Radioactive and analytical determination of free and esterified cholesterol following micro thin-layer silicic acid chromatography

1963 ◽  
Vol 6 (6) ◽  
pp. 555-559 ◽  
Author(s):  
George V. Vahouny ◽  
C.R. Borja ◽  
S. Weersing
Keyword(s):  
Thin Layer ◽  
Silicic Acid ◽  
Analytical Determination ◽  
Silicic Acid Chromatography

scholarly journals Analytical control of active substances of the class of imidazolinones in herbicide formulations

2021 ◽  
pp. 15-18
Author(s):  
L. Cherviakova ◽  
T. Panchenko ◽  
O. Borzykh
Keyword(s):  
Thin Layer ◽  
Thin Layer Chromatography ◽  
Polar Compounds ◽  
Analytical Determination ◽  
Analytical Control ◽  
Regression Equations ◽  
Detection Range ◽  
Layer Chromatography ◽  
Active Substances

Goal. The choice of a chromatographic method and the development of a method for the analytical determination of imazethapyr, imazamox, imazapyr in herbicide preparative forms in the joint presence. Methods. Active substances were analyzed by thin layer chromatography. The linear range of the dependence of the area of chromatographic zones on the amount of active substance was assessed by a mathematical-statistical method. Results. Determination of pesticides by thin-layer chromatography includes the main stages: classification of pesticides by polarity; extraction of active substances from the analyzed sample; chromatographic separation, detection and quantification. The decisive factor in the analysis stages is the dipole moment (μ, D), which characterizes the polarity of the compounds. Imazethapyr, imazamox and imazapir are polar compounds (μ≥6, D) with the corresponding values: 6.1; 6.4 and 6.8 D. Extraction of active substances is carried out with ethanol. Qualitative determination — in a thin layer of adsorbent silica gel in the mobile phase: a mixture of ethanol with acetic acid in a ratio of 4 : 1.5. Identify compounds at the wavelength of the spectrum λ 254 nm and using the developing reagent silver ammonia. The calibration dependence of the area of the chromatographic zone of the compound on its amount is linear in the detection range of 0.30—1.30 μg and is described by the regression equations for: imazethapyr S = 12.345 C + 0.7778, R2 = 0.99; imazapyr S = 9.3671 C + 1.081, R2 = 0.99; imazamox S = 7.6234 C + 1.4462, R2 = 0.98. The equation is used to quantify the active ingredients in the chromatogram. Conclusions. The use of the method of thin layer chromatography makes it possible to select selective conditions for the analysis of imazethapyr, imazamox, and imazapyr in the presence of herbicides in preparative forms. The developed technique is an express method of control and provides determination of active substances in the course of one analysis with high accuracy (relative error is less than 5% at n = 5, P = 0.95). The analytical support of the developed and patented method allows for analytical control of active substances of the imidazolinone class in the formulation of pesticides by analytical and toxicological laboratories, testing services without the use of expensive devices.

Isolation and Determination of Aflatoxin B1 in Cottonseed Meals

1965 ◽  
Vol 48 (4) ◽  
pp. 815-818
Author(s):  
R H Engebrecht ◽  
J L Ayres ◽  
R O Sinnhuber
Keyword(s):  
Rainbow Trout ◽  
Thin Layer ◽  
Ultraviolet Light ◽  
Cottonseed Meal ◽  
Silicic Acid ◽  
Aflatoxin B1 ◽  
Chloroform Solution ◽  
Fluorescent Material ◽  
Acetone Extraction

Abstract A method for the isolation and determination of aflatoxins in commercial samples of cottonseed meal has been devised. Meal samples were defatted with hexane and the aflatoxins removed from the meal by acetone extraction. The pigments and residual lipids were removed from the acetone by nitration of the cold solution. The anatoxin was further isolated by evaporating the acetone and redissolving the residue in hot methanol. After cooling, the insolubles were discarded and the methanol-soluble materials taken up in chloroform. The chloroform solution was spotted on silicic acid thin layer chromatographic plates along with suitable anatoxin standards. After development with 9:1 (v/v) chloroform :acetone, the chromatographic plates were examined under ultraviolet light. Four of the eight cottonseed meals examined contained fluorescent material chromatographically similar to aflatoxin B1 in amounts varying from 19 to 186 parts per billion (ppb). The identity of the material in the 186 ppb sample was verified as aflatoxin by duckling bioassay. Trials using rainbow trout confirmed the chemical findings. These trout experiments will be described in detail in another report.

A modified method for the determination of glyceride glycerol

1962 ◽  
Vol 29 (2) ◽  
pp. 141-147 ◽  
Author(s):  
J. H. Moore
Keyword(s):  
Silicic Acid ◽  
Chromotropic Acid ◽  
Routine Method ◽  
Modified Method ◽  
Lipid Mixtures ◽  
Silicic Acid Chromatography ◽  
High Degree

SummaryA routine method giving accurate results was required for the determination of the glyceride content of eluate fractions obtained in the silicic acid chromatography of lipid mixtures. The technique of determining glyceride glycerol by saponification, oxidation of the liberated glycerol to formaldehyde, reaction of the formaldehyde with chromotropic acid and measurement of the resulting chromogen at 570 mμ has been investigated. Procedures based on this principle have appeared in the literature but none of these has been found to be entirely satisfactory. Accordingly, a modification of the method has been developed that is capable of giving results of a high degree of accuracy.

Development of a method for multielemental determination in water by EDXRF with radioisotopic source of 238Pu.

2019 ◽  
Vol 7 (2A) ◽  
Author(s):  
Camilo Fuentes Serrano ◽  
Juan Reinaldo Estevez Alvares ◽  
Alfredo Montero Alvarez ◽  
Ivan Pupo Gonzales ◽  
Zahily Herrero Fernandez ◽  
...  
Keyword(s):  
Thin Layer ◽  
Expanded Uncertainty ◽  
Considerable Decrease ◽  
X Ray ◽  
Precipitation Efficiency ◽  
Method Of Determination ◽  
Sensitivity Curves ◽  
Order Of Magnitude ◽  
Metrological Parameters

A method for determination of Cr, Fe, Co, Ni, Cu, Zn, Hg and Pb in waters by Energy Dispersive X Ray Fluorescence (EDXRF) was implemented, using a radioisotopic source of 238Pu. For previous concentration was employed a procedure including a coprecipitation step with ammonium pyrrolidinedithiocarbamate (APDC) as quelant agent, the separation of the phases by filtration, the measurement of filter by EDXRF and quantification by a thin layer absolute method. Sensitivity curves for K and L lines were obtained respectively. The sensitivity for most elements was greater by an order of magnitude in the case of measurement with a source of 238Pu instead of 109Cd, which means a considerable decrease in measurement times. The influence of the concentration in the precipitation efficiency was evaluated for each element. In all cases the recoveries are close to 100%, for this reason it can be affirmed that the method of determination of the studied elements is quantitative. Metrological parameters of the method such as trueness, precision, detection limit and uncertainty were calculated. A procedure to calculate the uncertainty of the method was elaborated; the most significant source of uncertainty for the thin layer EDXRF method is associated with the determination of instrumental sensitivities. The error associated with the determination, expressed as expanded uncertainty (in %), varied from 15.4% for low element concentrations (2.5-5 μg/L) to 5.4% for the higher concentration range (20-25 μg/L).

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