催化荧光熄灭法测定天然水中微量铁

1 引言 根据Fe(Ⅱ、Ⅲ)可同时催化过氧化氢氧化二苯胺磺酸钠的反应,发现二苯胺磺酸钠被紫外光照射可发射荧光,而反应产物苯醌则不发荧光,借此可通过测量二苯胺磺酸钠的荧光熄灭,间接地测定天然水中总微量铁。     

三维荧光光谱技术在溶解有机质-吸附态砷相互作用中的应用进展

溶解有机质使含砷矿物还原溶解是地下水中砷富集的因素之一,三维荧光光谱技术可以进一步研究溶解有机质在砷迁移过程中的多重作用。本文从溶解有机质的组分、荧光特征指数以及荧光猝灭三个方面综述了三维荧光光谱技术在溶解有机质-砷相互作用中的应用。溶解有机质中的腐殖质组分会与砷形成络合物促进砷向地下水中迁移,还原性醌类充当电子穿梭体,增强了砷在水中的迁移性能。通过荧光指数、腐殖化指数和氧化还原指数可以判断溶解有机质的来源、腐殖化程度以及氧化还原态组分。地表水中砷浓度低,荧光指数高,腐殖化指数较低且以腐殖质物质为主;地下水中砷浓度和腐殖化指数较高,荧光指数低,且腐殖质的醌类部分较少,表明随着水中砷浓度升高,荧光指数成下降趋势,地表水中的腐殖质醌类充当电子穿梭加强了氧化铁的还原和砷迁移作用,促进地表水中的砷向地下水中迁移。砷和溶解有机质会形成砷-溶解有机质络合物,使溶解有机质发生荧光猝灭。pH值和金属离子会影响溶解有机质和砷的络合,但pH值主要影响溶解有机质自身的荧光强度,对砷-溶解有机质络合物的荧光强度影响不大,Ca²⁺能够明显增强溶解有机质-砷的类蛋白荧光。     

水相一步法合成具有双光子效应的高效橙红荧光聚合物碳点

聚合物碳纳米点是近年来新兴的一种荧光纳米探针,具有较低的生物毒性、良好的水溶性、较高的量子产率、优异的光/化学稳定性以及良好的生物相容性.目前所制备的碳点大都表现出蓝、绿色荧光发射.为实现碳点长波荧光发射,扩大其在生物标记与成像及光电显示方面的应用,本文采用水相一步法交联聚合反应制备了具有橙红荧光发射性质且具有双光子效应的聚合物碳点,发射波长为604 nm,荧光量子产率达到30.64%,并且应用在生物活体成像中.     

核酸对邻菲啰啉的荧光猝灭及其分析应用

邻菲啰啉受到 ２３０ｎｍ及２６７ ｎｍ紫外光激发，在３６７ ｎｍ处产生一荧光峰。而天然和热变性鱼精子脱氧核糖核酸以及酵母核糖核酸的加入会猝灭邻菲啰琳的这一荧光发射。实验表明，该体系可在较宽的范围内灵敏地测定核酸。     

核酸对邻菲Luo啉的荧光猝灭及其分析应用

邻菲Ｌｕｏ啉受到２３０ｎｍ及２６７ｎｍ紫外光激发，在３６７ｎｍ处产生一荧光峰。而天然和热变性鱼精子脱氧核糖核酸以及酵母核糖核酸的加和会猝灭邻菲Ｌｕｏ啉的这一荧光发射。实验表明，该体系可在较宽的范围内灵敏地测定核酸。     

新型荧光双重敏感响应性壳聚糖衍生物的合成及其发光性能研究

为了开发新型多功能天然高分子荧光材料，合成出一种新型含有环氧丙氧基荧光素(EPF)基团的水溶性壳聚糖衍生物GCS-EPF, 并用IR，1H NMR，UV光谱和荧光光谱等手段进行结构和发光性能的研究. 结果表明, 修饰后水溶性壳聚糖(GCS)的水溶液、 固体粉末和薄膜在520 nm附近具有较强的荧光发射, 其荧光强度不仅在0-60 ℃时对度有较快敏感响应， 同时在pH=0-13.5时对pH也有较快敏感响应， 具有双重敏感响应, 因此可将其作为温度荧光探针和pH荧光探针的高分子材料.     

红光/近红外光硫醇荧光探针

小分子生物硫醇,包括半胱氨酸(Cys)、同型半胱氨酸(Hcy)和谷胱甘肽(GSH),在生理活动中扮演了重要的角色,其浓度的异常变化常与多种疾病息息相关,因此对其进行检测就显得尤为重要。近几年来,荧光探针因具有操作简便、时空分辨率高、损伤小和可视化等优势,在硫醇的识别领域成为了研究热点之一。而在已报道的众多的硫醇荧光探针中,红光或近红外光发射的荧光探针又因其具有背景干扰小、穿透深度深、拉曼散射影响小等特点,而受到研究者的青睐。本综述重点回顾了近三年来文献中报道的性能优异、发射红光或近红外光信号的硫醇荧光探针,根据构成探针分子荧光团的种类不同而进行分类介绍,包括罗丹明类、二吡咯氟硼类、花菁类、天然色素类、给受体型共轭化合物和聚集诱导发光型化合物六类。本文主要从分子设计、荧光性质、识别机理和成像应用等方面对各种荧光探针进行综述,同时展望了长波长发射的硫醇荧光探针的应用前景及待解决的问题。     

Er^3＋掺杂TeO2-WO3-ZnO—ZnF2玻璃的光谱性质

制备了Er^3 离子掺杂的TeO2-WO3-ZnO-ZnF2(TWZOF)玻璃，测试了样品的吸收光谱和970nmLD激发下样品中Er^3 离子的荧光光谱与荧光寿命，计算了Er^3 离子的J—O强度参数Ωt(t=2，4，6)和1．5μm波段的吸收截面与发射截面，研究了Er^3 离子1．5μm发射强度、荧光寿命和发射带宽与玻璃中ZnF2含量的关系。实验得到Er^3 离子在TWZOF玻璃中1．5μm发射的最大荧光半高宽(TwHm)为83nm；随着ZnF2含量的增加，Er^3 离子1．5μm发射强度、荧光寿命均增加。     

一种红光发射三苯胺吡啶盐的合成及荧光探针性质

以双碘代芳醛4-[N,N-二(4-碘苯基)氨基]苯甲醛与4-乙烯基吡啶通过钯催化双位点Heck偶联反应制备了中间体TPAPy,TPAPy再与碘代十八烷反应得到吡啶盐衍生物TPAPyS.目标化合物的结构经过红外光谱、核磁共振谱、高分辨质谱确认,测定了吡啶盐TPAPyS在固态、水溶液中及乙醇/水混合溶液中的荧光光谱.吡啶盐TPAPyS在固体状态下发出暗红色荧光,荧光发射峰为654 nm,测得固体量子产率为3.83%.TPAPyS在水溶液中发出红色荧光,荧光发射峰为647 nm.在乙醇/水混合溶液中,化合物TPAPyS的荧光发射峰位于612~640 nm.测定了吡啶盐TPAPyS与牛血清蛋白(BSA)、胱氨酸(DCys)及半胱氨酸(Cys)在生理条件下的光谱行为,吡啶盐TPAPyS与BSA、氨基酸作用后荧光发射强度均增加.吡啶盐TPAPyS是一种可溶于水的红光发射材料,荧光发射峰位于近红外波段,可作为荧光探针用于牛血清蛋白和氨基酸的检测.     

分子荧光光谱法测定食品接触材料中荧光增白剂

建立了分子荧光光谱法对荧光增白剂的定性和定量测定方法。对14种荧光增白剂通过进行激发波长和发射波长的扫描确定了其最大激发波长和最大发射波长,可结合进行荧光增白剂定性判断,并以三种常用的二苯乙烯型荧光增白剂VBL、BA、CXT为例,通过其迁移建立了定量测定荧光增白剂含量的方法。结果表明,三种荧光增白剂在0~1.0μg/mL范围内线性关系良好(相关系数r^2>0.999),检出限均为2.3μg/g,加标回收率均为92.9%~106%,相对标准偏差均小于5%,方法能有效满足食品接触材料样品中荧光增白剂的测定。     

The role of selected cations in the formation of pseudomicelles in aqueous humic acid

The fluorescence intensity enhancement of a pyrene probe in aqueous humic acid solutions was assessed in terms of added lanthanide and thorium cations. Among the trivalent ions it was found that size played a role, with the small Lu(3+) ion producing the greatest increase in pyrene emission. This was attributed to its superior ability to cause pseudomicellization in the humic acid polymer. Slow kinetic effects were observed, leading to substantial fluorescence enhancement over a period of 7 h. This was ascribed to a continuous aggregation process in aqueous humic acid, leading to ever more viscous microenvironments for the probe molecule.     

不同水环境对纳米银颗粒聚集体粒径大小及界面电势的影响

研究了不同水环境对无稳定剂与PVP为稳定剂的纳米银颗粒的物化性能的影响。结果表明:随着电解质浓度的增加,纳米银颗粒的粒径与界面电势逐步增大;二价阳离子比一价阳离子更能有效地使纳米银粒径与界面电势增加;稳定剂PVP,腐植酸及其他天然有机物能够增加纳米银溶胶的稳定性;在天然水体中,纳米银在海水中的粒径颗粒与界面电势比湖水中更大。     

Analysis of trace actinide elements in soil organic matter: Optimization of sample processing to improve chemical separation of U and Pu

Chemical separation yield of actinide elements from soil samples containing high amounts of organic matters was often low as compared to that for samples containing low organic matters. We compared chemical yield of uranium and plutonium from organic-rich Japanese soil and humic acid samples which were subjected to three different pretreatment procedures ((1) pulverization only, (2) dry-ashing at 510 °C after pulverization, and (3) 680 kGy gamma-ray irradiation after pulverization) prior to acid digestion. Separation of U and Pu was performed by U-TEVA resin and AG1-X8 anion exchange resin, respectively. For organic samples, pretreatment procedures governed the yield of actinide elements significantly. Chemical separation yield of U was low (6±1%) for Aldrich humic acid sample after dry-ashing at 510 °C. For such samples, gamma-ray irradiation improved the yield of U to 35±22%. Recovery of Pu was lower for some organic soil samples which were dry-ashed at 510 °C (27±2%) as compared to those which were not dry-ashed (62±10%).     

Competitive adsorption of organic matter with phosphate on aluminum hydroxide

The effects of orthophosphate on the adsorption of natural organic matter (NOM) on aluminum hydroxide were investigated using three organic compounds as surrogates, including humic acid (HA), phthalic acid, and 2,3-dihydroxybenzoic acid (2,3-DHBA). The adsorption of phthalic acid and 2,3-DHBA was very limited compared to that of HA, whereas their adsorption was reduced much more significantly than that of HA by phosphate. The efficiency of phosphate in reducing HA adsorption increased with increasing phosphate concentration. Phosphate adsorption was slightly reduced by phthalic acid and 2,3-DHBA but moderately suppressed by HA. The adjacent carboxylic groups mainly contributed to the adsorption of humic acid at low pH, while the adjacent phenol groups were responsible for the adsorption of humic acid at high pH. HPLC-SEC and SUVA analysis revealed that HA molecules with high molecular weight were adsorbed preferentially but were easily displaced by the specifically adsorbed phosphate. TM-AFM images revealed that the aggregation of HA molecules and the protonation of carboxylic groups at low pH facilitated the adsorption under acidic conditions. The presence of phosphate increases the coagulant dosage for NOM removal as some sites on the coagulant precipitates become utilized by phosphate.     

Humic acid fouling during microfiltration

A major factor limiting the use of microfiltration for surface water treatment is membrane fouling by natural organic matter. The extent and mechanisms of humic acid fouling during microfiltration have been examined using stirred cell filtration experiments and scanning electron microscopy. The extent of fouling was strongly dependent on both the source and preparation of the humic acid solutions. The large flux decline observed during constant pressure microfiltration was caused by the formation of a humic acid deposit located on the upper surface of the membrane. Prefiltration of the humic acid solutions dramatically reduced the rate of fouling through the removal of large humic acid aggregates. The initial fouling in this system was determined almost entirely by the convective deposition of these large particles/aggregates on the membrane surface. This initial deposit accelerated the subsequent rate of humic acid fouling, possibly serving as a nucleation site for deposition of macromolecular humic acids.     

Multivariate curve resolution analysis excitation-emission matrices of fluorescence of humic substances

Excitation-emission matrices (EEM) of fluorescence of aqueous solutions of humic substances (HS), and sets of EEM acquired as function of the HS concentration, were analysed by multivariate curve resolution alternating least squares (MCR-ALS). Three types of HS samples were studied: one commercial humic acid; two samples of fulvic acid (FA) extracted from a pinewood soil; two samples of FA extracted from recycled wastes. The fluorescence measurements were carried out at HS concentration between 5 and 100 mg/L and at pH 6. The application of MCR-ALS algorithm on each individual EEM, as well as on column-wise augmented matrices, allows the identification of three major fluorophores in all HS samples analysed. The emission and excitation spectra of these fluorophores were recovered and are characteristic of each sample. Moreover, the variation of the fluorescence intensities of each fluorophore with HS concentration shows deviations from linearity at HS concentration higher than 30 mg/L, depending on the fluorophore and/or sample. This behaviour reveals the existence of inner filter effects that affect the proportionally between the fluorescent signal and concentration but do not provoke measurable distortions on the fluorescence spectra of the detected fluorophores.     

Simultaneous analysis of small organic acids and humic acids using high performance size exclusion chromatography

An accurate and fast method for simultaneous determination of small organic acids and much larger humic acids was developed using high performance size exclusion chromatography. Two small organic acids, i.e. salicylic acid and 2,3‐dihydroxybenzoic acid, and one purified humic acid material were used in this study. Under the experimental conditions, the UV peaks of salicylic acid and 2,3‐dihydroxybenzoic acid were well separated from the peaks of humic acid in the chromatogram. Concentrations of the two small organic acids could be accurately determined from their peak areas. The concentration of humic acid in the mixture could then be derived from mass balance calculations. The measured results agreed well with the nominal concentrations. The detection limits are 0.05 mg/L and 0.01 mg/L for salicylic acid and 2,3‐dihydroxybenzoic acid, respectively. Applicability of the method to natural samples was tested using groundwater, glacier, and river water samples (both original and spiked with salicylic acid and 2,3‐dihydroxybenzoic acid) with a total organic carbon concentration ranging from 2.1 to 179.5 mg C/L. The results obtained are promising, especially for groundwater samples and river water samples with a total organic carbon concentration below 9 mg C/L.     

Determination of Organic Compounds,Fulvic Acid,Humic Acid,and Humin in Peat and Sapropel Alkaline Extracts

Black, brown, and light peat and sapropel were analyzed as natural sources of organic and humic substances. These specific substances are applicable in industry, agriculture, the environment, and biomedicine with well-known and novel approaches. Analysis of the organic compounds fulvic acid, humic acid, and humin in different peat and sapropel extracts from Lithuania was performed in this study. The dominant organic compound was bis(tert-butyldimethylsilyl) carbonate, which varied from 6.90% to 25.68% in peat extracts. The highest mass fraction of malonic acid amide was in the sapropel extract; it varied from 12.44% to 26.84%. Significant amounts of acetohydroxamic, lactic, and glycolic acid derivatives were identified in peat and sapropel extracts. Comparing the two extraction methods, it was concluded that active maceration was more efficient than ultrasound extraction in yielding higher amounts of organic compounds. The highest amounts of fulvic acid (1%) and humic acid and humin (15.3%) were determined in pure brown peat samples. This research on humic substances is useful to characterize the peat of different origins, to develop possible aspects of standardization, and to describe potential of the chemical constituents.     

Characterization of aquatic dissolved organic matter by asymmetrical flow field-flow fractionation coupled to UV-Visible diode array and excitation emission matrix fluorescence

Flow field-flow fractionation (FlFFF) with on-line UV/Visible diode array detector (DAD) and excitation emission matrix (EEM) fluorescence detector has been developed for the characterization of optical properties of aquatic dissolved organic matter (DOM) collected in the Otonabee River (Ontario, Canada) and Athabasca River (Alberta, Canada). The molecular weight (MW) distribution of DOM was estimated using a series of organic macromolecules ranging from 479 to 66,000 Da. Both the number-average (M_n) and weight-average (M_w) molecular weights of Suwannee River fulvic acid (SRFA) and Suwannee River humic acid (SRHA) determined using these macromolecular standards were comparable to those obtained using polystyrenesulfonate (PSS) standards, suggesting that organic macromolecules can be used to estimate MW of natural organic colloids. The MW of eight river DOM samples determined by this method was found to have an M_n range of 0.8–1.1 kDa, which agrees with available literature estimates. The FlFFF-DAD-EEM system provided insight into the MW components of river DOM including the optical properties by on-line absorbance and fluorescence measurement. A red-shift in emission and excitation wavelength maxima associated with lower spectral slope ratios (S_R = S_275–295:S_350–400) was related to higher MW DOM. However, DOM of different origins at similar MW also showed significant difference in optical properties. A difference of 47 and 40 nm in excitation and emission peak C maxima was found. This supports the hypothesis that river DOM is not uniform in size and optical composition.     

The use of linear potentiometric titration curves in the determination of alkalinity and acid-base properties of diluted solutions of humic substances

A critical study of the use of Gran and modified Gran functions for the determination of alkalinity and acid-base properties of diluted solutions containing humic substances is presented. These solutions were composed of 340 muM HCO3(-)(3) in 0, 10, 20.5 and 41 mg/1. of sodium humate in order to simulate natural waters with different levels of dissolved organic carbon. The results showed that the alkalinity may be determined in good agreement with the expected value using both methodologies. The modified Gran functions give information about acid-base speciation in addition to the alkalinity. The application of the modified Gran functions for determination of humic acid pK(a)s and stoichiometry was studied under conditions simulating waters rich in natural organic matter in terms of humic acid concentrations.