Direct determination of selected trace elements in apple juice by ICP-OES

The knowlegde of the mineral contents of fruit juices is important not only for nutritional aspects, but also for toxicological reasons. Due to the increased awareness of healthy lifestyle the consumption and relevance of apple juice in human nutrition is rising. Furthermore the change of the Austrian fruit juice guideline “Fruchtsaftverordnung” in 2004 permitts supplementation of vitamins and trace elements to fruit juices. At the moment there is a lack of information about the mineral contents of fruit juices, especially concerning potentially toxic elements. A major problem of trace and especially ultratrace elemental analysis is the sample preparation procedure, since it may lead to contamination of the samples as well as to losses of analytes. Thus it is advisable to perform direct measurements of the metals instead of decomposing the sample prior to analysis. The trace elemental content of apple juices can be analysed directly by GF-AAS, but this method as single element method is time-consuming. ICP-OES however offers the possibilty of simultaneous quantification of the elements of interest. In order to reduce interferences and problems caused by the high sugar content of the fruit juices, the samples were diluted 1:20 with diluted HNO3.The method was optimized and validated for the following elements: Ag, Al, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, Sr, and Zn.