Reversed-phase liquid chromatographic characterization and analysis of air particulates humic (-like) substances in presence of pollens

Newly developed method for characterisation and analysis of humic substances (HS) and humic-like substances (HULIS) in air dust particles was tested for potential interferences caused by abundant co-sampled pollens (common dandelion, common wormwood-absinth, apple tree). RP-HPLC using 10-step gradient of dimethylformamide (DMF) in a buffered aqueous mobile phase and a wide-pore (30 nm) octadecylsilica column has been applied to the analysis of HS and HULIS using tandem of spectrophotometric (DAD) and fluorimetric detection (FLD). Achieved results suggest that the devised method is reliable for characterisation, fractionation and analysis of terrestrial HS, air dust HS and air particulate HULIS in liquid extracts at a trace concentration levels. Fluorimetric detection (ex. 470 nm/em. 530 nm; LOD, 3.1 μg/ml) enables sensitive, highly selective and interference free determination of HS and HULIS regardless the presence of pollen constituents, whereas spectrophotometric detection is susceptible to interferences in UV region above 260 nm. However, even in this case, the interfering substances can be revealed by both different pattern and shape of their peaks, as well as by spectral features different from HS or HULIS. Analytical procedure based on air sampling, extraction and above-mentioned HPLC method enables characterisation and analysis of HS and/or HULIS at relative concentration levels down to 0.1% (m/m) in 10 mg mass scale of sampled air dust and particulate material.