An electrochemical analyzer for Monitoring Hydrazines in Air

Abstract

A commercially available electrochemical carbon monoxide analyzer was used to selectively determine hydrazine, monomethylhydrazine and unsymmetrical-dimethylhydrazine in air in the concentration range from 0.5 to 20 ppm.     

Rapid Analysis of Trace Quantities (1 PPM) of Bromide in Natural Water

Abstract

An analytical procedure for the rapid assay of trace quantities of bromide ion is described. An exchange resin contained in a filter disk is used to separate the ion and the bromide concentration is then measured as an emission intensity on the x-ray spectrograph. Analytical error is estimated at 5% and 0.05 ppm Br is the statistical detectability limit when compared with a standard disk containing 100 ppm Br^?.     

119Sn NMR Spectra of Some Carbohydrate Organotin Derivatives

Abstract

The ¹¹⁹Sn NMR spectra of several sugar-tin derivatives were recorded. The geometric and steric isomers of all of the organotin derivatives studied were easily differentiated by ¹¹⁹Sn NMR. The appropriate ¹¹⁹Sn resonances are: ca - 50 ppm for trans and ?60 ppm for cis vinyltin derivatives (1-3), ca 16 ppm for allyltins 4-6, and ca ?32 ppm for tin-carbinols 9 and 11. When the hydroxyl group in carbinol 9 was converted to an O-acetyl group, the chemical shift of ¹¹⁹Sn was shifted to ?22 ppm.     

Structure de Modeles de Polyesters 2.-Determination de la Purete optique par RMN 13C et H de Dibenzoyloxy 1,2 Propane,l,3 Butane et 3-Methyl 1,4 Butane a l'Aide de Reactifs chiraux

Abstract

The enantiomeric purity of a series of polyester model compounds has been assayed by NMR spectroscopy, using chiral lantha-nide shift reagents. The dependencc of proton and ¹³ C NMR spectra on concentration and temperature has been investigated.     

Analysis of SO2 Concentration in Air by Microwave Spectroscopy

Abstract

Low concentrations of SO₂ in air were measured using a Stark modulated microwave spectrometer. Measurement of the intensity of absorption lines for rotational transitions gives a quantitative measure of the concentration of specific small molecules. Concentrations of 20 ppm of SO₂ In air were easily detected with a signal-to-noise ratio of over 20/1 with a 5 sec time constant using a straightforward sample concentration technique.     

Determination of Sulfide Using Reflectance Analysis and its Applicability to Sediment Samples

Abstract

The determination of a vertical profile of sulfide concentration in sediments is complicated by the wide range of concentrations encountered. Analytical techniques are typically limited to a range of two orders of magnitude for a particular sample. This paper describes a method for the determination of sulfide in sediment samples which is applicable from 0.32 to 120 ppm sulfide. The calibration curve is a power series of reflectance versus concentration.     

Etude des possibilites de dosage du lithium par activation au moyen de protons et de deutons de moyenne energie

The determination of lithium by measuring⁷Be, produced by proton or deuteron activation, has been studied. The extent of interference from boron or beryllium, which also form⁷Be, was measured. The calculated sensitivity limits when activating for one hour with 10μA beams of 14 MeV protons or 25 MeV deuterons are, for lithium, 1·10⁻¹ and 2.5·10⁻² ppm and for boron, 2·10⁻¹ and 1·10⁻¹ ppm, respectively.      

β-Naphthol as a Chromophore and Fluorophore Forming Reagent in the HPLC Determination of Alkyl Halides

Abstract

A suitable chromophore- and fluorophore- forming reagent for the detection of alkyl halide water contaminants is β-naphtol. The ether derivatives are separated from each other and excess β-naphthol reagent by reverse, phase HPLC and are detected by ultraviolet absorption or fluorescence. A method for the determination of alkyl halides is presented. The method is applicable to concentration levels in the ppm range for UV detection and in the ppb concentration range using fluorescence detection.     

Simultaneous Determination of Sodium,Potassium, and Ammonium Ions by Automated Direct Potentiometry

Abstract

Sodium, potassium and ammonium ions, in concentration ranges of natural and waste water samples, have been simultaneously determined by direct potentiometry, using sodium, potassium, and ammonia ion-sensitive electrodes. The results are printed out as concentration units directly from an automated continuous -flow system with on-line minicomputer and printer. The optimum sampling rate is 20 samples or 60 determinations per hour. Various water samples have been analyzed and the results compared to those obtained by the standard methods. The lower detection limits were 0.1 ppm for Na⁺ and NH₄ ⁺ and 1.0 ppm for K⁺. The values of standard deviation were < 10%, with the exception of the lowest concentrations. The relative error was in the range of ± 2%. The correlation of standard and proposed methods was very good.     

Determination of the Concentration of Gases by Measurement of Pressure

Abstract

For the determination of the concentration of gases by means of pressure measurement, a precise equation of state is given by which analysis can be carried out within an accuracy of 10 ppm. The parameters of the equation of state are explicitely reported for carbon dioxide, argon, and helium.     

Development of a Highly Sensitive and Selective Bismuth Optical Sensor Based on (2E,4E)-5-(2,4-Dinitrophenyl Amino)penta-2,4-dienal

Abstract

An optical sensor based on (2E,4E)-5-(2,4-dinitrophenyl amino)penta-2,4-dienal as ionophore has been developed for the determination of bismuth(III) ions in aqueous solutions. This proposed membrane works on the basis of a cation-exchange mechanism and shows a significant absorbance signal change on exposure to 1 M HCl solution of pH 0.0 containing bismuth ions. The optode membrane shows a reproducible and reversible response toward bismuth in the concentration range 0.2 to 60.5 ppm with a detection limit of 0.095 ppm. This sensor has been used for determination of bismuth in real samples.     

Novel Detection Method of Endocrine Disrupting Chemicals Utilizing Liposomes as Cell Membrane Model

Abstract

A novel detection method of endocrine disrupting chemicals (EDCs) is proposed. Liposomes encapsulating fluorescence dye was prepared as a cell membrane model and applied to detect EDCs. Leakages of dye from liposomes were observed after their exposure to EDCs. Fluorescence intensity increased significantly when the liposomes were exposed to 5 ppm EDCs. The increases showed a good correlation with EDCs' dipole moment. Therefore, polarizability is suggested as one of the factors of the liposome-EDC interaction. At lower than 5 ppm, the increases depended on EDCs' concentration. The tendency of the results was in accordance with reported estrogenic activity of EDCs.     

A Liquid Chromatographic Study of the Effect of Adsorption on the Concentration of Aqueous Temephos Solutions

Abstract

A new HPLC method to determine temephos in water was developed and tested. The method is reliable for measuring concentrations of temephos in aqueous solutions from 0.005 to 5.0 ppm. The detection limit at 254 nm is 1 ng. The standard curve is not linear over the entire range; separate curves are required for concentrations above and below 0.1 ppm. The method was used to study adsorption of temephos on plastic and glass surfaces. The size of the container, is important to minimize adsorption effects if solutions of 0.01 ppm or less are used. For these solutions, glass containers at least as large as a standard 50 mL beaker should be used for experiments in which a relatively constant concentration of temephos must be maintained for a period of hours.     

Rapid and Sensitive Screening Method for the Determination of Carbaryl and Propoxur Using p-Nitroaniline

Abstract

A rapid screening method for the determination of carbaryl and propoxur using p-nitroaniline is described. Carbaryl and propoxur are determined spectrophotometrically: carbaryl forms a stable blue coloured species with diazotized p-nitroaniline in a fairly alkaline medium while propoxur forms a purple coloured species with the same reagent under similar conditions. The blue and purple coloured species are extracted into 3-methyl-1-butanol showing absorbance maxima at 605 and 540 nm, respectively. The relationship between absorbance and concentration is linear in the range of 0.12 - 0.96 ppm and 0.19–1.5 ppm, respectively for carbaryl and propoxur. The method can successfully be applied for the determination of carbaryl and propoxur to levels as low as 0.04 and 0.06 and 0.12 and 0.19 ppm in water and grain samples, respectively.     

An antibacterial silver(I) supramolecular network assembled from thiophene-2,5-dicarboxylate and benzimidazole

Abstract

A silver(I) supramolecular network Ag(BIm)₂(HTDC) (1) was assembled from thiophene-2,5-dicarboxylic acid (H₂TDC) and benzimidazole (BIm) ligands and characterized by single-crystal X-ray diffraction, elemental analysis, FT-IR, and thermal gravimetric analysis. Complex 1 possesses a two-dimensional structure with a hydrogen-bonded grid network, in which the adjacent [Ag(BIm)₂]⁺ cations and (HTDC)^– are bridged via N–H···O hydrogen bonds forming undulating ribbons. The antibacterial properties of 1 were investigated by determining the minimal inhibitory concentration (MIC), the growth curve of bacteria and zone inhibition value assays against Gram-negative bacterium, Escherichia coli, and Gram-positive bacterium, Staphylococcus aureus. The MIC of 1 against E. coli and S. aureus are 15-20?ppm and 20-30?ppm which showed that 1 has higher antibacterial activity than commercial silver nanoparticles. The mechanism of antibacterial activity of 1 was also discussed.     

Evaluation of Allium sativum as corrosion inhibitor for carbon steel in sulphuric acid under hydrodynamic conditions

ABSTRACT

A study on the use of Allium sativum (garlic) as corrosion inhibitor for carbon steel in 0.5?M H₂SO₄ has been carried out in static and dynamic conditions by using potentiodynamic polarization curves and electrochemical impedance spectroscopy at 0, 200, 500, 1000 and 2000?rpm. Inhibitor concentrations included 0, 100, 200, 400, 600, 800 and 1000?ppm. Under static conditions, inhibitor efficiency increases with increasing its concentration up to 400?ppm, but it decreases with a further increase in its concentration. Under dynamic conditions and short testing times, inhibitor efficiency increases with increasing the rotating speed, due to a better inhibitor transfer towards the steel surface. However, for longer testing times, inhibitor efficiency increases only during the first 2?h, and then it decreases with a further increase in time, indicating a desorption of the inhibitor molecules from the steel surface.     

Bioaccumulative Behaviour of Some PCB Congeners in Lake Geneva Brown Trout (Salmo trutta lacustris L)

Abstract

The bioaccumulation of PCBs has been studied for 60 Brown trout in Lake Geneva (Switzerland). The contamination level (1–3 ppm in wet weight, 10–30 ppm in lipid weight) is rather high.

Bioaccumulation curves (concentration as a function of the weight of the fish) have been established for 6 congeners and total PCBs. The total concentration of PCBs in wet weight increased with the weight of the fish; highly-chlorinated congeners (I.U.P.A.C. nr. 180, 2,3,4,5,2′,4′,5′-heptachlorobiphenyl) presented a faster, and lightly-chlorinated (I.U.P.A.C. nr. 28, 2,4,4′-trichlorobiphenyl) a slower, bioaccumulation tendency.

The total concentration of PCBs in lipid weight was constant, the concentration of congener 28 increasing and of congener 180 decreasing with the weight of the fish. This is attributed to the antagonistic effects of “growth and lipid dilution” and of the decrease of elimination kinetics as a function of the weight (and age) of the fish.

The partitioning theory and the pharmacokinetic approach are complementary methods for analysing this field data.     

Analysis of 4-Tert-Butylpyrocatechol in Styrene by Solid Phase Extraction and High Performance Liquid Chromatography

Abstract

A solid phase extraction procedure has been developed to isolate and preconcentrate 4-tert-butylpyrocatechol and its oxidation products from etyrene. The eluted amount of 4-tert-butylpyrocatechol from the cartridges was determined by reversed phase HPLC, External calibration method was used in the concentration range between 3 and 80 ppm of 4-tert-butylpyrocatechol and mean recovery was found to be 97 % with a relative standard deviation of 3.4%.     

Detection of Sulfur Dioxide Using a Piezoelectric Quartz Crystal Microbalance

Abstract

Sulfur dioxide was detected and determined in air by a piezoelectric quartz crystal sensor coated with 4-aminoantipyrine 1-hydroxyetil-2-heptadecenyl imidazol (amine 220) solution (1:1 v/v in chloroform). The analytical response curve is linear over the concentration range from 0.70 to 5.0 ppm of SO₂. Good linearities (r = 0.9990, 0.9995 and 0.9968) and sensitivities (18.0, 33.4 and 50.7 Hz/ppm) were found, respectively for exposure times of 30, 60 and 90 seconds. The sensor can be used for more than six months without loss in sensitivity and presented good reversibility and reproducibility. Among some possible interferents tested, only nitrogen dioxide and moisture caused major frequency changes.     

Gas Chromatography and Catalysis Applied to Trace Metal Speciation. Determination of Cuprous Ion

Abstract

An indirect gas chromatographic procedure for the analysis of trace levels of Cu⁺ has been developed. The basis of the procedure is the Cu⁺ - catalyzed conversion of an aromatic diazonium salt to a chlorinated derivative which can be easily analyzed by GLC. The amount of derivative produced is related to the concentration of Cu⁺ catalyst; a limit of detection of less than 1 ppm Cu⁺ has been attained.