Flow injection determination of lactate based on a photochemical reaction using photometric and chemiluminescence detection

A photochemical method for the determination of lactate using a flow-injection system is proposed. The method is based on the decomposition of lactate in the presence of UO2(2+) and Fe3+ upon irradiation with UV or visible light. The Fe2+ produced in the photochemical process was monitored by measuring the absorbance after complexation with ferrozine (lambda max = 562 nm) or the chemiluminescence (CL) intensity in a luminol system without added oxidant. The range of measurements depended on the length of the irradiation time and the detection system used. The detection limits using CL and photometric detection were 2 ng ml-1 and 50 ng ml-1, respectively. The sample throughput was 45 samples h-1. The usefulness of the method was demonstrated by determining lactate levels in blood serum, milk, yoghurt, beer and pharmaceutical preparations.     

Simultaneous operation of plural separation modes in capillary electrophoresis with a chemiluminescence detector possessing a micro-space area for reaction/detection

Analysis of alpha-amino acids, proteins, and phenolic compounds was simultaneously performed using three capillaries in capillary electrophoresis with chemiluminescence detection, taking advantage of the micro-space area for reaction/detection at the tip of the capillary. The three capillaries included usual, polymer-containing, and sodium docley sulfate (SDS)-containing migration buffers for separation. The eluted samples from the capillaries, which were inserted into the chemiluminescence detection cell, were mixed with chemiluminescence reagent at the tips of the capillaries to generate visible light. The specific micro-space area for reaction/detection at the tips of the capillaries enabled the simultaneous operation of the three separation modes in the present system.     

Determination of nine pyrethroid insecticides by high-performance liquid chromatography with post-column photoderivatization and detection based on acetonitrile chemiluminescence

An HPLC method was developed to determine pyrethroids, including fenpropathrin, beta-cyfluthrin, lambda-cyhalothrin, deltamethrin, fenvalerate, permethrin, acrinathrin, tau-fluvalinate, and bifenthrin, by coupling HPLC, post-column irradiation with UV light and chemiluminescence detection of the resulting photoproducts. It is based on the observation that photolyzed pyrethroids take part in a chemiluminescent reaction in presence of K3Fe(CN)6 and NaOH, whose signal increases with the percentage of acetonitrile in the reaction medium. As the yield of the photoderivatization process and the chemiluminescent signals depend on the percentage of acetonitrile, the chromatographic column (a Gemini C18, Phenomenex 150 mm x 4.6 mm, 5 microm particle size) was chosen with the aim of using high percentages of this organic solvent in the mobile phase. Previous studies showed that the rate of the chemiluminescent reaction was very fast. Therefore, a modification was carried out in the detector in order to mix the analytes and reactives as near as possible to the measure cell. The optimised method was validated with respect to linearity, precision, limits of detection and quantification accuracy. Under the optimised conditions, linear working range extends three orders of magnitude with the relative standard deviation on intra-day precision below 10% and detection limits between 0.013 and 0.049 microg mL(-1), according to the compound. The proposed method has been successfully applied to the determination of pyrethroids in tomato with good results.     

Microchip capillary electrophoresis using on-line chemiluminescence detection

Chemiluminescence detection was used in capillary electrophoresis integrated on a microchip. Quartz microchips have two main channels and four reservoirs. Dansyl-lysine and -glycine were separated and detected with bis[(2-(3,6,9-trioxadecanyloxycarbony)-4-nitrophenyl]oxalate as peroxyoxalate chemiluminescent reagent. These dansyl amino acids came into contact with the chemiluminescence reagent to produce visible light at the interface between the separation channel and chemiluminescence reagent-containing reservoir. The detection limit (S/N = 3) for dansyl-lysine was 1 x 10(-5) M, which corresponded to the very small mass detection limit of ca. 0.4 fmol. However, the concentration sensitivity in the present system was approximately two orders of magnitude lower than that in the conventional capillary electrophoresis-chemiluminescence detection system. The relative standard deviations of migration time and peak height for dansyl-lysine were 4.2 and 4.5%, respectively. A channel conditioning before every run and an appropriate control of voltages were needed for the reproducible results. The present system had advantages in rapid separation time (within 40 s), small (several 10 pI) and accurate sample injection method using a cross-shaped injector, and simplification and miniaturization of the detection device.     

Application of Multi-step Excitation Schemes for Detection of Actinides and Lanthanides in Solutions by Luminescence/Chemiluminescence Laser Spectroscopy

The use of laser radiation with tunable wavelength allows the selective excitation of actinide/lanthanide species with subsequent registration of luminescence/chemiluminescence for their detection. This work is devoted to applications of the time-resolved laser-induced luminescence spectroscopy and time-resolved laser-induced chemiluminescence spectroscopy for the detection of lanthanides and actinides. Results of the experiments on U, Eu, and Sm detection by TRLIF method in blood plasma and urine are presented. Data on luminol chemiluminescence in solutions containing Sm(III), U(IV), and Pu(IV) are analyzed. It is shown that appropriate selectivity of lanthanide/actinide detection can be reached when chemiluminescence is initiated by transitions within 4f- or 5f-electron shell of lanthanide/actinide ions corresponding to the visible spectral range. In this case chemiluminescence of chemiluminogen (luminol) arises when the ion of f element is excited by multi-quantum absorption of visible light. The multi-photon scheme of chemiluminescence excitation makes chemiluminescence not only a highly sensitive but also a highly selective tool for the detection of lanthanide/actinide species in solutions.     

基于纳米TiO2的化学发光法检测铁(Ⅱ)

铁(Ⅱ)能在具有催化活性的纳米TiO2表面产生化学发光辐射,表面活性剂十六烷基三甲基溴化铵(CTAB)的存在能显著增敏此发光强度。此外,纳米氧化钛也能增强Fenton反应的化学发光强度,据此,建立了纳米TiO2-CTAB-Fenton化学发光新体系检测铁(Ⅱ)的新方法。在优化条件下,亚铁离子在1.0×10-8~1.0×10-6mol/L浓度范围内与其化学发光强度呈现良好的线性关系,对1.0×10-7mol/L浓度的亚铁离子平行测定5次,相对标准偏差为3.9%,检出限为4.0×10-9mol/L。文中还对化学发光反应机理进行了初步探讨。     

Chemiluminescence determination of 20 amino acids and the mechanism study

<正>It was found that 20 amino acids could inhibit the intensity of the luminol-H_2O_2-CuSO_4 chemiluminescence system.Using this character,a rapid and sensitive method for the determination of 20 amino acids was developed with flow injection coupled with chemiluminescence detection.Under the optimal conditions,the detection limits of 20 amino acids were in the range of 4.5×10~(-7)- 4.3×10~(-10) mol/L,and the relative standard deviations were less than 3.2%.The proposed method was successfully applied to drug analysis.The possible mechanism was also discussed.     

Structural, optical and photocatalytic studies of Fe doped ZnS nanoparticles

Fe doped ZnS nanoparticles (Zn_1?xFe_xS; where x = 0.00, 0.03, 0.05 and 0.10) were synthesized by a chemical precipitation method. The synthesized products were characterized by X-ray diffraction, scanning electron microscope, transmission electron microscope, ultraviolet–visible and photoluminescence spectrometer. The X-ray diffraction and transmission electron microscope studies show that the size of crystallites is in the range of 2–10 nm. Photocatalytic activities of ZnS and 3, 5 and 10 mol% Fe doped ZnS were evaluated by decolorization of methylene blue in aqueous solution under ultraviolet and visible light irradiation. It was found that the Fe doped ZnS bleaches methylene blue much faster than the undoped ZnS upon its exposure to the visible light as compared to ultraviolet light. The optimal Fe/Zn ratio was observed to be 3 mol% for photocatalytic applications.     

On-column complexation capillary electrophoretic separation of Fe2+ and Fe3+ using 2,6-pyridinedicarboxylic acid coupled with large-volume sample stacking

On-column complexation of Fe2+ and Fe3+ with 2,6-pyridinedicarboxylic acid (2,6-PDCA) formed anionic complexes, which were then separated by capillary zone electrophoresis with direct UV detection at 214 nm. To achieve reasonable separation selectivity and on-column complexation, the conditions such as pH, the concentration of 2,6-PCDA and the EOF modifiers in the electrolyte were examined. The electrolyte contained 5.0 mM 2,6-PDCA, 0.25 mM tetradecyltrimethlammonium bromide (TTAB) and 5% (v/v) acetonitrile at pH 4.0 was optimised for on-column complexation and the separation of Fe[PCDA]2(2-) and Fe[PCDA]2(-). To enhance the detection sensitivity, large-volume sample stacking (LVSS) was used for the on-line preconcentration of Fe[PCDA]2(2-) and Fe[PCDA]2(-). Under the optimised conditions, satisfactory working ranges (0.5-50 microM), lower detection limits (less than 0.1 microM) and good repeatability of the peak areas (R.S.D.: 5.2-7.8%, n = 5) was achieved using LVSS (300 s). With LVSS, the detection sensitivity was enhanced more than 50-fold compared to conventional hydrodynamic injection. The proposed method was used successfully for the determination of Fe2+ and Fe3+ in water samples.     

测定核黄素的化学发光新方法

研究了核黄素的化学发光性质，建立了一种测定核黄素的化学发光新方法，并应用于实际样品中核黄素的测定，与文献相比，本方法无需避光，而且分析体系和样品处理简单；干扰小，牛血清白蛋白、抗坏血酸、天冬氨酸等８种生物有机物质和 Ｃｕ（Ⅱ）、Ｚｎ（Ⅱ）、Ｆｅ（Ⅲ）等１５种常见金属离子的允许量较大；核黄素溶液浓度在０． １０～５０ ｍｇ／Ｌ范围内，与化学发光强度成正比，方法线性范围宽；测定１．０ｍｇ／Ｌ核黄素溶液１２次，求得相对标准偏差为２．９％，方法精密度高；方法的检测限为０．０７５ ｍｇ／Ｌ，灵敏度高。     

Photocatalytic hydrogen production from water over M-doped La2Ti2O7 (M = Cr, Fe) under visible light irradiation (lambda > 420 nm)

In the search for efficient photocatalysts working under visible light, we have investigated the effect of cation substitution on a layered perovskite, La2Ti2O7. Among various metal dopants, only Cr and Fe induced intense absorption of visible light (lambda > 400 nm), and only these catalysts produced H2 photocatalytically from water in the presence of methanol under visible light irradiation (lambda > 420 nm). The polymerized complex method was found to be more efficient for fabrication of the present catalysts producing a more homogeneous structure than the solid-state reaction. The characterization by XRD, UV-vis DRS, XPS, and XANES revealed that doped Cr and Fe were present in the Cr3+ and Fe3+ states substituting for Ti sites in the La2Ti2O7 lattice. The theoretical calculation indicated that the most significant feature in the electronic band structure of the metal-doped La2Ti2O7 was the formation of a partially filled 3d band in the band gap of La2Ti2O7, while the contribution of these dopants on the valence band was negligible. Excitation of electrons from this localized interband to the conduction band of La2Ti2O7 was responsible for visible light absorption and the H2 evolution from water under visible light.     

Determination of salbutamol using on-line solid-phase extraction and sequential injection analysis. Comparison of chemiluminescence and fluorescence detection

Determination of salbutamol using sequential injection analysis (SIA) with chemiluminescence and fluorescence detection has been devised. The chemiluminescence signal was emitted during the oxidation of salbutamol by potassium permanganate in sulfuric acid medium. Sodium polyphosphate was used as chemiluminescence enhancer. The fluorescence signal (excitation wavelength 230 nm) was also measured in sulfuric acid medium. Both detection techniques were compared with respect to the application of the methods to the determination of salbutamol in biological materials. The sample pre-treatment takes place directly in the SIA system, when salbutamol is adsorbed on the solid-phase (Baker-carboxylic acid) microcolumn integrated into the system. Sulfuric acid serves both as the reagent and the eluent. The lab-made SIA system consisted of a 2.5-mL Cavro syringe pump, ten-port Vici Valco selection valve and Spectra-Physics FS 970 fluorescence detector, which was lab-modified for chemiluminescence detection. The system was controlled by a PC using originally compiled LabVIEW-supported software. Concentrations, volumes of reagents and flow rates were optimised by a simplex method. Salbutamol was determined in the linear range 0.05-10 microg mL(-1) (RSD 1.53%), with the detection limit (3 sigma) 0.03 microg mL(-1) and sample throughput of 42 samples per hour with chemiluminescence detection in standard solutions. The fluorescence detection enabled the determination of salbutamol in standard solutions in the linear range 0.5-100 microg mL(-1) (RSD 2.69%), with the detection limit 0.2 microg mL(-1) and sample throughput of 24 h(-1). The proposed methods were applied to the determination of salbutamol in human serum and urine. However, serum is a very complicated matrix and the SIA-SPE analysis did not provide satisfactory results. It was possible to determine salbutamol in human urine using this technique. Better recovery was achieved with fluorescence detection.     

Dropping mode chemiluminescence system with a poly(dimethylsiloxane) cell for applications to semiconductor processes.

A lab-made chemiluminescence system with a polymer cell for the dropping mode was used to determine ultra-trace metal ions in hydrofluoric acid (HF) and the standard cleaning solution-1 (SC-1) used in semiconductor manufacturing processes. The cell was made of poly(dimethylsiloxane) (PDMS) with dimensions of about 10 mm i.d. and 8 mm in height, was cheap, disposable, chemically inert to alkalis and acids, especially HF, and was optically transparent in the visible region. A dropping method for sample injection was adopted to minimize pulsation and the dramatic pH change of the luminol-H2O2 reagent when adding the sample. The average sample weight of a single drop was 7.17 microg with a remarkable reproducibility of +/-0.37% relative standard deviation (RSD). This very small sample volume compared to the reagent volume made it possible to avoid any precipitation being formed when HF was added. For an application, Fe was determined in deionized (d.i.) water, sulfuric acid, SC-1, and a diluted HF (1:200 DHF) solution, which have been commonly used in semiconductor manufacturing processes. The limits of detections for Fe2+ in those solutions were found to be in the range of 42 to 62 pg ml(-1). Based on the analytical results, this chemiluminescence system with the PDMS cell was reproducible, resistant to HF, had less sample consumption and waste generation, and was sensitive enough to apply to the semiconductor industry as an on-line monitoring sensor. Although this chemiluminescence system does not have selectivity for each specific metal ion, it can be used as an on-line sensor to monitor the metal contamination level of Fe, Cu, Co, etc., which are major elements of concern in the semiconductor manufacturing process.     

Preparation and photocatalytic properties of Fe3+-doped Ag@TiO2 core-shell nanoparticles

Ag@TiO2 core-shell-type nanophotocatalysts have been prepared using a simple and convenient method. The products were characterized by TEM, XRD, and UV-vis spectra. To make the catalysts achieve the highest photocatalytic activity under UV light illumination, the Ag content of Ag@TiO2 was optimized. The results showed that Ag@TiO2-doped Fe3+ extend their absorption into the visible region. Among the Fe3+-doped samples, Ag@Fe-TiO2 with low Ag content showed higher photocatalytic activity under visible light illumination. An excessive added amount of Ag would reduce Fe3+ to Fe2+ and make them difficult to be incorporated into the lattice of titania. From the experiments, we found that Fe3+ ions could stabilize the Ag@TiO2 colloid by holding back the aggregation of the core-shell nanoparticles.     

Quantification of sugars and organic acids in hygroscopic pharmaceutical herbal dry extracts

Three chromatographic methods have been employed for the determination of hydrophilic compounds, namely carbohydrates and organic acids in herbal dry extracts of Eschscholtzia californica Cham. The hydrophilic compounds were separated from the other components of the dry extracts by solid-phase extraction methods, which were optimised with respect to recovery rates. Carbohydrates were quantified using high-performance anion-exchange chromatography with pulsed amperometric detection. Organic acids were analysed by ion-exclusion chromatography with evaporative light scattering detection and gas chromatography-mass spectrometry. Using the latter method, large amounts of glyceric acid were separated from the extracts of Eschscholtzia californica Cham. This substance together with sugars may be responsible for the increased hygroscopicity and the poor processing behaviour of the extracts.     

Automated pre-column derivatization of amines in biological samples with dansyl chloride and with or without post-column chemiluminescence formation by using TCPO-H2O2.

On-line automation of two different liquid chromatographic procedures, a pre-column derivatization system and a pre- and post-column system, in order to generate chemiluminescence is reported. Dansyl chloride (Dns-Cl) was used as a pre-column reagent to form fluorophores and bis(2,4,6-trichlorophenyl) oxalate (TCPO) and hydrogen peroxide (H2O2) as a post-column reagent to generate chemiluminescence. This procedure is based on the employment of a primary column packed with C18 material inserted in a multi-dimensional assembly for sample clean-up and derivatization with Dns-Cl. The dansyl derivatives formed are transferred and separated in a LiChrospher 100 RP18 analytical column (125 x 4 mm id, 5 microns film thickness) using acetonitrile-imidazole buffer (pH 6.8) (70 + 30) as eluent. The separated derivatives were transferred to the detector for fluorescence detection or to the post-column system where the chemiluminescence response was generated by using TCPO-H2O2 and the products were detected by chemiluminescence. The procedure was optimised for amphetamine and related compounds. A comparison between the on-line pre-column and pre- and post-column systems was performed. The results show that the sensitivity of chemiluminescence detection can be higher than that of fluorescence detection. The recoveries obtained ranged from 98 +/- 8 up to 108 +/- 8% for amphetamine and methamphetamine, respectively. The accuracy and precision of these methods were evaluated.     

Development of FIA equipped with a chemiluminescence detector using a mixed reagent of luminol and 1,10-phenanthroline.

We developed an FIA system equipped with a chemiluminescence detector using a mixed chemiluminescence reagent of luminol and 1,10-phenanthroline for the detection of metal ions and metal complexes. The carrier, mixed chemiluminescence reagent comprising luminol, 1,10-phenanthroline, and cethyltrimethylammonium bromide, and H2O2 solutions were fed by corresponding pumps at a definite flow rate. Sample solutions dissolving hematin, [Co(NH3)4(H2O)2]2(SO4)3, CuSO4, NiCl2, K3[Fe(CN)6], and K4[Fe(CN)6] were analyzed as models by the means of the present FIA system. Solutions of hematin, [Co(NH3)4(H2O)2]2(SO4)3, CuSO4, and NiCl2 were detected as positive peaks, as usual. The order of the catalytic activity of these samples for the present chemiluminescence reaction using the mixed chemiluminescence reagent was [Co(NH3)4(H2O)2]2(SO4)3 > hematin > CuSO4 > NiCl2. On the other hand, sample solutions of K3[Fe(CN)6] and K4[Fe(CN)6] were detected as negative peaks and were determined over the ranges of 1 x 10(-8) - 1 x 10(-6) M with a detection limit of 1 x 10(-8) M and 2 x 10(-8) - 4 x 10(-6) M with a detection limit of 2 x 10(-8) M, respectively. Their negative peaks were observed reproducibly with a relative standard deviation of 2 - 5%.     

Cooperation among N,F and Fe in tri-doped TiO<Subscript>2</Subscript> photocatalyst

TiO₂ photocatalysts tri-doped with N, F and Fe were synthesized by a sol–gel method. The cooperation of N, F and Fe in tri-doped TiO₂ was verified by monitoring NH₃ decomposition, X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and ultraviolet–visible (UV–Vis) absorption spectroscopy, and by the simulation based on the density functional theory (DFT). The results from NH₃ decomposition revealed that the cooperation of N, F and Fe broadened the optical response of TiO₂ to the visible light range and also enhanced the photocatalytic activity of TiO₂ under UV light. The reusability of the tri-doped TiO₂ sample after three cycles under UV and visible light irradiation was very good. XRD patterns and SEM and HRTEM images indicated that the tri-doped sample was nanometric anatase with a small amount of rutile with an average particle size of 18 nm. Tri-doping with N, F and Fe suppressed the phase transition from anatase to rutile and also resulted in some more lattice defects. XPS analysis showed that the N, F and Fe atoms were doped into the TiO₂ lattice. UV–Vis absorption spectra of the tri-doped TiO₂ showed that its optical absorption edge was moved up to 640 nm and its UV absorption was also enhanced. The DFT results confirmed that the cooperation of Fe 3d and N 2p orbits narrowed the band gap of TiO₂ and the F 2p orbit broadened the upper valence bands. The synergistic electron density around N, F and Fe in tri-doped TiO₂ was capable of enhancing the photochemical stability and reusability of TiO₂.     

PHOTOINDUCED LUMINESCENCE AND EPR SIGNALS OF POLYPHENOL AND QUINONE POLYMERS

Abstract— Aqueous basic solutions, pH 9.0 of humic acids and melanin-like, synthetic polymers, obtained with adrenochrome, hydroquinone and purpurogallin, were illuminated with visible light under N₂ or O₂ atmospheres. It has been found that light enhances a singlet electron-paramagnetic-resonance (EPR) signal of polymers both under N₂ and O₂, and induces ultra-weak luminescence in the presence of O₂. Degradative oxidation of polymers, accelerated by light, leads to a decrease of EPR signal intensity and generates weak chemiluminescence.     

一步火焰辅助热解法制备Fe掺杂嵌碳TiO2及其光催化性能

以钛酸四丁酯、无水乙醇和无水氯化铁为前驱体,通过一步火焰辅助热解法制备了Fe掺杂嵌碳TiO₂,并研究了样品的光催化活性. 利用扫描电子显微镜及能谱、X射线光电子能谱、X射线粉末衍射和紫外-可见漫反射吸收光谱等对样品的形貌、组分、晶型和光吸收进行了表征,并研究了样品在紫外和可见光下的光催化活性. 结果表明,无需后续热处理可直接得到主要是锐钛矿相TiO₂的样品,Fe³⁺以替位掺杂形式进入TiO₂晶格,随掺杂量增加,样品在可见光区域的吸光度提高,吸收带边红移. Fe掺杂量（摩尔分数）小于0.2%可改善样品的光催化活性,当Fe掺杂量为0.1%时,样品在可见光和紫外-可见光照射下均显示出最高的降解亚甲基蓝速率.