Sedimentation field-flow fractionation-inductively coupled plasma optical emission spectrometry: Size-based elemental speciation of air particulates

The applicability of sedimentation field-flow fractionation-inductively coupled plasma optical emission spectrometry (SdFFF-ICP-OES) was investigated for the elemental size characterization of air particulate matters less than 10 μm (PM₁₀). The effects of various dispersing agents and pH values on the dispersion stability of air particulates were examined by zeta potential measurement. Anionic surfactants, which were 0.1% FL-70® (a powerful alkaline detergent) and 0.1% sodium dodecyl sulfate (SDS), exhibited zeta potential values more negative than -30 mV, suggesting that both surfactants could efficiently disperse air particulates. A 0.1% FL-70 with pH 8 was chosen as both dispersing agent and carrier liquid. The developed SdFFF method provided satisfactory separation efficiency and reproducibility (<3% RSD). Broad size distributions were obtained for air particulate samples collected from five locations. Nonetheless, peak maxima and the distribution ranges of air particulates collected from one location were different from the others. Further, a hyphenated technique of SdFFF and ICP-OES was employed to study size-based elemental distribution of air particles. An ultrasonic nebulizer was used in order to increase sample transport efficiency and hence improve the sensitivity of ICP-OES detection. Aluminium, Fe, and Ti were detected across the whole size range of air particulate sample.