Journal of Chromatography A, 1354 (2014) 26–33 Contents lists available at ScienceDirect Journal of Chromatography A jo ur nal ho me pag e: www.elsevier.com/locate/chroma Stir-membrane solid–liquid–liquid microextraction for the determination of parabens in human breast milk samples by ultra high performance liquid chromatography-tandem mass spectrometry Rocío Rodríguez-Gómez a , Mercedes Roldán-Pijuán b , Rafael Lucena b , Soledad Cárdenas b , Alberto Zafra-Gómez a , Oscar Ballesteros a , Alberto Navalón a , Miguel Valcárcel b,∗ a Research Group of Analytical Chemistry and Life Sciences, Department of Analytical Chemistry, Campus of Fuentenueva, University of Granada, E-18071 Granada, Spain b Department of Analytical Chemistry, Institute of Fine Chemistry and Nanochemistry, Marie Curie Building, Campus of Rabanales, University of Córdoba, E-14071 Córdoba, Spain a r t i c l e i n f o Article history: Received 26 March 2014 Received in revised form 19 May 2014 Accepted 28 May 2014 Available online 2 June 2014 Keywords: Stir-membrane solid–liquid–liquid microextraction Lyophilized human milk samples Parabens UHPLC-MS/MS a b s t r a c t In this article, stir-membrane solid–liquid–liquid microextraction (SM-SLLME) is tailored for the analysis of solid matrices and it has been evaluated for the determination of parabens in l breast milk samples. A three-phase microextraction mode was used for the extraction of the target compounds taking advan- tage of their acid–base properties. The unit allows the simultaneous extraction of the target compounds from the solid sample to an organic media and the subsequent transference of the analytes to an aque- ous acceptor phase. The method includes the identification and quantification of the analytes by ultra high performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS). All the variables involved in the extraction procedure have been accurately studied and optimized. The ana- lytes were detected and quantified using a triple quadrupole mass spectrometer (QqQ). The selection of two specific fragmentation transitions for each compound allowed simultaneous quantification and identification. The method has been analytically characterized on the basis of its linearity, sensitivity and precision. Limits of detection ranged from 0.1 to 0.2 ng mL -1 with precision better than 8%, (expressed as relative standard deviation). Relative recoveries were in the range from 91 to 106% which demonstrated the applicability of the stir-membrane solid–liquid–liquid microextraction for the proposed analytical problem. Moreover, the method has been satisfactorily applied for the determination of parabens in lyophilized breast milk samples from 10 randomly selected individuals. © 2014 Elsevier B.V. All rights reserved. 1. Introduction The alkyl esters of p-hydroxybenzoic acid (parabens, PBs) are a group of compounds widely used as bactericide and antimicro- bial preservatives, especially against mold and yeast in cosmetic products, pharmaceuticals, and in food and beverage processing [1]. The biological activity of PBs is based on their inhibitory effects on membrane transport and mitochondrial function processes. These compounds are present, individually or in combination, in a large amount of commercial formulations. Although PBs have been considered for years to be relatively safe compounds with a low bioaccumulation potential [2], some studies suggest that they ∗ Corresponding author. Tel.: +34 957 218 616; fax: +34 957 218 616. E-mail addresses: qa1meobj@uco.es, qa1vacam@uco.es (M. Valcárcel). present a moderate endocrine disrupting activity and therefore they can cause adverse effects on humans and wildlife. In fact, the ability of PBs to disrupt physiologically important functions in both in vitro systems [3] and in vivo models [4–6] has been demonstrated. As well, the presence of non-metabolized PBs in breast cancer tis- sues [7] has focused the attention in their potential carcinogenic and toxic nature [2,6,8]. The human exposure to PBs may occur through ingestion, inhalation or dermal absorption. This exposure, estimated in 76 mg per day, involves different sources such as cosmetics and personal care products (50 mg/day), drugs (25 mg/day) or food (1 mg/day) [1]. After intake, PBs are metabolized by hydrolysis of the ester bond and by glucuronidation [9]. However, the parent compounds (free forms) can still be detected in biological samples such as urine [10], serum and seminal plasma [11] and human milk [12]. http://dx.doi.org/10.1016/j.chroma.2014.05.071 0021-9673/© 2014 Elsevier B.V. All rights reserved.