MASS-SPECTROMETRY OF A VOLATILE MG CHELATE IN THE MEASUREMENT OF STABLE MG-26 WHEN USED AS A TRACER

A method for the detection of 26Mg enrichment of natural Mg was developed based on mass spectrometry (MS) of a Mg chelate made by complexing Mg to 2,2',6,6'-tetramethylheptanedione (THD). The chelate [Mg(THD)2] was extracted at pH > 9 from dilute aqueous solutions into ethyl ether, recovered by sublimation at room temperature, and introduced by solid probe into a Finnigan 3300 mass spectrometer. The chelate was ionized by electron impact. Samples were heated to a maximum temperature of 200°C at a rate of 700°C/h. Each analysis required 1-5 μg Mg(THD)2. Enrichment levels as low as 5% above natural abundance could be detected satisfactorily. Precision was best at 26Mg enrichment levels of 8-40% above natural abundance, the levels most likely to be encountered in analysis of plasma, urine and fecal samples from experimental subjects who had received 26Mg as a tracer. The method was compared to neutron activation (NA) analysis and judged superior. © 1979.