Please cite this article in press as: A. Pelfrêne, et al., Investigation of DGT as a metal speciation tool in artificial human gastrointestinal fluids, Anal. Chim. Acta (2011), doi:10.1016/j.aca.2011.05.024 ARTICLE IN PRESS G Model ACA-231216; No. of Pages 10 Analytica Chimica Acta xxx (2011) xxx–xxx Contents lists available at ScienceDirect Analytica Chimica Acta j ourna l ho me page: www.elsevier.com/locate/aca Investigation of DGT as a metal speciation tool in artificial human gastrointestinal fluids Aurélie Pelfrêne a,b,∗ , Christophe Waterlot a,b , Francis Douay a,b a Université Lille Nord de France, Lille, France b Groupe ISA, Equipe Sols et Environnement, Laboratoire Génie Civil et géo-Environnement Lille Nord de France (LGCgE, EA 4515), 48 boulevard Vauban, 59046 Lille Cedex, France a r t i c l e i n f o Article history: Received 22 December 2010 Received in revised form 11 May 2011 Accepted 14 May 2011 Available online xxx Keywords: Trace elements Digestive fluids Bioaccessibility Diffusive gradient in thin film Computer modeling Absorption a b s t r a c t This paper reports the results of an investigation on the performance of the diffusive gradient in thin film technique (DGT) as a speciation tool for trace elements (TEs) in artificial human gastrointestinal fluids. The validity of Cd, Pb, and Zn sampling by DGT in digestive fluids was checked. The TE bioaccessibility in highly contaminated soils was determined using the in vitro Unified Barge Method (UBM) test. DGT devices were deployed in the gastrointestinal solutions obtained after carrying out the UBM test. The computer speciation code JESS (Joint Expert Speciation System) was used to predict the metal speciation of Cd, Pb, and Zn. Combining the in vitro test with the DGT technique and JESS provided an approach to the TE species available for transport across the intestinal epithelium. The gastrointestinal absorption of ingested TE ranged from 8 to 30% for Cd, 0.6 to 11% for Pb, and 0.8 to 7% for Zn and was influenced by TE speciation. In this original approach, the DGT technique was found to be simple and reliable in the investigation of TE chemical speciation in digestive fluids. Extrapolation to the in vivo situation should be undertaken very cautiously and requires further investigation. © 2011 Elsevier B.V. All rights reserved. 1. Introduction The accumulation of trace elements (TEs) in soils due to human activities constitutes a potential health risk if directly ingested. Ingestion of contaminated soil particles is a major route for human TE intake, especially by children via hand-to-mouth behavior [1–3]. Contaminants can be partially or totally released from soil by ingestion, depending on their speciation under gastrointestinal conditions [4]. The fraction of bioavailable TE is given by the total amount of elements that reaches the bloodstream and human organs [5]. The two limiting factors in oral TE bioavailability are dissolution and absorption [6]. Dissolution of ingested TE- containing soil particles is often estimated using in vitro tests (artificial saliva–gastrointestinal fluids) as surrogates for in vivo measurements [e.g., [7–10]]. In vitro tests provide estimates of bioaccessibility, which corresponds to the proportion of contam- inant that dissolves in the artificial gastrointestinal fluids and is potentially available for absorption [4,5,11]. These tests do not take into account the transport of ions across biological barriers [12]. The transport of TEs across biological membranes is highly dependent on the physicochemical form of the metal, i.e., its speciation [13]. The free metal ions can bind to and/or traverse ∗ Corresponding author at: Groupe ISA, Université Lille Nord de France, Lille, France. Tel.: +33 3 28 38 48 48; fax: +33 3 28 38 48 47. E-mail address: a.pelfrene@isa-lille.fr (A. Pelfrêne). the intestinal membrane. Apart from exceptions (e.g., hydropho- bic organometal complexes), metal complexes are not able to overcome the membrane as a whole. Assuming that only the free metal ions can be transported across the intestinal epithelium, a contribution from complexed forms to metal transport across the membrane via their dissociation should also be taken into account [14]. As a consequence, the kinetics of association and dissociation processes of metal complexes play a key role. In some cases, metal complexes can be dissociated, and the free metal ions produced are subsequently transported across the membrane [14]. The flux toward the intestinal membrane corresponds to both the free metal ion and labile metal species. In contrast, inert species cannot dissociate and thus do not contribute to transport across the intestinal membrane [14]. As a consequence, obtaining direct information on metal speciation in the gastrointestinal fluids could greatly help understand TE availability for transport across the intestinal epithelium. Within this objective, a number of studies were conducted in order to simulate human intestinal epithelium. Human enterocyte cell lines, such as the Caco-2 line, have been explored as a suitable absorption phase [15,16]. An alternative to Caco-2 cells, digestion in dialysis tubing, is a technique used in studies estimating TE bioaccessibility in soils and food [17–19]. In the present study, transport of bioaccessible Cd, Pb, and Zn across the intestinal epithelium was investigated using the diffu- sive gradient in thin film technique (DGT) as a model to simulate human intestinal membrane. The DGT technique was proposed by Davison and Zhang [20] as a convenient speciation tool for the 0003-2670/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.aca.2011.05.024