Determination of atmospheric organosulfates using HILIC chromatography with MS detection
Measurements of organosulfates in ambient aerosols provide insight to the extent of secondary organic aerosol (SOA) formation from mixtures of biogenic gases and anthropogenic pollutants. Organosulfates have, however, proved analytically challenging to quantify, due to lack of authentic standards an...
| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2015-06-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | http://www.atmos-meas-tech.net/8/2347/2015/amt-8-2347-2015.pdf |
| Summary: | Measurements of organosulfates in ambient aerosols provide insight to the
extent of secondary organic aerosol (SOA) formation from mixtures of
biogenic gases and anthropogenic pollutants. Organosulfates have, however,
proved analytically challenging to quantify, due to lack of authentic
standards and the complex sample matrix in which organosulfates are
observed. This study presents a sensitive and accurate new analytical
method for the quantification of organosulfates based upon ultra-performance
liquid chromatography (UPLC) with negative electrospray ionization mass
spectrometry (MS) with the aid of synthesized organosulfate standards. The
separation is based upon hydrophilic interaction liquid chromatography
(HILIC) with an amide stationary phase that provides excellent retention of
carboxy-organosulfates and isoprene-derived organosulfates. The method
is validated using six model compounds: methyl sulfate, ethyl sulfate,
benzyl sulfate, hydroxyacetone sulfate, lactic acid sulfate and glycolic
acid sulfate. A straightforward protocol for synthesis of highly pure
organosulfate potassium salts for use as quantification standards is
presented. This method is used to evaluate the efficiency and precision of two
methods of ambient PM<sub>2.5</sub> sample extraction. Spike recoveries averaged
98 ± 8% for extraction by ultra-sonication and 98 ± 10%
for extraction by rotary shaking. Ultra-sonication was determined to be a
better method due to its higher precision compared to rotary shaking.
Analysis of ambient PM<sub>2.5</sub> samples collected on 10–11 July 2013 in
Centreville, AL, USA during the Southeast Atmosphere Study (SAS) confirms
the presence of hydroxyacetone sulfate in ambient aerosol for the first
time. Lactic acid sulfate was the most abundant compound measured (9.6–19 ng m<sup>−3</sup>),
followed by glycolic acid sulfate (8–14 ng m<sup>−3</sup>) and
hydroxyacetone sulfate (2.7–5.8 ng m<sup>−3</sup>). Trace amounts of methyl
sulfate were detected, while ethyl sulfate and benzyl sulfate were not. Application of this HILIC separation method to ambient aerosol
samples further demonstrates its utility in resolving additional biogenic organosulfates. |
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| ISSN: | 1867-1381 1867-8548 |