Contribution to the Development of Indirect Atomic Absorption Methods: Application of the Ion Pair 1,10-phenanthroline-mercury(II)-iodide to Iodide Determination in Water and Infant Formulae Samples

A method to determine iodide is developed, based on the formation of an ion pair between 1, 10-phenanthroline, mercury(II) and iodide that can be selectively extracted into IBMK. When the IBMK layer is analyzed by electrothermal atomic absorption spectrometry (ETAAS) for mercury, iodide can be quantified too. Parameters related to the preparation of the ion pair and to the measuring process are studied. Thus, 7.2–7.4 reveals to be the best pH interval to carry out the extraction, and 250 and 1000?°C, respectively, the mineralization and atomization temperatures for mercury determination by ETAAS. The procedure is applied to drinking tap water and commercial infant formulae milk samples. The accuracy of the method has been investigated by means of the analytical recovery for water samples (mean analytical recovery obtained at different concentration levels 98.1%) and by using the certified reference material BCR CRM No 151 Skim Milk Powder (Spiked) for the infant formulae (results within certification interval). The repeatability of the measurements at different concentration levels gave a RSD lower than 10% for both types of samples and the repeatability of the whole procedure for infant formulae shows a RSD of 1.33%. In addition, the limits of detection and quantification were 2.5?μg/L and 8.5?μg/L, respectively, for drinking water and 1.1?μg/g and 3.8?μg/g, respectively, for infant formulae.