Micro and semi-micro determination of organic nitrogen by use of potassium bromate

After Kjeldahl digestion of an organic compound, nitrogen is determined by oxidation of the resultant ammonium sulphate with hypobromite produced in situ by the addition of an excess of potassium bromate and bromide in a special flask. The unreacted potassium bromate is determined iodometrically.     

鲁米诺-溴酸钾体系增敏化学发光法测定抗坏血酸

基于碱性条件下抗坏血酸对KBrO3-鲁米诺化学发光体系的增敏作用,结合流动注射技术建立了一种测定抗坏血酸的新方法,抗坏血酸测定的线性范围为1.0×10-8～3.0×10-7mol/L,线性相关系数为0.9981(n=7),检出限为7.0×10-9mol/L,对7.0×10-8mol/L的抗坏血酸进行了平行测定(n=11),其相对标准偏差为1.5%。方法可用于水果、VC药片和VC针剂中抗坏血酸的测定。     

New autooscillation chemiluminescence reaction of 4-oxyquinoline oxidation by bromate ions

A new autooscillation chemiluminescence reaction of 4-oxyquinoline oxidation by bromate ions, catalyzed by cerium ions and tris-(2,2-dipyridine) ruthenium complexes, has been discovered.

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Factorial analysis of a chemiluminescence system for bromate detection in water

A chemiluminescent flow system for bromate detection, based on the reaction of bromate with sulphite in acid medium and using the steroid hydrocortisone as sensitiser, was studied. A factorial analysis strategy for the study of the effect on the system response of the experimental factors, flow rates of two pumps (Q₁ — acid sulphite plus hydrocortisone aqueous solution; Q₂ — carrier, water), sample injection volume (V_L), reactor volume (V_R), sulphite concentration (C_S), hydrocortisone concentration (C_H) and acid concentration (C_A), was used. Screening analysis of the system performance was made using Plackett Burman designs. The system optimisation procedure was achieved by three levels three factors full factorial designs. V_L and C_H are the most significant factors — a quadratic C_H term was also observed to be significant. The optimised system responded linearly (logarithm of the detector signal as function of the logarithm of the bromate concentration) in the concentration range between 3.6×10⁻⁷ and 5.0×10⁻⁴ M with a limit of detection of about 8.0×10⁻⁸ M (about 10 microg/l). An analysis of some interfering ions was made and it was suggested that bromide and chloride begin to quench chemiluminescence when they are in a 10-fold excess relatively to bromate concentration.     

Spectrophotometric determination of bromate by sequential injection analysis

A simple and rapid on-line spectrophotometric method for the determination of bromate is proposed. The method is based on the reaction of bromate and 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-bromo-PADAP) with SCN⁻, a red complex is formed and monitored at 550 nm. The linear range found is between 0.18 and 3.00 mg l⁻¹ with a detection limit of 0.15 mg l⁻¹. The sampling rate was calculated to be 45 samples per hour. The proposed method has a precision of less than 0.8%.     

Measurement of bromate in bread by liquid chromatography with post-column flow reactor detection

This method is suitable for the determination of bromate residues in a variety of baked goods. The peer-verified method trial was performed on white bread, multigrain bread, and coffee cake spiked with known levels of potassium bromate. The analytical portion is extracted with deionized water to remove bromate from the bulk of the baked product. The aqueous extract is carried through a series of steps to remove co-extractives that would interfere with the liquid chromatography (LC) in the determinative step or hasten the deterioration of the LC column. The extract is filtered before passing it through a reversed-phase solid-phase extraction (SPE) column and a cation-exchange column in the silver form to remove lipids and chloride, respectively. Ultrafiltration is then used to remove proteins with molecular weights of >30,000 daltons. Finally, a cation-exchange column in the sodium form is used to remove silver ions from the extract. The determinative step uses LC with a reversed-phase column and an ion-pairing agent in the mobile phase. Detection is based on the post-column reaction of bromate with o-dianisidine to form an oxidation product that is quantitated spectrophotometrically at 450 nm. Overall agreement between the submitting and peer laboratories was quite good. For bromate levels of 10-52 ppb, overall mean recoveries were 76.9 and 78.8% for the submitting and peer laboratories, respectively. The standard deviations were higher for the results of the peer laboratory, probably because of the generally higher level of baseline noise present in the chromatograms. The results demonstrate that the method provides adequate accuracy with low-fat as well as high-fat foods. Bromate at levels as low as 5 ppb (ng/g) can be detected with the method.     

Oscillatory reduction of bromate by aspirin in acidic aqueous solution

Summary The experimental behavior of the uncatalyzed Belousov - Zhabotinsky reaction between aspirin and bromate in acidic media in the batch reactor has been studied for the first time. Aspirin is an interesting substrate because it is one of the most used medicines. The medical aspirin behaves also in an oscillatory manner with bromate. The oscillating process was investigated under aerobic and anaerobic conditions. The complex dynamic behavior has been observed in the mixed aspirin - vitamin C - _BrO3 - H₂SO₄ system.     

The determination of inorganic chlorine compounds by chemiluminescence reactions

A method is described for the determination of chlorine, chlorine dioxide and hypochlorite in aqueous solutions, involving measurement of the chemiluminescence produced during alkaline oxidation of luminol in the presence of hydrogen peroxide. Two different analytical procedures are employed, one based on a pulse technique and the other on continuous flow. Micromolar or submicromolar quantities can be detected.     

Enhanced chemiluminescence determination of alpha-amylase by use of amylose labelled with horseradish peroxidase

An enhanced chemiluminescence method for determining soluble and immobilized alpha-amylase has been developed, based on use of an insoluble amylose substrate labelled with horseradish peroxidase. Soluble peroxidase-labelled fragments of the substrate, released by the action of alpha-amylase, are quantified by the peroxidase-catalyzed luminol-peroxide-p-iodophenol reaction. The detection limit for alpha-amylase was 125 fmole (12.5 nM). An insoluble amylopectin labelled with horseradish peroxidase was also effective as a substrate for this type of assay.     

Identification and determination of corticosteroids in adrenal gland extracts for pharmaceutical use by HPLC

Summary Some HPLC procedures with isocratic or gradient elution are reported for the identification and determination of most of the characteristic components of cortical extracts. The proposed solvent systems were: A) for normal phase chromatography, mixtures of chloroform-methanol-water on silica columns. B) For reversed phase chromatography, mixtures of methanol-water or acetonitrile-water or tetrahydrofuran-water on octadecyl silica columns of different brands. With these systems it was possible to identify and determine, in addition to the principal corticosteroids, some minor components of the cortical extracts as the 20β-dihydroderivatives of compounds F, E, A, B, the 17-ketosteroids adrenosterone, 11β-hydroxyandrostendione and androstendione and finally, progesterone and 17-OH progesterone. In reversed phase chromatography it was also possible, by monitoring the effluent at 205 nm, to reveal the 5α- and 5β-tetrahydroderivatives of the main corticosteroids and to separate them from most of the steroidal components of the adrenal extracts; in these conditions it was also possible to reveal some characteristic, unknown components of the cortical extracts. Some results of quantitative analysis of cortical extracts are also reported, comparing different analytical procedures. Presented at the 15th International Symposium on Chromatography, Nürnberg, October 1984     

Demineralization of alkaline soil extracts by electrodialysis with inert and ion-exchange membranes

Mass-transfer in electrodialysis of alkaline soil extracts containing pyrophosphate ions with cellophane and MA-40 and MA-41 ion-exchange membranes was studied. The transport numbers of hydroxide- and phosphorus-containing ions and the degree of demineralization of the alkaline soil extracts were determined under the conditions under study.     

Biofunctionalization of aqueous dispersed, alumina membrane-templated polymer nanorods for use in enzymatic chemiluminescence assays

The noncovalent immobilization of alkaline phosphatase (ALP) onto aqueous dispersed nylon 6 nanorods ( approximately 310 nm mean diameter; approximately 6 microm mean length) prepared by anodic aluminum oxide (AAO) membrane templating was studied. Using multi-stacked layer-by-layer (LBL) assembly with the cationic quaternary ammonium polymer Sapphire II , the amount of ALP enzyme loaded onto the polymer nanostructures was found to be 115+/-7 microg mg(-1) nanorod. The biofunctionalized nanorods were also characterized for their chemiluminescent activity with the dioxetane substrate, CSPD . The results indicate that the kinetic parameters, K(m) and V(max), for the catalytic activity of the nanostructure-bound ALP enzyme are different from those of soluble ('free') ALP. While the K(m) value was measured to be 156 microM for free ALP, the apparent K(m) value determined for the LBL-immobilized ALP is approximately 20% lower (122 microM). Furthermore, despite the relatively high enzyme loading capacity of the nanorods, the specific activity of the bound ALP enzyme was found to be almost nine times lower than that measured for free ALP. Finally, additional experiments revealed that the catalytic activities of both free ALP and nanorod-conjugated ALP are affected similarly by changes in pH, with optimal performance levels occurring under conditions of pH 9.5. To the best of our knowledge, this study represents the first report examining the preparation of aqueous dispersed, AAO-templated polymer nanorods for potential application as enzyme scaffolds in chemiluminescent-based assay systems.     

The use of chemiluminescence methods for studying active inhibitors

Conclusions The use of chemiluminescence methods for studying active inhibitors leads to low values for the rate constant of the reaction of peroxy radicals with the inhibitor when k₇ > 0.1 k₆.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 468–469, February, 1969.     

Fluorimetric determination of bromate by ion-exchange separation and post-column derivatization

For the determination of bromate in drinking water a stopped-flow post-column reaction was developed following the separation of bromate from the matrix by an anion-exchange column. In the post-column reaction the analyte was used to oxidize the azo dye sulfonaphtholazoresorcinol, SNAR, and the residual amount was converted into a fluorescent binuclear complex by an excess of gallium ions. The fluorescence was monitored at 585 nm, with a maximum excitation wavelength at 521 nm. The determination of bromate is based on the decrease of the fluorescence intensity with increasing bromate concentration. The given hydrodynamic parameters and the condition of equal flow rates of the two branch streams at each T-piece have to be considered as an important criterion for the experimental set-up. The volume flows and the concentrations required for the reagent solutions in the influent of each T-piece were determined as a result of batch experiments and theoretical considerations. The limit of detection was 0.28 g L^–1bromate for the flow method, which shows linearity up to 15 gL^–1 bromate.     

New bienzymatic strategy for glucose determination by immobilized-gold nanoparticle-enhanced chemiluminescence

Bienzymatic biosensor for the determination of glucose by flow injection chemiluminescence (CL) detection was proposed. Hybrids of gold nanoparticles (GNPs) and chitosan were chosen as the immobilization matrix of glucose oxidase (GOD) and horseradish peroxidase (HRP) to fabricate the biosensors with silane-pretreated glass microbeads. After the enzyme catalyzing oxidation of glucose in GOD biosensor, the produced H₂O₂ flowed into HRP biosensor to react with luminol. The doped GNPs in chitosan were found to enhance the classical CL reaction of luminol-H₂O₂-HRP. The CL enhancement was investigated in detail by CL and UV-visible spectrum. Under the optimized experimental conditions, glucose could be determined in a linear range from 0.01 to 6.0 mmol/L with a detection limit of 5.0 μmol/L at 3σ. The accuracy of the proposed method was examined by detecting the glucose level in four clinical serum samples from hospital. The proposed method provides a new alternative to determine glucose. Supported by the Natural Science Foundation of Shandong Province (Grant No. Q2007B03), the Doctoral Fund of Qingdao University of Science and Technology (Grant No. 0022141), and the National Natural Science Foundation of China (Grant No. 20775038)     

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.     

快速化学发光联用流动注射技术测定西咪替丁

在NaOH-NaHCO3介质中,铁氰化钾氧化西咪替丁产生快速化学发光反应,0.5 s后发光达到最大,2 s后迅速衰减至零。本文结合流动注射技术,建立了一种化学发光测定西咪替丁的新方法。针对这一快速发光反应,设计了与之相应的管路系统和最短的反应管道来捕捉最大化学发光信号,发光强度与西咪替丁质量浓度在5×10-7~1×10-4g/mL范围内呈线性关系,检出限为1.1×10-7g/mL。对5×10-6g/mL西咪替丁进行11次平行测定,相对标准偏差为1.8%。本法已用于西咪替丁片剂的测定。     

N-bromosuccinimide-fluorescein system for the determination of protein by flow injection chemiluminescence

A method for flow injection with chemiluminescence (CL) detection has been developed for the determination of proteins. It is based on the luminescence of the N-bromosuccinimide-fluorescein-protein system, where fluorescein is used as an energy transfer reagent in alkaline medium. The CL of the system is strongly enhanced by hexadecyl trimethyl ammonium bromide. Optimum conditions and possible mechanisms have been investigated. Under optimum experimental conditions, the linear range is from 0.4 to 40 µg·mL^?1 for egg albumin, 0.2 to 20 µg·mL^?1 for bovine serum albumin, and from 1 to 100 µg·mL^?1 for bovine hemoglobin. The detection limits are 37, 62, and 240 ng·mL^?1, respectively.     

Cetyltrimethylammonium-coated magnetic nanoparticles for the extraction of bromate,followed by its spectrophotometric determination

We report on a combination of magnetic solid-phase extraction and spectrophotometric determination of bromate. Cetyltrimethylammonium ion was adsorbed on the surface of phenyl-functionalized silica-coated Fe₃O₄ nanoparticles (Ph-SiO₂@Fe₃O₄), and these materials served as the sorbent. The effects of surfactant and amount of sorbent, the composition of the desorption solution, the extraction time and temperature were optimized. Under optimized conditions, an enrichment factor of 12 was achieved, and the relative standard deviation is 2.9 % (for n?=?5). The calibration plot covers the 1–50 ng mL^?1 range with reasonable linearity (r ²?>?0.998); and the limit of detection is 0.5 ng mL^?1. The method is not interfered by ionic compounds commonly found in environmental water samples. It was successfully applied to the determination of bromate in spiked water samples.