Thermally condensed humic acids onto silica as SPE for effective enrichment of glucocorticoids from environmental waters followed by HPLC-HESI-MS/MS. - Speltini, Andrea; Merlo, Francesca; Maraschi, Federica; Sturini, Michela; Contini, Matteo; Calisi, Nicola; Profumo, Antonella (Journal of Chromatography A, 2018)