Phuket mar. biol. Cent. Res. Bull.76: 101–110 (2019) DETERMINATION OF POLYCYCLIC AROMATIC HYDROCARBON METABOLITES (1-HYDROXYPYRENE AND 2-NAPHTHOL) BY GAS CHROMATOGRAPHY-TANDEM MASS SPECTROMETRY IN SOME ROCKY SHORE MOLLUSCS CONTAMINATED WITH CRUDE OIL Jindarha Prempramote and Monthon Ganmanee* Faculty of Agricultural Technology, King Mongkut’s Institute of Technology Ladkrabang, Bangkok 10520 Thailand *Corresponding author: monthon.ga@kmitl.ac.th ABSTRACT: After an oil spill accident occurred along the coast of Rayong Province, Thailand in July, 2013, we investigated the efect of crude oil and polycyclic aromatic hydrocarbons (PAHs) on intertidal rocky shore molluscs in Ao Prao (Prao Bay), Samed Island. Gas chromatography-tandem mass spectrom- etry (GC-MS/MS) was used to determine 1-hydroxypyrene (1-HOP) and 2-naphthol (2-NAP) concentra- tions in three intertidal rocky molluscs; whelk (Morula musiva), coil snail (Planaxis sulcatus) and rock oyster (Saccostrea cucullata). We used those metabolites as biomarkers to identify molluscs con- taminated by petroleum hydrocarbons. Samples were collected 5 times during August 2013 to May 2015. Results showed that 1-HOP and 2-NAP were detected in the mean concentration range of 0.039–1.421 and 0.001–0.403 ng/g wet weight, respectively. 1-HOP concentrations in an intertidal rocky shore predator, whelk (M. musiva), were highest among all species probably due to its feeding behaviours. Metabolite concentra- tions in all molluscs decreased over time. In conclusion, 1-HOP is a suitable biomarker in intertidal rocky shore molluscs contaminated with petroleum hydrocarbon, and GC-MS/MS is an efective equipment to detect these metabolites. Keyword: 1-HOP, 2-NAP, bioaccumulation, biomarkers, GC-MS/MS, trophic chain INTRODUCTION PAHs are a class of high molecular weight organic compounds and compose of multiple carbon aromatic rings (Ma et al., 2010). Coastal marine environments can be contaminated by these compounds during incomplete combustion of fossil fuels in the atmosphere or by oil spills in the seawater (Pereira et al., 1999). These substances are readily assimilated by marine organisms through the skin, gills or gastro-intestinal tract and, they are bioaccumulated in organism’s fatty tissues causing severe illness, abnormalities or death (Connell, 1988; Fux et al., 2007). After entering the animal body, PAHs undergo a series of biotransformation processes. They are rapidly transformed into more hydrophilic metabolites that are excreted; thus, marine organisms exposed to these compounds show only trace amounts of PAHs in their tissues (Varanasi et al., 1991; Baumard et al., 1999). Pyrene and naphthalene are major constituents of PAHs, and both are listed as hazardous substances by the USEPA (Pengchai et al., 2009). Pyrene is metabolized to 1-hydroxypyrene (1-HOP), and naphthalene is metabolized to 2-naphthol (2-NAP); these specifc compounds alter the metabolism process of marine organisms (Shin et al., 2011). Measurements of 1-HOP and 2-NAP in excretory products of animals have gained considerable attention as a potential biomarker for PAHs exposure. This method has been widely used as a biomarker to study PAHs exposure in biota (Jongeneelen, 2001; Lim and Shin, 2013). Biomarker studies using l-hydroxypyrene have previously been reported with liquid matrices such as fsh bile, blood and urine (Schaller et al ., 1993; Lin et al., 1994). However, this approach cannot be utilized when dealing with small tissue samples from marine benthic invertebrates (Chaisuksant et al., 1999; McElroy et al., 2000). The presence of this petroleum hydrocarbon can be detected using the gas chromatography-mass spectrometry (GC-MS). As part of this techniques, the gas chromatography- tandem mass spectrometry analysis (GC-MS/MS)