Accurate measurement of stable isotopes 46Ca and 48Ca in human feces, plasma, and urine in relation to human nutrition of calcium

Absorption of Calcium in Premature Infants as Measured With a Stable Isotope 46Ca Extrinsic Tag

“…Stools passed during the collection period were individually weighed, homogenized with deionized water, and frozen at -70" C until needed for radiochemical neutron activation analysis of fecal calcium isotows as ~reviouslv described in detail (21). Briefly, the stool homogen'ates were spiked with 85-strontiuk (85Sr) radiotracer and then submitted to a series of chemical procedures that separated calcium from other constituents in the stool by precipitation with ammonium oxalate.…”

“…The chemical yield of calcium with these procedures was determined by assessing the recovery of 85Sr. After preirradiation chemical separation, each sample (and the appropriate standard) was subjected to two-irradiation-decay-count cycles, as described previously (21). The first cycle is designed to measure 48Ca content [48Ca ( n ,~) 49Ca: H = 8.72 min; y:3084 Kev]; the second cycle &Ca content [46Ca (n,y) 47Ca(p-) 47S~: Hca4, = 4.54 days; Hw7 = 3.41 days; ysc4,: 159 Kev].…”

“…This method has been previously utilized by Barltrop et al (7) to study calcium balance in premature infants fed one of three experimental formulas that varied widely in content of calcium and phosphorus, and by Ehrenkranz et al (1 1) to investigate zinc absorption in the premature infants described herein. In addition, this methodology has been extensively employed in human adults for assessment of the dietary availability of calcium (21), zinc (23,27), copper (36), iron (22,23), and selenium (1 9, 24).…”

Stable isotopes in clinical research

“…Truce element and mineral metabolism 28Mg, 42Ca, 44Ca, 65Cu, "Zn, 54Fe, 57Fe and 74Se have been used to determine intestinal absorbtion and turnover kinetics (28)(29)(30)(31)(32)(33). The most popular techniques to date have been thermal ionization mass spectrometry [28] and neutron-activation analysis [29], but inductively coupled plasma source mass spectrometry will be used increasingly because of the simplicity of sample preparation and analysis [34].…”

Measurements of calcium isotopes and isotope ratios: a new method based on helium plasma source “off-cone” sampling time-of-flight mass spectrometry

“…A report by Janghorbani et al showed that enriched stable isotopes can also be used for studying calcium absorption, which provide a safe method for human studies without the risk of radiation exposure. 7 A number of mass spectrometric methods have been used for stable calcium isotopes measurement, including thermal ionization mass spectrometry (TIMS), 8,9 fast atom bombardment mass spectrometry (FABMS), 10,11 secondary ion mass spectrometry (SIMS), 12 resonant ionization mass spectrometry (RIMS) 13 and laser desorption timeof-flight mass spectrometry (LDTOFMS). 14 Among these techniques, TIMS and FABMS are most frequently used for stable calcium isotopes measurement.…”