低硼富含有机质的河/雨水正热电离硼同位素的测定

对低硼富含有机质的河/雨水样品硼的分离方法及硼同位素组成的测定进行了研究.采用硼特效树脂富集河/雨水样品,结合微升华技术去除有机质;采用正热离子质谱法进行硼同位素组成的测定.全流程回收率在97.50%～101.17%之间,测试数据和多接受电感耦合等离子体质谱比较接近,测试精度小于0.05‰.经本方法处理后的样品能满足同...     

Boron Separation by the Two—step Ion—Exchange for the Isotopic Measurement of Boron

ＩｎｔｒｏｄｕｃｔｉｏｎＬａｒｇｅｖａｒｉａｔｉｏｎｓｉｎｔｈｅｉｓｏｔｏｐｉｃｃｏｍｐｏｓｉｔｉｏｎｏｆｂｏｒｏｎｏｃｃｕｒｉｎｎａｔｕｒｅ .ＴｈｅｂｏｒｏｎｉｓａｕｓｅｆｕｌｔｒａｃｅｒｏｆｔｈｅｓｏｕｒｃｅｓａｎｄｅｖｏｌｕｔｉｏｎｏｆａｑｕｅｏｕｓｆｌｕｉｄｓｉｎｔｈｅＥａｒｔｈ’ｓｃｒｕｓｔａｎｄｈｙｄｒｏｓｐｈｅｒｅ .1 6Ｏｗｉｎｇｔｏｉｍｐｒｏｖｅｍｅｎｔｓｏｆａｎａ ｌｙｔｉｃａｌｍｅｔｈｏｄｓ ,7,8ａｒａｐｉｄｉｎｃｒｅａｓｅｈａｓｂｅｅｎｓｅｅｎｉｎｍａｎｙｓｔｕｄｉｅｓｏｆｔ…     

负热电离质谱测定硼同位素的涂样试剂比较

目前人们并未注意到利用负热电离质谱方法测定硼同位素所采用涂样试剂中BO^-的同质异位素CNO^-离子的存在和影响。对硼同位素测定采用的不同涂样试剂进行比较，结果发现在去硼海水和硝酸盐溶液中存在BO2^-的同质异位素CNO^-离子，干扰离子不仅来自有机物，而且可能来自硝酸根。在硼同位素测定中，检查空白中的43峰和43／42比值是必要的。实验表明MgCl2 NaOH混合溶液是负热电离质谱测定硼同位素的较为理想的涂样试剂。     

Determination of boron isotopic variations in aquatic systems with negative thermal ionization mass spectrometry as a tracer for anthropogenic influences

A technique for precise boron isotope ratio measurements with a high detection power has been developed by negative thermal ionization mass spectrometry (NTIMS). Relative standard deviations in the range of 0.03-0.3% have been obtained for the determination of the (11)B/(10)B isotope ratio using nanogram amounts of boron. Ba(OH)(2) has been applied as ionization promoter for the formation of negative thermal ions. By adding MgCl(2) better reproducibilities of the measurement have been achieved. A possible interference of BO(-)(2) ions at mass number 42 by CNO(-) could be excluded by the sample preparation technique used. Contrary to other NTI techniques no dependence of the measured isotope ratio on the boron amount used has been observed. Anthropogenic and natural saline influences in ground water have been successfully identified by boron isotope ratio determinations with this NTIMS method, due to the different isotopic composition of boron in natural and anthropogenic substances. In sewage, the boron isotope ratio is substantially influenced by washing powder, which contains low (11)B/(10)B ratios (expressed in delta(11)B values normalized to the standard reference material NIST SRM 951). In contaminated ground water, low delta(11)B values are normally correlated with high boron and high chloride concentrations. On the other hand, delta(11)B shifts to higher values in less contaminated samples. For ground water with saline influences, only the delta(11)B determination, and not the boron or chloride content, allowed the correct identification of this natural source of contamination.     

Direct separation of boron from Na- and Ca-rich matrices by sublimation for stable isotope measurement by MC-ICP-MS

An improved technique for precise and accurate determination of boron isotopic composition in Na-rich natural waters (groundwater, seawater) and marine biogenic carbonates was developed. This study used a ‘micro-sublimation’ technique to separate B from natural sample matrices in place of the conventional ion-exchange extraction. By adjusting analyte to appropriate pH, quantitative recovery of boron can be achieved (>98%) and the B procedural blank is limited to <8 pg. An additional mass bias effect in MC-ICP-MS was observed which could not be improved via the standard-sample-standard bracketing or the ‘pseudo internal’ normalization by Li. Therefore a standard other than NBS SRM 951 was used to monitor plasma condition in order to maintain analytical accuracy. An isotope cross-calibration with results from TIMS shows that the space-charge mass bias on MC-ICP-MS can be successfully corrected using off-line mathematical manipulation. Several reference materials, including the seawater IAPSO and two groundwater standards IAEA-B-2 and IAEA-B-3, were used to validate this approach. We found that the δ¹¹B of the reference coral JCp-1 was 24.22 ± 0.28‰, corresponding to seawater pH based on the coral δ¹¹B-pH function.     

Determination of Boron Isotopic Composition in Natural Samples by Thermal Ionization Mass Spectrometry

Thermal ionization mass spectrometry has been used for the determination of isotopic composition of boron in natural samples, like water, with an improved degree of accuracy and precision. After concentration and separation boron is treated with an excess of sodium hydroxide in order to convert it completely to sodium metaborate. The excess of sodium hydroxide present in the sample causes problems in the isotopic analysis. This excess is neutralized with 0.1M nitric acid on the filament while loading the sample by a special technique. This procedure improves the precision and accuracy of the analysis to a large extent.     

An unusual isotopic fractionation of boron in synthetic calcium carbonate precipitated from seawater and saline water

Inorganic calcium carbonate precipitation from natural seawater and saline water at various pH values was carried out experimentally. The results show the clear positive relationships between boron concentration and δ11B of inorganic calcium carbonate with the pH of natural seawater and saline water. However, the variations of boron isotopic fractionation between inorganic calcite and seawater/saline water with pH are inconsistent with the hypothesis that B(OH)4- is the dominant spe-cies incorporated into the biogenic calcite structure. The isotopic fractionation factors α between synthetic calcium carbonate precipitate and parent solutions increase systematically as pH increases, from 0.9884 at pH 7.60 to 1.0072 at pH 8.60 for seawater and from 0.9826 at pH 7.60 to 1.0178 at pH 8.75 for saline water. An unusual boron isotopic fractionation factor of larger than 1 in synthetic calcium carbonate precipitated from seawater/saline water at higher pH is observed, which implies that a substantial amount of the isotopically heavier B(OH)3 species must be incorporated preferentially into synthetic inorganic carbonate. The results propose that the incorporation of B(OH)3 is attributed to the formation of Mg(OH)2 at higher pH of calcifying microenvironment during the synthetic calcium carbonate precipitation. The preliminary experiment of Mg(OH)2 precipitated from artificial seawater shows that heavier 11B is enriched in Mg(OH)2 precipitation, which suggests that isotopically heavier B(OH)3 species incorporated preferentially into Mg(OH)2 precipitation. This result cannot be applied to explain the boron isotopic fractionation of marine bio-carbonate because of the possibility that the unusual environment in this study appears in formation of marine bio-carbonate is infinitesimal. We, however, must pay more attention to this phenomenon observed in this study, which accidentally appears in especially natural environment.     

Rapid mass-spectrometric determination of boron isotopic distribution in boron carbide

Boron isotopic ratios are measured in boron carbide by thermionic ionization mass spectrometry with no prior chemical separation. A powder blend of boron carbide and sodium hydroxide is prepared, a small portion is transferred to a tantalum filament, the filament is heated to produce sodium borate, and the filament is transferred to the mass spectrometer where the(11)B/(10)B ratio is measured, using the Na(2)BO(2)(+) ion. Variables investigated for their effect on preferential volatilization of (10)B include the sodium hydroxide-boron carbide ratio and the temperature and duration of filament heating. A series of boron carbide pellets containing natural boron, of the type proposed for the control rods of the Fast Flux Test Facility reactor, were analysed with an apparently unbiased result of 4.0560 for the (11)B/(10)B ratio (standard deviation 0.0087). The pellets contained over 3% metal impurities typically found in this material. Time of analysis is 45 min per sample, with one analyst.     

Post-photosynthetic fractionation of stable carbon isotopes between plant organs--a widespread phenomenon

Discrimination against 13C during photosynthesis is a well-characterised phenomenon. It leaves behind distinct signatures in organic matter of plants and in the atmosphere. The former is depleted in 13C, the latter is enriched during periods of preponderant photosynthetic activity of terrestrial ecosystems. The intra-annual cycle and latitudinal gradient in atmospheric 13C resulting from photosynthetic and respiratory activities of terrestrial plants have been exploited for the reconstruction of sources and sinks through deconvolution by inverse modelling. Here, we compile evidence for widespread post-photosynthetic fractionation that further modifies the isotopic signatures of individual plant organs and consequently leads to consistent differences in delta13C between plant organs. Leaves were on average 0.96 per thousand and 1.91 per thousand more depleted than roots and woody stems, respectively. This phenomenon is relevant if the isotopic signature of CO2-exchange fluxes at the ecosystem level is used for the reconstruction of individual sources and sinks. It may also modify the parameterization of inverse modelling approaches if it leads to different isotopic signatures of organic matter with different residence times within the ecosystems and to a respiratory contribution to the average difference between the isotopic composition of plant organic matter and the atmosphere. We discuss the main hypotheses that can explain the observed inter-organ differences in delta13C.     

Biotic and abiotic experimental identification of bacterial influence on calcium isotopic signatures

In this study, we tested experimentally the influence of plant and bacterial activities on the calcium (Ca) isotope distribution between soil solutions and plant organs. Abiotic apatite weathering experiments were performed under two different pH conditions using mineral and organic acids. Biotic experiments were performed using either apatite or Ca-enriched biotite substrates in the presence of Scots pines, inoculated or not with the rhizosphere bacterial strain Bulkholderia glathei PML1(12), or the B. glathei PML1(12) alone. For each experiment, the percolate was collected every week and analyzed for Ca concentrations and Ca isotopic ratios. No Ca isotopic fractionation was observed for the different abiotic experimental settings. This indicates that no Ca isotopic fractionation occurs during apatite dissolution, whatever the nature of the acid (mineral or organic). The main result of the biotic experiments is the 0.22 ‰ (44)Ca enrichment recorded for a solution in contact with Scots pines grown on the bacteria-free apatite substrate. In contrast, the presence of bacteria did not cause Ca isotopic fractionation of the solution collected after 14 weeks of the experiments. These preliminary results suggest that bacteria influence the Ca isotopic signatures by dissolving Ca from apatite more efficiently. Therefore, Ca isotopes might be suitable for detecting bacteria-mediated processes in soils.     

Kinetic study on the sorption of dissolved natural organic matter onto different aquifer materials: the effects of hydrophobicity and functional groups

The subsurface sorption of Suwannee River fulvic acid (SRFA) and humic acid (SRHA) onto a synthetic aquifer material (iron-oxide-coated quartz) and two natural aquifer materials (Ringold sediment and Bemidji soils) was studied in both batch and column experiments. The hypothesis that hydrophobic effects followed by ligand exchange are the dominant mechanism contributing to the chemical sorption happening between dissolved natural organic matter (NOM) and the mineral surfaces is supported by observations of several phenomena: nonlinear isotherms, faster sorption rates versus slower desorption rates, phosphate competition, a solution pH increase during NOM sorption, and functional groups and aromaticity-related sorption. In addition, high-pressure size exclusion chromatography (HPSEC) and carboxylic acidity showed that lower molecular weight NOM components of SRHA are preferentially sorbed to iron oxide, a result in contrast to that for SRFA. Phosphate increased the desorption of sorbed NOM as well as soil organic matter. All of these trends support ligand exchange as the dominant reaction between NOM and the iron oxide surfaces; however, if the soil surface has been occupied by soil organic matter, then the sorption of NOM is more due to hydrophobic effect.     

Using a simple high-performance liquid chromatography separation and fraction collection methodology to achieve compound-specific isotopic analysis for dissolved organic compounds

A new application for the quantitative and isotopic analyses of dissolved inorganic and dissolved organic carbon compounds has been developed. Dissolved organic matter (DOM) in natural water samples can be separated on a high-performance liquid chromatography (HPLC) column and collected as fractions. Each discrete fraction can then be analyzed using the technique of St-Jean (Rapid Commun. Mass Spectrom. 2003; 17: 419-428) with a total inorganic carbon/total organic carbon (TIC/TOC) analyzer interfaced with a continuous-flow isotope ratio mass spectrometer. Experimental data using short-chain fatty acid standards (formic, acetic, and propionic acids) show that fraction recoveries of 100% are possible and that sample integrity is maintained. 13C-isotopic analyses of products prior to and subsequent to extraction and collection show no isotopic effects associated with the methodology, and errors are well within the accepted analytical uncertainty of the IRMS. Comparison of data from pure standards and organic-rich natural waters shows that quantitative analyses still need to be done with standards that more closely imitate the matrices of the samples, in order to acquire an appropriate calibration curve. Injections of organic-rich matrices on the HPLC column did not affect fraction recovery, nor did they create high background of partially retained organic compounds slowly released from the HPLC column, and hence 13C-isotopic results are relatively unaffected. The specific limitation on this methodology is the required use of carbon-free carrier solvents due to potential memory effects associated with the TIC/TOC analyzer. Further developments of this application could make routine compound-specific isotopic analyses (CSIA) for a wider range of organic materials possible.     

有孔虫中硼的分离及其正热电离质谱法测定

针对大洋钻探计划(0DP)钻孔中有孔虫数量少、硼含量低的特点，改进了硼特效树脂和阴、阳混合离子交换树脂相结合进行分离硼的方法，成功地实现了硼的分离，并且首次采用正热电离质语法测定了有孔虫中硼同位素的比值。由于硼的分离过程不产生同位素分馏，测定结果令人满意。     

Application of multivariate curve resolution-alternating least squares for the determination of boron isotope ratios by inductively coupled plasma-optical emission spectrometry

Multivariate curve resolution-alternating least squares (MCR-ALS) was applied to atomic emission data obtained from inductively coupled plasma-optical emission spectrometry analysis of boron for the quantification of ¹⁰B/¹¹B ratios. The determination of isotopic composition of boron is based on the isotopic shift of ¹⁰B and ¹¹B in the emission line of 208.957 nm. After recording of the emission spectra in the range of 208.940–208.970 nm, evaluation of isotopic composition of boron containing samples was performed with MCR-ALS algorithm. MCR-ALS was able to resolve the emission spectra of ¹⁰B and ¹¹B mixtures. The performance of the proposed methods was tested by determination of ¹⁰B/¹¹B ratios in synthetic mixtures and also water samples.     

Aqueous photolysis of the sunscreen agent octyl-dimethyl-p-aminobenzoic acid. Formation of disinfection byproducts in chlorinated swimming pool water

The photochemical behavior of the sunscreen agent octyl-dimethyl-p-aminobenzoic acid (ODPABA) was studied in different aqueous solutions and under different conditions. ODPABA photolysis was performed under laboratory conditions using a xenon light source and under natural sunlight conditions in sea, swimming pool as well as in distilled water. The influence of dissolved organic matter (DOM) on the degradation kinetics was also studied in the presence of various concentrations of humic acids (HA). The phototransformation was shown to proceed via pseudo-first-order reaction in all cases and the reaction rates followed the order: distilled water > swimming pool water > seawater, depending mainly on the presence of dissolved organic matter that retarded the photolysis reaction. Kinetic experiments were monitored with HPLC/UV-DAD and the half-lives (t 1/2) varied between 1.6 and 39 h in simulated solar irradiation and between 27 and 39 h in natural sunlight conditions. The product distribution during illumination was strongly dependent on the constitution of the irradiated media. Irradiation of the aqueous ODPABA solutions gave rise to several transformation products that were isolated by means of solid-phase extraction (SPE) and identified using GC-MS techniques. These were formed mainly through dealkylation and hydroxylation reactions and were detected in all aqueous solutions investigated. In the case of swimming pool water some additional byproducts were isolated and were tentatively identified as chlorinated intermediates, formed by the subsequent chlorination of the parent molecule as well as other intermediates.     

Determination of boron isotopic variations in aquatic systems with negative thermal ionization mass spectrometry as a tracer for anthropogenic influences

A technique for precise boron isotope ratio measurements with a high detection power has been developed by negative thermal ionization mass spectrometry (NTIMS). Relative standard deviations in the range of 0.03–0.3% have been obtained for the determination of the ¹¹B/¹⁰B isotope ratio using nanogram amounts of boron. Ba(OH)₂ has been applied as ionization promoter for the formation of negative thermal ions. By adding MgCl₂ better reproducibilities of the measurement have been achieved. A possible interference of BO^-₂ ions at mass number 42 by CNO^- could be excluded by the sample preparation technique used. Contrary to other NTI techniques no dependence of the measured isotope ratio on the boron amount used has been observed. Anthropogenic and natural saline influences in ground water have been successfully identified by boron isotope ratio determinations with this NTIMS method, due to the different isotopic composition of boron in natural and anthropogenic substances. In sewage, the boron isotope ratio is substantially influenced by washing powder, which contains low ¹¹B/¹⁰B ratios (expressed in ¹¹B values normalized to the standard reference material NIST SRM 951). In contaminated ground water, low ¹¹B values are normally correlated with high boron and high chloride concentrations. On the other hand, ¹¹B shifts to higher values in less contaminated samples. For ground water with saline influences, only the ¹¹B determination, and not the boron or chloride content, allowed the correct identification of this natural source of contamination.     

Reactions of B atoms and clusters with NO: experimental and theoretical characterization of novel molecules containing B, N, and O

Reactions of boron atoms and clusters with NO molecules in solid argon have been studied using matrix isolation infrared absorption spectroscopy. The reaction products were identified by isotopic substitution ((10)B, (11)B, (15)N(16)O, (14)N(18)O, and mixtures) and comparison with density functional calculations of isotopic frequencies. In solid argon, boron atoms spontaneously reacted with NO to form the insertion molecule NBO. The BNBO and OBNNO molecules were formed by the B and NO addition reactions to NBO. The linear BBNO and BBBNO nitrosyls also were formed spontaneously on annealing. These molecules photochemically rearranged to the more stable BNBO and BNBBO isomers, which have linear polyyne-like structures. The photosensitive OBNNO molecule decomposed to form the NNBO(2) van der Waals complex. In addition, the novel OBON diradical was also formed on photolysis in high-concentration NO experiments.     

Methods for the extraction of microplastics in complex solid,water and biota samples

The widespread distribution of plastics, their persistence and ability to act as a vector of toxic chemicals has rendered them concerning emergent pollutants. The quantification of these contaminants is highly relevant for the evaluation of anthropogenic impacts on aquatic and terrestrial ecosystems and dependent of the efficacy of methods to separate microplastics from environmental matrices. Little information is available about the microplastic extraction methods on complex samples – i.e. samples with multiple types of matrices. Herein, methods for the separation of microplastics from complex samples are summarized and discussed based on their advantages and drawbacks focused on a comparative analysis of their efficiency on organic matter removal, polymer recovery and preservation of plastic integrity. The efficiency on microplastic recovery and organic matter reduction, as well as the examination of the effects of treatments on plastics are closely linked to the density and digestion approaches selected, the polymer features and the environmental matrix analyzed. High-density salt solutions are more effective for density separation, while oxidative methods have recurrently shown better rates of organic matter reduction (particularly in vegetal-rich samples) and plastic recovery, with little impact on plastics, while 10 % KOH has been described as highly efficient in samples containing animal organic matter. This comparative analysis highlights the benefits and limitations of different approaches for the analysis of microplastics in complex samples which may be helpful for the optimization and harmonization of the methods.     

Determination of Cr(III) and Cr(VI) in industrial and environmental liquid samples by EDXRF method

A rapid, sensitive and selective procedure for determination of Cr(III) and Cr(VI) in environmental and industrial liquid samples via preconcentration with ammonium pyrrolidine dithiocarbamate (APDC) and determination by means of the EDXRF was described. The effect of pH in the range of 3-11 on the recovery of Cr(III) and Cr(VI) has been investigated separately and in combination of these two species. The influence of organic matter, carbonate species and elements V, Mn and Fe on the recovery of each chromium specie (separately/in combination) over whole pH range was also tested in order to simulate condition occurring in natural waters that usually contain certain amount of dissolved organic matter and carbonate ions. Cr(VI) and Cr(III) have shown different behaviors in reaction with APDC at different pH ranges and therefore it is possible to separate those two species. It was found that Cr(VI) creates complex with APDC only in the pH range from 3 to 5 with quantitative recovery (app. 98%) at pH 3, but there was no recovery of Cr(III) at that pH. On the contrary, in pH range from 6 to 11, reaction with Cr(III) and APDC reviled that the only reaction product is Cr(OH)₃ instead of the expected Cr(III)-APDC complex. All reaction products were characterized by IR spectroscopy.