Development and characterization of a single particle laser ablation mass spectrometer (SPLAM) for organic aerosol studies

A single particle instrument was developed for real-time analysis of organic aerosol. This instrument, named Single Particle Laser Ablation Mass Spectrometry (SPLAM), samples particles using an aerodynamic lens system for which the theoretical performances were calculated. At the outlet of this system, particle detection and sizing are realized by using two continuous diode lasers operating at λ = 403 nm. Polystyrene Latex (PSL), sodium chloride (NaCl) and dioctylphtalate (DOP) particles were used to characterize and calibrate optical detection of SPLAM. The optical detection limit (DL) and detection efficiency (DE) were determined using size-selected DOP particles. The DE ranges from 0.1 to 90% for 100 and 350 nm DOP particles respectively and the SPLAM instrument is able to detect and size-resolve particles as small as 110–120 nm. During optical detection, particle scattered light from the two diode lasers, is detected by two photomultipliers and the detected signals are used to trigger UV excimer laser (λ = 248 nm) used for one-step laser desorption ionization (LDI) of individual aerosol particles. The formed ions are analyzed by a 1 m linear time-of-flight mass spectrometer in order to access to the chemical composition of individual particles. The TOF-MS detection limit for gaseous aromatic compounds was determined to be 0.85 × 10<sup>−15</sup> kg (∼4 × 10<sup>3</sup> molecules). DOP particles were also used to test the overall operation of the instrument. The analysis of a secondary organic aerosol, formed in a smog chamber by the ozonolysis of indene, is presented as a first application of the instrument. Single particle mass spectra were obtained with an effective hit rate of 8%. Some of these mass spectra were found to be very different from one particle to another possibly reflecting chemical differences within the investigated indene SOA particles. Our study shows that an exhaustive statistical analysis, over hundreds of particles, and adapted reference mass spectra are further needed to understand the chemical meaning of single particle mass spectra of chemically complex submicrometer-sized organic aerosols

Importance of size representation and morphology in modelling optical properties of black carbon: comparison between laboratory measurements and model simulations

Black carbon (BC) from incomplete combustion of biomass or fossil fuels is the strongest absorbing aerosol component in the atmosphere. Optical properties of BC are essential in climate models for quantification of their impact on radiative forcing. The global climate models, however, consider BC to be spherical particles, which causes uncertainties in their optical properties. Based on this, an increasing number of model-based studies provide databases and parameterization schemes for the optical properties of BC, using more realistic fractal aggregate morphologies. In this study, the reliability of the different modelling techniques of BC was investigated by comparing them to laboratory measurements. The modelling techniques were examined for bare BC particles in the first step and for BC particles with organic material in the second step. A total of six morphological representations of BC particles were compared, three each for spherical and fractal aggregate morphologies. In general, the aggregate representation performed well for modelling the particle light absorption coefficient σabs, single-scattering albedo SSA, and mass absorption cross-section MACBC for laboratory-generated BC particles with volume mean mobility diameters dp,V larger than 100nm. However, for modelling Ångström absorption exponent AAE, it was difficult to suggest a method due to size dependence, although the spherical assumption was in better agreement in some cases. The BC fractal aggregates are usually modelled using monodispersed particles, since their optical simulations are computationally expensive. In such studies, the modelled optical properties showed a 25% uncertainty in using the monodisperse size method. It is shown that using the polydisperse size distribution in combination with fractal aggregate morphology reduces the uncertainty in measured σabs to 10% for particles with dp,V between 60-160nm. Furthermore, the sensitivities of the BC optical properties to the various model input parameters such as the real and imaginary parts of the refractive index (mre and mim), the fractal dimension (Df), and the primary particle radius (app) of an aggregate were investigated. When the BC particle is small and rather fresh, the change in the Df had relatively little effect on the optical properties. There was, however, a significant relationship between app and the particle light scattering, which increased by a factor of up to 6 with increasing total particle size. The modelled optical properties of BC are well aligned with laboratory-measured values when the following assumptions are used in the fractal aggregate representation: mre between 1.6 and 2, mim between 0.50 and 1, Df from 1.7 to 1.9, and app between 10 and 14nm. Overall, this study provides experimental support for emphasizing the importance of an appropriate size representation (polydisperse size method) and an appropriate morphological representation for optical modelling and parameterization scheme development of BC

VUV spectroscopy and photochemistry of five interstellar and putative prebiotic molecules

For many years, our group has been investigating the VUV spectroscopy and photochemistry of molecules of astrophysical (Jochims et al. 200

Impact of batch variability on physicochemical properties of manufactured TiO2 and SiO2 nanopowders

International audienceThe development, manufacturing and commercialization of nanomaterials require traceable characterisation processes for quality control and safety of both the exposed workers and final customers. Even if the production batches are considered to be compliant with the industrial applications intended by manufacturers, it is necessary to study the reproducibility of the manufacturing process of nanomaterials independently, so as to determine the variability of key physico-chemical properties of nano-objects from one batch to another.In this study, a metrological approach was employed, using different traceable analytical techniques (X-Ray Diffraction, Transmission Electron Microscopy, Nitrogen physisorption with Brunauer–Emmett–Teller method, X-Ray Fluorescence, Scanning Mobility Particle Sizer and Aerodynamic Particle Sizer) to develop robust, reproducible and statistical methods to evaluate the impact of batch variability on physico-chemical properties of manufactured titanium dioxide and silicon dioxide nano-powders (crystalline structure, crystallite size, primary particle size, specific surface area, chemical composition and the dustiness of nanopowders).Five references of manufactured titanium dioxide nanoparticles and silicon dioxide nanoparticles were characterized with the developed measurement protocols. The reproducibilities of five batches by reference were overall inferior to 10% for crystalline structures, primary particle sizes, specific surface areas and the chemical composition of major components (TiO2 and SiO2) of the nanopowders studied (k = 1). As for the size distributions of released particles from dustiness tests, reproducibility for the modal and mean diameters ranged between 2% and 27%. Moreover, a large variation of nanopowder dustiness was obtained for the same material type (TiO2 or SiO2). This could point out that the physico-chemical properties of nanopowders, linked to the manufacturing process, have a strong impact on the dustiness parameter

Release of Nano-objects, their aggregates and agglomerates from Masks: ambitions and scientific objectives of the RENAAME project

Le contexte pandémique a mis en avant la nécessité de disposer de masques (chirurgicaux, de protection respiratoire FFPx et à usage non sanitaire). Pour la fabrication de ces différents types de masques, l&#8217;ajout de nanomatériaux représente une voie majeure d&#8217;innovation mais est aussi source de préoccupation sanitaire en lien avec une possible exposition par inhalation aux nano-objets, leurs agrégats et agglomérats (NOAA). Ainsi, plusieurs produits commerciaux déclarant des propriétés biocides/virucides ont soulevé diverses interrogations au niveau national [1] et international [2] quant à leur innocuité, aboutissant à leur retrait dès la mise sur le marché. Plus récemment, la présence de NOAA de TiO2 dans des masques a été démontrée [3] alors qu&#8217;aucune mention n&#8217;était précisée sur leurs emballages. Ce sujet de préoccupation relativement émergent souffre cependant d&#8217;un manque de développement méthodologique en ce qui concerne l&#8217;évaluation de l&#8217;exposition par inhalation aux NOAA lors de l&#8217;utilisation de masques. Le projet RENAAME vise à développer une méthodologie d&#8217;évaluation du relargage potentiel en phase aérosol des nanomatériaux déclarés ou impliqués sans indication commerciale dans la fabrication de masques afin d&#8217;évaluer l&#8217;exposition par inhalation dans des conditions réalistes d&#8217;utilisation. L&#8217;originalité du projet RENAAME consiste à développer et valider une approche couplant analyse des matériaux constitutifs des masques et des aérosols potentiellement émis. Si des travaux prénormatifs sont en cours (ISO/TC229 et ISO/NP TS11353) sur ce sujet, le nombre d&#8217;études scientifiques dédiées s&#8217;avère très limité. La méthodologie proposée vise à quantifier la fraction mobilisable (FM) de NOAA dans les masques puis à caractériser la fraction relarguée (FR) en phase aérosol pour des conditions représentatives d&#8217;utilisation. Cette évaluation sera menée sur des masques déclarant commercialement la présence de nanomatériaux présentant un potentiel risque sanitaire (dans le cas de ce projet NOAA composés de TiO2 et d&#8217;Ag), mais également sur des masques ne mentionnant aucune utilisation explicite de NOAA. La détermination de ces deux fractions permettra in-fine d&#8217;aboutir à un classement des différents types de masques en fonction de leur pouvoir émissif (PE=FR/FM). L&#8217;objectif de cette communication est de présenter les actions visées dans le projet RENAAME ainsi que la méthodologie expérimentale associée et les étapes nécessaires à sa qualification et sa validation. Les premiers résultats, en ce qui concerne l&#8217;identification par spectroscopie de fluorescence des rayons X (XRF), la quantification par spectrométrie de masse/d&#8217;émission atomique de plasma à couplage inductif (ICP-MS/OES) et l&#8217;analyse dimensionnelle par microscopie électronique (MEB/MET) de NOAA potentiellement présents, seront présentés. Ce projet est financé par le Programme National de Recherche Environnement Santé-Travail de l&#8217;ANSES avec le soutien des ministères chargés de l&#8217;environnement, de l&#8217;agriculture et du travail (ANSES-22-EST-023). [1] https://www.anses.fr/fr/system/files/CONSO2021SA0089.pdf [2] https://recalls-rappels.canada.ca/fr/avis-rappel/masques-contenant-du-gr&#8230; [3] https://doi.org/10.1038/s41598-022-06605-w</p

A performance evaluation and inter-laboratory comparison of community face coverings media in the context of covid-19 pandemic

International audienceDuring the recent pandemic of SARS-CoV-2, and as a reaction to the worldwide shortage of surgical masks, several countries have introduced new types of masks named “community face covering” (CoFC). To ensure the quality of such devices and their relevance to slow down the virus spreading, a quick reaction of the certification organisms was necessary to fix the minimal acceptable performances requirements. Moreover, many laboratories involved in the aerosol research field have been asked to perform tests in a quick time according to (CEN, 2020) proposed by the European committee for standardization. This specification imposes a minimal air permeability of 96 L.m-2.s-1 and a minimal filtration efficiency of 70% for 3 µm diameter particles. In the present article, an intercomparison of efficiency and permeability measured by 3 testing laboratories has been performed. Results are in good agreement considering the heterogeneity of the considered material samples (within 27 % in terms of filtration efficiency and less than 20 % in terms of permeability). On this basis, an analysis of 233 materials made of woven, non-woven and mixed fibrous material has been done in terms of filtration efficiency and air permeability. For some of them, measurements have been performed for 0.2 µm, 1 µm and 3 µm particle diameters. As expected, no deterministic correlation could be determinated to link these efficiencies to the permeability of the considered samples; however, a trend could be identified. The same exercise has been conducted to link the filtration efficiency measured at 3 µm to the filtration for lower diameters. Finally, a discussion on the kind of material that is the most relevant to manufacture “community face covering” (CoFC) supported by spectral filtration efficiency (from 0.02 µm to 3 µm) is proposed

Comparability of Lipoprotein Particle Number Concentrations Across ES-DMA, NMR, LC-MS/MS, Immunonephelometry, and VAP: In Search of a Candidate Reference Measurement Procedure for apoB and non-HDL-P Standardization

Afdeling Klinische Chemie en Laboratoriumgeneeskunde (AKCL