A simple, fast and cheap non-SPE screening method for antibacterial residue analysis in milk and liver using liquid chromatography–tandem mass spectrometry Magda Targa Martins a,b,n , Jéssica Melo a , Fabiano Barreto a,b , Rodrigo Barcellos Hoff a,c , Louise Jank a,c , Michele Soares Bittencourt a , Juliana Bazzan Arsand a,c , Elfrides Eva Scherman Schapoval b a Ministério da Agricultura, Pecuária e Abastecimento, Laboratório Nacional Agropecuário—LANAGRO/RS, Porto Alegre, RS, Brazil b Faculdade de Farmácia, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil c Instituto de Química, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil article info Article history: Received 23 January 2014 Received in revised form 15 April 2014 Accepted 15 April 2014 Available online 2 June 2014 Keywords: LC–MS/MS Antibacterials Residues Milk Liver abstract In routine laboratory work, screening methods for multiclass analysis can process a large number of samples in a short time. The main challenge is to develop a methodology to detect as many different classes of residues as possible, combined with speed and low cost. An efficient technique for the analysis of multiclass antibacterial residues (fluoroquinolones, tetracyclines, sulfonamides and trimethoprim) was developed based on simple, environment-friendly extraction for bovine milk, cattle and poultry liver. Acidified ethanol was used as an extracting solvent for milk samples. Liver samples were treated using EDTA-washed sand for cell disruption, methanol:water and acidified acetonitrile as extracting solvent. A total of 24 antibacterial residues were detected and confirmed using liquid chromatography coupled to tandem mass spectrometry (LC–MS/MS), at levels between 10, 25 and 50% of the maximum residue limit (MRL). For liver samples a metabolite (sulfaquinoxaline-OH) was also monitored. A validation procedure was conducted for screening purposes in accordance with European Union requirements (2002/657/EC). The detection capability (CCβ) false compliant rate was less than 5% at the lowest level for each residue. Specificity and ruggedness were also discussed. Incurred and routine samples were analyzed and the method was successfully applied. The results proved that this method can be an important tool in routine analysis, since it is very fast and reliable. & 2014 Published by Elsevier B.V. 1. Introduction Pharmaceuticals are widely used in veterinary medicine, including mainly antibacterials, applied for both therapeutic and prophylactic purposes. When a veterinary drug is administered, it is necessary to observe the withdrawal period to avoid the presence of drug residues in tissues, eggs, milk and other products of animal origin. Antibacterial residues in food are a risk to human health and could be an important vehicle for the development of bacterial resistance, besides toxicological, immunological and allergic problems in susceptible individuals [1–4]. Maximum residue limits (MRLs) for veterinary drugs in food were set by regulatory agencies and government authorities worldwide [5–7]. In Brazil, the National Residue Control Plan (NRCP) defines which residues must be monitored and their MRLs, aiming mainly to monitor the incidence of residues and prevent potential risk to a population exposed to those products [8,9]. Different tissues can be considered for residue analysis, depend- ing on the animal species, drug pharmacokinetics and their physical– chemical properties. Milk is a universally consumed food, especially during childhood, and its safety is a permanent concern. Liver is organ responsible for enzymatic drug metabolism processes, and it is an appropriate matrix for monitoring veterinary drug residue. Liver can be considered the most complex matrix [10,11] and milk is a biological fluid that can be considered as a matrix, rich in proteins, lipids, carbohydrates, salts and minerals [12]. Tetracyclines (TCs), sulfonamides (SAs), quinolones (Qs), fluoro- quinolones (FQs) and trimethoprim (TMP) are antibacterials widely used in veterinary practice because of their advantages, including low price and broad spectrum. Residue monitoring programs require improved methods able to detect non-compliant samples with residues above the MRL in order to ensure food safety. A high throughput screening method is also a very useful tool for routine Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/talanta Talanta http://dx.doi.org/10.1016/j.talanta.2014.04.049 0039-9140/& 2014 Published by Elsevier B.V. n Correspondence to: Estrada da Ponta Grossa, 3036, Porto Alegre, Rio Grande do Sul, Brazil. Tel.: þ55 51 3248 2133. E-mail address: magdatm@terra.com.br (M.T. Martins). Talanta 129 (2014) 374–383