Methods Variability for Magnesium Determination in a Biological Standard and Other Biological Materials

Abstract

<p>The use and analysis of biological standard reference materials has increased rapidly over the past few years with the mounting concern over the environment and the upsurge in health-related chemistry. Laboratory and method intercomparisons are an essential part of any program involved in the issuance of calibration of instrumental systems. It relies on the precision and accuracy of such analyses, often for vital decisions affecting public welfare. The lack of agreement among qualified analysts can thus be viewed with some dismay.</p> <p>An attempt was made to examine in some detail the determination of magnesium in several biological materials using fundamentally different methods of analysis. Three procedures, a gravimetric precipitation with oxine, atomic absorption analysis and neutron activation, the latter both non-destructive and with chemical separation, were selected for the analysis in a biological standard (Bowen's kale). The latter two methods were then applied to a homogenized rat carcass and a feces sample.</p> <p>Procedures were developed which gave reproducible results for the gravimetric and atomic absorption analysis. Discrepancies in the analysis by atomic absorption with and without standard addition were studied. Neutron activation gave results which were in good agreement with the other methods provided that care was taken to account for flux variations within the pneumatic rabbit. A best value of 1663 ± 7, ppm was ascertained for the magnesium content of the dried kale.</p> <p>Analyses of the rat samples by atomic absorption and neutron activation were also in close agreement, thereby helping to establish the overall accuracy of the procedures. For these samples, best values of 1550 ppm and 7370 ppm were obtained for the carcass and feces, respectively. An existing method discrepancy was resolved.</p>