Search results for "analytical chemistry"

Preliminary photochemical studies of fluorene in various aqueous media

2014

- The current study investigates the direct photochemical degradation of aqueous fluorene with the aid of a 125W polychromatic medium, pressure Hg lamp. The purpose was to test the effectiveness of the lamp in irradiation using fluorene spiked solution as substrate. A 700 ml volume of fluorene solution of 0.002 mg/l was irradiated batch-wise at 1, 3, 6, 12, 18, 24 and 48 h. The amount of fluorene removal was studied for fluorene solutions prepared from , neutral (distilled water), acidic (by adjusting pH with hydrochloric acid, HCl), basic (by adjusting pH with sodium hydroxide, NaOH) and saline (addition of sodium chloride, NaCl) solutions and there was 95.95, 92.35, 96.65 and 97.15 % remo…

Characterization of Chlorolignins in Bleached Kraft Pulp Mill Effluents Using Elemental Analysis and Fingerprinting by CuO Oxidation And Hplc

1994

Abstract Elemental analyses and chemical degradation techniques were applied to characterize lignin compounds in different stages of the chlorine bleaching process and in total mill effluent. Ultrafiltration was used for separation of chlorolignins into three nominal molecular weight fractions. Alkaline CuO oxidation products were analyzed by HPLC with diode array detection. Major compounds were identified by reference to authentic compounds. For comparison, native lignins (MWL), kraft lignins, and humic substances were studied as well. The oxygen, carbon and organic chlorine contents were closely similar in the various mill samples and their fractions. In all mill samples, vanillin and 6-c…

On the inverse-voltammetric determination of zinc in acidic solution

1977

Zur Bestimmung kleiner Zinkmengen in salzsauren Losungen ist die inverse Wechselspannungsvoltammetrie geeignet. Besonderheiten des Einflusses der Elektrolysezeit und kleinerer Kupfergehalte werden beschrieben. Die Standardabweichung der Einzelbestimmung mit 50 ng Zn/ml betrug ± 1,6%.

Element-Selective Magnetic Imaging in Exchange-Coupled Systems by Magnetic Photoemission Microscopy

1998

We have used a photoemission microscope to obtain element-resolved magnetic contrast in stacked magnetic thin film systems. Magnetic information is thereby provided by X-ray magnetic circular dichroism. Elemental sensitivity, which is crucial for studying magnetic coupling phenomena in systems with several different layers, is achieved by tuning the energy of the illuminating photons to atomic absorption edges. We present measurements of a Ni-coated Co micropattern on Cu(001), and a wedged Co/Cr/Fe(001) sample. In the former sample the Ni magnetization is seen to follow the magnetization of the Co pattern, thereby changing from an out-of-plane easy axis in areas without underlying Co to in…

Über Tetrathiowolframsäure und Tetrathiomolybdänsäure

1966

Durch Behandeln mit einem Kationenaustauscher in der H+-Form werden aus verdunnten wasrigen Losungen von (NH4)2WS4 und (NH4)2MoS4 die entsprechenden freien Sauren hergestellt. Die Tetrathiomolybdansaure ist wesentlich unbestandiger als die Tetrathiowolframsaure.

Thin-layer chromatography of phenoxyacetic acid herbicides

1981

New Regularization Method for EXAFS Analysis

2007

As an alternative to the analysis of EXAFS spectra by conventional shell fitting, the Tikhonov regularization method has been proposed. An improved algorithm that utilizes a priori information about the sample has been developed and applied to the analysis of U L3‐edge spectra of soddyite, (UO2)2SiO4⋅2H2O, and of U(VI) sorbed onto kaolinite. The partial radial distribution functions g1(UU), g2(USi), and g3(UO) of soddyite agree with crystallographic values and previous EXAFS results.

Theoretical electronic spectra of 2-aminopurine in vapor and in water

2006

The accurate quantum chemical CASSCF and CASPT2 methods combined with a Monte Carlo procedure to mimic solvation effects have been used in the calculation of the spectroscopic properties of two tautomers of 2-aminopurine (2AP). Absorption and emission spectra have been simulated both in vacuum and in aqueous environment. State and transition energies and properties have been obtained with high accuracy, leading to the assignment of the most important spectroscopic features. The lowest-lying 1 (,*) ( 1 La) state has been determined as responsible for the first band in the absorption spectrum and also for the strong fluorescence observed for the system in water. The combined approach used in …

3,3?,5,5?-Tetramethylbenzidme for the colorimetric determination of manganese in water

1998

Manganese can be determined by colorimetry with previous oxidation of Mn(II) in a strong basic medium, using 3,3′,5,5′-tetramethylbenzidine as a chromogenic reagent. The molar absorptivity of the reaction product is 3.4 × 104 mol−1l cm−1l, the detection limit 3 ng/ml, the RSD (0.5 mg/l,n = 8) 0.9% and the calibration range (1-cm cells) 0.02–0.8 mg/1 V(V), Cr(VI) and Co(II) are the most significant interferences. The new method was compared with an AAS procedure (air-acetylene flame) with previous solvent extraction and also with a colorimetric method for the determination of manganese in sea and drinking water.

Thin-layer chromatography of 2-methyl-4-chlorophenoxyacetic acid and its soil metabolites

1980

Abstract The thin-layer chromatography of 2-methyl-4-chlorophenoxyacetic acid, 4-chloro- o -cresol and 3-methyl-5-chlorocatechol and their pentafluorobenzyl derivatives has been studied on silica gel as adsorbent with 19 solvent systems. The best separation of the individual components occurred with toluene-benzene-acetic acid (2:2:1). Chloroform-diethyl ether-toluene (1:1:1) was suitable for the group separation of the pentafluorobenzyl derivatives.