DOI: 10.5061/dryad.6q573n68z
title: WALL-E/Vocus AIM data: Online particle phase chemical composition

description: The spontaneous formation of OH radicals at the air-water interfaces of
 organic droplets was invstigated. In our study, we performed on line
 particle phase size resolved measurements, aiming to understand whether or
 not the oxidation process depends on the size of the particles. The on
 line measurements were performed using the WALL-E (wall free particle
 evaporator) particle phase inlet coupled with a Vocus AIM (adduct
 ionization mechanism) high resolution mass spectrometer. For the
 experiments of this study, iodide (I – ) was selected as the reagent ion,
 as it is suitable for the detection of carboxylic acids. We
 monitored the signal of the studied organic compounds (reactants) i.e.,
 citric, maleic and aconitic acid as a function of particle size, as well
 as the signals of the generated products.As final oxidation products we
 identified a) Citric acid + OH: malonic, malic, hydroxy maleic and
 oxyglutaric acids, and C5H6O6, b) Maleic acid + OH: malic and acrylic
 acids and c) Aconitic acid + OH: malonic, malic, hydroxy maleic and
 oxyglutaric acids, and C4H4O6. The product yield was determined by
 dividing the product signal by the reactant signal. These results are only
 qualitative. Our size resolved online measurements revealed that the
 product yield formation is increasing as a function of the
 surface-to-volume ratio, meaning that the oxidation is promoted at smaller
 particles. This observation is in excellent agreement with the offline
 measurements described in the main text of the manuscript.  The
 data given here contain all the raw signals of the above mentioned
 compounds as a function of sampling time (in minutes), i.e., time series.
 We also give the signals of water and iodine (reagent ion), with which we
 normalised the signals of the organics. Finally, we demonstrate some
 control experiments that we performed regarding the potential fragments of
 the parent compounds in the Wall-E source.
description: # WALL-E/Vocus AIM data: Online particle phase chemical composition
 Dataset DOI: [10.5061/dryad.6q573n68z](10.5061/dryad.6q573n68z) ##
 Description of the data and file structure We upload .txt files with the
 detected masses and the raw signals that led to the quantification of the
 product formation yields as a function of time (given in minutes). All
 data (txt format) contain the raw signals of the detected products
 (formula included) and the reactants, during the reaction of citric,
 maleic and aconitic acid with OH radicals. Water and iodide (reagent ion)
 signal are also given as they used for the normalisation of the data. The
 name of the files contains the type of acid and the number of experiment.
 ### Files and variables #### File: Aconitic\_acid\_exp1.txt
 **Description:** Aconitic acid particles at various sizes + OH radicals
 formed via water vapour (1st measurement) ##### Variables * C4H4IO5:
 Oxalaxetic/hydroxymaleic acid raw signal * C4H6IO5: Malic acid raw signal
 * C5H6IO4: Fragment 1 * C6H4IO5: Fragment 2 * C6H6IO6: Aconitic acid raw
 signal * H2O_: Humidity signal * Iodide: Reagent ion signal * Time_series:
 Time (min) #### File: Aconitic\_acid\_exp2.txt **Description:** Aconitic
 acid particles at various sizes + OH radicals formed via water vapour (2nd
 measurement) ##### Variables * C4H4IO5: Oxalaxetic/hydroxymaleic acid raw
 signal * C4H6IO5: Malic acid raw signal * C5H6IO4: Fragment 1 * C6H4IO5:
 Fragment 2 * C6H6IO6: Aconitic acid raw signal * H2O_: Humidity signal *
 Iodide: Reagent ion signal * Time_series: Time (min) #### File:
 Aconitic\_acid\_exp3.txt **Description:** Aconitic acid particles at
 various sizes + OH radicals formed via water vapour (3rd measurement)
 ##### Variables * C4H4IO5: Oxalaxetic/hydroxymaleic acid raw signal *
 C4H6IO5: Malic acid raw signal * C5H6IO4: Fragment 1 * C6H4IO5: Fragment 2
 * C6H6IO6:Aconitic acid raw signal * H2O_: Humidity signal * Iodide:
 reagent ion signal * Time_series: Time (min) #### File:
 Aconitic\_acid\_Fragments.txt **Description:** Control experiments -
 Fragmentation at different temperatures in the walle inlet ##### Variables
 * C5H6IO4: Fragment 1 * C6H4IO5: Fragment 2 * C6H6IO6: Aconitic acid raw
 signal * H2O_: Humidity signal * Iodide: Reagent ion signal * Time_series:
 Time (min) #### File: citric\_acid\_exp2.txt **Description:** Citric acid
 particles at various sizes + OH radicals formed via water vapour (2nd
 measurement) ##### Variables * C3H4IO4: Malonic acid raw signal * C5H6IO5:
 Oxyglutaric acid raw signal * C4H6IO5: Malic acid raw signal * C5H6IO6:
 C5H6O6 raw signal * C5H6IO4: Fragment 1 * C6H4IO5:Fragment 2 *
 C6H6IO6:Fragment 3 * C6H8IO7: Citric acid raw signal * H2O_: humidity
 signal * Iodide: reagent ion signal * time_series: time (min) #### File:
 citric\_acid\_exp3.txt **Description:** Citric acid particles at various
 sizes + OH radicals formed via water vapour (3rd measurement) #####
 Variables: * C3H4IO4:malonic acid raw signal *
 C5H6IO5:Oxyglutaric acid raw signal * C4H6IO5:malic acid raw signal *
 C5H6IO6:C5H6O6 raw signal * C5H6IO4:Fragment 1 * C6H4IO5:Fragment 2 *
 C6H6IO6:Fragment 3 * C6H8IO7: Citric acid raw signal * H2O_: humidity
 signal * Iodide: reagent ion signal * time_series: time (min) #### File:
 citric\_acid\_exp1.txt **Description:** Citric acid particles at various
 sizes + OH radicals formed via water vapour (1st measurement) #####
 Variables: * C3H4IO4:malonic acid raw signal *
 C5H6IO5:Oxyglutaric acid raw signal * C4H6IO5:malic acid raw signal *
 C5H6IO6:C5H6O6 raw signal * C5H6IO4: Fragment 1 * C6H4IO5: Fragment 2 *
 C6H6IO6: Fragment 3 * C6H8IO7:Citric acid raw signal * H2O_:humidity raw
 signal * Iodide: reagent ion raw signal * time_series: time (min) ####
 File: maleic\_acid\_exp1.txt **Description:** Maleic acid particles at
 various sizes + OH radicals formed via water vapour (1st measurement)
 ##### Variables * C3H4IO2_acrylic: Acrylic acid raw signal *
 C4H4IO4_maleic:Maleic acid raw signal * C4H6IO5_malic: Malic acid raw
 signal * H2O_: humidity signal * Iodide: reagent ion signal * Time_series:
 time (min) #### File: citric\_acid\_exp4.txt **Description:** Citric acid
 particles at various sizes + OH radicals formed via water vapour (4rth
 measurement) ##### Variables: Same as above * C3H4IO4: malonic acid raw
 signal * C5H6IO5:Oxyglutaric acid raw signal * C4H6IO5:malic acid raw
 signal * C5H6IO6: C5H6O6 acid raw signal * C5H6IO4: Fragment 1 * C6H4IO5:
 Fragment 1 * C6H6IO6: Fragment 1 * C6H8IO7: Citric acid raw signal * H2O_:
 humidity raw signal * Iodide: reagent ion signal * time_series: time (min)
 #### File: maleic\_acid\_exp2.txt **Description:** Maleic acid particles
 at various sizes + OH radicals formed via water vapour (2nd measurement)
 ##### Variables: same as exp1 * Iodide: reagent ion signal * H2O_:humidity
 raw signal * C3H4IO2_acrylic: acrylic acid raw signal * C4H4IO4_maleic:
 maleic acid raw signal * C4H6IO5_malic: malic acid raw signal *
 Time_series: time (min) #### File: maleic\_exp3\_fragments.txt
 **Description:** Maleic acid fragments at different temperatures #####
 Variables: same as above * C3H4IO2_acrylic: acrylic acid raw signal *
 C4H2IO3_maelicanhydride :maleic anhydride acid raw signal *
 C4H4IO4_maleic:maleic acid raw signal * C4H6IO5_malic: malic acid raw
 signal * H2O_: humidity ion signal * Iodide: reagent ion signal *
 Time_series: time (min)