Two flow methods, based, respectively, on flow-injection analysis (FIA) and on multicommutated flow analysis (MCFA), were compared with regard to their use for the determination of total selenium in infant formulas by hydride-generation atomic absorption spectrometry. The method based on multicommutation provided lower detection and quantification limits (0.08 and 0.27？μg？L？1 compared to 0.59 and 1.95？μ？L？1, resp.), higher sampling frequency (160 versus. 70 samples per hour), and reduced reagent consumption. Linearity, precision, and accuracy were similar for the two methods compared. It was concluded that, while both methods proved to be appropriate for the purpose, the MCFA-based method exhibited a better performance. 1. Introduction The importance of selenium for the life of animals has been known since the 1950s, while the essentiality of this element for humans was revealed in 1970s with the discovery of its ability to prevent the Keshan disease, first described in 1935 in China in a province of the same name [1]. Subsequently, it was discovered its important role as part of the body’s antioxidant mechanisms and also its role in protecting the body against heavy metals as well as its importance in the immune system [1, 2]. Cow’s milk and dairy products are usually a poor source of selenium in human nutrition. Human milk is considered the best source of selenium for young children and infants [3]. However, human milk is a poor source of selenium, so recently manufacturers of dairy-based infant formulas have added selenium to these products. Selenium has a very narrow range between dietary deficiency (<40？μg/day for adults) and toxic levels (>400？μg/day). For this reason, it is very important to have control of the selenium intake by human and animals. Several analytical techniques are suitable for determining total selenium in milk, such as neutron activation analysis (Instrumental Neutron Activation Analysis (INAA)), fluorimetry, gas chromatography (GC), and atomic absorption spectrometry (AAS) [4]. The neutron activation technique is not available in most laboratories; it is generally used for determinations of selenium in certified reference materials as an alternative method and in proficiency testing. It has the advantage of being a nondestructive technique, but the detection limits are usually higher than for other techniques [3, 4]. Other methods usually are based on the generation of a piazselenol complex, which is subsequently submitted to different detection techniques. For instance, a fluorimetric method is recommended in the bulletin of
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