Filters

20202

More filters

20212
Reset filters

Settings

End date: 2021 × Start date: 2021 × Publisher: Columbus, Ohio : American Chemical Society ×

Search Results

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Comparability of Raman Spectroscopic Configurations: A Large Scale Cross-Laboratory Study
    (Columbus, Ohio : American Chemical Society, 2020) Guo S.; Beleites C.; Neugebauer U.; Abalde-Cela S.; Afseth N.K.; Alsamad F.; Anand S.; Araujo-Andrade C.; Aškrabić S.; Avci E.; Baia M.; Baranska M.; Baria E.; Batista De Carvalho L.A.E.; De Bettignies P.; Bonifacio A.; Bonnier F.; Brauchle E.M.; Byrne H.J.; Chourpa I.; Cicchi R.; Cuisinier F.; Culha M.; Dahms M.; David C.; Duponchel L.; Duraipandian S.; El-Mashtoly S.F.; Ellis D.I.; Eppe G.; Falgayrac G.; Gamulin O.; Gardner B.; Gardner P.; Gerwert K.; Giamarellos-Bourboulis E.J.; Gizurarson S.; Gnyba M.; Goodacre R.; Grysan P.; Guntinas-Lichius O.; Helgadottir H.; Grošev V.M.; Kendall C.; Kiselev R.; Kölbach M.; Krafft C.; Krishnamoorthy S.; Kubryck P.; Lendl B.; Loza-Alvarez P.; Lyng F.M.; Machill S.; Malherbe C.; Marro M.; Marques M.P.M.; Matuszyk E.; Morasso C.F.; Moreau M.; Muhamadali H.; Mussi V.; Notingher I.; Pacia M.Z.; Pavone F.S.; Penel G.; Petersen D.; Piot O.; Rau J.V.; Richter M.; Rybarczyk M.K.; Salehi H.; Schenke-Layland K.; Schlücker S.; Schosserer M.; Schütze K.; Sergo V.; Sinjab F.; Smulko J.; Sockalingum G.D.; Stiebing C.; Stone N.; Untereiner V.; Vanna R.; Wieland K.; Popp J.; Bocklitz T.
    The variable configuration of Raman spectroscopic platforms is one of the major obstacles in establishing Raman spectroscopy as a valuable physicochemical method within real-world scenarios such as clinical diagnostics. For such real world applications like diagnostic classification, the models should ideally be usable to predict data from different setups. Whether it is done by training a rugged model with data from many setups or by a primary-replica strategy where models are developed on a 'primary' setup and the test data are generated on 'replicate' setups, this is only possible if the Raman spectra from different setups are consistent, reproducible, and comparable. However, Raman spectra can be highly sensitive to the measurement conditions, and they change from setup to setup even if the same samples are measured. Although increasingly recognized as an issue, the dependence of the Raman spectra on the instrumental configuration is far from being fully understood and great effort is needed to address the resulting spectral variations and to correct for them. To make the severity of the situation clear, we present a round robin experiment investigating the comparability of 35 Raman spectroscopic devices with different configurations in 15 institutes within seven European countries from the COST (European Cooperation in Science and Technology) action Raman4clinics. The experiment was developed in a fashion that allows various instrumental configurations ranging from highly confocal setups to fibre-optic based systems with different excitation wavelengths. We illustrate the spectral variations caused by the instrumental configurations from the perspectives of peak shifts, intensity variations, peak widths, and noise levels. We conclude this contribution with recommendations that may help to improve the inter-laboratory studies. © 2020 American Chemical Society.
  • Thumbnail Image
    Item
    No Evidence for a Significant Impact of Heterogeneous Chemistry on Radical Concentrations in the North China Plain in Summer 2014
    (Columbus, Ohio : American Chemical Society, 2020) Tan, Zhaofeng; Hofzumahaus, Andreas; Lu, Keding; Brown, Steven S.; Holland, Frank; Huey, Lewis Gregory; Kiendler-Scharr, Astrid; Li, Xin; Liu, Xiaoxi; Ma, Nan; Min, Kyung-Eun; Rohrer, Franz; Shao, Min; Wahner, Andreas; Wang, Yuhang; Wiedensohler, Alfred; Wu, Yusheng; Wu, Zhijun; Zeng, Limin; Zhang, Yuanhang; Fuchs, Hendrik
    The oxidation of nitric oxide to nitrogen dioxide by hydroperoxy (HO2) and organic peroxy radicals (RO2) is responsible for the chemical net ozone production in the troposphere and for the regeneration of hydroxyl radicals, the most important oxidant in the atmosphere. In Summer 2014, a field campaign was conducted in the North China Plain, where increasingly severe ozone pollution has been experienced in the last years. Chemical conditions in the campaign were representative for this area. Radical and trace gas concentrations were measured, allowing for calculating the turnover rates of gas-phase radical reactions. Therefore, the importance of heterogeneous HO2 uptake on aerosol could be experimentally determined. HO2 uptake could have suppressed ozone formation at that time because of the competition with gas-phase reactions that produce ozone. The successful reduction of the aerosol load in the North China Plain in the last years could have led to a significant decrease of HO2 loss on particles, so that ozone-forming reactions could have gained importance in the last years. However, the analysis of the measured radical budget in this campaign shows that HO2 aerosol uptake did not impact radical chemistry for chemical conditions in 2014. Therefore, reduced HO2 uptake on aerosol since then is likely not the reason for the increasing number of ozone pollution events in the North China Plain, contradicting conclusions made from model calculations reported in the literature. © 2020 American Chemical Society.