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Endogenous lithium determination in blood plasma and urine by isotope dilution mass spectrometry and preliminary isolation of lithium fraction using paper chromatography
Author(s) -
Fleishman D. G.,
Nikiforov V. A.,
Saulus A. A.
Publication year - 1992
Publication title -
biological mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 1052-9306
DOI - 10.1002/bms.1200210204
Subject(s) - chromatography , chemistry , isotope dilution , lithium (medication) , urine , mass spectrometry , dilution , extraction (chemistry) , sample preparation , analytical chemistry (journal) , biochemistry , medicine , physics , thermodynamics , endocrinology
A version of isotope dilution mass spectrometric technique elaborated for measuring endogenous lithium concentrations in human blood plasma and urine (10 −7 M region) and applicable in clinical practice is described. A tracer solution of lithium (LiCl) enriched in 6 Li (with abundances 6 Li 92%, 7 Li 8%) is added to a certain volume of human plasma (0.2–0.4 ml) or urine (0.05–0.1 ml) and dried under an infrared lamp. Thereupon a soluble part extracted from dried plasma with the aid of 0.1 N HCl is dried as well. Dry extracts from plasma and dried samples of urine are processed by 30% H 2 O 2 and subsequently subjected to paper chromatography (with ethanol as a solvent). Such processing of samples is simple and short (about an hour, 3 min of chromatographic process inclusive), achieving a good separation from organic matrix and interfering macroelements. Contamination of sample in processing is about 2–5 pmol; routine control of contamination and account of their influence are accomplished by measuring two different volumes of each sample. Measurements are made with high precision: cyclic repeated scanning of 7 Li and 6 Li peaks have a standard deviation of 7 Li/ 6 Li ratio no more than 0.7%. The method described was used to determine endogenous lithium clearance of hypertensive patients and patients with transplanted kidney.