Quality assurance and quality control of atmospheric organosulfates measured using hydrophilic interaction liquid chromatography (HILIC)

Abstract. As a crucial constituent of fine particulate matter (PM_2.5), secondary organic aerosols (SOA) influence public health, regional air quality, and global climate patterns. This paper highlights the use of Hydrophilic interaction liquid chromatography (HILIC) which effectively retains strongly polar analytes that might exhibit incomplete or no retention in reverse chromatography, resulting in superior separation efficiency.

A HILIC column was used to analyze 7 standards, environmental standards (1648a and 1649b), and samples collected in urban environments in the Pearl River Delta region of Guangzhou. That serve as valuable reference points for evaluating the organic composition of the atmospheric environment. The results indicate a high degree of accuracy in the analytical method, sodium octyl-d₁₇ sulfate serves as the internal standard, with a linear correlation coefficient of the 7 standards, boasting a linear correlation coefficient R ranging from 0.987–0.999 and a slope, k, of the linear equation from 0.9662–2.2927. The instrument detection limit (IDLs) is established at 0.0026–0.0300 μg mL^-1, while the method detection limit (MDLs) falls within the range of 0.0077–0.2300 ng m^-3, demonstrating the method's exceptional sensitivity.

Since isoprene sulphates are highly polar due to containing a hydrophilic bond to the hydroxyl group and a hydrophobic bond to the sulphate, and as such showed strong retention using this method. This technique employs Sodium ethyl sulfate and Sodium octyl sulfate standards for semi-quantitative compound analysis isoprene-derived OSs, the error in sample analysis (EA) ranged from 12.25–95.26 % and the two standards maintaining a consistent recovery rate between 116 %–131 % and 86 %–127 %. These findings indicate a high level of precision when semi-quantifying compounds with similar structural characteristics, affirming the analysis method's minimal relative error and underscoring its repeatability, process stability, and the reliability of its results for isoprene OSs. To enhance the method's reliability assessment, the study analyzed polar organic components of standard particulate matter samples (1648a and 1649b), providing precise determinations of several isoprene OSs using this method. Methyltetrol sulfate (m/z 215) is the highest concentration in the ambient samples, up to 67.33 ng m^-3 at daytime. These results serve as valuable reference points for assessing the organic composition of the atmospheric environment.