Optimization of aqueous acetylation for determination of hydroxy polycyclic aromatic hydrocarbons in water by stir bar sorptive extraction and thermal desorption-gas chromatography-mass spectrometry

Stir bar sorptive extraction (SBSE) using a 10 mm-long stir bar coated with 24 mu l of polydimethylsiloxane (PDMS) in combination with the thermal desorption technique and gas chromatography-mass spectrometry was used for determining hydroxy polycyclic aromatic hydrocarbons (OH-PAHs), particularly mono and diOH-PAHs having two- to four-ring structures, in water samples. To improve the recovery for OH-PAHs, in situ derivatization with acetic anhydride was applied prior to SB SE. The optimal conditions for a 10 ml water sample were attained with the addition of 100 mg of sodium hydrogen carbonate, followed by the addition of 20 mu l of acetic anhydride and extraction for 360 min. In the selected ion monitoring (SIM) mode, the limits of detection were found to range from 0.27 ng l(-1) for 2-hydroxynaphthalene (as 2-hydroxynaphthalene acetate) to 25 ng l(-1) for 1,4-dihydroxynaphthalene (as 1,4-naphthoquinone) (S/N = 3). The low total recovery (< 50%) of the entire procedure was mainly due to the low extraction efficiency of acetyl derivatives from water to PDMS, while the in situ derivatization step achieved more than 88% efficiency. Nine OH-PAHs, such as 1,4-naphthoquinone, 2-hydroxynaphthalene, 2,3-dihydroxynaphthalene, 1,5-dihydroxynaphthalene, 1,3-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 2,6-dihydroxynaphthalene, 2,7-dihydroxynaphthalene, and 9-hydroxyphenanthrene, were detected in environmental samples under the optimal conditions. The detection of OH-PAHs in environmental water samples has not been reported so far. (c) 2004 Elsevier B.V. All rights reserved.