Ion chromatographic separation and quantitation of alkyl methylamines and ethylamines in atmospheric gas and particulate matter using preconcentration and suppressed conductivity detection

Two methods based on ion chromatography (IC) were developed for the detection of methyl and ethyl alkyl amines (methylamine (MA), ethylamine (EA), dimethylamine (DMA), diethylamine (DEA), trimethylamine (TMA) and triethylamine (TEA)) and NH3/NH4+ in online atmospheric gas-particle and size-resolved particulate samples. The two IC methods were developed to analyze samples collected with an ambient ion monitor (AIM), an online gas-particle collection system, or with a Micro Orifice Uniform Deposit Impactor (MOUDI) for size-resolved particle samples. These methods enable selective and (semi-) quantitative detection of alkyl amines at ambient atmospheric concentrations (pptv and pg m−3) in samples where significant interferences can be expected from Na+ and NH4+, for example marine and rural air masses. Sample pre-concentration using a trace cation column enabled instrumental detection limits on the order of pmol (sub-ng) levels per sample, an improvement of up to 102 over current IC methods. Separation was achieved using a methanesulfonic acid gradient elution on Dionex CS12A and CS17 columns. The relative standard deviations in retention times during 3 weeks continuous (hourly) sampling campaigns ranged from 0.1 to 0.5% and 0.2 to 5% for the CS12A and CS17 across a wide dynamic range of atmospheric concentrations. Resolution of inorganic and organic cations is limited to 25 min for online samples. Mass-dependent coelution of NH4+/MA/EA occurred on the CS12A column and DEA/TMA coeluted on both columns. Calibrations of ammonium show a non-linear response across the entire calibration range while all other analytes exhibit high linearity (R2 = 0.984–0.999), except for EA and TEA on the CS12A (R2 = 0.960 and 0.941, respectively). Both methods have high analytical accuracy for the nitrogenous bases ranging from 9.5 to 20% for NH3 and <5–15% for the amines. Hourly observations of amines at Egbert, ON in October 2010 showed gaseous DMA and TMA + DEA at 1–10 pptv in air, while particulate DMA and TMA + DEA were present at 0.5–4 ng m−3. A size-resolved particulate sample collected over 23 h was found to contain DMA, TMA + DEA and MEA at 1.78, 8.15 and 0.03 ng m−3 mass loadings, with the amine mass enhanced in particle sizes between 100 and 1000 nm. These results highlight a need for very sensitive and selective detection of methyl and ethyl amines in addition to NH3 in continuous online monitoring strategies.

► Two quantitative IC separation methods developed for alkyl methyl and ethyl amines.
► Use of preconcentration improved LOD by up to a factor of 100 over recent reports.
► LOD of amines were on the order of picomoles and picograms per sample.
► Successful interface with AIM in online (hourly) and MOUDI in offline applications.
► Atmospheric composition of amines at the ng/m3 and pptv levels measured.