Breakthrough Method Enables Comprehensive Analysis of Secondary Formation Markers in Ambient Organic Aerosols

Scientists at the University of Iasi in Romania have developed a groundbreaking method for the accurate analysis of secondary formation markers in ambient organic aerosols. By utilizing high performance liquid chromatography coupled with dual orthogonal electrospray ionization time-of-flight mass spectrometry (HPLC–ESI-TOF-MS), the researchers achieved significant advancements in the quantitative determination of pinene markers, biomass-burning related phenols, and other relevant carboxylic acids present in atmospheric aerosol samples. Through systematic experiments targeting the optimization of chromatographic separation, ionization source, and mass spectrometer performance, the team obtained valuable insights into the composition and concentration of these organic compounds.

Spray stream from aerosol can on black background | Image Credit: © Soho A studio - stock.adobe.com

HPLC–ESI-TOF-MS is an advanced analytical technique used for the separation, identification, and quantification of complex mixtures of organic compounds. In this technique, liquid chromatography is employed to separate the individual components of a sample, and the eluted compounds are then introduced into the mass spectrometer through electrospray ionization. The ionized molecules are accelerated in an electric field and subsequently detected based on their time-of-flight, which is determined by their mass-to-charge ratio (m/z). HPLC–ESI-TOF-MS offers high sensitivity, resolution, and mass accuracy, making it a powerful tool for the analysis of a wide range of compounds in various fields including environmental, pharmaceutical, and biomedical research. This technique enables researchers to gain detailed information about the composition and structure of complex samples, facilitating the identification and characterization of target analytes.

The study involved testing various analytical columns, with the researchers identifying the Poroshell 120 EC—C18 column (4.6 × 50 mm, 2.7 µm) thermostated at 35 °C as the most effective in separating the compounds of interest. They employed a gradient elution mode using 0.1% acetic acid in water and acetonitrile at a flow rate of 0.8 mL min-1. Additionally, optimal operational conditions for the ESI-TOF-MS instrument were determined, including a drying gas temperature of 350 °C, a drying gas flow rate of 13 L min-1, a nebulizer pressure of 60 psig, and specific voltage settings for the ion transfer capillary, skimmer, and fragmentor: 3000V, 60V, and 150V, respectively.

The developed method exhibited remarkable sensitivity, with method quantification limits ranging from 0.88 to 48.0 μg L-1 (3.67–200 pg m-3 when considering a sampled air volume of 120 m3). This level of sensitivity enables the reliable quantification of the targeted compounds in real atmospheric aerosol samples. Furthermore, the accuracy in molecular mass determination, with a deviation of less than 5 ppm, and the acquisition of data in full scan mode provided additional insights into the organic constituents present in atmospheric aerosols.

This groundbreaking analysis technique has the potential to significantly enhance our understanding of secondary formation markers in ambient organic aerosols. By accurately quantifying and characterizing these compounds, scientists can gain valuable insights into the sources, transformation, and impact of organic aerosols on air quality and human health. The findings of this study, published in the Journal of Chromatography A, open new avenues for atmospheric research and contribute to the broader understanding of environmental chemistry (1).

Reference

(1) Amarandei, C.; Olariu, R. I.; Arsene, C. Offline analysis of secondary formation markers in ambient organic aerosols by liquid chromatography coupled with time-of-flight mass spectrometry. J. Chromatogr. A 2023, 1702, 464092. DOI: https://doi.org/10.1016/j.chroma.2023.464092