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.

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Structural formula of the "Janus-faced" THM 3,5-diiodo-L-thyronine (left), which has the same 3,5-iodine substitution pattern as its putative precursors L-T4 and L-T3 at the tyrosyl-ring, but lacks the iodine substitution in 3 ′-position of the phenolic ring which is essential for binding classical T3-receptors and conveying canonical and non-canonical thyromimetic effects. The roman god Janus symbolized "duality" and "jani" were ceremonial gateways in ancient Rome typically used for symbolically auspicious entrances or exits. Janus-face (right) source: This image comes from the 4th edition of Meyers Konversationslexikon (1885-90). The copyrights have expired and this image is in the public domain. Wikimedia, Meyers_b9_s0153_b1.png. HYPOTHESES AND THEORY a. 3,5-T2 is an endogenous metabolite of thyroid hormones T4 and T3 b. 3,5-T2 might represent the precursor of 3-iodothyronamine c. 3,5-T2 acts like T3 via canonical activation of T3 receptors albeit with lower potency d. 3,5-T2 exerts actions distinct from those of thyromimetically active T3 i) via mitochondrial targets ii) by its intrahepatic accumulation iii) by its intracrine mode of action e. 3,5-T2 formation and action might be altered in patients on T4 replacement therapy and causes adverse effects if abused.