Study of the GC–MS determination of the palmitic–stearic acid ratio for the characterisation of drying oil in painting: La Encarnación by Alonso Cano as a case study

The correct identification of drying oils plays an essential role in providing an understanding of the conservation and deterioration of artistic materials in works of art. To this end, this work proposes the use of peak area ratios from fatty acids after ensuring that the linear responses of the detector are tested. A GC-MS method, previously reported in the literature, was revisited to its developed and validated in order to identify and quantify of eight fatty acids that are widely used as markers for drying oils in paintings, namely myristic acid (C_14:0), palmitic acid (C_16:0), stearic acid (C_18:0), oleic acid (C_18:1), linoleic acid (C_18:2), suberic acid (2C₈), azelaic acid, (2C₉) and sebacic acid (2C₁₀). The quaternary ammonium reagent m-(trifluoromethyl)phenyltrimethylammonium hydroxide (TMTFAH) was used for derivatization prior to GC-MS analysis of the oils. MS spectra were obtained for each methyl ester derivative of the fatty acids and the characteristic fragments were identified. The method was validated in terms of calibration functions, detection and quantification limits and reproducibility using the signal recorded in SIR mode, since two of the methyl derivatives were not totally separated in the chromatographic run. The proposed method was successfully applied to identify and characterise the most widely used drying oils (linseed oil, poppy seed oil and walnut oil) in the painting La Encarnación. This 17th century easel painting is located in the main chapel of the cathedral in Granada (Spain) and was painted by the well-known artist of the Spanish Golden Age, Alonso Cano (1601-1667).     

水溶性聚噻吩的合成与可视化生物检测

共轭聚合物具有强的光捕获能力,可放大荧光传感信号,提高生物检测的灵敏度。基于共轭聚合物的新型生物传感体系对获取生命过程中的化学与生物信息、阐明生物体系中的信息传递、特别是对疾病的诊断与治疗都具有重要的意义。水溶性聚噻吩衍生物在外界环境影响下主链结构易发生变化,从而引起紫外吸收光谱与溶液颜色的变化,近年来在可视化生物检测...     

粉末压片-X-射线荧光光谱法分析砂岩型铀矿制样中粘结剂用量的探讨

由于砂岩型铀矿的成矿特性,样品粉末的内聚力小,采用直接压片法有时难以成型,样片表面常见裂纹,上机测量易碎裂。混合压片法适应性强,制样成功率高,但常见的问题是样品经粘结剂稀释会影响元素的检出限及结果的准确性。本文对粉末压片-X射线荧光光谱法测定砂岩型铀矿地质样品时,前期制样中添加粘结剂的比例进行了研究。试验按照不同比例在铀矿石标准物质GBW04101、GBW04102中添加粘结剂,在扫描电镜下观察到随着粘结剂用量的增加样片表面的光滑度及致密度都呈上升趋势,在X-射线荧光光谱仪上对主量元素进行测定后发现X射线强度在粘结剂添加量大于0.2 g时明显下降,经与GBW04101、GBW04102标准值进行对比后优选出粘结剂与样品的最佳比例为1：20,在此比例下制成的样片光滑平整,不易碎裂,用粉末压片-X射线荧光光谱法进行测定,标准物质测定结果的相对误差为0.56%～6.76 %,相对标准偏差(RSD,n=12)为0.013 %～7.68 %,均达到了《地质矿产实验室测试质量管理规范》DZ/T 0130-2006的要求。本文为粉末压片-X射线荧光光谱法分析砂岩型铀矿地质样品提供了可靠的实验参考依据。     

一定条件下硝酸酯炸药与聚氨酯胶的相互作用研究

用气相质谱(GC-MS)、FTIR对在100℃下处理数十小时后的硝酸酯炸药、聚氨酯胶及二者隔离体系和接触体系的气相组分、凝聚相进行了表征。结果表明:两者直接接触后,彼此之间发生的变化主要由硝酸酯炸药发生分解产生的NO2促使聚氨酯胶的降解并加速自身的分解,聚氨酯胶的降解产物又进一步催化硝酸酯炸药的分解;两者间接接触后,各自释出的气氛对彼此的结构没有影响。     

Nitrogen-Rich Oxetanes Based on the Combination of Azides and Tetrazoles

Literature known energetic oxetane derivatives have a nitrogen content of up to 49.98 %. Through the introduction of azide and tetrazole functionalities attached to an oxetane ring, energetic oxetanes with higher nitrogen contents than previously reported in the literature were obtained. The newly synthesized oxetane derivatives were extensively characterized via ¹H NMR, ¹³C{¹H} NMR, ¹⁴N NMR, ¹⁵N NMR, ¹H-¹⁵N HMBC, FT-IR spectroscopy and/or DTA. Their crystal structures were elucidated using X-ray diffraction, their sensitivities towards impact, friction and electrostatic discharge were determined and their energetic properties were calculated using the EXPLO5 code.     

Novel Synthetic Strategy for the Production of Fully Bio-Based Binders Using 2,5-Diformylfuran

In this work, resol based binders were prepared with lignin, resorcinol and the bio-based aldehydic platform chemicals 5-hydroxymethylfurfural (HMF) and 2,5-diformylfuran (DFF). In preliminary studies, the solubility and stability of DFF in aqueous-alkaline conditions was investigated. Various binders were prepared to investigate the influence of the HMF-DFF ratio and the influence of the aldehyde concentration on the molar mass, rheological properties and curing characteristics of the final binders. It is shown that significantly higher molecular weights and viscosities are obtained by using DFF instead of HMF. The properties of the final binder could also be affected by the precise choice of DFF concentration, as this resulted in higher levels of crosslinking. This work offers a novel type of fully bio-based binder that consists of non-toxic components and is therefore less hazardous than some conventional binders.     

Multivariate analysis of combined Raman and fibre‐optic reflectance spectra for the identification of binder materials in simulated medieval paints

The non‐invasive identification of paint materials used in works of art is essential, both for preserving and restoring them, and also for understanding and verifying the history surrounding their creation. As such, the development of suitable non‐invasive techniques has received much interest in recent years. We have investigated the use of Fourier transform (FT)‐Raman spectroscopy and fibre‐optic reflectance spectroscopy (FORS), together with multivariate principal‐component analysis (PCA) techniques, in order to identify the pigment and binding materials used in made‐up samples representative of real artwork. We demonstrate that both types of spectroscopy provide complementary information which can be used to identify the pigments and binders in paint samples. We show that PCA with FT‐Raman spectra can be used to assist in the identification of oil‐based binders, and that the additional data provided by FORS spectra enables PCA on combined spectra to identify more complex proteinaceious and polysaccharide‐based binding media. The results presented here demonstrate that multivariate analyses of lead‐based paints, using data measured by FT‐Raman and FORS in conjunction, have much potential for identifying individual pigments and binders in paint samples. This provides a path towards computer‐assisted characterisation of paint materials on artwork. Copyright © 2013 John Wiley & Sons, Ltd.     

Preparation of new full UV-absorbing carbon dots from quercetin and their application in UV-absorbing systems for waterborne polyurethane coatings

In this paper, a kind of novel fully UV absorbing carbon dots (QC-CDs) were prepared as UV absorbers by a one-step hydrothermal method using quercetin as raw material. The prepared QC-CDs have high absorption efficiency (over 98%) in the whole ultraviolet region (200–400 nm), and are almost completely transmitted in the visible light region. The prepared QC-CDs have good stability and resistance to photobleaching. After the treatment with different pH and temperature, the QC-CDs maintained good absorption stability. QC-CDs have a wider UV absorption range than commercial water-soluble organic UV absorbers-BP-4. In terms of aging resistance, QC-CDs can achieve the same effect as BP-4. After subjecting QC-CDs and BP-4 to different pH values, it was found that QC-CDs remain fully UV absorbing at different pH conditions and maintain good absorption stability, but BP-4 loses its function as a UV absorber under alkaline conditions. Then, the UV absorption mechanism of QC-CDs has also been investigated and applied to the UV absorption systems of waterborne coatings PU. Finally, the QC-CDs@PU with full UV absorption properties was applied in the photodegradation prevention experiment of Rhodamine B. At present, the preparation process of QC-CDs is simple and environmentally friendly. QC-CDs have the potential to become a new generation of water-soluble UV absorbers.     

Carbon nanotubes and carbon-coated current collector significantly improve the performance of lithium-ion battery with PEDOT:PSS binder

We report an approach for enhancing performance of PEDOT:PSS binder in Li-ion battery electrodes by introducing small amount of carbon additives. Coating of current collector with carbon increases adhesion and electrical contact to the binder while introduction of carbon nanotubes enhances the electrical contact between the binder particles. The combination of these factors improves rate and cycling capability of the electrode.