Evaluation of the measurement of Cu(II) bioavailability in complex aqueous media using a hollow-fiber supported liquid membrane device (HFSLM) and two microalgae species (Pseudokirchneriella subcapitata and Scenedesmus acutus) Erik A. Rodríguez-Morales, Eduardo Rodríguez de San Miguel * , Josefina de Gyves Departamento de Química Analítica, Facultad de Química, Universidad Nacional Aut onoma de Mexico, Ciudad Universitaria, 04510 Mexico, D.F., Mexico article info Article history: Received 12 June 2015 Received in revised form 5 August 2015 Accepted 9 August 2015 Available online xxx Keywords: Bioavailability Copper Chemical surrogate Hollow fiber Microalgae abstract The environmental bioavailability of copper was determined using a hollow-fiber supported liquid membrane (HFSLM) device as a chemical surrogate and two microalgae species (Scenedesmus acutus and Pseudokirchneriella subcapitata). Several experimental conditions were studied: pH, the presence of organic matter, inorganic anions, and concomitant cations. The results indicated a strong relationship between the response given by the HFSLM and the microalgae species with free copper concentrations measured by an ion selective electrode (ISE), in accordance with the free-ion activity model (FIAM). A significant positive correlation was evident when comparing the bioavailability results measured by the HFSLM and the S. acutus microalga species, showing that the synthetic device may emulate biological uptake and, consequently, be used as a chemical test for bioavailability measurements using this alga as a biological reference. © 2015 Elsevier Ltd. All rights reserved. 1. Introduction Currently, the study of metal ion bioavailability in natural sys- tems is important for the determination of water quality because the concept focuses specifically on the amount of metal that is capable of crossing biological membranes and not on the total amount of metal in the medium (McGeer et al., 2004). The different chemical forms in which the metal ions might be present in aqueous environments lead to different types of interactions with biological membranes, affecting the bioassimilation and the toxicity of such species (Slaveykova and Wilkinson, 2003; Wilkinson and Buffle, 2004; De Schamphelaere and Janssen, 2006). Bioavailability is a concept for which no simple generic definition can be formulated (Cui et al., 2013), although a large number of definitions can be found in the literature. The definition given in ISO 11074 (ISO, 2005) that “bioavailability is the degree to which chemicals present in the soil may be absorbed or metabo- lized by human or ecological receptors or are available for inter- action with biological systems” implies that the metals migrate from the environment into the organism through a boundary zone, i.e., it relates the environmental availability measured by chemical methods and the toxicologic bioavailability measured by biological procedures (Harmsen, 2007). By crossing this zone, the metals released by the soils are taken up by organisms, and for this reason, having an estimation of the magnitude of the process is necessary to evaluate the impact of the sorption performed by the organism. Common ways to make such measurements are to quantify the amount of internalized metal, evaluate the internalization fluxes, or determine the toxicity as a function of metal amount in the bio- logical systems (Franklin et al., 2002; Slaveykova et al., 2009). Numerous bioavailabilities could be measured depending on the type of target organisms and time scales using methods that are usually time consuming because of the manipulation of biological entities. For this reason, chemical measurements made in envi- ronmental matrices are usually employed to determine a fraction of a well-defined class of contaminants assumed to be available for specific receptors, e.g., free, labile, inert (Parthasarathy and Buffle, 1994), and lipophobic (Parthasarathy et al., 2010) fractions. Some of these methods include diffusion gradients in thin films (DGT) (Zhang and Davison, 2000; Han et al., 2014), voltamperometry (Buffle and Tercier-Waeber, 2000) and supported or permeation liquid membranes (SLM, PLM, respectively) (Parthasarathy et al., * Corresponding author. E-mail address: erdsmg@unam.mx (E. Rodríguez de San Miguel). Contents lists available at ScienceDirect Environmental Pollution journal homepage: www.elsevier.com/locate/envpol http://dx.doi.org/10.1016/j.envpol.2015.08.011 0269-7491/© 2015 Elsevier Ltd. All rights reserved. Environmental Pollution 206 (2015) 712e719