Development of a novel colorimetric indicator label for monitoring freshness of intermediate-moisture dessert spoilage

A colorimetric mixed pH dye-based indicator with potential for the development of intelligent packaging, as a “chemical barcode” for real-time monitoring of intermediate-moisture dessert spoilage, is described. This on-package indicator contains mixed pH-sensitive dyes, bromothymol blue and methyl red, that respond through visible color change to carbon dioxide (CO₂) as a spoilage metabolite. Both indicator solution and indicator label characteristics were studied, as well as their response to CO₂. A kinetic approach was used to correlate the response of the indicator label to the changes in intermediate-moisture dessert spoilage. Color changes, in terms of total color difference of a mixed pH dye-based indicator, correlated well with CO₂ levels of intermediate-moisture dessert. Trials on golden drop have verified that the indicator response correlates with microbial growth patterns in dessert samples, thus enabling the real-time monitoring of spoilage either at various constant temperatures or with temperature fluctuation.     

Epoxy-based polymer bearing activated azo dye (methyl orange) units: novel colorimetric indicator for amines

Novel epoxy-based polymer 2-bearing activated azo dye, 4-(4-sulphophenylazo)-N,N-dimethylaniline (methyl orange), moieties were synthesised by post-azo-coupling reaction of poly(hydroxy ether amine) 1 and investigated sensory responses towards amines. The reversible protonation–deprotonation chemistry of activated azobenzene moiety makes it of potential use as a colorimetric indicator for amines.     

Optical sensor for carbon dioxide combining colorimetric change of a pH indicator and a reference luminescent dye

A new optical CO₂ sensor based on the luminescence intensity change of the europium(III) complex tris(thenoyltrifluoroacetonato) europium(III) dihydrate ([Eu(tta)₃]) caused by the absorption change of various pH indicators—thymol blue, phenol red, or cresol red—with CO₂ was developed and its CO₂ sensing properties were investigated. For all the CO₂ sensors using pH indicators the observed luminescence intensity from [Eu(tta)₃] at 613 nm increased with increasing CO₂ concentration. The linear calibration method based on the plot of (I₁₀₀–I₀)/(I–I₀) versus the inverse of CO₂ concentration was suggested, where I₀ and I₁₀₀ were luminescence intensities at 613 nm of the CO₂ sensor film in 100% nitrogen and 100% gaseous CO₂. In all cases the plots showed good linearity and the correlation factors of the plots, r², were 0.991 for thymol blue, 0.990 for phenol red, and 0.998 for cresol red. The slopes of the plots (A/B) for thymol blue, phenol red, and cresol red were 2.2, 5.2, and 9.0%, respectively. The response times of the CO₂ sensor film were 4.0 s for thymol blue, 4.4 s for phenol red, and 8.8 s for cresol red for switching from nitrogen to CO₂, and the recovery times of films were 36 s for thymol blue, 39.2 s for phenol red, and 56.6 s for cresol red for switching from CO₂ to nitrogen. The signal changes were fully reversible and hysteresis was not observed during the measurements. The highly sensitive CO₂ sensor was developed using thymol blue as an indicator for the CO₂-sensing probe.     

A novel anthracene-based fluorescent colorimetric sensor for the simple naked-eye diagnosis of methylmalonic aciduria

A novel molecular sensor using anthracene bearing two amidopyridines emits blue fluorescence in the presence of succinic acid and green fluorescence in the presence of malonic acid, and its fluorescence intensity increased upon binding. Using this molecular sensor, we succeeded in detecting the difference of one carbon atom between succinic acid and malonic acid with the naked-eye. Furthermore, when methylmalonic acid was dissolved in urine to provide a model system for methylmalonic aciduria, the fluorescence changed from blue to green, and methylmalonic acid was successfully detected with the naked-eye.     

Iridium as a general catalyst for the decarbonylative addition of aldehydes to alkynes

A general catalytic system for the decarbonylative addition reaction of aldehydes with alkynes is developed by using an iridium catalyst system. Both aromatic and aliphatic aldehydes reacted with terminal alkynes efficiently to give the corresponding olefination products in high yields and up to 11:1 E/Z selectivity.     

Electrospun polystyrene/graphene nanofiber film as a novel adsorbent of thin film microextraction for extraction of aldehydes in human exhaled breath condensates

In the current study, we introduced a novel polystyrene/graphene (PS/G) composite nanofiber film for thin film microextraction (TFME) for the first time. The PS/G nanofiber film was fabricated on the surface of filter paper by a facile electrospinning method. The morphology and extraction performance of the resultant composite film were investigated systematically. The PS/G nanofiber film exhibited porous fibrous structure, large surface area and strong hydrophobicity. A new thin film microextraction-high performance liquid chromatography (TFME-HPLC) method was developed for the determination of six aldehydes in human exhaled breath condensates. The method showed high enrichment efficiency and fast analysis speed. Under the optimal conditions, the linear ranges of the analytes were in the range of 0.02–30 μmol L⁻¹ with correlation coefficients above 0.9938, and the recoveries were between 79.8% and 105.6% with the relative standard deviation values lower than 16.3% (n = 5). The limits of quantification of six aldehydes ranged from 13.8 to 64.6 nmol L⁻¹. The established method was successfully applied for the quantification of aldehyde metabolites in exhaled breath condensates of lung cancer patients and healthy people. Taken together, the TFME-HPLC method provides a simple, rapid, sensitive, cost-effective, non-invasion approach for the analysis of linear aliphatic aldehydes in human exhaled breath condensates.     

Reactivity of TEMPO anion as a nucleophile and its applications for selective transformations of haloalkanes or acyl halides to aldehydes

Sodium 2,2,6,6-tetramethylpiperidine-N-oxide (TEMPO⁻Na⁺), generated by reduction of TEMPO· with sodium naphthalenide in THF, reacted with alkyl halides or acyl halides to produce O-alkylated or acylated TEMPOs, which were in turn oxidized with mCPBA or reduced with DIBAL-H to afford the corresponding aldehydes, thus accomplishing a new protocol for the halides-carbonyls conversion.     

248 nm深紫外光刻胶用成膜树脂的研究进展

综述了用于248 nm化学增幅型深紫外光刻胶的不同种类和结构的成膜树脂,以及所使用单体的研发进展,包括聚甲基丙烯酸甲酯及其衍生物、聚对羟基苯乙烯及其衍生物、N取代的马来酰亚胺衍生物,以及其他聚合物等,对不同结构成膜树脂的曝光条件、对光刻胶性能的影响进行了介绍。     

Development and validation of a novel stability indicating RP-HPLC method for the quantitative determination of marbofloxacin in its tablets

A fast, feasible, isocratic, stability indicating reverse phase-high performance liquid chromatography (RP-HPLC) method has been developed and validated for the quantitative determination of marbofloxacin in marbofloxacin tablets. The method was developed using Zorbax SB C18 (150?mm?×?4.6?mm), 5-µm column thermostated at 30°C, mobile phase A (1?mL of trifluoroacetic acid in 1000?mL of water), mobile phase B (acetonitrile) in the ratio of 83:17?v/v at flow rate of 1.0?mL/min, and an injection volume of 10?µL. The analyte was monitored at a wavelength of 298?nm. The method was validated in accordance with the Food and Drug Administration (FDA) Veterinary International Conference on Harmonization guidelines. To demonstrate stability indicating ability of method, drug product was subjected to the stress condition of acidic, basic, humidity, thermal, oxidative, and photolytic degradation.     

Gas chromatographic indicator of the ability of five- and six-membered heterocyclic nitrogen-containing compounds for self-association in pure liquids

The retention indices of five- and six-membered nitrogen-containing heterocyclic compounds (pyrrole, pyrazole, imidazole, 1,2,4-triazole, pyridine, pyridazine, pyrimidine, pyrazine, 1,3,5-triazine, isoxazole, and oxazole) were determined on a capillary column with the OV-101 nonpolar stationary phase. The difference between the experimentally determined boiling point of the sorbate and that calculated from GC data (δT _b.p.) was proposed as a gas chromatographic indicator sensitive to the ability of substances to form self-associates in pure liquids. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 730–733, April, 1999.     

Charge decomposition analysis of the electron localizability indicator: a bridge between the orbital and direct space representation of the chemical bond

The novel functional electron localizability indicator is a useful tool for investigating chemical bonding in molecules and solids. In contrast to the traditional electron localization function (ELF), the electron localizability indicator is shown to be exactly decomposable into partial orbital contributions even though it displays at the single-determinantal level of theory the same topology as the ELF. This approach is generally valid for molecules and crystals at either the single-determinantal or the explicitly correlated level of theory. The advantages of the new approach are illustrated for the argon atom, homonuclear dimers N2 and F2, unsaturated hydrocarbons C2H4 and C6H6, and the transition-metal-containing molecules Sc(2)2+ and TiF4.     

新型三维可调共聚焦激光诱导荧光检测器的研制与评价

共聚焦结构是激光诱导荧光检测器(LIFD)中使用最广泛的光路结构之一,增强光路系统同轴精度和降低系统杂散光是降低仪器基线噪声水平、提高其信噪比(S/N)的两种有效手段。采用精密三维反光镜调节架和模块化设计光路系统,研制了一种高效液相色谱用高精度共聚焦激光诱导荧光检测器,对异硫氰酸荧光素(fluorescein isothiocyanate, FITC)的检出限为1×10~12 mol/L。基线噪声与漂移较改进前降低了一个数量级,分别达到8.0×10~3 mV和1.4×10~3 mV/h,且稳定性好,5×10~9 mol/L FITC样品连续5次进样分析的峰面积和峰高相对标准偏差(RSD)均小于0.5%。进一步用FITC衍生化生物胺对研制的检测器进行评价,检出限(S/N=3)达到0.01～0.02 nmol/L。新研制的LIFD噪声低、稳定性好、灵敏度高,适用于生物、食品和环境样品中痕量物质的分析。     

Development of a colorimetric microfluidic pH sensor for autonomous seawater measurements

High quality carbonate chemistry measurements are required in order to fully understand the dynamics of the oceanic carbonate system. Seawater pH data with good spatial and temporal coverage are particularly critical to apprehend ocean acidification phenomena and their consequences. There is a growing need for autonomous in situ instruments that measure pH on remote platforms. Our aim is to develop an accurate and precise autonomous in situ pH sensor for long term deployment on remote platforms. The widely used spectrophotometric pH technique is capable of the required high-quality measurements. We report a key step towards the miniaturization of a colorimetric pH sensor with the successful implementation of a simple microfluidic design with low reagent consumption. The system is particularly adapted to shipboard deployment: high quality data was obtained over a period of more than a month during a shipboard deployment in northwest European shelf waters, and less than 30 mL of indicator was consumed. The system featured a short term precision of 0.001 pH (n = 20) and an accuracy within the range of a certified Tris buffer (0.004 pH). The quality of the pH system measurements have been checked using various approaches: measurements of certified Tris buffer, measurement of certified seawater for DIC and TA, comparison of measured pH against calculated pH from pCO₂, DIC and TA during the cruise in northwest European shelf waters. All showed that our measurements were of high quality. The measurements were made close to in situ temperature (+0.2 ?C) in a sampling chamber which had a continuous flow of the ship’s underway seawater supply. The optical set up was robust and relatively small due to the use of an USB mini-spectrometer, a custom made polymeric flow cell and an LED light source. The use of a three wavelength LED with detection that integrated power across the whole of each LED output spectrum indicated that low wavelength resolution detectors can be used instead of the current USB mini spectrophotometer. Artefacts due to the polychromatic light source and inhomogeneity in the absorption cell are shown to have a negligible impact on the data quality. The next step in the miniaturization of the sensor will be the incorporation of a photodiode as detector to replace the spectrophotometer.     

再论化学元素周期表的形成和发展

以时间为序,将化学元素周期表的发现和发展分为萌芽、突破、发展和展望四个阶段,引用主要史实文献将其串联起来进行解读,以利于周期表的深入教学,并作为相应科学研究之参考。     

Development and validation of a RP-HPLC method for Roflumilast and its degradation products

Roflumilast is a phosphodiesterase type 4 inhibitor that is administered orally as a long-term, in the clinical treatment of chronic obstructive pulmonary disease and asthma. Launched in 2010 for the European market, it currently does not have an official monograph. Here, a reproducible gradient RP-HPLC method was developed and validated for the separation and determination of Roflumilast in the presence of its six major degradation products. Separation was performed on a C₁₈ analytical column (250?×?4.6?mm, 5?µm) with a mobile phase-A of ACN and a phase-B of ammonium acetate buffer (5?mM, pH 4.2) containing triethylamine (0.5% v/v). The most effective RP-HPLC gradient program was determined to be 0/80, 35/10, 36/80, 40/80 (time in minutes/% mobile phase-B). The flow rate was 1.0?ml/min and the column temperature was 25°C. The success of separation of the degradation products with different chemical characteristics was obtained by extending the time of the gradient, changing the proportion of the mobile phases and increasing the velocity of the flow. Two detectors were evaluated for the identification of degradation products and Roflumilast: a diode-arrary detector and a charged aerosol detector. The inability of the charged aerosol detector to dectect one of the six degradation products indicated that the method developed with RP-HPLC and the diode-array detector was more suitable for Roflumilast analysis. The method was validated according to specificity, linearity, LOD, LOQ, accuracy, precision and robustness.     

一种新型的杀螟丹分析方法及其在稻田杀螟丹残留动态分析中的应用

建立了一种水稻植株、糙米、稻壳、土壤和田水中的杀螟丹气相色谱-火焰光度检测(GC-FPD)方法。样品中的杀螟丹使用稀盐酸提取,然后在碱性条件下使用氯化镍(NiCl₂)将其衍生为沙蚕毒素,最后采用在线连接的支撑液液萃取(SLE)和固相萃取(SPE)进行萃取和富集。在优化好的条件下,杀螟丹在5种空白样品中低、中、高3种添加浓度的回收率为80.0%~114.4%,相对标准偏差(RSD)小于13.7%,表明所建立的方法具有良好的准确度和精密度。将所建立的方法用于大田条件下杀螟丹的残留动态分析,为建立杀螟丹的最大残留限量(MRL)提供参考,同时也可对农药施用技术的安全性进行评价。     

Development of a microfluidic paper-based analytical device for the determination of salivary aldehydes

A low cost, disposable and easy to use microfluidic paper-based analytical device (μPAD) was developed for simple and non-invasive determination of total aldehydes in saliva with a potential to be used in epidemiological studies to assess oral cancer risk. The μPAD is based on the colour reaction between aldehydes (e.g. acetaldehyde, formaldehyde), 3-methyl-2-benzothiazolinone hydrazone (MBTH) and iron(III) to form an intense blue coloured formazan dye. The newly developed μPAD has a 3D design with two overlapping paper layers. The first layer comprises 15 circular detection zones (8 mm in diameter), each impregnated with 8 μL of MBTH, while the second layer contains 15 reagent zones (4 mm in diameter). Two μL of iron(III) chloride are added to each one of the second layer zones after the addition of sample to the detection zones in the first layer. All hydrophilic zones of the μPAD are defined by wax printing using a commercial wax printer.     

A quantitative assessment of chemical techniques for detecting traces of explosives at counter-terrorist portals

Previous reviews have discussed in a qualitative manner the various highly sensitive analytical techniques for detecting minute traces of explosive material. However, there is no review available which compares quantitatively the sensitivities of the different analytical methods for detecting explosives. In view of the importance of this area to the present day planning of counter-terrorist strategies, this review makes a comprehensive and quantitative comparison of the analytical chemical methods which can be used for the detection of trace explosives in the luggage and on the persons of travelers. Possible directions of future development in this area are also discussed.     

微小型氢火焰离子化检测器及在色谱中的应用

构建了一种微小型氢火焰离子化检测器(μ-FID).与传统FID不同,助燃空气从收集极上部侧面导入,沿收集极与检测器壳体之间的缝隙向下流动,以环状气流沿壁流入燃烧室,流向反转后从中空的收集极内流出.火焰喷口位于燃烧腔的正中心轴线上,该区域助燃气的流动非常稳定,因此噪音电平非常低.采用更高的极化电压以提高离子化效率.对喷口材料及其内径、收集极长度、收集极至喷口的距离等结构参数进行了优化.在最优条件下,极化电压800 V时,检测器的信噪比比极化电压为150 V时提高一个数量级以上,检出限达1×10-12 g/s.相对于常规FID,μ-FID的气体消耗降低了70%,仅需要氢气和空气两种气体;具有体积小、重量轻、结构简单、灵敏度高、成本低廉等优点,适合作为便携式微型色谱的通用型检测器.