Analytica Chimica Acta 523 (2004) 21–28 Development of a screening method for analytical control of antibiotic residues by micellar electrokinetic capillary chromatography L. Nozal, L. Arce 1 , A. R´ ıos 2 , M. Valcárcel ∗ Analytical Chemistry Department, University of Córdoba, Campus de Rabanales, Edificio Anexo Marie Curie, E-14071 Córdoba, Spain Received 5 December 2003; received in revised form 18 March 2004; accepted 21 March 2004 Available online 18 August 2004 Abstract Capillary electrophoresis was used for the separation of penicillin compounds. Micellar electrokinetic capillary chromatography (MEKC), by the addition of sodium dodecyl sulphate (SDS) to the buffer solution, demonstrated to be the appropriate mode for the separation of these compounds and their monitoring in drug residues. The method allowed to separate a mixture of antibiotics, such as amoxicillin, ampicillin, penicillin G, oxacillin, penicillin V, and cloxacillin. A mixture of 40 mM sodium tetraborate and 100 mM SDS at pH 8.5 was used as running buffer. The analysis was performed with a voltage of 10kV at a temperature of 20 ◦ C. The samples were hydrostatically introduced (10 s) into the capillary and electropherograms were recorded at 210 nm. Statistical analysis by Student’s t-test showed no significant evidence of systematic errors in the proposed method. This method proved to be highly suitable for the separation and determination of penicillins (at g ml -1 level) in farm water samples, where the presence of these compounds can produce an environmental problem. © 2004 Elsevier B.V. All rights reserved. Keywords: Micellar electrokinetic capillary chromatography; Penicillins; Environmental monitoring; Water analysis 1. Introduction One of the most relevant topics in today’s environmental analytical chemistry is water quality control. In addition to pesticides, industrial chemicals and their metabolites, phar- maceutical substances have experienced a fast growing in- terest. Recent studies have shown that a multitude of drugs are present in aquatic systems [1–3]. The interest in the de- termination of antibiotic residues in the environment arises from the fact that they are suspected of being responsible for the appearance of bacterial strains that are resistant to antibiotics [4]. Drug residues have become a noteworthy contamination factor in surface water during the last years. The excretion of drugs and their metabolites, together with improper waste disposal, has led to considerable concentra- tions of various compounds. Even the treatment of commu- ∗ Corresponding author. Tel.: +34-957-218-616; fax: +34-957-218-616. E-mail address: qa1vacam@uco.es (M. Valc´ arcel). 1 Present address: Environmental Science Department, University Pablo de Olavide Carretera de Utrera Km. 1, 41013 Sevilla, Spain. 2 Present address: Analytical Chemistry and Food Technology Depart- ment, University of Castilla-La Mancha, 13004 Ciudad Real, Spain. nal wastewater in purification plants cannot avoid the entry of some drugs because of the high stability of some of them or of their metabolites against biological degradation. An- other reason for controlling drug residues in surface water is that under certain circumstances these compounds may enter in the drinking water produced from groundwater, as recent studies have shown [5–7]. The term “antibiotic” is normally reserved for a very di- verse range of compounds, both natural and semi-synthetic, that possess antibacterial activity. The antibiotics can be classified in a variety of groups; penicillins, tetracyclines, macrolides, aminoglycosides, and amphenicols [8]. Peni- cillin antibiotics have been widely used for livestock as veterinary drugs to prevent and treat infectious diseases. Such usage may lead to problems with residues in live- stock products. One of the major roles of the public health agencies is to provide safe products for consumers through quantification of these residues in livestock products [9]. Antibiotics (penicillin) used for veterinary purposes and excreted after incomplete metabolisation will be present in manure [10,11]. Manure however is often used as top soil dressing and can contaminate river water via run-off or drainage. Through leaching, it is possible for ground water to be exposed to pharmaceutical residues. This will 0003-2670/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.aca.2004.04.058