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At least 19 recordsLinked to original sources
PubMed2006

Chromatographic zinc isotope separation by phenol formaldehyde benzo crown resin.

New types of phenol formaldehyde resin having benzo crown as a functional group were synthesized and applied to zinc isotope chromatographic operation. Zinc adsorption and isotope separation capacities were dramatically improved by using phenol formaldehyde benzo-15-crown-5 resin. Zinc batch adsorption tests were performed by various dehydrated organic solvents. Separation coefficient, epsilon 8.1 x 10(-4) and height equivalent to a theoretical plate (HETP) 0.105 cm for the isotopic pair of 68Zn/64Zn in phenol formaldehyde benzo-15-crown-5 resin were obtained in the case of acetone as the solvent at 298+/-1K.

Adsorption↗
PubMed1989

Intrinsic and extrinsic stable isotopic zinc absorption by infants from formulas.

The kinetics of fecal elimination and the extent of fractional absorption of intrinsic and extrinsic zinc from infant formula were studied in 11 human infants by using a direct, simultaneous dual-label method based on fecal monitoring of unabsorbed stable isotope labels. The relative positions of the two stable isotopic tags (67Zn, 70Zn) as extrinsic and intrinsic labels were reversed in two separate determinations of fractional absorption. Administration of doubly labeled formula for 24 h or less permitted elimination of unabsorbed labels before the end of a 72-h metabolic interval. The extent of enrichment and the kinetics of fecal elimination of unabsorbed extrinsic stable isotopic zinc tag were observed to agree closely with the corresponding values for the intrinsic tag. Fractional absorption of intrinsic and extrinsic tags was highly correlated and did not differ significantly. The ratio of fractional absorption of extrinsic tag to that of intrinsic tag was 1.05 +/- 0.19 (mean +/- SD). The results constitute strong support for validation of the use of enriched stable isotopes at low levels (less than or equal to 10%) of extrinsic addition to milk-based diets for studies of zinc absorption by humans.

Analysis of Variance↗
PubMed2005

Measurement of iron and zinc isotopes in human whole blood: preliminary application to the study of HFE genotypes.

Multi-collector inductively coupled plasma--sector field mass spectrometry was applied to the measurement of Fe and Zn isotopes in human whole blood samples. For the Fe present in the blood of healthy adults, enrichment of the lighter isotopes relative to a standard material was observed, in agreement with earlier studies. The level of fractionation was found to be lower in hemochromatosis patients exhibiting homozygous (C282Y/C282Y) mutation of the HFE gene. On the one hand, this reinforces the hypothesis that Fe fractionation in blood decreases with enhanced dietary absorption. On the other hand, this contradicts predictions made on the basis of determinations of Fe fractionation in blood samples collected from subjects characterized by milder HFE mutations. In healthy subjects, the Zn in blood is depleted in lighter isotopes, consistent with the limited number of prior observations. As for Fe, the Zn isotopic composition exhibited a tendency toward lower levels of fractionation in the blood of subjects with hereditary hemochromatosis with homozygous mutation (C282Y/C282Y) of the HFE gene. The results therefore suggest that both Fe and Zn isotopic signatures in whole blood, at least to some extent, reflect polymorphisms in the HFE gene.

Adult↗
PubMed1999

Polyatomics in zinc isotope ratio analysis of plasma samples by inductively coupled plasma-mass spectrometry and applicability of nonextracted samples for zinc kinetics.

Inductively coupled plasma-mass spectrometry (ICP-MS) is a powerful tool for both quantitative multielement analyses of inorganic elements and measurement of isotope ratios (IRs). The main disadvantage of this technique is the existence of polyatomic isobaric interferences at some key masses. Zinc has been investigated for such potential interferences in serum or plasma. The Zn isotopes, 66Zn and 68Zn, have no apparent interferences, but 32S1602 and 32S2 are isobaric with 64Zn. The possible effects of S and other major components of blood plasma-Na, K, Cl, P, Ca-on Zn IRs were investigated using a series of mineral solutions which simulated human plasma with respect to these elements. The mixture of all mineral elements interfered only with 64Zn (6.66 ng/mL) and 70Zn (8.51 ng/mL). Interferences to 66Zn, 67Zn, and 68Zn were minimal containing 0.90, 0.94, and 0.39 ng/mL, respectively. The copresence of Na or S shifted 35Cl16O2 (atomic mass 67 coming from Cl solution) to 35Cl2 which reduced the contribution to 67Zn. The hypothesis that Zn IRs obtained from plasma at various intervals after the intravenous administration of enriched 67Zn to humans would reflect those obtained after extraction of Zn was therefore tested. To compare the two pretreatment methods, "extraction" versus "nonextraction," specimens were collected from 10 human subjects at intervals of 5 min to 24 h postinjection, and in 4 subjects from 5 min to 9 d postinjection. Two separate aliquots of plasma from each time-point were dried and digested with hydrogen peroxide, and the residue dissolved in nitric acid. One specimen was subjected to zinc extraction using ammonium diethyldithiocarbamate chelate followed by back extraction into nitric acid. The matching aliquot received no further pretreatment. The normalized IRs obtained from 67Zn/66Zn and 67Zn/68Zn in both the "extracted" and "nonextracted" samples agreed well (r2 = 0.976 and r2 = 0.985, respectively) compared to those from other ratios (r2 = 0.838 for 67Zn/64Zn and r2 = 0.747 for 67Zn/70Zn). Considering the minimum possibility of isobaric interferences in plasma samples, 67Zn/68Zn obtained from "nonextracted" samples is sufficient for routine Zn kinetic analysis by ICP-MS.

Argon↗
PubMed1989

Radiochemical neutron activation analysis of zinc isotopes in human blood, urine, and feces for in vivo tracer experiments.

Enriched stable isotopes are being increasingly used for study of trace element nutrition in humans who cannot be studied by use of in vivo radioactive tracers (e.g., subjects under age 18 and pregnant women). Zinc metabolism in these subjects can be evaluated by administration of Zn enriched to 65% in the minor isotope, 70Zn (0.6% natural abundance). The enhanced 70Zn is detected later in red blood cells, plasma, urine, and feces by measuring 70Zn/64Zn or 70Zn/68Zn ratios. Stable isotope concentrations are measured by neutron activation of the samples and observation of their products: 244-day 65Zn, 14-h 69mZn, and 4-h 71mZn. Zinc-65 can be observed in these samples without chemical separations 3 weeks after irradiations, but large amounts of 24Na and other short-lived species preclude direct observation of the short-lived Zn activities. Preirradiation chemistry was developed to remove most interferences, the major steps being to place the sample on Chelex resin, elute alkali metals and alkaline earths from it, and irradiate the resin containing the Zn. gamma-Rays of 69mZn can be observed on the irradiated resin, but additional precipitation and solvent extraction steps are needed to remove 56Mn and 64Cu for clear observation of 71mZn and 65Zn within hours after irradiation. Yields for pre- and postirradiation separations are typically 85% and 70%, respectively. The stable isotope tracer method was validated by simultaneous in vivo tracing with radioactive 65Zn in four subjects.

Feces↗
PubMed1987

Intrinsic labeling of bovine milk with enriched stable isotopes of zinc.

Bovine milk was labeled intrinsically with enriched stable isotopic zinc for human bioavailability studies. Intrajugular administration of zinc isotopes temporarily increased the plasma zinc concentration of Ayrshire cows by as much as 76%, but milk zinc concentration and the distribution of zinc between casein and whey did not change appreciably. Milk zinc isotopic enrichment reached 105 and 613 atom % excess for 67Zn and 70Zn, respectively within 4-12 hr of zinc administration and decreased gradually over several days. This degree of isotopic enrichment is sufficient for testing bioavailability to infants of intrinsic zinc from milk-based formulas.

Animals↗
PubMed1995

Zinc absorption estimated by fecal monitoring of zinc stable isotopes validated by comparison with whole-body retention of zinc radioisotopes in humans.

Knowledge about zinc availability from human diets is limited due to methodological difficulties. Recently developed stable isotope techniques for estimating dietary zinc absorption were compared with radioisotope techniques in five men and three women. Stable and radioactive zinc isotopes were simultaneously administered. Fecal excretion of the isotopes as well as whole-body retention of the radioactive zinc isotope was monitored. Concentration of stable zinc isotope label in fecal samples was determined by inductively coupled plasma mass spectrometry by fully quantitative measurements and from inductively coupled plasma mass spectrometry isotope ratios combined with analysis of total zinc content using atomic absorption spectrometry. Zinc absorption estimated from whole-body retention was 27 +/- 6% (mean +/- SD), estimated zinc absorption obtained by fecal monitoring of radioisotope was 26 +/- 9%, and the two stable zinc measurements resulted in values of 29 +/- 12 and 33 +/- 12%, respectively. There was no significant difference in zinc absorption estimated from whole-body retention and with the fecal monitoring methods. Recovered stable zinc isotope label was significantly lower than recovered radioisotope. For individual fecal samples, systematic differences of 16% and 12%, respectively (P < 0.05), between the radioisotope recovery and the recovery of stable isotopes with the two methods for measurement was observed. The stable zinc isotope technique for measurement of zinc absorption resulted in mean results similar to those of the radioisotope technique, but with a larger variation in the measurements.

Adult↗
PubMed2002

The use of zinc stable isotopes in the study of iron-zinc interactions in Chilean women.

The objective of this study was to compare the fractional zinc absorption (FAZ) and the size of the rapidly exchangeable zinc pool (EZP) after three months of iron supplementation in women consuming ferrous sulfate between meals. Twenty-one non-anemic apparently healthy women received on average 55.1 +/- 18.5 mg elemental iron per day as ferrous sulfate, and five received no supplemental iron. Fractional absorption of zinc was determined before and three days after finishing the third month of iron supplementation by using an extrinsic labeling with zinc stable isotopes and a dual isotope enrichment method in urine. EZP was determined from urine enrichment following intravenous administration of 70Zn. Results of selected zinc-related variables in the iron supplemented women were (before vs. after iron supplementation): FAZ with meal 0.22 vs. 0.24, p = .23; FAZ in fasting state 0.58 vs. 0.69, p = .005; EZP 177 mg vs. 160 mg, p = .058; plasma zinc 90.6 vs. 86.1 micrograms/dl, p = .065. The control group remained unchanged. The capacity to absorb zinc was increased three days after terminating a period of iron supplementation as compared with the pre-iron period. This may be attributable to impairment of zinc status by the iron supplements as evidenced by a trend for lower plasma zinc and EZP.

Adolescent↗
PubMedDate not supplied

Determination of isotope ratios in human tissues enriched with zinc stable isotope tracers using inductively coupled plasma-mass spectrometry (ICP-MS).

Enriched fecal and urine samples were prepared using ion-exchange column chromatography for analysis by Inductively Coupled and Fast Atom Bombardment Mass spectrometry (ICP-MS, FAB-MS) to compare precision between methods. Unenriched samples of human milk, feces, and whole blood were prepared similarly to monitor instrumental precision and analytical error. A least squares fit of the ICP-MS results vs the FAB-MS for 70Zn/64Zn gave a slope of 0.98, with a relative standard deviation (RSD) of only 0.7%. The results for 68Zn/64Zn gave a slope of 0.82, with a RSD of 14%. For unenriched tissues, all potential interferences were removed by the preparation procedure with no significant differences between preparation for isotope ratios of 70Zn/64Zn, 68Zn/64Zn, 67Zn/64Zn, and 66Zn/64Zn. Poisson counting statistics are a major contribution to the total analytical error indicating the usefulness of this procedure for enrichment studies.

Animals↗
PubMed2003

[Studies on the zinc bioavailability using stable isotope techniques].

Zinc is one of essential trace elements in humans. Zinc homeostasis is mainly regulated by the changes of intestinal absorption efficiency and endogenous excretion, namely the regulation of bioavailability. Studies on zinc bioavailability play an important role on a thorough understanding of zinc metabolism and reliable assessment on population zinc status. Stable isotopes are valuable tools for research on mineral bioavailability and metabolism. Zinc stable isotopes can be used for all population as tracers with no exposure to radiation. Since 1980s' many different stable isotope methods have been applied to the zinc metabolism research. However, limitations to these approaches and methodological problems remain to be resolved. In addition, the introduction and development of new analytical instruments not only make it possible to use zinc stable isotope, also greatly diminish the difficulty and cost on it. The paper is mainly focused on the zinc bioavailability and present a review of its development history, main research methods and analytical skills.

Biological Availability↗
PubMed2000

Prenatal iron supplements impair zinc absorption in pregnant Peruvian women.

Prenatal iron supplements may adversely influence zinc absorption during pregnancy. To examine the impact of prenatal iron supplements on supplemental zinc absorption, fractional zinc absorption was measured in 47 pregnant Peruvian women during the third trimester of pregnancy (33 +/- 1 wk gestation). Of these 47 women, 30 received daily prenatal supplements from wk 10-24 of pregnancy until delivery. Supplements contained 60 mg of Fe and 250 microg of folate without [iron group (Fe), n = 16] or with [iron and zinc supplemented group (Fe + Zn), n = 14] 15 mg of Zn. The remaining 17 women [unsupplemented control group (C)] received no prenatal supplementation. Zinc concentrations were measured in plasma, urine and cord blood and percentage zinc absorption was determined following dosing with oral ((67)Zn) and intravenous ((70)Zn) stable zinc isotopes. Percentage zinc absorption was significantly lower than controls in fasting women receiving iron- containing prenatal supplements (20.5 +/- 6.4 vs. 20.2 +/- 4.6 vs. 47.0 +/- 12.6%, Fe, Fe + Zn and C groups, respectively, P: < 0.0001, n = 40). Plasma zinc concentrations were also significantly lower in the Fe group compared to the C group (8.2 +/- 2.2 vs. 9.2 +/- 2.2 vs. 10.9 +/- 1. 8 micromol/L, Fe, Fe + Zn and C groups, respectively, P: = 0.002), and cord zinc concentrations were significantly related to maternal plasma Zn levels (y = 6.383 + 0.555x, r = 0.486, P: = 0.002). The inclusion of zinc in prenatal supplements may reduce the potential for iron supplements to adversely influence zinc status in populations at risk for deficiency of both these nutrients.

Adult↗
PubMed2005

Zinc stable isotope fractionation during its adsorption on oxides and hydroxides.

Adsorption of Zn on goethite, hematite, birnessite, pyrolusite, corundum, and gibbsite was studied using a batch adsorption technique as a function of pH, zinc concentration in solution, and time of exposure. Adsorption from 0.01 M NaNO3 solutions undersaturated with respect to zinc (hydr)oxide at 3 MeOZn+ complexes, where Me=Fe, Mn, and Al, was used to describe the dependence of adsorption equilibria on aqueous solution composition in a wide range of pH and Zn concentration. The logarithms of surface stability constant for Zn interaction with metal oxy(hydr)oxides (>MeOH0+Zn2+-->MeOZn+) vary from -2.5 to 0.5. They are higher for oxy(hydr)oxides than for anhydrous oxides. Stable isotopes of zinc in several filtrates were measured using an ICP-MS Neptune multicollector which made it possible, for the first time, to assess the degree of isotopic fractionation between 66Zn and 64Zn during zinc adsorption on mineral surfaces. The isotopic offset between aqueous solution and mineral surfaces (Delta(66/64)Zn(soln/solid)=delta((66/64)Zn)(solution)-delta((66/64)Zn)(surface)) was found to be weakly dependent on percentage of adsorbed metal and equals 0.20+/-0.03, 0.17+/-0.06, -0.10+/-0.03, -0.10+/-0.09, and -0.13+/-0.12 per thousand for goethite, birnessite, pyrolusite, corundum, and Al(OH)3. For hematite, Delta(66/64)Zn varies from -0.61+/-0.10 per thousand at pH 5.5 to -0.02+/-0.09 per thousand at 5.8 MeOZn(H2O)(n) complexes (available literature data on X-ray absorption spectroscopy). Apparently, the fine structure of surface complexes and the position and bond strength for second neighbors of zinc are likely to control its isotopic fractionation during adsorption on mineral surfaces. Our results strongly suggest that inorganic processes controlling zinc isotope adsorption on soil and sediment minerals should be of second-order importance compared to biological factors.

Journal Article↗
PubMed1981

Intrinsic labelling of chicken meat with stable isotopes of zinc, for intended use in human feeding studies: feasibility and design considerations.

1. The feasibility of intrinsically labelling poultry meat with the stable isotopes 68Zn and 70Zn was investigated. 2. Chickens (1-d-old) were gavaged with solutions of 68Zn and 70Zn several times over a 42 d period. 3. Isotopic analysis of edible tissues has shown that they were significantly enriched with respect to the gavaged isotope and that the extent of isotopic enrichment achieved was sufficient to permit their use in human feeding experiments designed to investigate availability of native Zn from such food models. 4. The absolute efficiency of retention of the stable isotopes from gavage solutions in the edible tissues has been calculated to be 2-3% of the administered dose; methods have been suggested to enhance this value, based on considerations of utilization of dietary Zn.

Animals↗