Determination of elevated levels of dysprosium in serum by electrothermal atomic absorption spectrometry

Abstract

A method has been developed for the determination of elevated levels of dysprosium in serum, from human beings or animals exposed to a dysprosium magnetic resonance imaging (MRI) contrast agent, by electrothermal atomic absorption spectrometry. Several potential chemical modifiers were tested in order to increase the sensitivity and to overcome the memory effect normally experienced with dysprosium. The following elements were tested as potential modifiers: lanthanum, europium, gadolinium, holmium, thulium, ytterbium, lutetium, thorium, tungsten, rhodium and palladium. Among these, lanthanum and gadolinium gave the most obvious positive effects on the analytical performance. By adding 5 µg lanthanum or 10 µg gadolinium to the tube, after the introduction of the sample, increased sensitivity, lowered limit of detection, reduced memory effect and improved precision of the method were obtained. Gadolinium was chosen as the most suitable modifier of the two. The analytical performance of the method was validated by adding dysprosium, as the MRI contrast agent dysprosium diethylenetriaminepentaacetic acid bis(methylamide)(DyDTPA-BMA), to the serum reference material Seronorm. The accuracy for the concentration range 10–400 ng ml^–1 dysprosium was between 95 and 104%(recovery), the repeatability was typically < 2.6% RSD, the reproducibility was between 2.3 and 5.8% RSD and the limit of detection (3s) was 1.1 ng ml^–1 of Dy (absolute mass 11 pg) in Seronorm. The characteristic mass based on area measurements was 18 pg. The memory effect of the final method was < 6%, measured as the % carryover of the previous atomization signal when a blank was atomized. The effect of adding CHF₃(Freon 23) to the purge gas was also investigated.