Determination of atmospheric organosulfates using HILIC chromatography with MS detection

Abstract

Abstract. 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 PM2.5 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 PM2.5 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−3), followed by glycolic acid sulfate (8–14 ng m−3) and hydroxyacetone sulfate (2.7–5.8 ng m−3). 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.

Inconsistency of ammonium–sulfate aerosol ratios with thermodynamic models in the eastern US: a possible role of organic aerosol

“…There thus remains a difficulty in reconciling their simultaneous observations of significant gas-phase ammonia (indicating ammonia in excess) and low values of R (indicating ammonia in deficit). A low value of R could be explained if alkaline cations other than ammonium contributed to sulfate neutralization, or if part of S(VI) was in the form of organosulfates; however, observations in the Southeast show that neither of these effects is significant (Budisulistiorini et al, 2015;Hettiyadura et al, 2015;Kim et al, 2015;Rattanavaraha et al, 2016). The chemical composition of individual sulfate particles may deviate from the bulk, but it is not clear how such inhomogeneity could explain the observed departure from simple thermodynamics.…”

Organosulfates in atmospheric aerosol: synthesis and quantitative analysis of PM<sub>2.5</sub> from Xi'an, northwestern China

“…Staudt et al (2014) quantified benzyl sulfate ranging from 4 to 90 pg m −3 in PM 2.5 samples from Lahore (Pakistan), Godavari (Nepal), and Pasadena (California), while methylbenzyl sulfates, phenyl sulfate, and methylphenyl sulfates were observed intermittently in these three locations. Furthermore, Hettiyadura et al (2015) developed a hydrophilic interaction liquid chromatography method using an amide stationary phase providing excellent retention of carboxy-organosulfates and isoprene-derived organosulfates, which was validated using six model organosulfates including aliphatic and aromatic organosulfates.…”

“…In this study, nine organosulfate standards (phenyl sulfate, 3-methylphenyl sulfate, benzyl sulfate, 2-methyl benzyl sulfate, 3-methyl benzyl sulfate, 2, 4-dimethyl benzyl sulfate, 3, 5-dimethyl benzyl sulfate, hydroxyacetone sulfate and glycolic acid sulfate) were synthesized using an approach modified from Staudt et al (2014) and Hettiyadura et al (2015). These authentic standards were used to optimize an ultra performance liquid chromatography electrospray ionizationtandem mass spectrometric method (UPLC-ESI-MS/MS) for the quantification of organosulfates.…”

“…General scheme for the synthesis of organosulfate, modified from Staudt et al (2014) and Hettiyadura et al (2015).…”

Online gas and particle phase measurements of organosulfates, organosulfonates and nitrooxyorganosulfates in Beijing utilizing a FIGAERO ToF-CIMS

“…Hansen et al, 2014). Mechanistic studies reveal multiple possible pathways for OS formation, which depend on availability of reactants in the atmosphere (Hettiyadura et al, 2015), increasing the complexity of understanding their occurrence and abundance within models. Measurements of 10…”