A novel method for determination of low molecular weight dicarboxylic acids in background atmospheric aerosol using ion chromatography |
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Authors: | Tsai Ying I Hsieh Li-Ying Weng Tzu-Hsiang Ma Yu-Chien Kuo Su-Ching |
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Institution: | a Department of Environmental Engineering and Science, Chia Nan University of Pharmacy and Science, 60, Sec. 1, Erh-Jen Road, Jen-Te, Tainan 717, Taiwan b Department of Chemistry, National Cheng Kung University, 1, University Road, Tainan 701, Taiwan c Department of Applied Chemistry, Chia Nan University of Pharmacy and Science, 60, Sec. 1, Erh-Jen Road, Jen-Te, Tainan 717, Taiwan |
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Abstract: | This paper describes a novel gradient elution ion chromatographic method using a Dionex AS11 system for the determination of low molecular weight dicarboxylic acids (low-Mw DCAs) in background atmospheric aerosol. Interference with the oxalic acid peak from sulfate in background PM2.5 aerosol, 15.8 times the oxalic acid concentration, was remedied by removing sulfate using a barium cartridge, whilst interference with the malonic acid peak from carbonate was reduced by using a carbonate removal device. An alternative remedy to sulfate interference was use of an AS14 system using isocratic eluent, and this produced good resolution of oxalic acid from a high sulfate peak. In both the AS11 and the AS14 system, linear correlation coefficients were at all times >0.9990 with excellent linear range, the recoveries ranged from 92.8 to 106%, with relative standard deviation of 3.67-6.30%, whilst method detection limits (MDLs) ranged from 0.36 μg L−1 for malic acid to 3.87 μg L−1 for maleic acid. These data indicate that the analytical methods developed herein produce excellent separation efficiency and good determination of low-Mw DCAs with satisfactory accuracy, recoveries, and MDLs. Samples left at room temperature (20 °C) for 300 min in a simulation of the ‘waiting time’ involved in the proposed IC analysis decayed to between 86% (oxalic acid) and 39% (succinic and malonic acids) of their original concentration, whilst at 4 °C concentrations remained at 96-101% of original, indicating that maintaining samples at a low temperature prior to injection into the IC analyzer is vital for obtaining accurate results when analyzing low-Mw DCAs. Oxalic acid was found to be the most prevalent low-Mw DCA in background aerosol, comprising 57% of the total low-Mw DCAs and 0.959% of the PM2.5 aerosol mass, followed by succinic acid and malonic acid. |
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Keywords: | Background aerosol Dicarboxylic acids Gradient elution Interference Effect of temperature |
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