Analytical Methods Fast determination of myo-inositol in milk powder by ultra high performance liquid chromatography coupled to tandem mass spectrometry María Isabel Alarcón Flores a , José Luis Fernández Moreno b , Antonia Garrido Frenich a,⇑ , José Luis Martínez Vidal a a Group Analytical Chemistry of Contaminants, Department of Analytical Chemistry, University of Almería, E-04071 Almeria, Spain b Laboratory of Pesticide Residues, LAB. Scientific and Technologic Park of Almeria, University of Almería, E-04071 Almeria, Spain article info Article history: Received 25 February 2011 Received in revised form 29 April 2011 Accepted 7 May 2011 Available online 14 May 2011 Keywords: Inositol Liquid chromatography Tandem mass spectrometry Milk powder abstract A simple and fast method has been developed and validated for the determination of myo-inositol in milk powder samples, using solid–liquid extraction with water (0.01% formic acid, v/v):methanol (1:1, v/v). The determination was carried out by ultra-high-performance liquid chromatography coupled to tandem mass spectrometry (UHPLCMS/MS) using an electrospray ionisation source (ESI) in positive mode. Chro- matographic separation was carried out using as mobile phase water (0.01% formic acid, v/v) and meth- anol in gradient mode. Data acquisition under MS/MS was achieved by applying selected reaction monitoring, using 181.0!109.0 and 181.0!81.0 for quantification and confirmation purposes, respec- tively. The technique provides a sensitive and selective determination of myo-inositol in the analysed samples, with a run time of 4 min. The limit of detection and quantification were 0.2 and 0.5 mg kg 1 , respectively. The method was applied to six fortified commercial milk powder samples containing myo-inositol amounts ranging from 290 to 2200 mg kg 1 . Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Inositol is an isomer of glucose (Rastogi, 2003) widely distrib- uted in plant and animal tissues (Joshi & Saraswat, 2004). Cur- rently, its determination is of great interest in several areas, such as nutrition, medical cell biology and biotechnology research, since this compound is often used as a food additive (Cataldi, Margiotta, & Zambonin, 1998). Inositol has nine different isomers, but only one of them, myo- inositol (Turner, Richarson, & Mullaney, 2007)(Fig. 1), is important in animal and plant metabolism (Raboy, 2003). Previous studies have demonstrated that myo-inositol has chemopreventive and chemotherapeutic properties in human cancer cells, and animal cancer models, including prostate, breast, colon, pancreas, liver and lung cancer (Grases et al., 2002; Nishino et al., 1999; Rizvi et al., 2006; Schlemmer et al., 2009). Moreover, myo-inositol con- tent has been linked to the prevention of certain diseases, such as diabetes (Corrado et al., 2011), cataracts, neuropathy, nephrop- athy (Lauro et al., 1989) and human neuropsychiatric disorders (Liu, Villalta, & Sturla, 2009). myo-Inositol is a compound necessary for babies, and when this substance cannot be administered through breast milk, it must be supplied in the diet by inositol-enriched milk or formula (Bolees, 2003; Mikko Hallman, Pirkko Arjomaa, & Kalle Hoppu, 1987). Now- adays, the maximum limits permitted for myo-inositol in infant formula range from 4.0 to 40.0 mg/100 kcal 1 (Codex Alimentarius Commission, 2007), and the requirements for premature ranged from 27.0 to 67.5 mg/100 kcal 1 (Varela Moreiras, Cuadrado Vives, Fraga Bermúdez, Martín Esteban, & Román Riechmann, 2005). The analysis of myo-inositol is a relevant issue, in order to en- sure that powdered milk or infant formula does not contain amounts of myo-inositol over the established limits. Currently, there are many food products enriched with this compound; there- fore, fast and easy methodologies to determine myo-inositol con- tent are needed. In general, reported methods for the extraction of myo-inositol require the hydrolysis of the sample. An alkaline hydrolysis with potassium hydroxide was used for the extraction of myo-inositol from infant formulae and products for enteral feeding (Tagliaferri, Bonetti, & Blake, 2000). Another approach was based on the hydro- lysis of infant formulae containing inositol with hydrochloric acid (Indyk & Woollard, 1994). In general, both procedures required a complex treatment of the sample. Recently, a more simple method which does not require a hydrolysis step has been described, using an aqueous solution of ethanol (80%, v/v) for the extraction of myo- inositol in carrots (Soria, Sanz, & Villamiel, 2009) showing ade- quate trueness and precision values. On the other hand, several analytical methods have been de- scribed for the analysis of myo-inositol in food matrices, such as 0308-8146/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodchem.2011.05.045 ⇑ Corresponding author. Fax: +34 950015483. E-mail address: agarrido@ual.es (A.G. Frenich). Food Chemistry 129 (2011) 1281–1286 Contents lists available at ScienceDirect Food Chemistry journal homepage: www.elsevier.com/locate/foodchem