Effect of Adsorption of Histamine to Glass Surfaces on Its Estimation

1982 ◽  
Vol 65 (1) ◽  
pp. 71-75
Author(s):  
John Murray ◽  
Alister S McGill

Abstract Histamine is rapidly adsorbed on the surface of glass containers when stored in aqueous or 10% methanol solution at ambient or sub-zero temperatures. This effect can lead to marked errors in the determination of histamine. Addition of acid to the holding medium or storage in polyethylene containers eliminates this effect

2019 ◽  
Vol 7 (4) ◽  
pp. 132-137
Author(s):  
Gelareh Ehsani ◽  
Foad Fahmide ◽  
Dariush Norouzian ◽  
Seyed Mohammad Atyabi ◽  
Parastoo Ehsani ◽  
...  

1972 ◽  
Vol 55 (6) ◽  
pp. 1226-1227
Author(s):  
Mark A Litchman ◽  
Lewis A Turano ◽  
Ronald P Upton

Abstract A method is described for the quantitative determination of hexane in modified hop extract by head-space gas-liquid chromatography. A sample of extract is weighed into a serum vial and water-methanol solution is added. The vial is sealed tightly and heated 1 hr in a 70°C bath. A sample of the head-space gas over the solution is injected onto a Porapak Q gas chromatographic column for determination. Recovery of 2–29 ppm hexane added to potassium isohumulone was 95.5–114.8%. The method may be applicable to other hop extracts.


1985 ◽  
Vol 68 (5) ◽  
pp. 952-954
Author(s):  
Maria Luisa Serralheiro ◽  
Maria Lurdes Quinta

Abstract A method has been developed for the detection of aflatoxin Mi in milk. The toxin is extracted with chloroform, the extract is evaporated, and the residue is partitioned between carbon tetrachloride and an aqueous saline-methanol solution. The toxin is once again extracted with chloroform from the methanol solution and analyzed by thin layer chromatography. The limit of detection of Mi in powdered milk is 0.5 μg/ kg; recoveries of added Mj are about 83%. The limit of detection can be improved to 0.3 μg/kg if the plate is sprayed with an aqueous solution of H2S04 after development.


1999 ◽  
Vol 82 (3) ◽  
pp. 614-619 ◽  
Author(s):  
Steven M Plakas ◽  
Kathleen R El Said ◽  
F Aladar Bencsath ◽  
Steven M Musser ◽  
Calvin C Walker

Abstract Rapid methods are described for determination of flumequine (FLU) residues in muscle and plasma of farm-raised channel catfish (Ictalurus punctatus). FLU residues were extracted from tissues with an acidified methanol solution, and extracts were cleaned up on C18 solid-phase extraction cartridges. FLU concentrations were determined by liquid chromatography (LC)using a C18 analytical column and fluorescence detection (excitation, 325 nm; emission, 360 nm). Mean recoveries of FLU from fortified muscle were 87–94% at 5 levels ranging from 10 to 160 ppb (5 replicates per level). FLU recoveries from fortified plasma were 92–97% at 5 levels ranging from 20 to 320 ppb. Limits of detection (signal-to-noise ratio, 3:1)for the method as described were 3 and 6 ppb for muscle and plasma, respectively. Relative standard deviations (RSDs) for recoveries were ≤12%. Live catfish were dosed with 14C-labeled or unlabeled FLU to generate incurred residues. Recoveries of 14C residues throughout extraction and cleanup were 90 and 94% for muscle and plasma, respectively. RSDs for incurred FLU at 2 levels in muscle and plasma ranged from 2 to 6%. The identity of FLU in incurred tissues was confirmed by LC/mass spectrometry.


1999 ◽  
Vol 65 (11) ◽  
pp. 5082-5088 ◽  
Author(s):  
Paula M. van Schie ◽  
Madilyn Fletcher

ABSTRACT In order to exploit the ability of anaerobic bacteria to degrade certain contaminants for bioremediation of polluted subsurface environments, we need to understand the mechanisms by which such bacteria partition between aqueous and solid phases, as well as the environmental conditions that influence partitioning. We studied four strictly anaerobic bacteria, Desulfomonile tiedjei,Syntrophomonas wolfei, Syntrophobacter wolinii, and Desulfovibrio sp. strain G11, which theoretically together can constitute a tetrachloroethylene- and trichloroethylene-dechlorinating consortium. Adhesion of these organisms was evaluated by microscopic determination of the numbers of cells that attached to glass coverslips exposed to cell suspensions under anaerobic conditions. We studied the effects of the growth phase of the organisms on adhesion, as well as the influence of electrostatic and hydrophobic properties of the substratum. Results indicate thatS. wolfei adheres in considerably higher numbers to glass surfaces than the other three organisms. Starvation greatly decreases adhesion of S. wolfei and Desulfovibrio sp. strain G11 but seems to have less of an effect on the adhesion of the other bacteria. The presence of Fe3+ on the substratum, which would be electropositive, significantly increased the adhesion ofS. wolfei, whereas the presence of silicon hydrophobic groups decreased the numbers of attached cells of all species. Measurements of transport of cells through hydrophobic-interaction and electrostatic-interaction columns indicated that all four species had negatively charged cell surfaces and that D. tiedjei andDesulfovibrio sp. strain G11 possessed some hydrophobic cell surface properties. These findings are an early step toward understanding the dynamic attachment of anaerobic bacteria in anoxic environments.


1973 ◽  
Vol 56 (6) ◽  
pp. 1480-1482
Author(s):  
Glenn M George ◽  
Marven A Albrecht ◽  
Larry J Frahm ◽  
J Patrick McDonnell

Abstract Dibutyltin dilaurate is extracted from finished feed with warm chloroform. The chloroform extract is filtered and a 25 ml aliquot is concentrated in the presence of methanol until all traces of chloroform are removed. The methanol solution is diluted and feed interferences are removed by filtration. The filtered solution is aspirated into an atomic absorption spectrophotometer with a triple-slot burner head, using an air-acetylene flame. The instrument response to tin at 286.3 nm is recorded. Essentially theoretical recovery (100.5— 101.9%) has been obtained for tin in laboratory-mixed feeds.


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