Time-dependent excretion of lithium, sodium, potassium, rubidium, magnesium and strontium in the urine of a multiple sclerosis patient.

Abstract

Field desorption mass spectrometry and stable isotope dilution have been used for direct trace analysis of metals in urine. Samples were collected over 24 h at 2 h intervals from a hospitalized multiple sclerosis patient. Quantitative determinations of Li+, Rb+, Mg2+ and Sr2+ from individual samples have been made and correlated with the amounts of urine excreted as well as with the time of day. The concentrations of Na+ and K+ were determined by flame photometry. The quantities of metals excreted in urine during the course of 24 h were 0.0129 mg for lithium, 4700 mg for sodium, 2100 mg for potassium, 1.4 mg for rubidium, 78.8 mg for magnesium and 0.2356 mg for strontium. The maximal absolute quantities excreted of all metals determined correspond with the largest volume of urine. The highest amounts of potassium, rubidium and strontium were found in urine during the daytime (8.00-20.00), whilst magnesium was excreted increasingly during the night hours (20.00-8.00). The excretion of lithium and sodium is fairly even over the entire 24 h period. It is noteworthy that similarities in the excretion profile and the concentration course are observed between Li+ and Na+ on one hand and between K+ and Rb+ on the other. Moreover, the lower concentration of Rb+ ions in urine of multiple sclerosis patients, in comparison to healthy individuals and clinical controls as reported previously, was confirmed.