title: Accurate quantification of PAHs in water in the presence of dissolved humic acids using isotope dilution mass spectrometry.
abstract: The effect of dissolved humic acids on the recovery of PAHs from water samples has been investigated using a commercially available humic acid preparation as colloid model and a mixture containing the 16 EPA PAHs. The presence of humic acid reduced the extraction efficiency down to between 10 and 75%. An analytical protocol was therefore developed for the accurate determination of PAHs in the presence of humic acids based on isotope dilution mass spectrometry. The procedure compensates for losses due to sorption of PAHs and can be used for the determination of the total PAH concentration in water, i.e. dissolved PAHs plus PAHs adsorbed on colloids. To obtain reliable estimates it is essential to allow a certain time for equilibration between the isotope spike and the aqueous matrix which may vary between 5 and 24 h, in correlation with the water solubility of PAHs. The protocol allows one to recover the 16 PAHs studied at 94 to 105%. The expanded uncertainty of the measurements was 5-7% for all PAHs. Liquid-liquid extraction and solid-phase extraction in combination with the developed isotope dilution protocol performed equally well for the quantification of PAHs from water samples rich in colloidal material.
authors.affiliation: European Commission, Joint Research Centre, Institute for Reference Materials and Measurements, IRMM, Retieseweg 111, 2440 Geel, Belgium. ofelia.bercaru@cec.eu.int
authors.forename: Ofelia
authors.initials: O
authors.lastname: Bercaru
authors.forename: Franz
authors.initials: F
authors.lastname: Ulberth
authors.forename: Hendrik
authors.initials: H
authors.lastname: Emons
authors.forename: Carlo
authors.initials: C
authors.lastname: Vandecasteele
mesh_terms: D000327:Adsorption; D003102:Colloids / Q000737:chemistry; D003903:Deuterium; D008401:Gas Chromatography-Mass Spectrometry / Q000295:instrumentation / Q000379:methods*; D006812:Humic Substances / Q000032:analysis; D007700:Kinetics; D011084:Polycyclic Aromatic Hydrocarbons / Q000032:analysis*; D012680:Sensitivity and Specificity; D013997:Time Factors; D014867:Water / Q000737:chemistry
chemical_list: D003102:Colloids; D006812:Humic Substances; D011084:Polycyclic Aromatic Hydrocarbons; D014867:Water; D003903:Deuterium