title: Determination of lithium in microlitre amounts of human body fluids at therapeutic and normal levels by stable isotope dilution and field desorption mass spectrometry.
abstract: The use of field desorption mass spectrometry for the determination of lithium in body fluids at therapeutic levels--ppm region--as well as at the normal level--ppb region--has been developed. The use of a stable isotope enriched internal standard, together with the outstanding sensitivity of field desorption for alkali cations and the high specificity of mass spectrometry, allows a quantitative determination of lithium in microlitre amounts of body fluids, such as plasma, saliva and urine. The assay allows a determination of lithium even at ultratrace concentrations where routine spectroscopic procedures cannot be applied. Analysis of plasma required a simple protein precipitation, whereas saliva and urine could be analysed without treatment. The precision of the data obtained ranged from 2--10%. The time consumption for one analysis in routine work is about 20--30 min.
mesh_terms: D006801:Humans; D008094:Lithium / Q000032:analysis* / Q000097:blood / Q000652:urine; D013058:Mass Spectrometry / Q000379:methods; D008832:Microchemistry; D012463:Saliva / Q000032:analysis
chemical_list: D008094:Lithium