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Separation and Analysis of Boron Isotope in High Plant by Thermal Ionization Mass Spectrometry

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Separation and Analysis of Boron Isotope in High Plant by Thermal Ionization Mass Spectrometry Hindawi Publishing Corporation International Journal of Analytical Chemistry Volume 2015, Article ID 364242, 6 pages http://dx.doi.org/10.1155/2015/364242 Research Article Separation and Analysis of Boron Isotope in High Plant by Thermal Ionization Mass Spectrometry Qingcai Xu,1 Yuliang Dong,1 Huayu Zhu,1 and Aide Sun1,2 1 Shandong Provincial Key Laboratory of Water and Soil Conservation and Environmental Protection, College of Chemistry and Chemical Engineering, Linyi University, Linyi 276005, China 2State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China Correspondence should be addressed to Aide Sun; [email protected] Received 5 October 2015; Revised 24 November 2015; Accepted 8 December 2015 Academic Editor: David M. Lubman Copyright © 2015 Qingcai Xu et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Knowledge of boron and its isotope in plants is useful to better understand the transposition and translocation of boron within plant, the geochemical behavior in the interface between soil and plant, and the biogeochemical cycle of boron. It is critical to develop a useful method to separate boron from the plant for the geochemical application of boron and its isotope. A method was developed for the extraction of boron in plant sample, whose isotope was determined by thermal ionization mass spectrometry. The results indicated that this method of dry ashing coupled with two-step ion-exchange chromatography is powerful for the separation of boron in plant sample with large amounts of organic matters completely. The ratios of boron isotope composition in those plant tissue samples ranged from −19.45‰to+28.13‰(totalrange:47.58‰) with a mean value of 2.61±11.76‰SD.Thestemandroot isotopic compositions were lower than those in flower and leaf. The molecular mechanism of boron isotope may be responsible for the observed variation of boron isotopic composition and are considered as a useful tool for the better understanding of boron cycling process in the environment and for the signature of living systems. 1. Introduction a wide range of geochemical, cosmochemical, and geophysi- cal problems. Recent concerns about the use of B isotope in Boron (B) is a critical micronutrient in the growth of plant, biological systems have been taken into consideration for its which was undoubtedly considered as a part of the structure important role in embryonic development and organogenesis inthecellwall[1–3].Moreincreasingevidencewaspresent in plant growth [1, 3] and its isotopic fractionation in the for a possible role of B in metabolism processes, such as cyclingofBintheuptakebyplantfromsoilandprocessing the maintenance of plasma membrane function and several within plant by a series of chemical or biochemical reactions. metabolic pathways. Park and Schlesinger [4] reported that The presence of lots of organic matters in plant can influ- + most B is fixed into cell wall and is not recycled internally encetheemissionofCs2BO2 ion current in the chamber once used by plant, but some B would be emitted to atmo- of TIMS [9, 10]. In plant, the appropriate pretreatment of sphere in plant aerosol or during the biomass burning. When sample should effectively remove organic contaminants and plantdied,themajorityisreturnedtosoil.Theglobaluptake meanwhile keep B isotopic composition stable. The method of B by plant from soils can be calculated as 4.5 Tg B/yr [4]. using Amberliter IRA 743 resin coupled with cation and AlloftheseindicatedthatthecyclingofBandtheequilibrium anion ion-exchange mixing resin developed by Xiao et al. [11] ofBisotopeintheprocessbetweenplantandsoilwouldbe and Wang et al. [12] was applied as a proxy for the separation changed. of B, especially in the water samples. The techniques of micro- 10 11 In nature, B has two stable isotopes: Band B. Because sublimation [13–15] and digestion with H2O2 were fit for the B shows a large variation in the stable isotopic composition samples with few organic matters. The wet chemical digestion (∼90‰) [5–8], B and its isotope have been used to investigate with HNO3/H2O2 in common was used to digest plant 2 International Journal of Analytical Chemistry Table1:Samplingsitesandplantspecies. Species Sampling location Altitude (m) Longtitude Latitude Habit type Soil type ∘ ∘ W. florida Linyi, Shandong 71 118 17 13.21 E356 21.24 N Sand Shantung soil ∘ ∘ E. angustifofia Pingyi, Shandong 242 117 4023.52 E3515 56.88 N Sand Cinnamon soil ∘ ∘ C. songaricum Jilantai, Inner Mongolia 1060 105 37 13.83 E3934 42.61 N Sand Sandy soil ∘ ∘ S. mussotii Yushu, Qinghai 3585 97 53 23.28 E3320 12.12 N Shrub grassland Alpine steppe soil ∘ ∘ H. elliptica Banma, Qinghai 3514 100 47 3.48 E3246 27.12 N Bottomland meadow Meadow soil sample; however, this method would produce the isobaric was of 99.994% purity. High-purity graphite was added to a + Cs2CNO ion of / 308 and 309, which affected the deter- mixture of ethanol solution (80%) to obtain the final solution minationofBisotope.Weietal.[16]developedamethod corresponding to 13 mg/g graphite. The isotopic reference using HF, H2O2, and mannitol mixed solution to separate standard used in this study was NIST SRM 951 boric acid B from the silicate rock sample successfully, and B isotope (Gaithersburg, MD, USA). A solution of mannitol of 1.82% + ratio was determined by multicollector inductively coupled (w/v) and Cs2CO3 solution containing 12.3 mg/mL of Cs was plasma mass spectrometry (MC-ICP-MS). These techniques also prepared. Sodium carbonate, ammonia hydroxide, and mentioned above were not suitable to eliminate large number sodium chloride were of the analytical grade reagent. Borax of organic matters in plant sample. Wieser et al. [17] and Serra and boric acid were of Guaranteed grade Reagent. et al. [18] attempted B isotopic composition for biogeochem- The resins, B specific resin Amberlite IRA 743, strong ical plant-soil interaction and provenance on the coffee bean. cation exchange resin Dowex 50W X8, and weakly anion However, methods for determining B isotopic composition exchange resin Amberlite IRA 67, were purchased from in different plant tissues are scarce [19]. Sigma-Aldrich Co. LLC, China. In this study, a series of dry ashing experiments coupled High purity water with a B blank less than 0.008 gwas with ion-exchange resin chromatography were performed to redistilled by subboiling distillation and passed through a separate B in plant tissue sample. The B isotopic composition resin column filled with B specific resin (Amberlite IRA 743), in plant tissue was determined by positive TIMS based on + which was used to prepare the standard solution and working Cs2BO2 ion. The recoveries of B separation in dry ashing, solution. ion-exchange chromatography, and the whole procedure An inductively coupled plasma optical emission spec- were examined. And the characteristics and fractionation trometer (ICP-OES, Vista MPX, Varian, USA) with a 40 MHz in the B isotope composition of plant tissue samples were radio frequency generator and a charge coupled device investigated and discussed. detector (Vista Chip) was used to detect B. 2. Material and Methods 2.3. Separation of B. Dry ashing was also used to decompose 2.1. Plant Sample and Site. To examine the fractionation of plant sample to eliminate the organic impurities [19]. Tradi- B isotopes in different plant species and within plant tissues, tionally, plant sample was decomposed using wet chemical digestion method of HNO3/H2O2,whichcanleadtothe plant samples investigated in this study include various + formation of the isobaric interference Cs2CNO ions of 308 tissues of Swertia mussotii Franch. and Halenia elliptica D. 133 10 + 133 11 + Don collected in the Qinghai-Tibet Plateau area, Weigela ( Cs2 BO2 )and309( Cs2 BO2 )intheionization florida cv. Red Prince and Echinacea angustifolia in Shandong chamber in TIMS. About 0.3–0.5 g of dried plant sample area and Cynomorium songaricum Ruper. in Inner Mongolia was weighted and placed into a quartz crucible. The crucible area, China. The samples of S. mussotii and H. elliptica were together with plant sample was placed in a closed microwave- assist Muffle burner. To avoid the bubbling in sample from collected in September and October (the flowering and fruit- ∘ ing period), 2012, in Yushu and Banma counties of Qinghai, rapid heating, at first the temperature was raised to 200 Cfor 1 h for the carbonization of organic matter. Then, the temper- China, respectively. The root holoparasite C. songaricum, ∘ known in Chinese herbal medicine as “suoyang,” is a classic ature was raised to 550 C for 4 h until the ash was whitish Mongolian pharmaceutical plant and usually parasitizes the to black. After cooling down, 1 mL of 0.5 mol/L HCl solution roots of Nitraria spp. [20]. E. angustifolia and W. florida were wasusedtodissolvetheashandthesolutionwastransferred collectedinJune,2012.Thecollectedsamplesincludetheroot, to a polypropylene tube. stem, leaf, and flower tissues of W. florida, S. mussotii,and The B specific resin was used to selectively extract B H. elliptica, stem, leaf, and flower tissues of E. angustifolia, and to remove the remaining impurities meanwhile. The pH and stem and flower of C. songaricum. The information about in the sample solution was adjusted to 8-9 using 0.1 mol/L sample site, plant species, and soil conditions in the regions NH3⋅H2O solution and then transferred to the conditioned B is summarized in Table 1. specific resin at a flow rate of 2.5 mL/min. After rinsing with ∘ ultrapure water, 10 mL of 0.1 mol/L HCl at 75 Cwasusedto 2.2. Instruments and Reagents. Hydrochloric acid (Guaran- eluteBintheresin;then,thecollectedeluateswereevapo- ∘ teed Reagent) was redistilled in a sealed vessel to remove rated under a clear air flow at 60 Cuntil0.5mLsolutionwas the exogenous B. The cesium carbonate (spectroscopic pure) left. International Journal of Analytical Chemistry 3 Table 2: Workflow of the separation of B in plant sample.
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