laser mass spectrometry
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Abstract In order to clarify the necessity and urgency of dioxin detection, the characteristics and emission sources were firstly studied in this paper. The current dioxin detection techniques were then summarized, including chemical detection technique represented by HRGC/MS, biological detection technique covering immunology and biotechnology, and laser mass spectrometry technique using fusion ionization technology and time-of-flight mass spectrometry. Then the advantages and disadvantages, representative technologies, development directions and application prospects of various detection methods were analyzed. Eventually, the future development direction of dioxin detection technology was prospected.

Abstract. Aerosol intercomparisons are inherently complex as they convolve instrument-dependent detection efficiencies vs. size (which often change with pressure, temperature, or humidity) and variations in the sampled aerosol population, in addition to differences in chemical detection principles (e.g., inorganic-only nitrate vs. inorganic plus organic nitrate for two instruments). The NASA Atmospheric Tomography Mission (ATom) spanned four separate aircraft deployments which sampled the remote marine troposphere from 86∘ S to 82∘ N over different seasons with a wide range of aerosol concentrations and compositions. Aerosols were quantified with a set of carefully characterized and calibrated instruments, some based on particle sizing and some on composition measurements. This study aims to provide a critical evaluation of inlet transmissions impacting aerosol intercomparisons, and of aerosol quantification during ATom, with a focus on the aerosol mass spectrometer (AMS). The volume determined from physical sizing instruments (aerosol microphysical properties, AMP, 2.7 nm to 4.8 µm optical diameter) is compared in detail with that derived from the chemical measurements of the AMS and the single particle soot photometer (SP2). Special attention was paid to characterize the upper end of the AMS size-dependent transmission with in-field calibrations, which we show to be critical for accurate comparisons across instruments with inevitably different size cuts. Observed differences between campaigns emphasize the importance of characterizing AMS transmission for each instrument and field study for meaningful interpretation of instrument comparisons. Good agreement (regression slope =0.949 and 1.083 for ATom-1 and ATom-2, respectively; SD =0.003) was found between the composition-based volume (including AMS-quantified sea salt) and that derived from AMP after applying the AMS inlet transmission. The AMS captured, on average, 95±15 % of the standard PM1 volume (referred to as the URG Corp. standard cut 1 µm cyclone operated at its nominal efficiency). These results support the absence of significant unknown biases and the appropriateness of the accuracy estimates for AMS total mass and volume for the mostly aged air masses encountered in ATom. The particle size ranges (and their altitude dependence) that are sampled by the AMS and complementary composition instruments (such as soluble acidic gases and aerosol, SAGA, and particle analysis by laser mass spectrometry, PALMS) are investigated to inform their use in future studies.

Laboratory experiments are essential in exploring the mechanisms involved in stardust formation. One key question is how a metal is incorporated into dust for an environment rich in elements involved in stardust formation (C, H, O, Si). To address experimentally this question we have used a radiofrequency cold plasma reactor in which cyclic organosilicon dust formation is observed. Metallic (silver) atoms were injected in the plasma during the dust nucleation phase to study their incorporation in the dust. The experiments show formation of silver nanoparticles (~15 nm) under conditions in which organosilicon dust of size 200 nm or less is grown. The presence of AgSiO bonds, revealed by infrared spectroscopy, suggests the presence of junctions between the metallic nanoparticles and the organosilicon dust. Even after annealing we could not conclude on the formation of silver silicates, emphasizing that most of silver is included in the metallic nanoparticles. The molecular analysis performed by laser mass spectrometry exhibits a complex chemistry leading to a variety of molecules including large hydrocarbons and organometallic species. In order to gain insights into the involved chemical molecular pathways, the reactivity of silver atoms/ions with acetylene was studied in a laser vaporization source. Key organometallic species, AgnC2Hm (n = 1–3; m = 0–2), were identified and their structures and energetic data computed using density functional theory. This allows us to propose that molecular Ag–C seeds promote the formation of Ag clusters but also catalyze hydrocarbon growth. Throughout the article, we show how the developed methodology can be used to characterize the incorporation of metal atoms both in the molecular and dust phases. The presence of silver species in the plasma was motivated by objectives finding their application in other research fields than astrochemistry. Still, the reported methodology is a demonstration laying down the ground for future studies on metals of astrophysical interest, such as iron.

Introduction. The work is devoted to evaluating the results of our own research of sanitary-microbiological monitoring of environmental objects in diversified treatment-and-prophylactic institutions of stationary type and of the analysis both of domestic and foreign data in order justify of the list of priority controlled sanitary-microbiological indices of air and surfaces to ensure the safety of hospital environment, medical organizations stationary type, regardless of their functional purpose. Material and methods. The survey was conducted in various premises in the medical-prophylactic institutions of stationary type for two years. Studies included determination of microbial contamination of the air environment, working surfaces, hands of personnel with the detection of bacteriological, virological, and mycological parameters, followed by macroscopic and microscopic identification of microorganisms and identification using automated systems with the method of time-of-flight matrix-assisted laser mass spectrometry platform MALDI-TOF, based on the study of the mass spectra of ribosomal proteins in the range of 1000-10000 Daltons and bioinformatic comparison of the obtained spectrum with database reference spectra and PCR. Results. As a result, the research of surface washings in the premises of a multidisciplinary clinic revealed microbial contamination with conditionally pathogenic gram-positive cocci, including S.aureus, gram-positive and gram-negative bacteria posing a serious epidemiological danger to patients in these wards regardless of the MOST profile and requires mandatory monitoring taking into account of the used disinfectants. Conclusion. Our own research and analysis of domestic and foreign literature showed that it is not enough to monitor the air in the MOST premises only in terms of total microbiological contamination. In the operating, procedural and dressing blocks, as well as in the wards, physiotherapeutic, diagnostic, laboratory rooms and auxiliary units, it is also necessary to take into account other sanitary and microbiological indices: total microbes count, gram-positive rods and cocci, including S.aureus, fungi, adeno-, entero-, astroviruses, coliphages.

Introduction. The work is devoted to evaluating the results of our own research of sanitary-microbiological monitoring of environmental objects in diversified treatment-and-prophylactic institutions of stationary type and of the analysis both of domestic and foreign data in order justify of the list of priority controlled sanitary-microbiological indices of air and surfaces to ensure the safety of hospital environment, medical organizations stationary type, regardless of their functional purpose. Material and methods. The survey was conducted in various premises in the medical-prophylactic institutions of stationary type for two years. Studies included determination of microbial contamination of the air environment, working surfaces, hands of personnel with the detection of bacteriological, virological, and mycological parameters, followed by macroscopic and microscopic identification of microorganisms and identification using automated systems with the method of time-of-flight matrix-assisted laser mass spectrometry platform MALDI-TOF, based on the study of the mass spectra of ribosomal proteins in the range of 1000-10000 Daltons and bioinformatic comparison of the obtained spectrum with database reference spectra and PCR. Results. As a result, the research of surface washings in the premises of a multidisciplinary clinic revealed microbial contamination with conditionally pathogenic gram-positive cocci, including S.aureus, gram-positive and gram-negative bacteria posing a serious epidemiological danger to patients in these wards regardless of the MOST profile and requires mandatory monitoring taking into account of the used disinfectants. Conclusion. Our own research and analysis of domestic and foreign literature showed that it is not enough to monitor the air in the MOST premises only in terms of total microbiological contamination. In the operating, procedural and dressing blocks, as well as in the wards, physiotherapeutic, diagnostic, laboratory rooms and auxiliary units, it is also necessary to take into account other sanitary and microbiological indices: total microbes count, gram-positive rods and cocci, including S.aureus, fungi, adeno-, entero-, astroviruses, coliphages.