Authentication of Iranian Saffron (Crocus sativus) Using Stable Isotopes δ13C and δ2H and Metabolites Quantification

Saffron is a very high value-added ingredient used in the food supplement market and contains a high level of safranal. Adding synthetic safranal to saffron, which is significantly cheaper, and falsifying the origin of saffron may represent recurrent fraud. Saffron from different countries was analyzed to determine the stable isotope ratios δ¹³C and δ²H from safranal by gas chromatography coupled with isotope-ratio mass spectrometry (GC-C/P-IRMS) and the concentration of saffron metabolites with ultra-high performance liquid chromatography coupled with diode array detector (UHPLC-DAD). The isotopic analysis highlighted a higher ratio of δ²H in synthetic safranal than in natural safranal; the mean values were 36‰ (+/− 40) and −210‰ (+/− 35), respectively. The δ¹³C between Iranian, Spanish and other saffron was significantly different and represents median values of −28.62‰, −30.12‰ and −30.70‰, respectively. Moreover, linear and quadratic discriminant analyses (LDA and QDA) were computed using the two isotope ratios of safranal and the saffron metabolites. A first QDA showed that trans-crocetin and the δ¹³C of safranal, picrocrocin, and crocin C3 concentrations clearly differentiated Iranian saffron from other origins. A second model identified δ¹³C, trans-crocetin, crocin C2, crocin C3, and picrocrocin as good predictors to discriminate saffron samples from Iran, Spain, or other origins, with a total ability score classification matrix of 100% and a prediction matrix of 82.5%. This combined approach may be a useful tool to authenticate the origin of unknown saffron.     

氢及其同位素宽区状态方程的核量子效应

应用大规模第一性原理分子动力学数值模拟方法,系统研究了氢及其同位素在极端条件下的分子解离规律及状态方程,并给出了参数化的解函数拟合公式。结合分子、原子流体量子振动的一阶修正,揭示了氢及其同位素的核量子效应,解析获得了氢、氘分子在温稠密区域分子解离规律的差别。由第一性原理状态方程给出了雨贡纽曲线,与气炮、化学炸药、磁驱动、高能激光等实验数据相符合,并详细讨论了由核量子效应导致的氢、氘雨贡纽曲线的同位素效应。     

氢及其同位素在溴化丁基橡胶中渗透的分子模拟

使用分子动力学（MD）和巨正则蒙特卡罗（GCMC）的方法,对H2,D2,T2在溴化丁基橡胶（BIIR）中的扩散和溶解行为进行了计算模拟,运用自由体积理论探讨了气体分子在聚合物内的扩散机理,并得出气体的运动轨迹。结果表明：对氢及其同位素而言,质量越小,运动速度越快,扩散系数越大,溶解度系数比较接近,渗透系数的模拟值与实验值基本吻合,为提高材料的阻隔性能提供了一定理论基础,同时预测出硫化溴化丁基橡胶对氚水也有较好的阻隔性能。     

氢元素教学内容的重构

近二十年来,有关氢元素的化学研究在基础研究和应用领域都得到了迅速的发展,尤其是氢键和氢能领域的研究。氢键已成为化学、生物、物理和材料科学等多学科所共同关注的基本学科问题,而氢能则是未来新能源中最重要的清洁能源之一,与此相关的氢能制备、储氢材料等研究也取得了重要的进展。然而,在氢元素的教学中,却未能及时补充这些研究成果。此外,与放射性、核能等相关的氢原子同位素也需要更新。本文从氢的同位素、氢键、氢能三个方面,探讨了无机化学教学中氢元素教学内容的重构。     

Investigating Hydrogen Isotope Variation during Heating of n-Alkanes under Limited Oxygen Conditions: Implications for Palaeoclimate Reconstruction in Archaeological Settings

This paper reports on a series of heating experiments that focus on n-alkanes extracted from leaf, bark, and xylem tissues of the Celtis australis plant. These lipid biomarkers were analysed for their compound-specific hydrogen isotopic composition (δ²H_wax) under limited oxygen conditions at 150, 250, 350, and 450 °C. Our results reveal isotopic variations in wax lipids of different plant organs during short-term low-temperature combustion. We conclude that, in the absence of a detailed characterisation of the depositional environment in advance of sampling, δ²H_wax values in archaeological or otherwise highly anthropogenic environments should be interpreted cautiously. In addition, we observed that variation in δ²H_wax of leaves is minimal at temperatures ≤ 350 °C, highlighting the potential for δ²H_wax in thermally altered combustion substrates to yield palaeoclimate information, which could allow researchers to investigate links between archaeological and climatic records at a high spatial and temporal resolution.     

多接收电感耦合等离子体质谱(MC-ICP-MS)法测定土壤的铁同位素组成

随着分析技术的发展，铁（Fe）同位素（δ56/54Fe）在土壤科学中得到了广泛的应用，可以用来研究铁在土壤圈中的迁移、转化等过程。为了确保不同类型样品中的铁同位素测量的准确性，需要标定一系列标准物质的铁同位素组成。但是目前对于土壤标准物质铁同位素数据的报道几乎没有，这阻碍了不同实验室间铁同位素数据质量进行对比。为了对不同实验室间的铁同位素数据进行比较，需要对土壤标样的铁同位素进行标定。在本研究中，我们使用硝酸-氢氟酸-高氯酸混酸对土壤样品中的硅酸盐和有机质进行消解，利用阴离子交换树脂（AG1-X8，0.038-0.074 mm）对土壤样品中的铁与基质元素进行了分离。为了获得可靠的纯化流程，我们检验了不同浓度的盐酸对基质的淋洗效果。结果表明，当盐酸浓度从4.0 mol/L变化到7.0 mol/L时，基质元素都能有效地被分离干净。最后我们采用5.0 mol/L的盐酸将基质元素从阴离子树脂中淋洗出来，然后利用0.3 mol/L的盐酸将铁元素收集起来。铁同位素组成利用多接收电感耦合等离子体质谱仪进行测定。通过对实验室标准铁溶液（ISS-Fe和USTC-Fe）的长期的监测，本分析方法δ56/54Fe的外精度好于±0.05‰（2SD）。我们分析了两个玄武岩标样（BCR-2和BHVO-2）的铁同位素组成，其δ56/54Fe值分别为0.08±0.05‰和0.09±0.05‰，均与文献值在误差范围内是一致的。此外，我们测量了六个土壤标样（SRM2709，SRM2709a，SRM2710a，SRM2711，SRM2711a和GBW07453）的铁同位素组成，其δ56/54Fe值分别为0.05±0.01‰，0.07±0.02‰，-0.11±0.02‰，0.15±0.03‰，0.14±0.03‰和0.10±0.01‰。该研究为土壤铁同位素研究提供了有用的数据库。