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In the last decades, there has been an increasing interest in the presence of amino acids in atmospheric aerosols, either free or in combination (e.g., proteinaceous compounds). The fact that these compounds play an important role in the chemistry and physics of air particles and atmosphere, in atmosphere/biosphere nutrient cycling, and have a direct impact in human health has encouraged further studies. The diversity in origin, type, and ambient concentrations of these amino compounds considerably complicates, thus indicating their environmental impact. Studies for the determination of amino acids in the atmosphere are extremely diverse, encompassing an array of different analytical methodologies; however, it is not possible to conduct a comparative study of these methods. In this critical review, we evaluate and compare the procedures involved in the analytical methods and studies developed thus far for the identification and quantification of amino acids in different ambient particle sizes and in different atmospheric environments (i.e., background/pristine, rural, and urban environments). [ABSTRACT FROM AUTHOR]

Methodology for detection of native (underivatized) amino acids (AA) in atmospheric aerosols has been developed. This article describes the use of LC-MS (Q-TOF) and microwave-assisted gas phase hydrolysis for detection of free and combined amino acids in aerosols collected in a Southeastern U.S. forest environment. Accurate mass detection and the addition of isotopically labeled surrogates prior to sample preparation allows for sensitive quantitation of target AA in a complex aerosol matrix. A total of 16 native AA were detected above the reporting threshold as water-soluble free AA, with an average concentration of 22 ± 9 ng m ( N = 13). Following microwave-assisted gas phase hydrolysis, the total AA concentration in the forest environment increased significantly (70 ± 35 ng m) and additional compounds (methionine, isoleucine) were detected above the reporting threshold. The ability to quantify AA in aerosol samples without derivatization reduces time-consuming preparation procedures while providing the advancement of selective mass determination for important organic nitrogen (ON) species. Details on sample preparation that eliminates the freeze-drying approach typically practiced for water removal with biological samples, and vapor phase microwave hydrolysis parameters are provided. Method application for determination of atmospheric ON is discussed. [ABSTRACT FROM AUTHOR]