Extraction of serum and urine calcium with ion exchange membrane filters for isotope enrichment determination using thermal ionization mass spectrometry.
The extraction of calcium from water, serum, and urine using Bio-Rex 25 mm ion exchange membrane filters was compared with the oxalate precipitation procedure currently used in our laboratory. Total recoveries of a known quantity of calcium loaded onto the membrane filters for water, serum and urine were as follows: (a) cation exchange filter, 85%, 74%, and 66%; (b) Chelex, 65%, 98%, and 20%; and (c) oxalate precipitation, 93%, 100%, and 96%, respectively. Regression analysis for precipitation versus ion exchange isotope ratio measurements of standards prepared using highly enriched calcium-44 showed slopes of unity. An improvement of automated sample analysis was observed for water and urine calcium samples extracted with ion exchange filters.
Vieira
N E
NE
Laboratory of Theoretical and Physical Biology, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA.
Yergey
A L
AL
D002118:Calcium / Q000032:analysis* / Q000097:blood / Q000652:urine; D002127:Calcium Isotopes; D005374:Filtration; D006801:Humans; D013058:Mass Spectrometry
D002127:Calcium Isotopes; D002118:Calcium