A novel and selective spectral method for the determination of trace chlorine in water basing on the resonance scattering effect of rhodamine B-I(3) association nanoparticles

In Na₂HPO₄-citric acid buffer solution, Cl₂ can oxidize I⁻ to form I₂ and then it reacts with excess I⁻ to form I₃⁻. The I₃⁻ combines respectively with rhodamine dyes, including rhodamine B (RhB), butyl rhodamine B (b-RhB), rhodamine 6G (RhG) and rhodamine S (RhS), to form association particles which give stronger resonance scattering (RS) effect at 400 nm. The RS intensity of the RhB, b-RhB, RhG and RhS systems is proportional to chlorine concentrations in the range of 0.008-1.74, 0.019-1.33, 0.021-2.11 and 0.019-2.04 μg/mL Cl₂, respectively. The detection limits of the systems were 0.0020, 0.0048, 0.0063 and 0.0017 μg/mL, respectively. In them, the RhB system has good stability and high sensitivity, and has been applied to the analysis of chlorine in drinking water, with satisfactory results which is in agreement with that of the methyl orange (MO) spectrophotometry.     

A new and sensitive resonance-scattering method for determination of trace nitrite in water with rhodamine 6G

In the medium HCl–KI–rhodamine dye, NO₂^– reacts with excess I^– to form I₃^– and the I₃^– and rhodamine dye combine to form an association particle which gives three resonance-scattering (RS) peaks at 320 nm, 400 nm, and 595 nm. In systems containing rhodamine 6G (Rh6G), rhodamine B (RhB), rhodamine S (RhS), and butyl rhodamine B (BRhB) the resonance scattering intensity at 400 nm is proportional to nitrite concentrations in the range 2.3–276 ng mL^–1, 9.2–184 ng mL^–1, 9.2–184 ng mL^–1, and 9.2–92 ng mL^–1, respectively. Because of the high sensitivity, wide linear range, and good stability of the Rh6G system, it has been used for determination of nitrite in water samples, with satisfactory results. The spectral results have been used to verify that the formation of (Rh6G·I₃)_n association particles and their interface with the system are main factors that cause the RS enhancement.     

Gas-diffusion flow injection assay for the selective determination of chlorine dioxide based on the fluorescence quenching of chromotropic acid

The present work reports the first spectrofluorimetric gas-diffusion flow injection (GD-FI) assay for the determination of chlorine dioxide in water samples (tap, mineral and soda water). The method is based on the fluorescence quenching of chromotropic acid (CA) (λ_ex. = 347 nm, λ_em. = 371 nm) caused by the analyte. The chemical and instrumental variables of the system were studied in terms of maximum sensitivity. The gas-diffusion cell was thermostated at 40 °C to enhance the vaporization of chlorine dioxide and thus the sensitivity of the method. The quenching effect of chlorine dioxide on CA was linear in the range 0.09-3.41 mg l^− 1, while the precisions either close to the quantitation limit or near to the middle of the linear section of the calibration graph were satisfactory in both cases (s_r = 2.6% and 1.5% (n = 10) at 0.17 and 1.71 mg l^− 1 level, respectively). The developed method proved to be adequately selective and sensitive with 3σ limit of detection equal to c_L = 0.03 mg l^− 1. The application of the assay to spiked tap, mineral and soda water samples yielded accurate results with recovery values in the range 94.1-105.9%.     

A simple and sensitive resonance scattering spectral method for determination of hydroxyl radical in Fenton system using rhodamine S and its application to screening the antioxidant

Based on resonance scattering (RS) effect of rhodamine dye association particles, a new resonance scattering method for the determination of hydroxyl free radical from Fenton reaction was developed. In HCl-NaAc buffer solution, the OH of Fenton reaction oxidized the excess I⁻ to I₃⁻. The I₃⁻ combined, respectively, with rhodamine B (RhB), butyl rhodamine B (b-RhB), rhodamine 6G (RhG) and rhodamine S (RhS) to form association particles that exhibit stronger resonance scattering effect at 420 nm and 610 nm. However, the RS peak at about 610 nm was interfered with its synchronous fluorescence peak at 580 nm for RhB, 580 nm for b-RhB, 560 nm for RhG and 560 nm for RhS, respectively. The concentration of H₂O₂ in the range of 0.648-21.6 μmol/L, 0.423-13.0 μmol/L, 0.216-13.0 μmol/L and 0.092-13.0 μmol/L was linear to its resonance scattering intensity at 420 nm. Its detection limit was 0.15 μmol/L, 0.10 μmol/L, 0.092 μmol/L and 0.044 μmol/L, H₂O₂, respectively. This RhS RS method was applied to selection of the antioxidant, with satisfactory results.     

Characterization of rhodamine B hydroxylamide as a highly selective and sensitive fluorescence probe for copper(II)

Rhodamine B hydroxylamide (1) is characterized as a highly selective and sensitive fluorescence probe for Cu²⁺. Under the optimized conditions, the probe exhibits specific absorbance-on and fluorescence-on responses to Cu²⁺ only. This remarkable property may allow Cu²⁺ to be detected directly in the presence of the other transition metal ions, and such an application has been demonstrated to human serum. The reaction mechanism is also investigated and proposed as that the hydroxylamide group of 1 binds Cu²⁺, and the subsequent complexation of Cu²⁺ displays a high catalytic activity for the hydrolytic cleavage of the amide bond, causing the release of fluorophore (rhodamine B) and thereby the retrievement of absorbance and fluorescence. The recovered fluorescence intensity is proportional to the concentration of Cu²⁺ in the range 1-20 μM. The detection limit for Cu²⁺ is 33 nM (k = 3). The reaction mechanism described here may be useful for developing excellent spectroscopic probes with cleavable active bonds for other analytes.     

高浓度二氧化氯气体的在线检测研究

在40℃下,高浓度ClO2气体在盘管中迅速溶解于水中达到平衡,使用分光光度法检测平衡溶液的浓度,从而间接测定出ClO2气体的浓度。该方法可检测体积分数大于0.14%的ClO2,响应时间为15~30s,相对标准偏差为0.3%,与连续碘量法相比测定结果没有显著性差异(P<0.01),全过程中未使用化学试剂,操作简便,干扰小,适用于的高浓度ClO2气体在线检测。     

Review of analytical methods for the determination of chlorine dioxide

The present study reviews more than twenty years (1985-present) of published research on the development and application of analytical procedures for the determination of chlorine dioxide, a widely used disinfectant and bleaching agent. The review covers a variety of techniques including batch and automated spectrophotometry and fluorimetry, electroanalysis and chromatography. The analytical figures of merit to the methods are presented, while critical discussion regarding their advantages and disadvantages is addressed.      

A highly sensitive and selective fluorescent probe for trivalent aluminum ion based on rhodamine derivative in living cells

A rhodamine spirolactam derivative (1) is developed as a colormetric and fluorescent probe for trivalent aluminum ions (Al³⁺). It exhibits a highly sensitive “turn-on” fluorescent response toward Al³⁺ with a 70-fold fluorescence intensity enhancement under 2 equiv. of Al³⁺ added. The probe can be applied to the quantification of Al³⁺ with a linear range covering from 5.0 × 10⁻⁷ to 2.0 × 10⁻⁵ M and a detection limit of 4.0 × 10⁻⁸ M. Most importantly, the fluorescence changes of the probe are remarkably specific for Al³⁺ in the presence of other metal ions, which meet the selective requirements for practical application. Moreover, the experiment results show that the response behavior of 1 towards Al³⁺ is pH independent in neutral condition (pH 6.0–8.0) and the response of the probe is fast (response time less than 3 min). In addition, the proposed probe has been used to detect Al³⁺ in water samples and image Al³⁺ in living cells with satisfying results.     

Deterioration of polyethylene pipes exposed to water containing chlorine dioxide

Chlorine species used as disinfectants in tap water have a deteriorating effect on many materials including polyethylene. There are only very few scientific reports on the effect on polyethylene pipes of water containing chlorine dioxide. Medium-density polyethylene pipes stabilized with hindered phenol and phosphite antioxidants were pressure tested with water containing 4 ppm chlorine dioxide at 90 °C and pH = 6.8 as internal medium. The stabilizers were rapidly consumed towards the inner pipe wall; the rate of consumption was four times greater than in chlorinated water (4 ppm, pH = 6.8) at the same temperature. The depletion of stabilizer occurred far into the pipe wall. A supplementary study on a polymer analogue (squalane) containing the same stabilizer package showed that the consumption of the phenolic antioxidant was 2.5 times faster when exposed water containing chlorine dioxide than on exposure to chlorinated water. The subsequent polymer degradation was an immediate surface reaction. It was confirmed by differential scanning calorimetry, infrared spectroscopy and size exclusion chromatography that in the surface layer which came into contact with the oxidising medium, the amorphous component of the polymer was heavily oxidized leaving a highly crystalline powder with many carboxylic acid chain ends in extended and once-folded chains. Scanning electron microscopy showed that propagation of cracks through the pipe wall was assisted by polymer degradation.     

An improved colorimetric method for chlorine dioxide and chlorite ion in drinking water using lissamine green B and horseradish peroxidase

Lissamine Green B (LGB) was carefully selected as a potential candidate for the development of a new U.S. Environmental Protection Agency (EPA) method that is intended for use at water utilities to determine chlorine dioxide (ClO₂) in drinking water. Chlorine dioxide reacts with LGB in aqueous solution to decrease the absorbance of LGB in direct proportion to the ClO₂ concentration. LGB was confirmed to have adequate sensitivity, and to suffer less interference than other dyes reported in the literature. The stoichiometry for the reaction between LGB and ClO₂ was found not to be 1:1 and is dependent on the LGB concentration. This required calibration of each LGB stock solution and prompted the investigation of alternate means of calibration, which utilized a horseradish peroxidase (HRP)-catalyzed conversion of chlorite ion (ClO₂⁻) to ClO₂. This approach allowed the simultaneous determination of ClO₂⁻ concentration, which is also required each day at water plants that use ClO₂. Studies were conducted to characterize and carefully optimize the HRP-conversion of ClO₂⁻ to ClO₂ in order to yield reaction conditions that could be accomplished in less than 30 min at modest cost, yet meet EPA's sensitivity and robustness requirements for routine monitoring. An assessment of method detection limit, linearity and slope (or sensitivity), precision, and accuracy in finished drinking water matrices indicated that this approach was suitable for publication as EPA Method 327.0.     

A sensitive and selective detection method for thiol compounds using novel fluorescence probe

In this work, a sensitive and selective detection method based on fluorescence resonance energy transfer (FRET) was developed for analyzing thiol compounds by using a novel fluorescent probe. The new fluorescent probe contains a disulfide bond which selectively reacts with nucleophilic thiolate through the thiol-disulfide exchange reaction. An obvious fluorescence recovery can be observed upon addition of the thiol compound in the fluorescent probe solution due to the thiol-disulfide exchange reaction and the destruction of FRET. This novel probe was successfully used to determine dithiothreitol (DTT), glutathione (GSH) and cysteine (Cys). The limits of detection (LOD) were 2.0 μM for DTT, 0.6 μM for GSH, and 0.8 μM for Cys. This new detection method was further investigated in the analysis of compound amino acid injection.     

Sensitive and selective spectrofluorimetric determination of chromium(VI) in water by fluorescence enhancement

A new fluorogenic method for the selective and sensitive determination of chromium(VI) in acidic water using rhodamine B hydrazide was developed. This method was based on the oxidation of non-fluorescent rhodamine B hydrazide by potassium dichromate in acidic aqueous conditions to give rhodamine B, which was highly fluorescent, as a product. With the optimum condition described, the fluorescence enhancement at 585 nm was linearly related to the concentration of chromium(VI) in the range of 5.0 × 10⁻⁸ to 2.0 × 10⁻⁶ mol L⁻¹ (2.60-104 ng mL⁻¹) with a correlation coefficient of R² = 0.9993 (n = 18) and a detection limit of 5.5 × 10⁻⁹ mol L⁻¹ (0.29 ng mL⁻¹). The R.S.D. was 2.2% (n = 5). The proposed method was also applied to the determination of chromium(VI) in drinking water, river water and synthetic samples.     

A new resonance scattering spectral method for the determination of trace amounts of iodate with rhodamine 6G

Under the conditions of 0.04 mol L⁻¹ HCl-8.0 × 10⁻⁴ mol L⁻¹ KI, there is a fluorescence peak at 540 nm and a synchronous fluorescence peak at 540 nm for rhodamine 6G (RhG). When there is IO₃⁻, it reacts with exceed I⁻ to form I₃⁻. And I₃⁻ and RhG combine into ion association particles. The particles exhibit three resonance scattering peaks at 320, 400 and 595 nm. And there is fluorescence quenching at 540 nm. Iodine concentration is proportional to the intensity of the resonance scattering intensity at 400 nm in the range of 1.0-20 × 10⁻⁷ mol L⁻¹. And a new resonance scattering spectral (RSS) method has been described for the determination of IO₃⁻ in salt samples. The spectral results have been verified that the formation of (RhG-I₃)_n association particles and solid-liquid interfaces are the main factor that cause the fluorescence quenching and resonance scattering effects.     

一种简单灵敏的盐酸文拉法辛测定方法

四苯硼钠对罗丹明B具有荧光猝灭作用,使其荧光信号强度减弱甚至消失,而盐酸文拉法辛可以跟四苯硼钠反应生成更稳定的疏水性离子缔合物沉淀,使罗丹明B重新释放出来,又使该体系荧光信号强度增强,且荧光信号的增强程度与盐酸文拉法辛的加入量成正比关系,据此建立了一种反荧光猝灭法测定盐酸文拉法辛新方法。以365nm为激发波长,610nm为发射波长,测量了试液和空白液荧光强度之差ΔF。盐酸文拉法辛的质量浓度在2.423～43.94mg/L范围内与△F值呈线性关系,线性回归方程为△F=1.1789ρ-9.158,相关系数R为0.9995,检出限为0.7268mg/L,方法 RSD为0.87%。用本方法对不同厂家生产的盐酸文拉法辛缓释片及盐酸文拉法辛胶囊样品进行测定,测定值与药品标示量基本相符,加标回收率在95%～103%之间。     

二氧化氯催化氧化难降解有机废水在我国的研究进展

难降解有机废水的处理对环境保护有十分重要的意义.在本文中,对用二氧化氯催化氧化技术在不同领域中难降解有机废水的处理和其催化氧化反应机理在我国的研究进展进行了介绍和评述,也指出了该技术未来的发展前景和进一步的研究方向.     

A selective and sensitive off–on probe for palladium and its application for living cell imaging

A new rhodamine B derivative T1 has been rationally synthesized and displayed selective Pd(Ⅱ)-amplified absorbance and fluorescence emission above 540 nm in methanol–water. Upon the addition of Pd(Ⅱ), the spirolactam ring was unfolded and a 1:1 metal-ligand complex formed, which can be used for ‘‘naked-eyes" detection. In addition, fluorescence imaging experiments of Pd~(2+) in HepG2 living cells showed its valuable application in biological systems.     

A review on the electrochemical production of chlorine dioxide from chlorates and hydrogen peroxide

Chlorine dioxide is one of the most interesting oxidants because it combines a strong capacity of oxidation with low formation of hazardous byproducts such as chlorinated organics during its application. Because of that, it is widely used in disinfection of drinking water and, currently, it is aimed to be used in the disinfection of surfaces or buildings. Although it is usually produced by the chemical interaction of chlorite with hypochlorite/chlorine or hydrochloric acid, one interesting alternative for its production is the combination in strongly acidic media of chlorate and hydrogen peroxide. Both compounds are known to be efficiently manufactured with electrochemical technology, opening the possibility of a complete electrochemical process to produce this important oxidant. This review summarizes the recent progress in the electrochemical production of the two raw materials, as well as the complete electrochemical production of chlorine dioxide, not only paying attention to the scientific literature but, most importantly, to recent patents, trying to see in which technology readiness level are each of the technologies and what are the elements of the value chain required for a complete implementation of the technology.     

A new fluorescence method for determination of ozone in ambient air

A new simple method for determination of ozone in ambient air is presented. The reaction employed is based on the known ozonolysis of indigo dye. The indigotrisulfonate molecule contains one carbon–carbon double bond (C═C), which reacts with ozone and generates isatinsulfonates and sulfoanthranilate. The quantitatively formed sulfoanthranilate presents fluorescence (λ_ex 245 nm, λ_em 400 nm). Ozone was collected using two cellulose filters coated with 40 μL of 1.0 × 10^{− 3} mol L^{− 1} of indigotrisulfonate. The analytical response was linear in the range 0–150 ppbv ozone, and a detection limit of 7 ppbv was achieved using a sampling time of 15 min and an optimum sampling air flow rate of 0.4 L min^{− 1}. There was no interference from sulfur dioxide, formaldehyde or nitrogen dioxide. The ozonolysis mechanism and the reaction products are discussed.     

A new fluorescent probe of rhodamine B derivative for the detection of copper ion

A new fluorescent probe, rhodamine B hydrazide oxalamide (RBHO), which shows very weak fluorescence, was synthesized, and its fluorescence could be substantially enhanced by the addition of copper ion. The probe shows a high selectivity and sensitivity to copper ion by forming a 1:1 complex in acetonitrile, and the chelating is reversible. Limit of detection for copper ion in acetonitrile was found to be 3.7 × 10⁻⁸ mol L⁻¹. It was also found that copper ion could catalyze the hydrolysis of the probe in 50% (v/v) buffered (10 mM Tris–HCl, pH 7.0) water/acetonitrile giving a highly fluorescent product, and the fluorescence detection of copper ion was developed in this neutral buffered media with a detection limit of 6.4 × 10⁻⁷ mol L⁻¹. Determination of copper ion in water and synthetic samples in the presence of different interfering metal ions was successfully carried out with the new probe RBHO.     

Highly selective and sensitive fluorescence turn-on probe for proline

A weakly fluorescent coumarinyl aldehyde was transformed into a strongly fluorescent aldol product by a catalytic amount of proline. The aldehyde probe has shown a highly selective fluorescence turn-on response toward proline over other amino acids with micromolar sensitivity.