High precision measurements of lithium isotopic composition at sub-nanogram by MC-ICP-MS with membrane desolvation.

The geochemistry of Li and Li isotopes is a promising tracer of chemical weathering processes for both modern and ancient times. Therefore, accurate and precise determination of the isotopic composition of Li is required for a large variety of complex geological samples with different Li concentrations and matrix/Li ratios. Especially, geochemical studies of precious geological samples with ultra-low lithium content and high matrix. In this study, the accuracy and the precision corresponding to Li isotopic measurements of low-level samples using multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) with membrane desolvation introduction system was evaluated. The method of MC-ICP-MS with membrane desolvation and a high-sensitivity X-skimmer cone, together with a simple one-step column separation enabled the high-precision isotopic analysis of Li quantities as small as 2 ng. The long-term instrumental external reproducibility of δ7Li values for the L-SVEC and SPEX-Li were 0.0 ± 0.1‰ (n = 20) and 12.1 ± 0.4‰ (n = 20), respectively. Based on the measurements on a series of international reference materials over the last two years. The measured δ7Li values for the standards with a variety of matrices, including BHVO-2, AGV-2 and seawater (NASS-6). The δ7Li values of BHVO-2 (4.58 ± 0.35‰), AGV-2 (6.85 ± 0.40‰) and NASS-6 (30.88 ± 0.20‰) are in agreement with the published data within the uncertainty. We also present analytical results for South China Sea surface seawater water, meteorite, limestones and rain water. These results demonstrate the validity of the method for obtaining highly precise and accurate outcomes.

An improved calibrated mass spectrometry for absolute copper isotope-ratio measurement using two strategies for mass bias correction factor.

Modern advances in multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS) have greatly promoted the investigation of copper isotopes in various research fields. To meet the demand, an improved calibrated mass spectrometry for the absolute determination of copper isotopic composition was developed in this study. The method has made progress in the investigation of instrumental mass bias correction factor for copper isotopic analysis using MC-ICPMS through employing two independent strategies. One is the conventional mathematical iterative method based on the MC-ICPMS measurement data; the other one is direct calculation using the absolute copper isotopic compositions in isotopically enriched 63Cu and 65Cu materials by developing a TE-TIMS method. The results of Kiter = 0.95563(16)k = 1 and KTE = 0.95551(17)k = 1 were consistent in their standard uncertainties, demonstrated the first cross-validation of these two strategies. Thereafter, the proposed calibrated mass spectrometry were applied to re-measure the copper isotope amount ratios in three isotopic reference materials, resulted in RNIST SRM 97665/63 = 0.44547(16)k = 2, RERM®-AE63365/63 = 0.44549(16)k = 2, and RERM®-AE64765/63 = 0.44557(16)k = 2, respectively. These expended uncertainties were only one third or one fifth of the stated uncertainties in their certificates. Furthermore, the absolute copper isotopic compositions in four natural-abundance samples and a new copper isotopic reference material GBW04624 were determined, given an average atomic weight of copper as Ar(Cu) = 63.5456(4)k = 2. The δ65Cu values of GBW04624 relative to NIST SRM 976, ERM®-AE633 and ERM®-AE647 were also applied by implementing the C-SSBIN calibration model. This provides an additional independently certified and SI-traceable copper isotopic reference material, in support of various scientific researches.

Physiologic requirement for iron in pregnant women, assessed using the stable isotope tracer technique.

BACKGROUND: Knowledge of the physiologic requirement for iron, the core index for the formulation of a dietary reference intake (DRI), is of great importance for the health of a pregnant woman and her fetus, and can help a mother accurately plan her iron supplementation. However, direct measurements of the physiologic requirement for iron during pregnancy are still lacking. METHOD: Eleven women of reproductive age from Hebei Province, China, who planned to become pregnant in the near future, were enrolled between January and March 2015 and included in the final analysis. Subjects participated in a 2-week metabolic trial in which they consumed 50 mg of the stable isotope 58Fe, and were then followed for ~ 2 years. The abundance of 58Fe and the total iron concentration in the circulation were measured using Multi-collector Inductively-Coupled Plasma Mass Spectrometry and Atomic Absorption Spectroscopy, respectively. The physiologic requirement for iron during pregnancy was then calculated by the formula derived from our previously published work. RESULTS: The mean physiologic requirement for iron in the 11 subjects, across their entire pregnancies, was 3.05 mg.d- 1 in total and 44.0 µg.kg- 1.d- 1 after adjustment for body mass. The physiologic requirements for iron in the first, second, and third trimesters were 2.04 mg.d- 1, 3.26 mg.d- 1, and 4.13 mg.d- 1, respectively. When adjusted for body mass, the physiologic requirements for iron in different trimesters were 32.3 µg.kg- 1.d- 1, 46.9 µg.kg- 1.d- 1, and 55.7 µg.kg- 1.d- 1, respectively. CONCLUSION: We preliminarily explored the physiologic requirement for iron in pregnant women. The data demonstrated that pregnant women needed about twice iron than non-pregnant women. This research may be helpful for the design of future studies and the modification of iron DRIs. TRIAL REGISTRATION: ChiCTR, ChiCTR-OCH-14004302. Registered 14 February 2014, http://www.chictr.org.cn/showproj.aspx?proj=5267.

Physiological requirements for iron in women of reproductive age assessed by the stable isotope tracer technique.

BACKGROUND: Iron nutrition is important for the health of women of reproductive age, and defining the physiologic requirement for iron can help them accurately plan the iron intake. However, research on the physiologic requirement for iron in women is insufficient worldwide. This study aimed to further improve the methodology and get more precise data for the physiological requirements for iron in women of reproductive age on the basis of our previous study. METHOD: Sixty-one women of reproductive age who had not been pregnant before and during the whole study were included from Hebei province, China in 2015. Each subject participated in a 2-week metabolic trial with consuming 50 mg of the stable isotope 58Fe, and were then followed for ~ 800 days. The abundance of 58Fe and the total iron concentration in the circulation were measured using multi-collector inductively-coupled plasma mass spectrometry and atomic absorption spectroscopy. The physiologic requirement for iron in women of reproductive age was then calculated. RESULTS: The average iron circulation rate was 80.4%, and the steady period started from about 1 year. The average physiological requirement for iron of 21 subjects obtained by formula calculation was 1.55 mg/d and 23.63 µg.kg- 1.d- 1 after adjustment for body mass, and that of 33 subjects obtained by linear regression was 1.29 mg/d, 20.98 µg.kg- 1.d- 1 after adjustment for body mass. The results by two methods showed no significant difference. The EAR and RNI calculated from this results was 11-13 mg/d and 15-18 mg/d, respectively, both of which were slightly lower than the recommended value in Chinese Dietary Reference Intake (2013). CONCLUSION: The physiological requirements for iron in women of reproductive age were in accordance with other studies, while the EAR and RNI calculated from which were slightly lower than Chinese present recommended value. TRIAL REGISTRATION: ChiCTR, ChiCTR-OCH-14004302. Registered 14 February 2014, http://www.chictr.org.cn/enindex.aspx.

Bioavailability and incorporation of nonheme iron from a representative Chinese diet in young urban Chinese women.

BACKGROUND AND OBJECTIVES: This study assessed the bioavailability and biological incorporation of nonheme iron from staple food diets in healthy young urban Chinese women and determined the relevant effects of typical regional patterns of staple foods in South and North China. METHODS AND STUDY DESIGN: Twenty-two young urban Chinese women aged 20-23 years were enrolled and randomly allocated to two groups, with rice (rice group) and steamed buns (steamed buns group) as the staple food, respectively. Each participant received three meals daily containing approximately 3.25 mg of stable 57FeSO4 for 2 consecutive days, along with daily intravenous injection of approximately 2.0 mg of 58FeSO4. Nonheme iron absorption and infused iron incorporation rates were assayed. RESULTS: In all participants, the rice group, and the buns group, nonheme iron intake was 7.2±1.6, 5.9±0.6, and 8.4±1.2 mg, respectively; mean 57FeSO4 absorption rate was 22.2%±9.6%, 22.2%±10.6%, and 22.2%±8.9%, respectively; and the mean infused 58FeSO4 incorporation rate was 91.6%±8.2%, 93%±7.3%, and 90%±9.1%, respectively. No substantial differences existed in the nonheme iron intakes and the 57FeSO4 absorption and 58FeSO4 incorporation rates between the rice and buns groups (all p>0.05). CONCLUSIONS: The bioavailability and incorporation rates of nonheme iron from representative comprehensive Chinese diets in healthy young urban Chinese women were evaluated. Our results can facilitate the establishment of dietary reference intake for iron in Chinese women.

Investigation of the crucial factors affecting accurate measurement of strontium isotope ratios by total evaporation thermal ionization mass spectrometry.

RATIONALE: An absolute method that does not require calibration is very important in several areas of isotope analysis due to the shortage of suitable certified reference materials (CRMs). As total evaporation thermal ionization mass spectrometry (TE-TIMS) theoretically overcomes mass fractionation through integrating the ion currents till the sample on the filament is completely exhausted, it could be an absolute method that does not require the use of CRMs for calibration. However, the lack of reliable method verification and reasonable uncertainty evaluation restricts its extensive application, and these effects need to be quantitatively evaluated. METHODS: A series of different amounts of strontium reference material SRM987 was deposited on both single and triple tantalum filament sources, and analyzed by TE-TIMS. The work function of the tantalum filament loaded with the sample was measured by ultraviolet photoelectron spectroscopy. In order to evaluate the change in ion transmission efficiency, we terminated the total evaporation process manually after running for a certain period of time, and recorded the ion beam intensity before and after this operation. RESULTS: The TE results obtained with the triple filament source agreed well with the reference values of SRM987, while the TE results obtained with the single filament source changed significantly with the amount of sample loading. The crucial effect factors on TE-TIMS, including ionization temperature fluctuation, variation of ion transmission efficiency and ion loss before data acquisition, were quantitatively assessed. These factors were used to correct the single filament TE results and the measurement uncertainty was quantitatively evaluated. CONCLUSIONS: The reliability of strontium isotopic ratio measurement with triple filament TE-TIMS was verified. The mathematical model for correction of each crucial effect factor was successfully established, thus providing a feasible way for the correction of single filament TE-TIMS results.

Iron physiological requirements in Chinese adults assessed by the stable isotope labeling technique.

BACKGROUND: Iron is a kind of essential trace mineral in the human body, while the studies on its physiological requirement are very limited recently, especially in China. And most studies were performed with the radioisotope tracer technique, which was harmful to health. This study aimed to first get the value of iron physiological requirements in Chinese adults assessed by the stable isotope labeling technique. METHODS: Forty-four eligible young Chinese healthy adults were randomly recruited from the Bethune Military Medical College (Shijiazhuang, Hebei, China) between January 2010 and March 2011, and 19 subjects were included in the final data analysis. After adaptive diets and observation, subjects received 58Fe intravenously. The baseline venous blood sample and general information were collected on day 0. Venous blood samples were also collected on day 14, 30, 60, 100, 120, 150, 240, 330, 425, 515, 605, 767, 1155, respectively. The blood samples were acid digested by a Microwave Digestion System and then analyzed by the MC-ICP-MS and Atomic Absorption Spectroscopy to get the abundance of Fe isotopes and the total iron concentration respectively. The circulation rate (the proportion of blood iron to whole body iron) could be calculated by the intake amount, background content and the peak isotope content. When the abundance changed stably, the iron physiological requirement could be calculated by the iron loss in a period of time. RESULTS: The abundance of 58Fe reached its peak on day 14, and changed stably from day 425. The average circulation rate was 84%, with no significance difference between the 2 genders. The mean iron requirement in females was 1101.68 µg/d, and the mean requirement adjusted by body weight was 20.69 µg/kg.d. For males, the mean iron requirement was 959.9 µg/d, and the requirement adjusted by body weight was 14.04 µg/kg.d. CONCLUSION: Our study has obtained the data about the iron physiological requirements of Chinese adults using stable isotope labeling technique, which could provide the basis for adjusting iron DRIs of Chinese people in the future. TRIAL REGISTRATION: The trial was registered at the Chinese Clinical Trial Registry (No: ChiCTR-TRC-09000581).

Accurate Determination of the Absolute Isotopic Composition and Atomic Weight of Molybdenum by Multiple Collector Inductively Coupled Plasma Mass Spectrometry with a Fully Calibrated Strategy.

A fully calibrated strategy has been investigated for the first time for the accurate determination of absolute isotopic composition and atomic weight of molybdenum using multiple-collector inductively coupled plasma mass spectrometry. The correction for instrumental mass bias was performed using synthetic isotope mixtures, which were gravimetrically prepared with all of the seven high-purity and isotopically enriched molybdenum isotope materials together. Six natural molybdenum materials, including molybdenum standard solution NIST SRM 3134, were accurately measured and yielded the absolute isotopic composition (in atom %, k = 1) of 92Mo-14.690(18), 94Mo-9.173(6), 95Mo-15.865(5), 96Mo-16.666(3), 97Mo-9.588(4), 98Mo-24.307(16), and 100Mo-9.711(13). These isotopic data enable an atomic weight Ar(Mo) of 95.9466(34) (k = 2) to be calculated, which is slightly lower than the current standard atomic weight 95.95(1) and with a much improved uncertainty. The associated uncertainties were evaluated according to the Guide to Expression of Uncertainty in Measurement of ISO/BIPM and Monte Carlo simulation to ensure that all sources of uncertainty were fully accounted for. A particular characteristic of the proposed new approach is that mass bias correction factor K for each isotope ratio of molybdenum can be achieved via fully experimental determination without using the traditional semiempirical correction mathematical models. In addition, the relationship between mass of isotope and bias per mass unit ß was investigated based on the thorough measurement data.

Non-Heme Iron Absorption and Utilization from Typical Whole Chinese Diets in Young Chinese Urban Men Measured by a Double-Labeled Stable Isotope Technique.

BACKGROUND: This study was to observe the non-heme iron absorption and biological utilization from typical whole Chinese diets in young Chinese healthy urban men, and to observe if the iron absorption and utilization could be affected by the staple food patterns of Southern and Northern China. MATERIALS AND METHODS: Twenty-two young urban men aged 18-24 years were recruited and randomly assigned to two groups in which the staple food was rice and steamed buns, respectively. Each subject received 3 meals containing approximately 3.25 mg stable 57FeSO4 (the ratio of 57Fe content in breakfast, lunch and dinner was 1:2:2) daily for 2 consecutive days. In addition, approximately 2.4 mg 58FeSO4 was administered intravenously to each subject at 30-60 min after dinner each day. Blood samples were collected from each subject to measure the enrichment of the 57Fe and 58Fe. Fourteen days after the experimental diet, non-heme iron absorption was assessed by measuring 57Fe incorporation into red blood cells, and absorbed iron utilization was determined according to the red blood cell incorporation of intravenously infused 58Fe SO4. RESULTS: Non-heme iron intake values overall, and in the rice and steamed buns groups were 12.8 ±2.1, 11.3±1.3 and 14.3±1.5 mg, respectively; the mean 57Fe absorption rates were 11±7%, 13±7%, and 8±4%, respectively; and the mean infused 58Fe utilization rates were 85±8%, 84±6%, and 85±10%, respectively. There was no significantly difference in the iron intakes, and 57Fe absorption and infused 58Fe utilization rates between rice and steamed buns groups (all P>0.05). CONCLUSION: We present the non-heme iron absorption and utilization rates from typical whole Chinese diets among young Chinese healthy urban men, which was not affected by the representative staple food patterns of Southern and Northern China. This study will provide a basis for the setting of Chinese iron DRIs.

Effect of NaFeEDTA-fortified soy sauce on zinc absorption in children.

NaFeEDTA has been applied in many foods as an iron fortificant and is used to prevent iron deficiency in Fe-depleted populations. In China, soy sauce is fortified with NaFeEDTA to control iron deficiency. However, it is unclear whether Fe-fortified soy sauce affects zinc absorption. To investigate whether NaFeEDTA-fortified soy sauce affects zinc absorption in children, sixty children were enrolled in this study and randomly assigned to three groups (10 male children and 10 female children in each group). All children received daily 3 mg of (67)Zn and 1.2 mg of dysprosium orally, while the children in the three groups were supplemented with NaFeEDTA-fortified soy sauce (6 mg Fe, NaFeEDTA group), FeSO4-fortified soy sauce (6 mg Fe, FeSO4 group), and no iron-fortified soy sauce (control group), respectively. Fecal samples were collected during the experimental period and analyzed for the Zn content, (67)Zn isotope ratio and dysprosium content. The Fe intake from NaFeEDTA-fortified and FeSO4-fortified groups was significantly higher than that in the control group (P < 0.0001). The daily total Zn intake was not significantly different among the three groups. There were no significant differences in fractional Zn absorption (FZA) (P = 0.3895), dysprosium recovery (P = 0.7498) and Zn absorption (P = 0.5940) among the three groups. Therefore, NaFeEDTA-fortified soy sauce does not affect Zn bioavailability in children.

Surface modification induced shielding effects on electron orbital coupling in metallofullerene.

The electronic properties of four metallofullerenol samples (La@C82(OH)32, La@C82(OH)24, La@C82(OH)18, La@C82(OH)12) and La@C82 were investigated by synchrotron radiation photoelectron emission spectra (PES). A new emission peak with binding energy of 13.9 eV, which is attributed to La 5d orbitals coupling with nanocage orbitals, is observed in PES of La@C82 for the first time. This suggestion is also supported by previous DFT calculations. Furthermore, the new emission peak disappears when the surface of La@C82 is modified with specific numbers of OH groups, which means the electron orbital coupling between inner metallic atoms and outer nanocage in metallofullerene could be shielded by surface modifications on the outer nanocage.

Chain fullerene C60 = C = C60 = C = C60: possible way to all-carbon polymers.

In this paper, we firstly report a simple but very useful process to extend fullerene chains from monomers via C-bridges: C60 --> C60 -- C -- C60 --> C60 -- C -- C60 -- C -- C60, similar to extending CH4 or CH2 = CH2 to synthesize longer alkyl or alkene chains and these-based materials. The self-assembled formation of C60 -- C -- C60 -- C -- C60 from C60 -- C -- C60 was found to be an isomer-selective process. The results offer a valuable access to C60-based new materials of diverse functionalities, and an implication to the large scale utilization of C60 in polymer science.

Photochemical and photophysical properties of three carbon-bridged fullerene dimers: C121 (I, II, III).

The photochemical and photophysical properties of the three C121 isomers (I, II, III) were investigated with MADLI-TOF-MS, UV-vis spectra, fluorescence spectra, absorption spectra of their DMA complexes, and theoretical calculations. The three isomers of C121 (I, II, III) have different stabilities under laser irradiation, but isomer I and isomer II show good stability against the heat-induced conversion between different isomers: No conversion between the isomers was found after heating the mixture of isomer I and isomer II at 353 K for 12 h in Ar atmosphere. The results of UV-vis absorption and fluorescence spectra indicate that interactions between two C60 moieties of C60=C=C60 in the ground and singlet states are not significant, C121 (I, II, III) behaves as an electron-acceptor similar to C60. These indicate that the formation of the fullerene chain structure (e.g., C60=C=C60) does not disturb the photochemical and photophysical properties of the C60 monomer itself, even that the properties were enhanced by the formation of the polymer. This is significant for the C60 polymer in photochemical or photoelectronic applications in which C60=C=C60 can be an excellent basic unit of polymers.