Identification of Weak and Strong Organic Acids in Atmospheric Aerosols by Capillary Electrophoresis/Mass Spectrometry and Ultra-High-Resolution Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

Abstract

A novel approach using a combination of capillary electrophoresis/mass spectrometry (CE/MS) and off-line Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) revealed the structural details of acidic constituents of atmospheric organic aerosol. Both techniques utilized electrospray ionization (ESI), a soft ionization method, to facilitate the analysis of complex mixtures of organic compounds. CE/ESI-MS using an UltraTrol LN-precoated capillary and acidic background electrolytes at different pH values (2.5 and 4.7) was used to differentiate between weak (carboxylic) and strong (sulfonic) organic acids. On the basis of the electrophoretic mobility, m/z constraints from CE/ESI(−)-MS, and elemental composition information retrieved from off-line FTICR-MS, a variety of aliphatic and aromatic carboxylic acids (CHO-bearing molecules), nitrogen-containing carboxylic acids (CHON-bearing molecules), organosulfates (CHOS-bearing molecules), and (nitrooxy)organosulfates (CHONS-bearing molecules) were tentatively identified in the Oasis-HLB-extracted urban PM 2.5 (particulate matter with an aerodynamic diameter of <2.5 μm). The chemical known/unknown structures of detected compounds were confirmed by the semiempirical Offord model (effective mobility linearly correlated to Z/M 2/3 ). The majorities of the identified compounds are products of atmospheric reactions and are known contributors to secondary organic aerosols.

Quantification of Fumarate and Investigation of Endogenous and Exogenous Fumarate Stability in Rat Plasma by LC–MS/MS

“…To investigate isotope effects, a comparison of the respective P/R ratio was conducted by spiking fumaric acid and 13 C 4 -fumaric acid into rat plasma. Fumaric acid, after subtraction of the endogenous level, showed an 80% decrease in 1 h, similar to that observed for 13 Table 3). The results suggest that there are no isotope effects while using 13 C 4 -fumaric acid for the stability evaluation (p < 0.01).…”

“…Furthermore, fumaric acid/fumarate is highly polar, and not retained well on a reversephase column. Other analytical methods for fumarate include GC and CE coupled to MS [12,13]. GC enables the separation and retention of hydrophilic compounds but requires derivatization to improve volatility, therefore complicating sample preparation.…”

“…CE works well for the analysis of charged and polar analytes without the need of derivatization. Nevertheless, it suffers from poor sensitivity and is generally not rugged for highthroughput bioanalysis [13]. Here we report a rapid, sensitive and high-throughput LC-MS/MS method for the quantitative measurement of fumarate in rat plasma using a reverse phase column, generic mobile phases and simple sample preparation procedures.…”

Sources of humic-like substances in the Pearl River Delta, China: positive matrix factorization analysis of PM&lt;sup&gt;2.5&lt;/sup&gt; major components and source markers

“…One study also reported that HULIS could have a marine source (Cavalli et al, 2004). The molecular composition of HULIS was also studied using ultrahigh resolution mass spectrometer (e.g., Wozniak et al, 2008;Lin et al, 2012a, b;Yassine et al, 2012). Through composition study, it was confirmed that biomass burning and secondary formation process were sources of HULIS (Lin et al, 2012a).…”

Structural characterization of organic aerosol using Fourier transform ion cyclotron resonance mass spectrometry: Aromaticity equivalent approach

“…This high degree of chemical complexity of atmospheric organics has inspired a number of sophisticated approaches that are capable of identifying and detecting a variety of different analytes in OA . Among them, ultrahigh‐resolution Fourier transform ion cyclotron mass spectrometry (FTICRMS) involving electrospray ionization has contributed substantially to organic aerosol research . The ultrahigh resolution (over 400 000 at nominal mass of 400) and high mass accuracy (less than 200 ppb) achieved by FTICRMS allow for assignment of a unique elemental composition, and enable the calculation of molecular formulae for these species .…”