ORBAS

The instrument ORBAS (ORBITRAPTM for Aerosols) is currently under development in the LPC2E (VOLTER and PIVOTS projects) with an objective to implement the high resolution mass spectrometry (HRMS) for the in situ characterization of the chemical composition of the atmospheric aerosols. The HRMS approach will allow the detailed characterization of the extremely complex mixture of organic and inorganic species composing the secondary aerosols of biogenic and anthropogenic origin. The measurements of this type are of great interest for the studies related to the formation, evolution and properties of the atmospheric aerosols.

DESCRIPTION / PRINCIPLES / REALISATION / PERFORMANCE

The ORBAS is essentially a modification of the commercial mass spectrometer (ORBITRAPTM Exactive, Thermo) equipped with electrospray ion source for the laboratory analysis of liquid samples. The main modifications of the instrument are the following:

  1. Introduction of a new system for the automated filter collection of aerosols and programmable evaporation of the collected particles;
  2. Replacement of the electrospray by a chemical ionisation ion source;
  3. Replacement of the existing ion transfer system consisting of a heated capillary and an electrostatic ion optics by a double radio frequency ion guide (“ion funnel”);

Current state:

  • The concept, calculations, drawings, fabrication and assembling of the pumping system and of the ion guides are finished;
  • The interface comprising the air sampling, the pumping, chemical ionisation and the ion guides is presently under testing;
  • The aerosol sampling is presently under development;

Expected performance:

  • Quantitative characterization of the composition of organic aerosols: organic acids, aldehydes, ozonolysis products, …
  • Lower Limit of Detection (LDL): several pg / m3;
  • Time resolution of 5-10 minutes

Tests, Validation, application for the ground measurements:

  • Measurements with the environmental chamber of ICARE:
    • Analysis of the aerosol formed during the ozonolysis of different terpenes and isoprene;
    • Intercomparison with other available instruments, e.g., CIMS TOF of ICARE
  • Measurements in situ on the “super-site” of Orléans (validation, tests, field studies)
  • Field studies (participation in future field campaigns)