Accurate Quantification of PAHs in Water in the Presence of Humic Acid Colloids using Isotope Dilution Mass Spectrometry

The effect of colloids on the analytical recovery of PAHs from water samples has been investigated. The studies were performed using synthetic humic acid as colloid model and a mixture containing the 16 PAHs on the priority list of the US Environmental Protection Agency. The presence of humic acid reduced the extraction efficiency between 10 to 75 % confirming that hydrophobic compounds are strongly bound to colloidal organic material and the real content of the PAHs might be underestimated. Therefore an analytical protocol was developed for the accurate determination of PAHs in the presence of colloids 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 realistic estimates it is essential to allow a certain time for equilibration between the isotope spike and the aqueous matrix. This time may vary between 5 and 24 h and is correlated to the water solubility and hydrophobicity of PAHs. The achieved protocol allows to obtain recoveries ranging from 94 to 105 %. Expanded uncertainty of the measurement was between 5-7 % for all PAHs. A comparison between liquid extraction and solid phase extraction for extraction of PAHs from water samples rich in colloidal material showed that both extraction methods produced comparable results.

BERCARU Ofelia;  ULBERTH Franz;  EMONS Hendrik;  VANDECASTEELE C.; 

2006-03-31

SPRINGER

JRC30515

https://publications.jrc.ec.europa.eu/repository/handle/JRC30515,   

10.1007/s00216-005-0265-5,