applied to the determination of ROS in a model secondary organic aerosol (SOA) system generated by ozonolysis of nicotine, as well as in secondhand tobacco smoke (SHS). ROS concentrations between 50-565 nmol m(-3) were detected in fresh SOA and SHS samples. After SHS aging for 22 h, 13-18% of the initial ROS mass remained, suggesting the presence of persistent ROS. The new method offers better stability and reproducibility along with sensitivity comparable to that of DCFH (method detection limit of 3.2 and 1.4 nmol m(-3) of equivalent H2O2 for PF and DCFH respectively). The PF probe was stable during storage at room temperature and not reactive with ozone or NOx, whereas DCFH in the particle-collecting liquid system was strongly influenced by ozone and NOx interferences. This case study provides a good basis for employing solid-phase supported PF for field measurement of specific ROS in other combustion systems (i.e. biomass burning, candles, and diesel exhaust) and environmental aerosols.

Investigation of formaldehyde and acetaldehyde sampling rate and ozone interference for passive deployment of Waters Sep-Pak XPoSure samplers

This study investigated formaldehyde and acetaldehyde passive sampling rates and ozone interference for the DNPH-based Waters Sep-Pak XPoSure sampler. Previous studies have shown that ozone interferes with active sampling by this cartridge. Our study included one laboratory and six field experiments conducted in Northern California homes. Passive sampling rates of 1.10 ± 0.09 and 0.86 ± 0.10 mL min−1 determined for formaldehyde and acetaldehyde are lower than previously reported. In a controlled laboratory experiment there were small, statistically insignificant impacts of subsequent ozone exposure on formaldehyde and acetaldehyde mass passively collected on the samplers. This sampler is inexpensive, easy to deploy and to transport by mail, and has a high sampling capacity when used passively; it is suitable for a wide-range of monitoring applications. However, the passive sampling rate remains in question given the internally consistent, but different results obtained in our study and the previous study.

Fractional factorial experiments using a test atmosphere to assess the accuracy and precision of a new passive sampler for the determination of formaldehyde in the atmosphere

A new analytical method was developed for the determination of formaldehyde in ambient air based on the use of a modified configuration of the Analyst ® passive sampler. It consists of a polyethylene cylinder filled with appropriate reactive adsorbent and a special anti-turbulence net which works as an ozone scrubber. The performance of a diffusive sampler depends critically on the selection and use of a suitable adsorbent and on environmental factors, such as temperature, humidity and the interference of oxidant species. In this study two adsorbent types were investigated: 2,4-dinitrophenylhydrazine (2,4-DNPH) coated silica gel and Florisil ® particles. Interference of ozone was removed by using a silver net upstream as an anti-turbulence device. The performance of this net was then compared with that of stainless steel. Furthermore, the aim of the work was the optimization of the adsorbent type and the study of the interference of ozone with particular attention placed on the effect of relative humidity and temperature. A dynamic system for generating a known concentration of the test gas (formaldehyde) in an appropriate exposure chamber was used to evaluate the performance of the passive sampler and to allow the calibration of the methodology. Inter-comparisons with a reference method, active sampling using 2,4-DNPH-silica gel coated cartridges, were also carried out. Results were in accordance with each other. Tests were planned using a statistical method based on Design of Experiment methodology. The operating conditions were chosen in order to obtain the best configuration of the passive device by evaluating the statistical significance of the different factors and their interactions by analysis of variance. Results showed that the best configuration was achieved using 2,4-DNPH Florisil ® coated particles as an adsorbent and a silver anti-turbulence net as an ozone scrubber. With the aim of achieving further results in realistic conditions, some field experiments were also carried out.

단기 측정용 오존 간이 측정기의 실험 챔버 내에서 성능에 관한 연구

Passive sampler is a simple and cost-effective measuring equipment for ambient and indoor air pollution. We studied the performance of a short term (1 hour mean concentration) ozone passive sampler which was coated with a colorant (indigo carmine) to a filter substrate. Acetone and sulfamic acid added ozone passive sampler was investigated to measure short term mean ozone concentration. Ozone response and interference of criteria air pollutant(, CO) on a short term ozone passive sampler was tested through experimental chamber. The results show sulfamic acid added passive ozone sampler have good response in ozone exposure. Interference of gas is larger than other two criteria gases.

A Passive Sampler for the Determination of Carbonyl Compounds in Indoor Air Employing O-(4-cyano-2-ethoxybenzyl)hydroxylamine as Reactive Adsorbent

Author sh av ed eveloped a new analytical method for gaseous carbonyl compounds in indoor air using a passive sampler. The sampler consists of a porous polyethylene cylinder uniformly packed with O-(4-cyano-2ethoxybenzyl)hydroxylamine (CNET) coated silica gel as a reactive adsorbent. After sampling, CNET derivatives were eluted by acetonitrile and subsequently determined by HPLC. Sampling rates for formaldehyde, acetaldehyde and acetone were determined by a small chamber experiment with a constant gas generation system and resulted in 74 ml/min for formaldehyde, 44 ml/min for acetaldehyde and 42 ml/min for acetone. Effects of exposure time (8 and 24 hr), temperature (10, 25 and 40 ◦ C) and relative humidity (31–94%) on the rate were not apparent under the given conditions. The passive sampler was then applied for field measurements of carbonyl compounds in indoor air and gave similar results when compared to active samplings using 2,4-dinitrophenylhydrazine (DNPH) coated cartridges. The Ames test showed the CNET is preferable in safety handling because of its lower mutagenic activities than those of DNPH. Carbonyl compounds can be determined with reduced interference of ozone, because the CNET was less degradable when exposed to ozone compared with DNPH. Therefore, the CNET is a possible alternative to DNPH as trapping reagent in the passive sampling device for the determination of formaldehyde, acetaldehyde and acetone in indoor air.

A Sensitive Method for the Quantification of Acrolein and Other Volatile Carbonyls in Ambient Air

Acrolein, an unsaturated aldehyde found in both indoor and outdoor air, is considered one of the greatest noncancer health risks of all organic air pollutants. Current methods for determining acrolein often employ sorbent-filled cartridges containing a carbonyl derivatizing agent (e.g., dinitrophenylhydrazine). These methods are of limited use for unsaturated compounds due to the formation of unstable derivatives, coelution of similar compounds, long sample collection times, and ozone interferences that result in poor sensitivity, selectivity, and reproducibility. The goal of this research was to develop an analytical method for determining ppt concentrations of acrolein and other carbonyls in air with short sampling times (10 min). The method uses a mist chamber to collect carbonyls by forming water-soluble carbonyl-bisulfite adducts. The carbonyls are then liberated from the bisulfite, derivatized, and quantified by gas chromatography/electron capture negative ionization mass spectrometry. The method was applied to determine atmospheric acrolein concentrations at three sites in northern California reflecting hemispheric background concentrations, biogenic-dominated regions, and urban environments. The resulting acrolein concentrations were 0.056, 0.089, and 0.29 microg/m3, respectively, which are all above the EPA Reference Concentration of 0.02 microg/m3. The minimum detection limit of 0.012 microg/m3 is below that of other published methods. Methacrolein, methyl vinyl ketone, crotonaldehyde, glyoxal, methyl glyoxal, and benzaldehyde were also quantified.

Selectivity improvement of semi-conducting gas sensors by selective filter for atmospheric pollutants detection

The monitoring of atmospheric pollution using chemical gas sensors is a challenge due to the lack of selectivity of most existing devices. However, their performances can be improved using filtering films achieving the separation or the removal of some gases. This study is focused on the detection of carbon monoxide and of oxidant pollutants (nitrogen dioxide and ozone) by sensors constituted of SnO 2, or phthalocyanine compounds. Two types of filters were investigated. Filters based on MnO 2 powder are successful to remove ozone while preserving nitrogen dioxide in a large temperature range from ambient to 400 °C, but they partially convert carbon monoxide. The second type of filter constituted of indigo powder is also efficient to remove ozone without modification of nitrogen concentration at ambient. Then, these filters were associated with sensing element. MnO 2 thick films were deposited by screen-printing on SnO 2. With resulting sensors, the interference of ozone for the detection of CO or of NO 2 is reduced, but some technological problems such as adhesion of MnO 2 layer have to be solved. For phthalocyanine devices, the indigo filter placed upstream to the sensitive layer makes the sensor selective to nitrogen dioxide.

Portable instrument for electrochemical gas sensing

The instrument features up to four individual sensors, which may be used in the amperometric or voltammetric mode. A small pump is employed in order to make use of the enhanced sensitivity obtained with active transport of the sample gas to the sensor membranes. A Pt/air system serves as reference electrode. For the amperometric detection of acetaldehyde, as an example, a detection limit of 12 ppb was obtained. Several approaches to optimize selectivity and sensitivity are demonstrated on the portable, battery powered instrument. These include the use of a preconcentration trap for acetaldehyde and of chemical filters for the elimination of the interference of ozone on the measurement of NO, as well as voltammetric and concurrent measurements from two sensors in order to determine both NO and SO 2 in mixtures.

Intermethod comparisons of active sampling procedures and analysis of aldehydes at environmental levels.

Within the framework of a European interlaboratory exercise, the Vito facility for the generation of controlled atmospheres was used to test the suitability of four sampling techniques for priority aldehydes namely formaldehyde, acrolein, acetaldehyde, and glutaraldehyde at the ranges of 0.5 to 150 microg x m(-3). The samplers are DNPH-containing impingers, DNPH-impregnated cartridges and filters, and 2-HMP coated XAD-2 tubes. The three first DNPH samplers are to be analyzed by HPLC and the latter by GC-MS for the oxazolidine derivatives. The intermethod comparison comprises two to five sets of experiments depending on the compounds of interest. The aim of the exercise was also to assess the chemical interferences caused by ozone, nitrogen dioxide, and ammonia when using different techniques for sampling and analysis. The active DNPH method (with minor modifications such as shorter sampling time, immediate elution after sampling, and/or eventually wetting of samplers) delivered results within the 30% overall relative uncertainty for formaldehyde, acetaldehyde, and acrolein at the upper microg x m(-3) levels. However, the results suggest that the current DNPH methods for aldehydes do not comply with the 30% minimum performance criteria at the sub microg x m(-3) level. Sampling of aldehydes in the presence of ozone and NO2 interferences by using a "scrubber" cartridge appears to be beneficial to the quality of results.

Ozone and water-vapor measurements by Raman lidar in the planetary boundary layer: error sources and field measurements

A new lidar instrument has been developed to measure tropospheric ozone and water vapor at low altitude. The lidar uses Raman scattering of an UV beam from atmospheric nitrogen, oxygen, and water vapor to retrieve ozone and water-vapor vertical profiles. By numerical simulation we investigate the sensitivity of the method to both atmospheric and device perturbations. The aerosol optical effect in the planetary boundary layer, ozone interference in water-vapor retrieval, statistical error, optical cross talk between Raman-shifted channels, and optical cross talk between an elastically backscattered signal in Raman-shifted signals and an afterpulse effect are studied in detail. In support of the main conclusions of this model study, time series of ozone and water vapor obtained at the Swiss Federal Institute of Technology in Lausanne and during a field campaign in Crete are presented. They are compared with point monitor and balloon sounding measurements for daytime and nighttime conditions.

Front-side micromachined porous silicon nitrogen dioxide gas sensor

In this paper a new C-MOS compatible fabrication process is presented for a nitrogen dioxide porous silicon (PS) sensor. Electrically insulated PS sensing layers and even free-standing PS membranes have been obtained by front side electrochemical micromachining, reducing in this way electrical leakage towards the crystalline substrate. The electrical behavior of the device in a controlled environment was measured by means of a volt–amperometric technique at constant bias. A huge variation of the current was detected at RT for NO 2 concentrations as low as 200 ppb (Δ G/ G=111). The interference of humidity, ethanol, methanol, CO and ozone is also discussed.

An enzymatic-fluorimetric method for monitoring of ethanol in ambient air

A method is described for the continuous monitoring of ethanol in ambient air. The system consists of a scrubber coil for enrichment of the analyte from air in an aqueous solution and a directly connected fluorescence detector. Because of using a reagent solution containing alcohol dehydrogenase (ADH) and nicotinamide adenine dinucleotide (NAD+) for absorption, ethanol can react directly with ADH and NAD+ during air sampling, producing NADH, which can be measured by fluorescence detection. The influence of reagent concentrations, gas flow rate and scrubber solution flow rate on the performance of the instrument was tested. Possible ozone interferences can be avoided by placing a KI coated filter in front of the scrubber inlet. The response time of the system was found to be 2.3 min and the detection limit about 1 ppbV. The applicability of the developed method was demonstrated during a field campaign in Brazil.

Use of C 18 and silica-gel coated Sep-Pak cartridges for the determination of carbonyls in air by liquid chromatography

C 18 and silica-gel cartridges coated with 2,4-dinitrophenylhydrazine (2,4-DNPH) were compared for the determination of formaldehyde, acetaldehyde, acetone, propionaldehyde and butyraldehyde levels from ambient air. Liquid chromatography (LC) was used for the analysis, and clear differences were found for acetone retention on each type of coated cartridge. Moreover, double peaks of acetaldehyde were observed in LC analysis from samples simultaneously collected in both impregnated C 18 and silica-gel cartridges. By using a KI filter during sampling to avoid ozone interference, retention and analysis were improved for some relevant carbonyl compounds in air. 2,4-DNPH silica-gel cartridges were used to determine carbonyls in ambient air from `Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas' (CIEMAT), located in Madrid surroundings.

Intercomparison of six ambient [CH2O] measurement techniques

From May 29 to June 3, 1995 a blind intercomparison of six ambient formaldehyde measurement techniques took place at a field site near the National Center for Atmospheric Research in Boulder, Colorado. The continuous measurement methods intercompared were tunable diode laser absorption spectroscopy, (TDLAS); coil/2,4‐dinitrophenylhydrazine, (CDNPH); 1,3‐cyclohexanedione‐diffusion scrubber (CHDDS); and the coil enzyme method (CENZ). In addition, two different cartridge methods were compared: silica gel‐2,4‐dinitrophenylhydrazine (DPNH) systems and a C‐18‐DNPH system. The intercomparison was conducted with spiked zero air (part 1) and ambient air (part 2). The CH2O standards for part 1 were calibrated by several independent methods and delivered to participants via a common glass manifold with potential trace gas interférants common to ambient air (O3, SO2, NO2, isoprene, H2O). The TDLAS system was used to confirm the absolute accuracy of the standards and served as a mission reference for part 1. The ambient phase lasted 44 hours with all participants sampling from a common glass tower. Differences between the ambient [CH2O] observed by the TDLAS and the other continuous methods were significant in some cases. For matched ambient measurement times the average ratios (±1σ) [CH2O]measured/[CH2O]TDLAS were: 0.89±0.12 (CDNPH); 1.30±0.02 (CHDDS); 0.63±0.03 (CENZ). The methods showed similar variations but different absolute values and the divergences appeared to result largely from calibration differences (no gas phase standards were used by groups other than NCAR). When the regressions of the participant [CH2O] values versus the TDLAS values, (measured in part 1), were used to normalize all of the results to the common gas phase standards of the NCAR group, the average ratios (±1σ), [CH2O]corrected/[CH2O]TDLAS for the first measurement period were much closer to unity: 1.04±0.14 (CDNPH), 1.00±0.11 (CHDDS), and 0.82±0.08 (CENZ). With the continuous methods used here, no unequivocal interferences were seen when SO2, NO2, O3, and isoprene impurities were added to prepared mixtures or when these were present in ambient air. The measurements with the C‐18 DNPH (no O3 scrubber) and silica gel DNPH cartridges (with O3 scrubber) showed a reasonable correlation with the TDLAS measurements, although the results from the silica cartridges were about a factor of two below the standards in the spike experiments and about 35% below in the ambient measurements. Using the NCAR gas‐phase spike data to calibrate the response of the silica gel cartridges in the ambient studies, the results are the same within statistical uncertainty. When the same gas phase calibration was used with the C‐18 cartridges, the results showed a positive bias of about 35%, presumably reflecting a positive ozone interference in this case (no ozone scrubber used). The silica DNPH cartridge results from the second participant were highly scattered and showed no significant correlation with the TDLAS measurements.