Analysis of particulate matter (PM) by TOCA-PIMS
Thermo-optical carbon analysis (TOCA) is a standard method for characterizing fine particulate matter. Particulate matter collected on quartz fiber filters is subjected to a specific temperature program, whereby organic matter is desorbed and pyrolyzed into four thermal fractions in an inert helium atmosphere. The resulting compounds are oxidized to CO2 using a manganese dioxide catalyst. The carbon dioxide formed is catalytically reduced to methane, which is quantified using a flame ionization detector (FID). The carbon that can be detected in the first four fractions is referred to as organic carbon (OC), while the carbon that can only be detected in a He/O2 atmosphere is referred to as elemental carbon (EC).
The project addresses modifications to the TOCA instrument whereby a small portion of the desorbed gas stream is passed into a photoionization time-of-flight mass spectrometer (PIMS) prior to the oxidation unit. The resulting compounds are gently ionized and detected in real time by a time-of-flight mass spectrometer, providing insight into the molecular chemistry of the various carbonaceous fractions. Other modifications include a seven-wavelength laser to determine the absorption characteristics of PM samples and a quadrupole mass analyzer to extend elemental analyses.
Analysis of particulate matter (PM) by TOCA-PIMS
Thermo-optical carbon analysis (TOCA) is a standard method for characterizing fine particulate matter. Particulate matter collected on quartz fiber filters is subjected to a specific temperature program, whereby organic matter is desorbed and pyrolyzed into four thermal fractions in an inert helium atmosphere. The resulting compounds are oxidized to CO2 using a manganese dioxide catalyst. The carbon dioxide formed is catalytically reduced to methane, which is quantified using a flame ionization detector (FID). The carbon that can be detected in the first four fractions is referred to as organic carbon (OC), while the carbon that can only be detected in a He/O2 atmosphere is referred to as elemental carbon (EC).
The project addresses modifications to the TOCA instrument whereby a small portion of the desorbed gas stream is passed into a photoionization time-of-flight mass spectrometer (PIMS) prior to the oxidation unit. The resulting compounds are gently ionized and detected in real time by a time-of-flight mass spectrometer, providing insight into the molecular chemistry of the various carbonaceous fractions. Other modifications include a seven-wavelength laser to determine the absorption characteristics of PM samples and a quadrupole mass analyzer to extend elemental analyses.