Densitometric equipment for rapid quantitation of aflatoxins on thin layer chromatograms 1

A densitometric instrument (Spotmeter) has been designed for rapid measurement of aflatoxin on thin layer chromatographic plates. The Spotmeter measures the total amount of fluorescence of the aflatoxin spot and thus eliminates the need for scanning mecha-nisms, plotters and integrators incorporated into most commercially available densitometers used for aflatoxin analyses. In comparison with a Schoeffel SD 3000 Spectrodensitometer, the Spotmeter was more accurate in one test and at least equally accurate in another test. The Spotmeter made measurements in 1/4 the time required for the Spectrodensitometer and would cost about 1/6 as much as commercially available densitometers suitable for aflatoxin analyses. 1 Paper Number 6203 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, NC.     

The thin layer chromatography of vat dyes

The identification and separation of vat dyes by thin layer chromatography has been investigated with reducing and non-reducing systems. The results showed that the chromatograms on silica gel plates obtained by non-reducing systems at 100 or 120°C were fast, reproducible and easy to control. Nine non-reducing eluents were developed, producing good migration and resolution of 21 vat dyes. Analyses of the chromatograms revealed that the R_f, values varied with the temperature of the system, the chemical structure of the vat dyes and the nature of adsorbent, as well as with the eluents used. The effects of molecular masses of the vat dyes on the R_f values were less significant. Despite the successful use of a novel reducing agent for vat dyes, the chromatography of reduced dye was largely unsatisfactory. The use of reversed-phase t.l.c. plates was examined and showed little benefit.     

Identification of nylons by thin layer chromatography

The composition of nylons by ω-amino-carboxylic acid monomers, dicarboxylic acids, and diamines is identified by thin layer chromatography, using their acid hydrolysates and determining the corresponding R_f values.     

薄层色谱分析在层析分离过程中的应用

介绍了薄层色谱分析方法对层析分离过程的控制性分析和优化作用。     

Reversed-phase thin layer chromatography of some common sterols

The chromatographic mobilities of 17 sterols and squalene on reversed-phase thin layer plates with four nonaqueous solvent systems is described. A degree of separation adequate to identify several of the sterols was obtained. It was possible to separate the pairs: cholestanol, epicholestanol; coprostanol, epicoprostanol; 5β-cholestan-3α and 3β-ol and lanosterol, dihydrolanosterol.     

Improved separation of phospholipids in thin layer chromatography

The mobile phases described permit separation of the six major phospholipids of amniotic fluid in one dimension with either conventional or high performance thin layer chromatography. An example of this separation with an extract of amniotic fluid is given.     

Analysis of long chain sultones by thin layer chromatography

The separation and semiquantitative estimation of nine C₁₄ sultones by thin layer chromatography (TLC) on silica gel is reported. Vapor phase charring gives detection limits of several ppm in olefin sulfonate, ethoxylated alcohol sulfates, and formulated products. Isopropyl ether is the solvent of choice, and two-dimensional TLC with this and a chlorinated solvent mixture gives an exclusive sultone area, as well as added sensitivity. Simplified preparative TLC on plates with preadsorbent is described for confirmation by independent analytical methods.     

Programmed multiple development: High performance thin layer chromatography

Poor resolution and sensitivity are not inherent in thin layer chromatography (TLC). They merely re-flect the fact that TLC, as normally practiced, is not a high performance (efficient) technique. When efforts are made to improve the efficiency of TLC, the re-sulting improvements in resolution and sensitivity make high performance TLC fully comparable to high performance liquid chromatography (HPLC). Two approaches to improved TLC performance are the use of small-particle TLC plates and the technique of Programmed Multiple Development (PMD). Prelimi-nary PMD methods for limonin in citrus juice and for caffeine in cola beverages clearly illustrate the use of PMD.     

Analysis of soybean lecithin by thin layer and analytical liquid chromatography

The application of thin layer and analytical liquid chromatography to the analysis of two samples of commercial soybean lecithins is described. A combination of column chromatography and quantitative thin layer chromatography showed that these products consisted of ca. 82% mixture of the major phospholipids of soybeans, phosphatidyl choline, phosphatidyl ethanolamine, and phosphatidyl inositol. The remainder of these products contained essentially the entire spectrum of lipid classes found in soybean oil-some 24 known and unknown glycolipids and phospholipids, in addition to the neutral lipids. Applications of analytical liquid chromatography to these lecithins gave a composition profile of the lipid classes comparable to two-dimensional thin layer chromatography. The potential of this method for the complete analysis of complex lipids, such as soybean lecithins, is indicated.     

Determination of available lysine in pulses by thin layer chromatography

Estimation of available lysine in five pulse samples was carried out by a thin layer chromatographic technique. Results revealed that the available lysine values in all the cases were to some extent lower than the total lysine values.     

Detection of palm oil in vanaspati by thin layer chromatography

Palm oil (raw or refined), as such, or the unsaponifiable matter of palm oil and vanaspati (mostly hydrogenated soybean oil containing 5% sesame oil), when separated on a silver nitrate impregnated Silica Gel G plate or a Silica Gel G plate using (a) hexane/ether/acetic acid (80:20:1.5) or (b) chloroform, respectively, for development showed distinct differences. On the basis of this, two systems have been suggested for the detection of palm oil in vanaspati. About 5% adulteration can be detected by the first method and 10% by the second.     

Separation of polyunsaturated fatty acids by argentation thin layer chromatography

A single step, silver nitrate thin layer chromatographic procedure which separates a methyl ester mixture containing 0–6 double bonds is described. Purity of each ester recovered from the silver nitrate plate was 98–99%. Recovery of the esters ranged from 100% for saturates to 77% for pentaenes.     

A complete separation of lipids by three-directional thin layer chromatography

A novel three-directional thin layer chromatography (TLC) method is reported by which all the polar and neutral lipids are isolated on a single TLC plate. Following resolution of the phospholipids by two-directional TLC, lipids are visualized by ultraviolet light after spraying with 2′,7′-dichloro-fluorescein. A line is drawn across the plate, parallel to the second direction of development, separating the resolved phospholipids and the neutral lipids concentrated along the solvent front. The TLC plate is then chromatographed in the reverse direction of the second development to resolve the neutral lipids. By exposing the lipids to HCl fumes after the first development, the plasmalogen content of the lipids may also be determined. This new technique is rapid and lends itself to qualitative and quantitative analyses of total lipids. Contribution no. 1163 from the Animal Research Centre.     

Complexities in lipid quantitation using thin layer chromatography for separation and flame lonization for detection

The use of thin layer chromatography (TLC) for separation (using silica gel coated quartz rods) and subsequent flame ionization for detection (FID) was examined to determine whether this method could be used for the quantitation of lipids. However, response factors (RF) for various lipids were different and depended upon several variables including the amount of material analyzed. For example, RF were 3-fold greater when 10 μg of tripalmitin was analyzed as compared to 1 μg of the same material. The amount of lipid detected by FID was also dependent upon the rate at which it passed through the flame. During analysis of methylpentadecanoate, detector response increased with scan speed, while at all speeds it was completely removed from the rod. On the other hand, depending upon the amount of cholesterol or phospholipid analyzed, the response either increased, remained unchanged or decreased with scan speed. During a fast scan, detector response was reduced because some material remained on the rod. Thus, the detector response is influenced by sample volatility. In conclusion, there appears to be a complex relationship between detector response and the amount of heat available per microgram of sample. Since we could not find a direct correlation between detector response and sample quantity, it would be difficult to use TLC-FID as a tool for quantitating the components of a lipid mixture. Presented at the 73rd Annual AOCS Meeting, Toronto, May 1982.     

Determination of specific activity of isotopic materials by thin layer chromatography

A modified method for determination of specific activity by thin layer chromatography (TLC) is described. Based on in situ spectrodensitometry after separation by TLC, the method is rapid and requires amounts of reference material in the microgram range. Presented in part at the AOCS Meeting, Atlantic City, October 1971.     

Detection of adulteration of olive oil by argentation thin layer chromatography

Minute amounts of adulterant seed oils in olive oil can be detected by GLC analysis of fatty acids of the polyunsaturated triglyceride fraction, obtained by TLC on silver nitrate impregnated silica gel. Every possible effort was made to avoid any critical or time consuming manipulation in this method in order to develop it as a routine testing procedure. A complete analysis is possible in less than 2 hr and the detection of as low as 2% adulteration by other seed oils is accurate and reliable.     

Separation of conjugated bile acids by reverse phase thin layer chromatography

Seven conjugated bile acids were separated by 1-dimensional reverse phase thin layer chromatography using ethanol/0.3 M calcium chloride/dimethylsulfoxide (25∶25∶2) as mobile phase.     

Rapid densitometric determination of triglyceride groups by argentation thin layer chromatography

A method has been developed for the quantitative thin layer chromatographic determination of the triglyceride groups, differing in unsaturation, based on densitometry of the charred bands. Complete separation was achieved by continuous development in an open glass jar. The need for correction coefficients was avoided through addition of bromine to the double bonds prior to charring in the presence of sulphuryl chloride. The accuracy and precision of the method were evaluated on a standard mixture and on sunflower oil, olive oil, lard, cocoa butter, and beef tallow. The method is applicable for triglyceride group analysis of the most common fats and oils which contain saturated, monoene, and diene acids.     

Identification of surface active agents in admixture by thin layer chromatography

The qualitative identification of the surface active agents commonly used in household detergent formulations is possible using thin layer chromatography (TLC). Successful separations have been made when the samples are spotted on Aluminum Oxide G and developed with isopropanol. A variety of specific reagents may be used to color the spots and thereby supplement the Rf values as a means to identify the surfactants. The analysis can be made semi-quantitative if the separations are made using an aluminum oxide column and collecting and fractions eluted with isopropanol and methanol. Presented at the AOCS Meeting in Minneapolis, 1963.