A novel method for determination of low molecular weight dicarboxylic acids in background atmospheric aerosol using ion chromatography

• Published in: Analytica chimica acta 2008-09, Vol.626 (1), p.78-88
• Main Authors: Tsai, Ying I., Hsieh, Li-Ying, Weng, Tzu-Hsiang, Ma, Yu-Chien, Kuo, Su-Ching
• Format: Article
• Language: English
• Subjects: Aerosols - chemistry; Analytical chemistry; Atmosphere - chemistry; Background aerosol; Carbonates - chemistry; Chemistry; Chromatographic methods and physical methods associated with chromatography; Chromatography - methods; Dicarboxylic acids; Dicarboxylic Acids - analysis; Dicarboxylic Acids - chemistry; Effect of temperature; Exact sciences and technology; Gradient elution; Injections; Interference; Linear Models; Molecular Weight; Other chromatographic methods; Reproducibility of Results; Sensitivity and Specificity; Sulfates - chemistry; Temperature
• ISSN: 0003-2670; 1873-4324
• DOI: 10.1016/j.aca.2008.07.041

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- M w DCAs) in background atmospheric aerosol. Interference with the oxalic acid peak from sulfate in background PM 2.5 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- M w 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- M w DCAs. Oxalic acid was found to be the most prevalent low- M w DCA in background aerosol, comprising 57% of the total low- M w DCAs and 0.959% of the PM 2.5 aerosol mass, followed by succinic acid and malonic acid.