Contents lists available at ScienceDirect Journal of Chromatography B journal homepage: www.elsevier.com/locate/jchromb Simultaneous quantification of antibiotics in wastewater from pig farms by capillary electrophoresis Carlos A. Díaz-Quiroz a , J. Francisco Hernández-Chávez b , Gabriela Ulloa-Mercado a, ⁎ , Pablo Gortáres-Moroyoqui a , Rosario Martínez-Macías c , Edna Meza-Escalante c , Denisse Serrano-Palacios c a Departamento de Biotecnología y Ciencias Alimentarias, Instituto Tecnológico de Sonora, 5 de febrero 818 Sur. Ciudad Obregón, Sonora 85000, Mexico b Departamento de Ciencias Agronómicas y Veterinarias, Instituto Tecnológico de Sonora, 5 de febrero 818 Sur. Ciudad Obregón, Sonora 85000, Mexico c Departamento de Ciencias del Agua y Medio Ambiente, Instituto Tecnológico de Sonora, 5 de febrero 818 Sur. Ciudad Obregón, Sonora 85000, Mexico ARTICLE INFO Keywords: Capillary electrophoresis Antibiotics Fluoroquinolones Tetracyclines Wastewater ABSTRACT Pig farming is an important activity in the economic development of Mexico with millions of tons of meat produced annually. Antibiotics are used in therapeutic dose to prevent diseases, and sometimes as growth promoters. These compounds are not completely metabolized; they are carried into the environment in its active form at concentrations that could induce antibiotic resistance in bacteria, which could be transferred to human pathogens by horizontal gene transfer. The objective of this work was to develop methods of analysis for si- multaneous quantification of the antibiotics Oxytetracycline (OXT), Chlortetracycline (CLT), Enrofloxacin (ENRO) and Ciprofloxacin (CIPRO) by field-amplified sampling injection in capillary zone electrophoresis (FASI- CZE). The method was validated by parameters of (1) linearity, obtaining a lineal range of 0.05 at 1 μg mL -1 for ENRO and CIPRO, and from 0.1 to 1 μg mL -1 for OXT and CLT; (2) precision, obtaining values < 5% of standard deviation for CIPRO and ENRO and < 10% of standard deviation for OXT and CLT; (3) accuracy, with recovery values from 93 to 115%; (4) selectivity, with values of resolution > 2 for the all antibiotics tested. To prove the method, a sample of wastewater from a local pig farm was analyzed, detecting a concentration of 0.140 ± 0.009 for OXT. This concentration was higher than the minimal selective concentration, indicating the point in which resistance to a determined antibiotic could develop. The methods were validated with precision and sensitivity comparable to chromatographic methods, which can be used to analyze wastewater from pig farms directly. 1. Introduction Pig and aquaculture farming in Mexico are important economic activities that generate more than six thousand million tons of meat and aquaculture products [1]. To guarantee this productivity, antibiotics and hormones are frequently used as therapeutic agents and growth promoters. In this sense, Mexico should establish the official regulations on their use. These antibiotics, included in feed, are partially metabo- lized and discarded in the environment in its active form [2]. Generally, its concentrations are found in the nanomolar range, so they are con- sidered micro-contaminants [3]. Antibiotics could induce resistance to bacterial communities while increasing the availability of resistant genetic determinants [4]. For example, some enterococcus that cause urinary infections have evolved in nosocomial pathogens, such as the case of Enterococcus faecium, which has mobilized from pig to human microbiota and resistant genes transferred of tetracyclines, macrolides, and fluoroquinolones to other pathogen bacteria as Staphylococcus aureus [5]. The relationship between resistance transfer and the use of antibiotics is of complex nature and data are insufficient. Thus, precise knowledge should exist of antibiotics present in the different environ- mental matrices: soil, water, and biota. The majority of the data comes from China, the United States, and some European countries [3]. In Mexico, not enough qualitative and quantitative information of these contaminants in water and sediments is available, although there is evidence of its use in some intensive livestock activities [6]. For these reasons, it is a priority to develop methods for their identification and quantification. The most used analytic techniques in the environmental field are high-pressure liquid chromatography (HPLC) and gas chromatography (GC). On the other hand, the use of capillary electrophoresis (CE) has gained interest because of its high separation efficiency and low ana- lysis cost [7, 8]. Different authors have quantified antibiotics using CE, https://doi.org/10.1016/j.jchromb.2018.06.017 Received 16 December 2017; Received in revised form 5 June 2018; Accepted 6 June 2018 ⁎ Corresponding author. E-mail address: ruth.ulloa@itson.edu.mx (G. Ulloa-Mercado). Journal of Chromatography B 1092 (2018) 386–393 Available online 15 June 2018 1570-0232/ © 2018 Elsevier B.V. All rights reserved. T