Analytica Chimica Acta 754 (2012) 61–66 Contents lists available at SciVerse ScienceDirect Analytica Chimica Acta j ourna l ho me page: www.elsevier.com/locate/aca pH-controlled dispersive liquid–liquid microextraction for the analysis of ionisable compounds in complex matrices: Case study of ochratoxin A in cereals Luca Campone, Anna Lisa Piccinelli ∗ , Rita Celano, Luca Rastrelli Dipartimento di Scienze Farmaceutiche e Biomediche, Università degli Studi di Salerno, via Ponte Don Melillo, 84084 Fisciano (SA), Italy h i g h l i g h t s ◮ A new and selective extraction tech- nique, pH-controlled DLLME, was developed. ◮ pH-DLLME is able to analyse OTA in cereals without additional sample pretreatment. ◮ pH-DLLME is a suitable technique for a wide range of ionisable com- pounds. ◮ Additional advantages are a higher selectivity and a wider range of appli- cation. g r a p h i c a l a b s t r a c t a r t i c l e i n f o Article history: Received 31 July 2012 Received in revised form 2 October 2012 Accepted 3 October 2012 Available online 12 October 2012 Keywords: pH controlled DLLME Ochratoxin A HPLC-FLD Cereal Sample preparation a b s t r a c t A new sample preparation procedure, termed pH-controlled dispersive liquid–liquid microextraction (pH-DLLME), has been developed for the analysis of ionisable compounds in highly complex matrices. This DLLME mode, intended to improve the selectivity and to expand the application range of DLLME, is based on two successive DLLMEs conducted at opposite pH values. pH-DLLME was applied to determination of ochratoxin A (OTA) in cereals. The hydrophobic matrix interferences in the raw methanol extract (disperser, 1 mL) were removed by a first DLLME (I DLLME) performed at pH 8 to reduce the solubility of OTA in the extractant (CCl 4 , 400 L). The pH of the aqueous phase was then adjusted to 2, and the analyte was extracted and concentrated by a second DLLME (extractant, 150 L C 2 H 4 Br 2 ). The main factors influencing the efficiency of pH-DLLME including type and volume of I DLLME extractant, as well as the parameters affecting the OTA extraction by II DLLME, were studied in detail. Under optimum conditions, the method has detection and quantification limits of 0.019 and 0.062 g kg -1 , respectively, with OTA recoveries in the range of 81.2–90.1% (n = 3). The accuracy of the analytical procedure, evaluated with a reference material (cereal naturally contaminated with OTA), is acceptable (accuracy of 85.6% ± 1.7, n = 5). The applicability of pH-DLLME to the selective extraction of other ionisable compounds, such as acidic and basic pharmaceutical products was also demonstrated. The additional advantages of pH-DLLME are a higher selectivity and the extension of this microextrac- tion technique to highly complex matrices. © 2012 Elsevier B.V. All rights reserved. ∗ Corresponding author. Tel.: +39 089969794; fax: +39 089969602. E-mail address: apiccine@unisa.it (A.L. Piccinelli). 1. Introduction Dispersive liquid–liquid microextraction (DLLME) [1] is an emerging miniaturised sample-preparation technique that is becoming increasingly popular because of simplicity of operation, 0003-2670/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.aca.2012.10.010