Online differentiation of mineral phase in aerosol particles by ion formation mechanism using a LAAP-TOF single-particle mass spectrometer
Mineralogy of silicate mineral dust has a strong influence on climate and ecosystems due to variation in physiochemical properties that result from differences in composition and crystal structure (mineral phase). Traditional offline methods of analysing mineral phase are labour intensive and th...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2018-01-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | https://www.atmos-meas-tech.net/11/195/2018/amt-11-195-2018.pdf |
| Summary: | Mineralogy of silicate mineral dust has a strong influence on
climate and ecosystems due to variation in physiochemical
properties that result from differences in composition and crystal
structure (mineral phase). Traditional offline methods of analysing
mineral phase are labour intensive and the temporal resolution of
the data is much longer than many atmospheric processes. Single-particle mass spectrometry (SPMS) is an established technique for
the online size-resolved measurement of particle composition by
laser desorption ionisation (LDI) followed by time-of-flight mass
spectrometry (TOF-MS). Although non-quantitative, the technique is
able to identify the presence of silicate minerals in airborne dust
particles from markers of alkali metals and silicate molecular ions
in the mass spectra. However, the differentiation of mineral phase
in silicate particles by traditional mass spectral peak area
measurements is not possible. This is because instrument function
and matrix effects in the ionisation process result in variations in
instrument response that are greater than the differences in
composition between common mineral phases.</br></br>In this study, we introduce a novel technique that enables the
differentiation of mineral phase in silicate mineral particles by
ion formation mechanism measured from subtle changes in ion arrival
times at the TOF-MS detector. Using a combination of peak area and
peak centroid measurements, we show that the arrangement of the
interstitial alkali metals in the crystal structure, an important
property in silicate mineralogy, influences the ion arrival times of
elemental and molecular ion species in the negative ion mass
spectra. A classification scheme is presented that allowed for the
differentiation of illite–smectite, kaolinite and feldspar minerals
on a single-particle basis. Online analysis of mineral dust aerosol
generated from clay mineral standards produced mineral fractions
that are in agreement with bulk measurements reported by traditional
XRD (X-ray diffraction) analysis. |
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| ISSN: | 1867-1381 1867-8548 |