Comparison of the performance of different silica hydride particles for the solid-phase extraction of non-volatile analytes from dark chocolate with analysis by gas chromatography–quadrupole mass spectrometry Yada Nolvachai a,b , Chadin Kulsing b , Reinhard I. Boysen b , Maria T. Matyska c , Joseph J. Pesek c , Philip J. Marriott a,b , Milton T.W. Hearn b,⇑ a Australian Centre for Research on Separation Science, School of Chemistry, Monash University, Melbourne, Victoria 3800, Australia b School of Chemistry, Monash University, Melbourne, Victoria 3800, Australia c Department of Chemistry, San Jose State University, San Jose, CA 95192, USA article info Article history: Received 22 July 2014 Received in revised form 9 October 2014 Accepted 15 October 2014 Available online 22 October 2014 Keywords: Solid-phase extraction Silica hydride phases Gas chromatography/mass spectrometry Linear solvation energy relationship abstract The extraction capabilities of a Diamond Hydride™ phase, as well as silica hydride phases modified with bidentate octadecyl (BDC 18 ), phenyl or cholesteryl groups, were evaluated for the analysis of fatty acids, amino acids, sugars and sterols in a dark chocolate extract. These batch adsorption performances were investigated using either methanol or aqueous methanol as the solvent. The compositions of the extracted fractions were assessed by gas chromatography interfaced with quadrupole mass spectrometry (GC–qMS). The batch binding propensities of the various compound classes with silica hydride particles modified with immobilised phenyl groups or larger ligands followed trends predicted from linear solva- tion energy relationships. Both prediction and experiment revealed that better extraction results could be obtained with the phenyl, BDC 18 and cholesteryl hydride particles for the major chocolate components. Based on these results, separations in micro-pipette tip format with these three types of stationary phase particles have been undertaken. Ó 2014 Published by Elsevier Ltd. 1. Introduction Silica-hydride-based stationary phases are well known in liquid chromatography for the separation of peptides, proteins, nucleotides, metabolites, pharmaceuticals and other compound classes (Buszewski & Noga, 2012; Ge, Liu, Holmes, Ostrander, & Li, 2012; Hellmuth, Koletzko, & Peissner, 2011; Pesek, Matyska, Boysen, Yang, & Hearn, 2013; Soukup & Jandera, 2013; Weisenberg, Butterfield, Fischer, & Rhee, 2009; Zhang, Creek, Barrett, Blackburn, & Watson, 2012). Compared to type-B silica, sil- ica hydride phases, with 95% of the surface silanols replaced by Si–H groups, as confirmed by 1 H HR/MAS NMR measurements (Yeman, Nicholson, Matyska, Pesek, & Albert, 2013), are less polar and adsorb a lower amount of water onto their surfaces (Pesek et al., 2013; Soukup, Janas, & Jandera, 2013; Soukup & Jandera, 2013). However, silica hydride materials become more negatively charged in aqueous organic solvents, as shown from zeta potential measurements, and this affects the separation performance of sev- eral types of basic analytes (Kulsing et al., 2014; Yang, Matyska, Boysen, Pesek, & Hearn, 2013). The surface of silica hydride mate- rials can be further chemically modified to result in highly stable stationary phases with utility in a large array of aqueous-organic solvent systems (Pesek & Matyska, 2009). Depending on the water content of the mobile phases, these silica hydride materials can display either a reversed-phase or aqueous normal-phase (ANP) characteristics, thus broadening the selectivity range for the sepa- ration of polar analytes in the gradient elution mode (Boysen et al., 2011), as well as extending the capabilities of two-dimensional liquid chromatography (Gilar, Olivova, Daly, & Gebler, 2005). One objective of analytical green chemistry is rapid high throughput analyses at the small (micro- or nano-) scale, with simultaneous reduction in the number of experiments, time of analysis, energy and reagent consumption. The use of micropipette http://dx.doi.org/10.1016/j.foodchem.2014.10.083 0308-8146/Ó 2014 Published by Elsevier Ltd. Abbreviations: ANP, aqueous normal-phase; BSTFA, N,O-bis(trimethylsilyl) trifluoroacetamide; LSER, linear solvation energy relationship; MeOH, methanol; TMCS, trimethylchlorosilane. ⇑ Corresponding author. Tel.: +61 3 99054547; fax: +61 3 99058501. E-mail address: Milton.Hearn@monash.edu (M.T.W. Hearn). Food Chemistry 174 (2015) 434–439 Contents lists available at ScienceDirect Food Chemistry journal homepage: www.elsevier.com/locate/foodchem