DETERMINATION OF ELEVATED LEVELS OF DYSPROSIUM IN SERUM BY ELECTROTHERMAL ATOMIC-ABSORPTION SPECTROMETRY

A method has been developed for the determination of elevated levels o f dysprosium in serum, from human beings or animals exposed to a dyspr osium magnetic resonance imaging (MRI) contrast agent, by electrotherm al atomic absorption spectrometry. Several potential chemical modifier s were tested in order to increase the sensitivity and to overcome the memory effect normally experienced with dysprosium. The following ele ments were tested as potential modifiers: lanthanum, europium, gadolin ium, holmium, thulium, ytterbium, lutetium, thorium, tungsten, rhodium and palladium. Among these, lanthanum and gadolinium gave the most ob vious positive effects on the analytical performance. By adding 5 mu g lanthanum or 10 mu g gadolinium to the tube, after the introduction o f the sample, increased sensitivity, lowered limit of detection, reduc ed memory effect and improved precision of the method were obtained. G adolinium was chosen as the most suitable modifier of the two. The ana lytical performance of the method was validated by adding dysprosium, as the MRI contrast agent dysprosium diethylenetriaminepentaacetic aci d bis(methylamide) (DyDTPA-BMA), to the serum reference material Seron orm. The accuracy for the concentration range 10-400 ng ml-1 dysprosiu m 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 li mit 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 p g. The memory effect of the final method was <6%, measured as the % ca rryover of the previous atomization signal when a blank was atomized. The effect of adding CHF3 (Freon 23) to the purge gas was also investi gated.