Single-use optical sensor for the determination of iron in water and whitewines

A new method, based on the use of a disposable sensor, for the determinatio n of Fe(II) in waters and wines is proposed. The sensor is formed by an ine rt rectangular strip of polyester (Mylar) and a circular film (6 mm in diam eter) adhered on its surface. This film, which contains the required reagen ts for the fixation of the analyte by means of a complexation reaction, for ms the sensing zone of the sensor. When the sensor is introduced in an acid ified (pH 2.5) sample solution containing between 4.0 and 300.0 mug/L of Fe (II), a violet-red colour develops in the initially colourless sensing zone . The linear range of the method depends of the equilibration time of the s ensor with the sample solution. Thus, when the equilibration time was 5 min , the linear range was 41.0-300.0 mug/L, while for 60 min the range was 4.0 -50.0 mug/L Detection and quantification limits were 12.0 and 41.0 mug/L, r espectively, for an equilibration time of 5 min. The precision of the metho d, expressed as relative standard deviation of ten samples of 100.0 mug/L o f Fe(II), was 4.9%. Interferences produced by other species usually present in waters or wines have been studied. Cu(II) and Co(II) interfered serious ly at concentration levels higher than 100.0 and 150.0 mug/L, respectively. The method was applied to the determination of Fe(II) in different types o f waters and wines, using atomic absorption spectrometry as a reference met hod.