Fast determination of oleic acid in pork by flow injection analysis/mass spectrometry Rebeca Muñoz 1 , Francisca Vilaró 2 , Jordi Eras 2 , Joan Estany 1 and Marc Tor 1 * 1 Departament de Producció Animal, Universitat de Lleida, Rovira Roure 191, 25198 Lleida, Spain 2 Departament de Química, Universitat de Lleida, Rovira Roure 191, 25198 Lleida, Spain In some Mediterranean products such as olive oil or ham, oleic acid is the most abundant component of the total fat. Due to the large volume of trade in these products, it may be necessary to analyze oleic fatty acids in high numbers of samples in short periods of time. However, using classic lipid analysis techniques, it is not always possible to cope with these high demands. To solve this problem, a high‐throughput analytical method for oleic fatty acid quantification in pork is presented. The purpose of the method is to avoid liquid chromatography processes using a flow injection analysis (FIA) system based on electrospray ionization mass spectrometry. The use of pentadecanoic fatty acid as an internal standard overcame matrix effects. The oleic FIA technique could be used as a suitable method for discriminating carcass samples for selection and labeling by oleic acid content when large numbers of pork samples must be processed in a short period of time. Copyright © 2011 John Wiley & Sons, Ltd. Throughout the last decade, dietary fat intake has received increasing interest because of its effect on human health. Presently, the relationship between dietary fat and coronary heart disease and cancer are not definitive. However, there is evidence on the modification effects of total, saturated, monounsaturated and polyunsaturated fats on cardiovascular morbidity and mortality. [1] Thus, the control of dietary fat intake and analysis of fat composition have become preventative strategies for some chronic diseases. The Dietary Guidelines for Americans [2] recommends that people consume less than 10% of their total daily calories from saturated fatty acids. For these reasons, the screening of lipid composition arises as an important area of interest in food analysis and the fatty acid profile is now a frequently requested piece of information, both by food producers and consumers. In some cases, this situation makes necessary the analysis of a high number of samples in short periods of time. Using classic lipid analysis techniques, however, it is not always possible to cope with these demands. Particularly in animal production, fatty acid profiles are increasingly requested, because they play an important role in the health properties of meat, but also because the health properties of meat are improvable by means of animal breeding or environmental factors. [3] Therefore, it is essential to have information on fatty acid composition from a large number of samples in a fast and accurate fashion. From an analytical point of view, the most common technique to obtain fatty acid profiles is gas chromatography (GC). The most usual methods of analysis involve lipid extraction and the conversion of the fatty acids into methyl esters. [4] However, other possibilities have been proposed for analysis, including the direct transesterification of fatty acids in freeze‐dried raw materials [5,6] or the silylation of fatty acids. [7] Measurement time then depends on the number and type of fatty acids present in the oil, but these procedures are time‐consuming, requiring at least 10 min to raise a fatty acid profile by GC. A good resolution of isomers requires longer analysis times. [8] More recently, as a consequence of the application of ionization techniques [9] such as electrospray ionization (ESI), atmospheric pressure chemical ionization (APCI) and atmo- spheric pressure photoionization (APPI), lipid analysis by high‐ performance liquid chromatography/mass spectrometry (HPLC/MS) has become fairly common. Using these tech- niques, the derivatization of fatty acids prior to analysis is not essential, so measurements can be carried out rapidly and simply. Derivatization does have some advantages, however, such as working in the positive ion mode using common LC mobile phases or increasing detection sensitivity. [10] Despite these advantages, several methods have been proposed for using ESI as the ion source and operating in the negative ion mode to analyze fibroblasts, [11] chocolate, [12] vegetable and animal oils, [13] and blood plasma. [11,14] In pork production systems in the Mediterranean, a characteristic way to improve meat health properties is by increasing oleic fatty acid content. [15] In practice, this means having to make a rapid oleic analysis on a large number of pigs. The objective of this study is then to create a fast and matrix‐effect‐free analytical method for oleic fatty acid quantization in fresh pork. The main purpose of this new method is to shorten the time required for analysis by avoiding chromatography and using a flow injection system based on ESI‐MS. This method is expected to reduce analysis costs because the boron trifluoride, which is used in the transesterification step, is around 20‐fold cheaper than the potassium hydroxide in methanol/water (50:50, v/v) which is used in the saponification step. * Correspondence to: M. Tor, Departament de Producció Animal, Universitat de Lleida, Rovira Roure 191, 25198 Lleida, Spain. E-mail: Mtor@prodan.udl.cat Copyright © 2011 John Wiley & Sons, Ltd. Rapid Commun. Mass Spectrom. 2011, 25, 1082–1088 Research Article Received: 8 October 2010 Revised: 3 December 2010 Accepted: 23 January 2011 Published online in Wiley Online Library Rapid Commun. Mass Spectrom. 2011, 25, 1082–1088 (wileyonlinelibrary.com) DOI: 10.1002/rcm.4958 1082