Flow injection determination of cationic surfactants by using N-bromosuccinimide and N-chlorosuccinimide as new oxidizing agents for luminol chemiluminescence

Two highly sensitive chemiluminescence (CL) systems are described. The method is based on the CL generated during the oxidation of luminol by N-bromosuccinimide (NBS) and N-chlorosuccinimide (NCS) in alkaline medium. The emission intensity is reduced by the presence of some surfactants at concentrations lower than critical micelle concentration (cmc).A new, simple, rapid and selective flow injection CL method for the determination of cationic surfactants such as dodecyltrimethylammonium bromide (DTAB), cetyltrimethylammonium bromide (CTAB) and cetylpyridinium chloride (CPC) is proposed. Their determinations are based on the reducing effect on the emission intensity of NBS-luminol and NCS-luminol chemiluminescent reactions. The effect of analytical and flow injection analysis (FIA) variables on these CL systems and on the determination of the cationic surfactants are discussed. The optimum parameters for the determination of cationic surfactants were studied and were found to be the following: luminol, 1×10⁻⁶ M; NBS and NCS both, 5×10⁻² M; NaOH, 5×10⁻² M and flow rate, 3.5 ml min⁻¹.     

Flow-injection chemiluminescence determination of fluoroquinolones by enhancement of weak chemiluminescence from peroxynitrous acid

A flow-injection chemiluminescence (CL) method is described for the determination of fluoroquinolones including ciprofloxacin, norfloxacin and ofloxacin. The method is based on the enhancement by these compounds of the weak CL from peroxynitrous acid. The linear ranges are 1.0×10⁻⁷ to 1.0×10⁻⁵ mol l⁻¹ for ciprofloxacin and norfloxacin, and 3.0×10⁻⁷ to 3.0×10⁻⁵ mol l⁻¹ for ofloxacin, respectively. The detection limits (S/N=3) are 4.5×10⁻⁸ mol l⁻¹ ciprofloxacin, 5.9×10⁻⁸ mol l⁻¹ norfloxacin and 1.1×10⁻⁷ mol l⁻¹ ofloxacin, respectively. The proposed method was applied to the determination of fluoroquinolones in pharmaceutical preparations.     

流动注射化学发光法测定水中的苯胺

基于在多聚磷酸介质中,KMnO4氧化苯胺能产生强化学发光,建立了流动注射化学发光测定苯胺的新方法.在优化条件下,化学发光强度ⅠCL与苯胺的浓度在2.0×10～1.0×10-6 mol/L范围内呈良好的线性关系,回归方程为ⅠCL=63.11 2.37×108c(r=0.9997,n=9),检出限为5.0×10-10 mol/L,对1.0×10-7 mol/L苯胺进行11次测定,其相对标准偏差为0.8%(n=11).已用于环境水体中苯胺的测定,回收率在95.1%～105.1%之间.     

Flow-injection chemiluminescence determination of formaldehyde in water

A modification of the Trautz-Schorigin reaction into a flow-injection analysis configuration is described. Different approaches were used at the optimization of chemiluminescence determination of formaldehyde in water based on the reaction of formaldehyde, gallic acid and hydrogen peroxide in an alkaline solution. Detection system with a 218 μl chemiluminescence cell was optimized by both a one-variable-at-a-time method, and a modified simplex method. A calibration graph is linear in the concentration range 4 × 10⁻⁸ to 1 × 10⁻⁵ M HCHO. The detection limit of formaldehyde for a signal-to-noise ratio of 3 is 4 × 10⁻⁸ M. The relative standard deviations for 15 repeated measurements of 1 × 10⁻⁶ and 5 × 10⁻⁶ mol l⁻¹ HCHO are 4.32 and 3.33%, respectively. The analysis time is 1.5 min. The method was applied to the determination of formaldehyde in urban rainwater. A comparison of results found by proposed method with those obtained by fluorimetric reference method provided a good agreement.     

Flow-injection chemiluminescence determination of dihydralazine sulfate based on hexacyanoferrate(III) oxidation sensitized by eosin Y

A novel flow-injection chemiluminescence (CL) method for the determination of dihydralazine sulfate (DHZS) is described. The method is based on the reaction between DHZS and hexacyanoferrate(III) in alkaline solution to give weak CL signal, which is dramatically enhanced by eosin Y. The CL emission allows quantitation of DHZS concentration in the range 0.02-2.8 μg ml⁻¹ with a detection limit (3σ) of 0.012 μg ml⁻¹. The experimental conditions for the CL reaction are optimized and the possible reaction mechanism is discussed. The method has been applied to the determination of DHZS in pharmaceutical preparations and compared well with the high performance liquid chromatography (HPLC) method.     

Flow-injection chemiluminescence determination of ascorbic acid by use of the cerium(IV)-Rhodamine B system

A highly sensitive flow-injection (FI) method with chemiluminescence (CL) detection is used for the determination of l-ascorbic acid. The method is based on the CL reaction of Rhodamine B with cerium(IV) in sulfuric acid media. l-Ascorbic acid is suggested to be a catalyst utilized in the energy-transferred excitation process. The proposed procedure allows quantitation of l-ascorbic acid in the range 3.8×10⁻¹³ to 1.0×10⁻¹⁰ mol l⁻¹ with a correlation coefficient of 0.9998 (n=5) and relative standard deviation (R.S.D.) of 0.92% (n=11) at 1.0×10⁻¹¹ mol l⁻¹. The detection limit (3×blank) was 1.0×10⁻¹³ mol l⁻¹. The method is successfully used to determine l-ascorbic acid in fresh vegetables. The possible mechanism of the chemiluminescence in the system is discussed.     

Flow-injection chemiluminescence determination of tryptophan using galangin-potassium permanganate–polyphosphoric acid system

A high sensitive flow-injection chemiluminescence （FI-CL） method for the determination of tryptophan has been developed. The method is based on the chemiluminescence reaction of galangin-potassium permanganate-tryptophan in polyphosphoric acid （PPA） media. Under the optimized conditions, tryptophan was determined in the range 0.05-10 μg/mL with the detection limit （3tr） of 5.0 × 10^-3 μg/mL. The relative standard deviation （RSD） was 1.0% for 11 replicate determinations of 1.0 μg/mL tryptophan. Three synthetic samples were determined selectively with recoveries in the range from 99.6% to 102.0% in the presence of other amino acids.     

流动注射化学发光法测定肉桂酸

碱性条件下,肉桂酸对Luminol-H2O2-纳米银化学发光体系有较强的增敏作用,据此,结合流动注射技术,建立了测定肉桂酸的新方法。该法线性范围为2.5×10-8～2.5×10-6mol/L,检出限为6.0×10-9mol/L,对1.0×10-7 mol/L的肉桂酸平行测定9次,相对标准偏差为2.5%。该法可用于尿液中肉桂酸的测定。     

Flow-injection chemiluminescence determination of tetracyclines with in situ electrogenerated bromine as the oxidant

By designing a novel flow-through electrolytic cell (FEC), bromine was produced near to the surface of the platinum electrode by electrochemical oxidation of acidic KBr. The fast and weak chemiluminescence signal produced by the chemical reaction of the electrogenerated bromine with H₂O₂ was greatly enhanced by tetracyclines Based on these observations, a new, sensitive and simple electrogenerated chemiluminescence (ECL) method for the determination of tetracyclines was developed. Under the optimum experimental conditions, the calibration graphs are linear over the range 3.0×10⁻⁸ to 5.0×10⁻⁵ g ml⁻¹ for tetracycline, 2.0×10⁻⁷ to 2.4×10⁻⁵ g ml⁻¹ for oxytetracycline and 1.0×10⁻⁷ to 5.0×10⁻⁵ g ml⁻¹ for chlortetracycline. The limits of detection (S/N=3) are 1.0×10⁻⁸ g ml⁻¹ for tetracycline, 7.0×10⁻⁸ g ml⁻¹ for oxytetracycline and 1.5×10⁻⁷ g ml⁻¹ for chlortetracycline. For the determination 5.0×10⁻⁷ g ml⁻¹ tetracycline, the relative standard deviation was <5%. The proposed method was used to determine tetracyclines in pharmaceutical formulations.     

流动注射化学发光法测定兽药制剂中沙拉沙星

基于沙拉沙星对Ag(III)络合物-H2SO4体系化学发光信号的增敏作用,提出了一种流动注射-化学发光测定沙拉沙星的新方法。考察和优化了影响化学发光强度的条件。沙拉沙星在2.0×10-7～1.0×10-5g/mL范围内,其校准曲线具有良好的线性。方法的检出限为1.2×10-7g/mL,相对标准偏差0.5%～1.2%。该方法已用于沙拉沙星兽药制剂的质量检测,回收率为83.3%～96.3%。通过比较其荧光光谱和化学发光光谱,讨论了该体系的化学发光机理。     

Flow-injection chemiluminescence determination of chloroquine using peroxynitrous acid as oxidant

A new flow-injection chemiluminescence (CL) method for determination of chloroquine is proposed based on a stronger chemiluminescence of chloroquine in hydrogen peroxide-nitrite-sulfuric acid medium. The proposed method allows the measurement of chloroquine over the range of 3.0×10⁻⁷ to 1.0×10⁻⁵ mol l⁻¹. The detection limit is 8.6×10⁻⁸ mol l⁻¹, and the relative standard deviation for 1.0×10⁻⁶ mol l⁻¹ chloroquine (n=11) is 1.6%. The CL mechanism is also discussed.     

MnO_2纳米溶胶-抗坏血酸化学发光反应的研究

在中性条件下利用Na2S2O3还原KMnO4制备出平均粒径约40 nmMnO2溶胶。研究发现,该溶胶在酸性条件下可氧化抗坏血酸产生化学发光。基于此,结合流动注射技术,对影响化学发光反应的各种因素进行了考察,建立了测定抗坏血酸的流动注射化学发光新方法。该方法测定抗坏血酸的线性范围为2.0×10-6~1.0×10-4g/mL,检出限为4×10-7g/mL,相对标准偏差为2.1%(1.0×10-5g/mL抗坏血酸溶液,n=11)。该方法已用于片剂中抗坏血酸的测定,结果与药典方法一致。     

Highly sensitive method for determination of N-nitrosamines using high-performance liquid chromatography with online UV irradiation and luminol chemiluminescence detection

A new method for the measurement of N-nitrosamines in part-per-trillion concentrations from water samples without preconcentration steps has been developed. This method is based on online UV irradiation after high-performance liquid chromatographic separation and subsequent luminol chemiluminescence detection without addition of an oxidant. It was confirmed that N-nitrosamines in basic aqueous solution were transformed to peroxynitrite by UV irradiation. The detection limits for this method were 1.5 ng/L, 2.9 ng/L, 3.0 ng/L, and 2.7 ng/L for N-nitrosodimethylamine, N-nitrosomorpholine, N-nitrosomethylethylamine, and N-nitrosopyrrolidine, respectively, at a signal-to-noise ratio of 3. The calibration graphs were linear in the range of 5–1000 ng/L for these N-nitrosamines. This method was used for the determination of N-nitrosamines in tap water, river water, and industrial plant effluent samples. The recoveries of N-nitrosodimethylamine, N-nitrosomorpholine, N-nitrosomethylethylamine, and N-nitrosopyrrolidine present in tap water sample at a concentration of 10 ng/L (mean ± standard deviation, n = 4) were (94.8 ± 2.7)%, (102.0 ± 6.9)%, (99.3 ± 3.9)%, and (102.8 ± 2.5)%, respectively. These results indicate that our proposed method can be applied satisfactorily to the determination of N-nitrosamines in water samples.     

Flow-injection chemiluminescence assay for ultra-trace determination of DNA using rhodamine B-Ce(IV)-DNA ternary system in sulfuric acid media

A novel flow-injection chemiluminescence method for the determination of DNA at ultra-trace level has been established. In 0.8 M sulfuric acid media, the chemiluminescence of the rhodamine B-cerium (IV) or Ce(IV) system is enhanced by DNA, activated previously by imidazole-HCl buffer solution (pH 7.0). The enhanced intensity of chemiluminescence is in proportion to log DNA concentration 1.0×10⁻⁸ to 0.1 μg ml⁻¹ for herring sperm DNA and 2.0×10⁻⁶ to 0.2 μg ml⁻¹ for calf thymus DNA with 3σ detection limits of 8.3×10⁻⁹ μg ml⁻¹ for herring sperm DNA and 3.5×10⁻⁷ μg ml⁻¹ for calf thymus DNA, respectively. The relative standard deviation for 1.0×10⁻⁴ μg ml⁻¹ herring sperm DNA was 0.99% and 2.0×10⁻³ μg ml⁻¹ for calf thymus DNA was 1.1% (n=11). Using the optimized system, DNA contents in six synthetic samples has been determined with recoveries of 99.5-109.0%. The possible mechanism has also been studied in this paper.     

Determination of folic acid by chemiluminescence based on peroxomonosulfate-cobalt(II) system

Based on the chemiluminescence (CL) phenomena of folic acid in peroxomonosulfate-cobalt(II) system, a rapid and sensitive CL method was developed for determination of folic acid in pharmaceutical preparations and its urinary metabolism processes. Under the optimum conditions, the relative CL intensity was linear over the concentration ranging from 10⁻⁹ to 8 × 10⁻⁷ mol L⁻¹ (R² = 0.9991) with a detection limit as low as 6 × 10⁻¹⁰ mol L⁻¹ (S/N = 3) and relative standard deviation was 2.63% for 2 × 10⁻⁸ mol L⁻¹ folic acid (n = 11). This method has been successfully applied to the determination of folic acid in tablets and human urine. The blank CL emission was yielded owing to the formation of singlet oxygen molecular pair from the quenching experiment of 1,4-diazabicyclo[2.2.2]octane, and pterine-6-carboxylic acid might be the degradation intermediate in this system and it also acts an energy acceptor and sensitizes the chemiluminescence based on the studies of the CL and fluorescence spectra.     

固相萃取—化学发光法测定植物中的吲哚乙酸

植物拟南芥中吲哚乙酸用甲醇超声提取,后经固相萃取小柱净化用化学发光法测定.在多聚磷酸(PPA)介质中,吲哚乙酸对高良姜素-高锰酸钾体系的发光有很强的增敏作用,据此建立了固相萃取-流动注射化学发光测定吲哚乙酸的新方法.在优化条件下,相对化学发光的对数值与吲哚乙酸浓度的对数值在8.0 ×10-9～1.0×10 -7g/mL...     

Flow-injection catalytic spectrophotometic determination of molybdenum(VI) in plants using bromate oxidative coupling of p-hydrazinobensenesulfonic acid with N-(1-naphthyl)ethylenediamine

A novel flow-injection spectrophotometry has been developed for the determination of molybdenum(VI) at nanograms per milliliter levels. The method is based on the catalytic effect of molybdenum(VI) on the bromate oxidative coupling of p-hydrazinobenzenesulfonic acid with N-(1-naphthyl)ethylenediamine to form an azo dye (λ_max = 530 nm). Chromotropic acid (4,5-dihydroxy-2,7-naphthalenedisulfonic acid) acted as an effective activator for the molybdenum(VI)-catalyzed reaction and increased the sensitivity of the method. The reaction was monitored by measuring the change in absorbance of the dye produced. The proposed method allowed the determination of molybdenum(VI) in the range 1.0-20 ng mL⁻¹ with sample throughput of 15 h⁻¹. The limit of detection was 0.5 ng mL⁻¹ and a relative standard deviation for 10 ng mL⁻¹ molybdenum(VI) (n = 10) was 2.5%. The interfering ions were eliminated by using the combination of a masking agent and on-line minicolumn packed with cation exchanger. The present method was successfully applied to the determination of molybdenum(VI) in plant foodstuffs.     

Chemiluminescence determination of carbofuran at trace levels in lettuce and waters by flow-injection analysis

A simple, fast chemiluminescence (CL) flow-injection (FI) method based on the reaction of luminol with KMnO₄ in alkaline medium has been described for the direct determination of carbofuran. The method is based on the enhancing effect in the emission light from the oxidation of luminol produced in presence of carbofuran. The optimisation of instrumental and chemical variables influencing the CL response of the method has been carried out by applying experimental design, using the proposed flow-injection manifold. Under the optimal conditions, the CL intensity was linear for a carbofuran concentration over the range of 0.06-0.5 μg ml⁻¹, with a detection limit of 0.02 μg ml⁻¹. The method has been successfully applied to the determination of carbofuran residues in spiked water and lettuce samples.     

Flow-injection chemiluminescence simultaneous determination of cobalt(II) and copper(II) using partial least squares calibration

A flow-injection chemiluminescence (CL) system is proposed for simultaneous determination of Co²⁺ and Cu²⁺ using partial least squares (PLS) calibration. This method is based on the fact that both Co²⁺ and Cu²⁺ catalyse the CL reaction of luminol-H₂O₂, and that their kinetic characteristics of Co²⁺ and Cu²⁺ are significantly different in the luminol-H₂O₂ system. The CL intensity was measured and recorder at different reaction times of luminol-H₂O₂Co²⁺Cu²⁺, and the obtained data were processed by the chemometric approach of partial least squares. The experimental calibration set was composed of 16 sample solutions using an orthogonal calibration design for two component mixtures. The proposed method offers the potential advantages of high sensitivity, simplicity and rapidity for Co²⁺ and Cu²⁺ determination, and was successfully applied to the simultaneous determination of both analytes in real water sample. The present paper demonstrated that the simultaneous determination of two metal ions without any prior separation has been possible using flow-injection CL system.     

鲁米诺-焦性没食子酸体系抑制化学发光法测定5-磺基水杨酸

基于碱性介质中5-磺基水杨酸对鲁米诺-焦性没食子酸体系化学发光的抑制作用,建立了流动注射化学发光测定5-磺基水杨酸的新方法.在最佳实验条件下,测定5-磺基水杨酸的线性范围为1.0×10-7～1.0×10-5mol/L,相关系数为0.9996(n=5),检出限为6.8×10-8mol/,L(n=11),对1.0×10-6...