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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]

Abstract: A liquid chromatography–tandem mass spectrometry analytical procedure has been developed for the detection and quantitative determination of underivatized amino acids at low concentrations in a Standard Reference Material—urban dust. In order to minimize interferences of other compounds, an accelerated solvent extraction followed by a solid phase extraction on two different cartridges was applied prior to LC–MS–MS. Fourteen amino acids were separated by high resolution liquid chromatography, detected and quantified by multiple reaction monitoring on a triple quadrupole. The proposed methodology has been applied for the first time on Standard Reference Material 1649a (urban dust) from the National Institute of Standards and Technology, that does not report certification values for these compounds. This methodology avoids the derivatization step and allows the amino acid quantification in a complex matrix, such as that of atmospheric particulate matter, and represent a good method suitable to analyze this class of compounds in atmospheric aerosol. The selected strategy demonstrated to be fit-for-purpose, by applying it to a real atmospheric sample with the aim to verify the efficacy of the study and to provide information about the organic matter content. [Copyright &y& Elsevier]

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]