Detection of Organic Components in Atmospheric Aerosols

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Detection of Organic Components in Atmospheric Aerosols Atmospheric particles that can be natural or anthropogenic, are defined as a suspension of fine solid or liquid particles in air. They are either emitted or formed in the atmosphere and their particle sizes affect their transport and deposition. Their most important impacts, such as respiratory health hazards, visibility reduction, and climate effects are dependent upon the particle size that ranges from a few nanometers to a few hundred micrometers. Chemical composition of aerosol particles is generally determined by gas- and liquid-chromatographic techniques, mostly with mass spectrometric detection. Use of liquid chromatography (LC) has increased in atmospheric analysis due to the recently recognized importance of highly oxidized compounds in aerosol formation and growth, improved separation efficiency of the columns, and high-resolution mass spectrometric detection. Sampling and Sample Preparation Sample preparation techniques used for solid samples, such as extraction, clean-up, and concentration, are also suitable for aerosol samples, in general. The analysis mode (target, nontarget) and analysis technique determine the choice of sample preparation method. Liquid extraction, assisted with temperature, pressure, ultrasound, or microwaves, is frequently used (Table 1). Soxhlet extraction, which gives the best recoveries, is less used, because of long extraction time and high solvent consumption. Sonication, instead, is the most popular due to cheap instrumentation, low solvent consumption, and short extraction time. Concentrations of aerosol constituents are relatively low; thus samples are usually concentrated after extraction with nitrogen flow. Table 1. Examples of Sampling and Sample Preparation Methods for the Analysis of Different Compound Classes in Atmospheric Aerosols2 Compound Class Sampling Sample Preparation Analysis PAHs HVS (quartz), 24 h, 550 m3 Microwave (120°C, 900 V, 40 min, 20 mL CH2Cl2) HPLC (C18)-FLD Hydroxy-PAHs HVS (quartz), 24 h,