Monitoring dihydrodiol polyaromatic hydrocarbon metabolites produced by the freshwater microalgae Selenastrum capricornutum Fernando Jos  e Hern  andez Blanco, Martha Patricia García de Llasera * Facultad de Química, Departamento de Química Analítica, Universidad Nacional Aut onoma de M exico, Ciudad Universitaria, M exico. D. F., 04510, Mexico highlights graphical abstract  PAH metabolites produced by Sele- nastrum capricornutum were monitored.  Metabolite identities were confirmed using HPLC-MS.  The metabolites were quantified in liquid medium and biomass at different times.  Benzo(a)pyrene and benzo(a)anthra- cene metabolites were in greater quantity.  Benzo(b)fluoranthene and benzo(k) fluoranthene metabolites were identified. article info Article history: Received 26 January 2016 Received in revised form 5 May 2016 Accepted 22 May 2016 Handling Editor: Caroline Gaus Keywords: PAHs biodegradation Selenastrum capricornutum Dihydrodiol metabolites HPLC-FD abstract We found that microalgae exposed to a mixture of polycyclic aromatic hydrocarbons (PAHs) did not show growth inhibition. Thus, we assumed that they could metabolize these compounds. In this study, the dihydrodiol-type PAH metabolites of benzo(a)pyrene (BaP), benzo(a)anthracene (BaA), benzo(b)fluo- ranthene (BbF) and benzo(k)fluoranthene (BkF) produced by the freshwater microalgae Selenastrum capricornutum were monitored and quantified using high-performance liquid chromatography with fluorescence detection (HPLC-FD) techniques. Exposure bioassays with S. capricornutum were performed using a 266 ng mL 1 mixture of PAHs at different exposure times (0.75, 1, 3, 8, 16, 24 and 48 h) under controlled temperature (25  C); the dihydrodiol metabolites formed in the liquid medium and the biomass were quantified. Metabolite identities were confirmed using HPLC-mass spectrometry; most of the metabolites formed were derived from BaA degradation. At 48 h after exposure 5,6-dBaA and 8,9- dBaA/10,11-dBaA were present in the liquid medium at 20% and 67% of the initial mass of BaA, respectively. Three metabolites of BaP were monitored in the liquid medium and biomass and, at 24 h, 4,5-dBaP accounted for 19%; , 7,8-dBaP, 5%; and 9,10-dBaP, 5% relative to the initial BaP mass. Microalgae exposed to BbF showed the presence of 1,2-dBbFand 9,10-dBbF (at 0.3% and 0.1% of the initial BbF mass, respectively) and those exposed to BkF produced 8,9-dBkF (6.5% of the initial BkF mass) in the liquid medium. Seven unknown compounds were formed after exposure; two compounds were identified as Abbreviations: PAH, polyaromatic hydrocarbon; BaP, benzo(a)pyrene; BaA, benzo(a)anthracene; BbF, benzo(b)fluoranthene; BkF, benzo(k)fluoranthene; BghiP, benzo(g,h,i)perylene; Phe, phenanthrene; Flu, fluoranthene; Ant, anthracene; Pyr, pyrene; DBA, dibenzo(a,h)anthracene; IP, indeno(1,2,3-c,d)pyrene; HPLC-FD, high- performance liquid chromatography with fluorescence detection; USEPA, United States Environmental Protection Agency; ESI, electrospray ionization source; SPE, solid phase extraction; MSPD, matrix solid phase dispersion. * Corresponding author. E-mail address: pgcllas@unam.mx (M.P. García de Llasera). Contents lists available at ScienceDirect Chemosphere journal homepage: www.elsevier.com/locate/chemosphere http://dx.doi.org/10.1016/j.chemosphere.2016.05.065 0045-6535/© 2016 Elsevier Ltd. All rights reserved. Chemosphere 158 (2016) 80e90