Accurate measurement of stable isotopes of magnesium in biological materials with inductively coupled plasma mass spectrometry

Schuette, Sally A.; Vereault, Donald; Ting, Bill T. G.; Janghorbani, Morteza

doi:10.1039/an9881301837

Cited by 35 publications

(18 citation statements)

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“…Isotope ratio measurements were obtained with ICP-MS using an Elan Model 250 system (SCIEXIPerkin Elmer, Norwalk, CT). We have recently demonstrated that measurement precision (%CV) for the isotope pairs 25Mg/24Mg and 26Mg/ 24Mg with this method is in the range of 0.1-1 % for a number of different biologic matrices (6).…”

Section: Icp-ms Inductively Coupled Plasma Mass Spectrometrymentioning

confidence: 99%

“…Serum, urine, and fecal samples were prepared for isotopic analysis as described previously (6). Isotope ratio measurements were obtained with ICP-MS using an Elan Model 250 system (SCIEXIPerkin Elmer, Norwalk, CT).…”

Section: Icp-ms Inductively Coupled Plasma Mass Spectrometrymentioning

confidence: 99%

“…Such studies require the use of isotopic probes. In our investigations we made use of our newly developed techniques for the precise measurement of Mg isotope ratios in biologic samples (6) to test the feasibility of using isotopic techniques to study Mg absorption and metabolism in full-term human infants. More specifically, we investigated the effect of size of isotope dose (20 or 60 mg) and mode of administration (bolus versus distributed) on isotope absorption and retention, on tissue isotope enrichment (plasma and erythrocytes), and on the relationship between plasma and urine isotope enrichment.…”

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Feasibility of Using the Stable Isotope 25Mg To Study Mg Metabolism in Infants

et al. 1990

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ABSTRACT. The feasibility of using isotopic techniques to study Mg absorption and metabolism was explored in three full-term human infants. 25Mg (98.8 atom %) was administered orally as an in vivo tracer. Fractional 25Mg absorption, isotope retention, endogenous fecal Mg losses, and apparent Mg exchangeable pool size were then determined under three conditions of isotope administration: I) 20 mg 25Mg, with single feeding; 2) 20 mg "Mg, distributed over a 24-h period; and 3) 60 mg 25Mg, over a 24-h period. Mg isotope ratios were determined by inductively coupled plasma mass spectrometry. Fractional absorption was increased in all three infants after distributed versus bolus administration at the 20 mg dose; mean ( f SD) fractional absorption was 64.0 f 3.9 versus 54.3 f 5.9%, respectively. 25Mg retention was also more in all three infants after distributed administration (55.8 f 3.0 versus 44.3 2 1.3% of dose). At the 60-mg "Mg dose, compared to 20 mg, fractional absorption was reduced but absolute isotope absorption more than doubled in all infants; urine isotope losses represented a similar fraction of the absorbed dose, thus, 25Mg retention also more than doubled. Compared to the results of the isoto~e studies. net ME absor~tion and balance were uninfluenced by tdtal M; intake. Isotope retention with distributed isotope administration resulted in measurable isotopic enrichment of plasma and erythrocytes at 72 h (i.e. plasma isotope enrichment was 6.3-10.2 and 19.2-23.5% for the 20-and 60-mg dose, respectively). With these doses, apparent Mg exchangeable pool size ranged from 5.5 to 7.6 mmollkg body wt; these values showed a decrease with age both within and between infants. Our results indicate that Mg stable isotope studies may offer sufficient accuracy and reproducibility to permit meaningful investigations of Mg bioavailability and developmental changes in Mg metabolism in human infants. (Pediatr Res 27: 36-40,1990) Abbreviations Important aspects of Mg homeostasis such as developmental changes in Mg absorption and endogenous fecal excretion, source of urinary Mg losses (endogenous or dietary), body Mg pool sizes, etc. need to be explored if we are to understand the requirement for Mg during growth and developmental changes in Mg metabolism. Such studies require the use of isotopic probes. In our investigations we made use of our newly developed techniques for the precise measurement of Mg isotope ratios in biologic samples (6) to test the feasibility of using isotopic techniques to study Mg absorption and metabolism in full-term human infants. More specifically, we investigated the effect of size of isotope dose (20 or 60 mg) and mode of administration (bolus versus distributed) on isotope absorption and retention, on tissue isotope enrichment (plasma and erythrocytes), and on the relationship between plasma and urine isotope enrichment. MATERIALS AND METHODS Subjects.The subjects were normal Caucasian term infants (two males, one female) who lived at home and were each admitted to the Lora N. Thomas Me...

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Section: Icp-ms Inductively Coupled Plasma Mass Spectrometrymentioning

confidence: 99%

Section: Icp-ms Inductively Coupled Plasma Mass Spectrometrymentioning

confidence: 99%

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Feasibility of Using the Stable Isotope 25Mg To Study Mg Metabolism in Infants

et al. 1990

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“…New generations of mass spectrometers with improved accuracy and requiring smaller doses of isotopes to be administered have been developed, but sample preparation remained time consuming (4)(5)(6). The development of inductively coupled plasma mass spectrometry (ICP-MS) brought about higher sensitivity, rapid throughput, and less time-consuming sample preparation, simplifying magnesium isotopic ratio measurements (7).…”

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Comparison of stable-isotope-tracer methods for the determination of magnesium absorption in humans

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et al. 2003

The American Journal of Clinical Nutrition

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Background:The double-labeling (DL) method for determining magnesium absorption is less cumbersome than is the fecal monitoring method, which has been used most often, but it has not been validated. Objective: The aim of this study was to compare methods and several sampling protocols for determining magnesium absorption to establish a simple and reliable alternative to the fecal monitoring approach. Fecal monitoring was used as the standard against which the DL methods based on urine data (DLU), plasma data (DLP), and plasma kinetics with the use of a deconvolution analysis (DP) were compared. Design: Six healthy adult men received 70 mg 26 Mg orally and 30 mg 25 Mg intravenously. Multiple blood samples and complete urine and fecal samples were collected over 12 d. Stable-isotope ratios were determined by inductively coupled plasma mass spectrometry. Results: Results from DLU were not significantly different from the fecal monitoring reference value (0.48 ± 0.05; x -± SD) when based on 3-d urine pools from 72 to 144 h (0.54 ± 0.04) and when based on the 24-h urine pools from 48 to 72 h (0.49 ± 0.06), 72 to 96 h (0.51 ± 0.11), and 96 to 120 h (0.50 ± 0.06). Results with the DLP method 72 h after isotope administration also compared well with those with the fecal monitoring method (0.54 ± 0.09). Magnesium absorption was 0.47 ± 0.06 with the DP method, which also agreed with the fecal monitoring value. Conclusions: The DL methods are an alternative to fecal monitoring when applied within the appropriate time intervals. Therefore, DLU-the simplest and least invasive approach-is recommended for determining magnesium absorption.

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“…In addition to the radioactive isotopes, three stable Mg 2ϩ isotopes exist. These stable isotopes, i.e., 24 Mg, 25 Mg, and 26 Mg, have a respective natural abundance of 79, 10, and 11% and can be distinguished by inductively coupled plasma mass spectrometry (ICP-MS) (39) …”

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