UV-VIS and FTIR spectroscopic analyses of inclusion complexes of nonylphenol and nonylphenol ethoxylate with b-cyclodextrin Danielle Bonenfant a , Patrick Niquette a , Murielle Mimeault b , Alexandra Furtos-Matei c , Robert Hausler a, * a STEPPE-E ´ cole de Technologie Supe ´rieure, De ´partement de ge ´nie de la construction, 1100, rue Notre-Dame Ouest, Montre ´al (Que ´bec), H3C 1K3, Canada b Department of Biochemistry and Molecular Biology, College of Medicine, Eppley Cancer Institute, 7052 DRC, University of Nebraska Medical Center, 985870 Nebraska Medical Center, Omaha, NE 68198-5870, USA c Centre Re ´gional de Spectrome ´trie de Masse, De ´partement de Chimie, Universite ´ de Montre ´al, 2900 Edouard Montpetit, Montre ´al (Que ´bec), H3T 1J4, Canada article info Article history: Received 12 December 2008 Received in revised form 27 April 2009 Accepted 5 May 2009 Published online 19 May 2009 Keywords: Inclusion complexes b-cyclodextrin Nonylphenol Nonylphenol ethoxylate UV–vis spectroscopy FTIR spectroscopy Mass spectrometry abstract A study of inclusion complexation of liquid non-ionic surfactants, nonylphenol (NP) and nonylphenol 9 mole ethoxylate (NP9EO), with b-cyclodextrin (b-CD), was carried out by mass spectrometry, surface tension, and ultraviolet–visible (UV-VIS) and Fourier transform infrared (FTIR) spectroscopies. The inclusion complexation was effectuated by heating at 80  C and filtration of aqueous NP þ b-CD and NP9EO þ b-CD suspensions. The mass spectrometry and surface tension measurements revealed that NP and NP9EO form inclusion complexes with b- CD and b-CD possesses a higher affinity for NP. These results are supported by the data from UV-VIS spectroscopic analyses that have indicated that a three times greater amount of NP is entrapped into b-CD than NP9EO. This phenomenon has been associated with the smaller size and a higher degree of hydrophobicity of NP that favours its entrapment into b-CD as compared to that of NP9EO. At the structural level, the data from FTIR spectroscopic study have indicated that alkyl chains of NP and NP9EO can form van der Waals interactions with the cavity of b-CD. Moreover, NP and NP9EO seem to cause a reorganization of the intramolecular hydrogen bonds and change of the hydration of b-CD, but did not appear to strongly interact with C–C, C–O–C, and OH groups of b-CD. Together these results suggest that the formation of inclusion complexes by NP and NP9EO with b-CD molecules could constitute an effective and advantageous technique to remove liquid non-ionic surfactants from wastewater due to the non-toxic character of b-CD to humans and the environment. ª 2009 Elsevier Ltd. All rights reserved. 1. Introduction Cyclodextrins are polycyclic glucose oligosaccharides resulting from the degradation of starch by bacterial enzymes (Bizzigotti et al., 1997; McCray and Brusseau, 1998; Saenger et al., 1998). There are three common types of cyclodextrins (a-, b-, and g- cyclodextrins), which are constituted of six, seven, or eight glucose units respectively, linked by a-1,4-glucosidic bonds (Bizzigotti et al., 1997; McCray and Brusseau, 1998; Saenger et al., 1998; Szente et al., 1999). The doughnut-shaped structure * Corresponding author. Tel.: þ1 514 396 8499; fax: þ1 514 396 8584. E-mail address: robert.hausler@etsmtl.ca (R. Hausler). Available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/watres 0043-1354/$ – see front matter ª 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.watres.2009.05.010 water research 43 (2009) 3575–3581