Determination of Methylamines and Methylamine- N -oxides in Particulate Matter Using Solid Phase Extraction Coupled with Ion Chromatography

Abstract

Abstract Currently, the concentrations of methylamines in fine particulate matter (PM) are most often measured by aerosol time-of-flight mass spectrometry. A novel method for identification and determination of methylamines and methylamine-N-oxides in fine particles based on solid phase extraction (SPE) coupled with ion chromatography (IC) was developed. The experimental conditions including SPE conditions and chromatographic conditions were optimized. The quartz filter loaded with particulate matter (PM) samples was ultrasonically extracted with 20 mL of methanol and water (1:3, V/V) and the extraction process was repeated twice. After extraction, a total of 60 mL of extraction solvent was dropped into the extraction equipment for SPE. The Agilent AccuBond C18 was chosen for enriching the methylamine, dimethylamine, trimethylamine and trimethylamine-N-oxide in fine particles. Under the optimum conditions, the target species on Agilent AccuBond C18 were washed by 0.5 mL of acetonitrile solution and then concentrated (2 mL) before injecting into IC for analysis. A PRP X-200 (250 mm × 4 mm i.d.) was used for separation of analytes at 25 °C. The mobile phase was a mixture of 3% (V/V) acetonitrile solution and 5 mM nitric acid with the flow rate of 1 mL min–1. The four aliphatic amine species were fully resolved and completely separated within 30 min. The linearity of the four compounds ranged from 0.45 μg kg–1 to 1000 μg kg–1 with precisions of 2%–4% and detection limits of 0.002–0.003 μg m–3. The recoveries of the four aliphatic amine species in real PM samples were higher than 90%. This method was successfully applied in the analysis of real fine PM samples collected in Beijing. The concentrations of trimethylamine and methylamine-N-oxides were in the range of (0.01 ± 0.001) μg m–3–(0.08 ± 0.002) μg m–3 and (0.05 ± 0.001) μg m–3–(0.14 ± 0.002) μg m–3 for Beijing dust and haze PM samples, respectively.