Determination of the Basicities of a Series of Substituted Benzyldimethylamines in 50% Aqueous Methanol

1973 ◽  
Vol 51 (15) ◽  
pp. 2542-2545 ◽  
Author(s):  
Donald G. Lee ◽  
R. Srinivasan
Keyword(s):  
Ammonium Ions ◽  
Aqueous Methanol ◽  
Hammett Correlation

The basicities of a series of substituted benzyldimethylamines have been determined potentiometrically in 50% (by weight) aqueous methanol. An excellent Hammett correlation (ρ = −1.38) is obtained. The larger value of ρ in aqueous methanol as compared to water (−1.14) is interpreted in terms of a greater capability of water to solvate ammonium ions, thus suppressing the stabilizing or destabilizing effect of ring substituents.

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

1974 ◽  
Vol 7 (7) ◽  
pp. 463-472 ◽  
Author(s):  
Ivan Sekerka ◽  
Joseph F. Lechner
Keyword(s):  
Simultaneous Determination ◽  
Ammonium Ions ◽  
Sodium Potassium ◽  
Direct Potentiometry

Flow injection gas-diffusion amperometric determination of trace amounts of ammonium ions with a cupric hexacyanoferrate

Talanta ◽  
1996 ◽  
Vol 43 (7) ◽  
pp. 1049-1054 ◽  
Author(s):  
R LIU ◽  
B SUN ◽  
D LIU ◽  
A SUN
Keyword(s):  
Flow Injection ◽  
Gas Diffusion ◽  
Ammonium Ions ◽  
Amperometric Determination

Evaluation of flow injection analysis for determination of urea in sheep's and cow's milk

2002 ◽  
Vol 50 (3) ◽  
pp. 263-271 ◽  
Author(s):  
Martina Baumgartner ◽  
Martina Flöck ◽  
Petra Winter ◽  
Keyword(s):  
Bovine Milk ◽  
Reference Method ◽  
Measurement Procedure ◽  
Ammonium Ions ◽  
Routine Diagnostics ◽  
Urea Content ◽  
Teflon Membrane ◽  
Accuracy And Precision ◽  
Spectral Photometry

Difficulties in measuring the urea content in sheep's milk often occur with spectral photometry due to the high protein and fat concentrations of the milk. In this study an enzymatic flow procedure (QuickChem 8000 Ion Analyser, Lachat Instruments, Milwaukee, USA) to determine the urea content in ovine and bovine milk was evaluated. Urea content is determined by the Berthelot reaction after splitting it enzymatically with urease. The free ammonia diffuses through a teflon membrane into a stream of reagent solutions. Detection takes place by means of a reaction between the ammonium ions with hypochlorite and salicylate producing a green colour, which is measured spectrometrically in a flow meter at 660 nm. By using a diffusion cell chemical deproteinisation of milk is not necessary and capacity is high. The assessed procedure exhibited high accuracy and precision and reached a sample capacity of 55 samples an hour. Storage of the milk samples for several days as well as chemical preservation with bronopol had no effect on the measurement procedure. Due to the complexity of the apparatus and the costs associated therewith, the device proves less suitable for routine diagnostics but rather serves as a reference method for the measurement of urea concentration in milk.

Extraction, Cleanup, and Quantitative Determination of Aflatoxins in Corn

1980 ◽  
Vol 63 (3) ◽  
pp. 631-633 ◽  
Author(s):  
James E Thean ◽  
David R Lorenz ◽  
David M Wilson ◽  
Kathleen Rodgers ◽  
Richard C Gueldner
Keyword(s):  
High Pressure ◽  
Liquid Chromatography ◽  
Quantitative Determination ◽  
Ammonium Sulfate ◽  
Silica Gel ◽  
Normal Phase ◽  
Aqueous Methanol ◽  
Normal Phase Hplc ◽  
Water Saturated

Abstract A method is proposed for extraction and cleanup of corn samples for the quantitation of 4 aflatoxins by high pressure liquid chromatography (HPLC). After aqueous methanol extraction, ammonium sulfate treatment, and partition of aflatoxins into chloroform, sample extracts are partially purified on Sep-Pak cartridges or small columns packed with HPLC grade silica; cleanup requires only 13 mL solvent/sample. Aflatoxins B1, B2, G1, and G2 in the purified extract are resolved in ca 10 min by normal phase HPLC on a microparticulate (5 μm) silica gel column with a 50% water-saturated chloroform-cyclohexaneacetonitrile- ethanol solvent, and are measured by ultraviolet fluorescence in a silica gel-packed flowcell. Recoveries of added aflatoxins B1, B2, G1, and G2 were 84–118 % at levels of 1.5–125 μg/kg

scholarly journals Arthroderma tuberculatum and Arthroderma multifidum Isolated from Soils in Rook (Corvus frugilegus) Colonies as Producers of Keratinolytic Enzymes and Mineral Forms of N and S

2020 ◽  
Vol 17 (24) ◽  
pp. 9162
Author(s):  
Justyna Bohacz ◽  
Michał Możejko ◽  
Ignacy Kitowski
Keyword(s):  
Amino Acids ◽  
Culture Medium ◽  
Agricultural Practice ◽  
Ammonium Ions ◽  
Mineral N ◽  
Corvus Frugilegus ◽  
Keratinolytic Fungi ◽  
Sulfate Release ◽  
Proteins And Peptides

Keratinolytic fungi representing the genus Arthroderma that were isolated from the soils of a rook (Corvus frugilegus) colony were used as biological agents for the disposal of waste feathers. The aim of this study was to assess the abilities of Arthroderma tuberculatum and Arthroderma multifidum fungi with a varied inflow of keratin matter to biodegrade waste feathers. The evaluation was based on the determination of feather mass loss, the activity of keratinolytic enzymes, and the content of mineral N and S forms. It was found that the activity of protease released by the fungi contributed to an increase in the level of soluble proteins and peptides and the concentration of ammonium ions, as well as alkalization of the culture medium. Keratinase activity was significantly correlated with sulfate release, especially in A. tuberculatum cultures. The strains of A. tuberculatum fungi isolated from the soil with the highest supply of organic matter, i.e., strains III, IV, and V, had the lowest enzymatic activity, compared to the A. multifidum strains, but they released mineral nitrogen and sulfur forms that are highly important for fertilization, as well as nutritionally important peptides and amino acids. A. tuberculatum strains can be used for the management of waste feathers that can be applied in agricultural practice.

Method for the Detection and Estimation of Ochratoxin A in Some Cereal Products

1967 ◽  
Vol 50 (2) ◽  
pp. 366-370
Author(s):  
P M Scott ◽  
T B Hand
Keyword(s):  
Ochratoxin A ◽  
Aqueous Methanol ◽  
Whole Wheat Flour ◽  
Cereal Products ◽  
Whole Wheat ◽  
Sample Extract ◽  
Final Sample ◽  
Aoac Method ◽  
Layer Chromatography

Abstract A method for the detection and semiquantitative estimation of ochratoxin A in flour and other cereal products is described which can be used in conjunction with analysis of the foodstuff for aflatoxins. The sample is extracted with aqueous methanol and n-hexane and the toxin is partitioned on a Celite column, as in the AOAC method for determination of aflatoxins in peanut products. Ochratoxin A is separated by thin layer chromatography and estimated by the intensity of fluorescence compared with that of a reference standard. By this procedure, 0.01 μg ochratoxin A can be detected in 10 μl final sample extract, corresponding to a detection limit of about 25 μg/kg cereal foodstuff. The method is applicable to whole wheat flour, corn meal, barley cereal, and rice cereal. Recoveries of 80—100% of added ochratoxin A were obtained

Simultaneous Detection of Several Fusarium Mycotoxins in Cereals, Grains, and Foodstuffs

1981 ◽  
Vol 64 (5) ◽  
pp. 1067-1073 ◽  
Author(s):  
Hisashi Kamimura ◽  
Motohiro Nishijima ◽  
Kazuo Yasuda ◽  
Kazuo Saito ◽  
Akihiro Ibe ◽  
...  
Keyword(s):  
Gas Chromatography ◽  
Thin Layer ◽  
Simultaneous Determination ◽  
Simultaneous Detection ◽  
Fusarium Mycotoxins ◽  
Aqueous Methanol ◽  
Systematic Method ◽  
Chromatographic Procedure ◽  
Cereal Samples

Abstract A systematic method is described for the simultaneous determination of Fusarium mycotoxins (nivalenol, deoxynivalenol, fusarenon-x, diacetoxyscirpenol, neosolaniol, T-2 toxin, HT-2 toxin, butenolide, moniliformin, and zearalenone) in cereals, grains, and foodstuffs. Mycotoxins were extracted with aqueous methanol and purified by a 2-step chromatographic procedure using Amberlite XAD-4 and Florisil columns. The column eluates were concentrated and spotted on a thin layer chromatographic (TLC) plate which was then developed in CHCL3-methanol (93 + 7) and toluene-acetonemethanol (5 + 3 + 2). Each mycotoxin was quantitated by gas chromatography (GO and TLC densitometry. The minimum detectable concentrations (μg/kg) in various test materials were: nivalenol, deoxynivalenol, and fusarenon-x, 2.0; diacetoxyscirpenol, neosolaniol, T-2 toxin, and HT-2 toxin, 80; zearalenone, 10; butenolide, 30; and moniliformin, 50. Recoveries of the mycotoxins added to various cereal samples at 1.0-2.0 Mg/g were greater than 71% and averaged 85%.

Amperometric determination of ammonium ions with a microbial sensor

2007 ◽  
Vol 47 (2) ◽  
pp. 109-116 ◽  
Author(s):  
K. Riedel ◽  
J. Huth ◽  
M. Kuehn ◽  
P. Liebs
Keyword(s):  
Ammonium Ions ◽  
Amperometric Determination ◽  
Microbial Sensor

Polarographic determination of azobenzene

1986 ◽  
Vol 51 (1) ◽  
pp. 25-33 ◽  
Author(s):  
Jiří Barek ◽  
Roman Hrnčíř
Keyword(s):  
Detection Limit ◽  
Electrode Surface ◽  
Linear Sweep Voltammetry ◽  
Polarographic Determination ◽  
Hanging Mercury Drop Electrode ◽  
Linear Sweep ◽  
Aqueous Methanol ◽  
Mercury Drop Electrode

Conditions were found for the determination of azobenzene by means of DC, AC, TAST, DP, and FSDP polarography and linear sweep voltammetry on a hanging mercury drop electrode in the medium of aqueous methanol, which ensures a sufficient solubility of azobenzene. In the latter two methods, the detection limit was around 10-8 mol/l; a still lower value could be attained by preliminary accumulation of azobenzene, i.e. adsorption on the electrode surface.

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