Types Of Silica Gel Research Articles

Observation on the Thin Layer Chromatographic Development of Corn Extracts with Ethyl Ether

Abstract The separation of aflatoxin from interfering lipids in one rapid thin layer chromatographic development is achieved by selecting the proper combination of a specified type of silica gel and grade of ethyl ether.

Quantitative Fluorodensitometric Measurements of Aflatoxin B1 with a Flying-Spot Densitometer. I. Fluorodensitometric Study of the Behavior of Aflatoxin B1 Standard Spots on Different Types of Silica Gel

Abstract TLC plates were scanned after development with a reflectance flying-spot densitometer. The procedure for routine measurements of standard B1 spots is described herein. Three different types of silica gel layers were spotted with standard aliquots of aflatoxin B1 covering a range of 0.4–20 ng. Silica gel H plates were developed with a mixture of chloroform– trichloroethylene–n-amyl alcohol–formic acid (80 + 15 + 4 + 1), while silica gel G and MNG- HR plates were developed with a mixture of chloroform-acetone (90 + 10). Sharp and defined separation patterns for anatoxins B1, B2, G1, and G2 were recorded on H and MN-G-HR plates, while unsatisfactory separation was found on G plates. The relationship between peak area and concentration was linear for II and MN-G-IIR plates, but not for G plates. Variations of ±15–20% were calculated among the fluorescence of standard B1 spots between plates with same sorbent layers. Coefficients of variation of ±5–7% for single densitometric measurements on one plate under normal routine conditions were calculated for a series of 3 or 4 standard aflatoxin B1 spots ranging from 1 to 4 ng on H and MN-GHR plates. Coefficients of variation of ±11–12% were calculated for G plates. Results obtained in this investigation are compared with those found by previous investigators.

A Mössbauer effect study on crystallites of supported ferric oxide

Crystallite size measurements and interaction with the support material of ferric oxide with silica gel and alumina have been studied using Mössbauer spectroscopy and x-ray diffraction techniques. No compound formation from reaction of the ferric oxide with the silica gel was detected, but changes in size distribution of the microcrystalline ferric oxide with the extent of calcination and type of silica gel used were observed. Similar results were obtained for alumina supported samples calcined for a prolonged period of time. Reoxidation of alumina-supported ferric oxide reduced in flowing hydrogen at 500–600 °C, unlike the silica gel samples, did not result in a Mössbauer spectrum identical to that of the sample in its initial state. Reaction of the support with the iron in its reduced state is indicated by a temperature study of the reoxidized samples. The data may be interpreted as reaction with the alumina, or bimodal size distribution of the microcrystalline ferric oxide, or both. Common to both the silica gel and alumina supported samples was the observation of the existence of a ferric oxide phase that was either amorphous or consisted of crystallites too small to be detected by x-ray diffraction.

The characterization of acid-set silica hydrosols, hydrogels, and dried gel

Acid-set silica hydrosol, hydrogel, and the dried desiccant silica gel have been characterized by various types of measurements and discriminating tests. Acidic silica hydrosols have a molecular weight of about 2,000 at formation and reach about 2,500,000 at the point of gelation. Molecular growth of silicic acid in this hydrosol was found to be linear. Cross-linking of the polysilicic acid chains occurs in the hydrogel state, and the number of cross-links between chains have been estimated. Silicic acid bonding in acidic hydrosols is believed to be by hydrogen bonding between the silanol groups through water. The siloxane bonding in hydrogels aged beyond syneresis was determined by a depolymerization rate study; a low degree of siloxane type bonding was found. To account for the remaining bonding in the hydrogel, a high degree of hydrogen bonding is suspected. The reasons for hydrogen bonding are given. Most of the silanol condensation must occur during the drying of this type silica gel.

Glass Fiber-Silica Gel Sheets for Insect Phospholipid Fractionation

The introduction of commercially prepared thin-layer chromatography sheets of silica gel on a glass-fiber support provides a convenient and rapid means for fractionating naturally occurring lipid mixtures. Gelman Instant Thin Layer Chromatography Sheets, Type Silica Gel, were used for the separations described in this communication.

A comparison of new techniques for the detection and quantitative determination of triazine herbicides separated by thin-layer chromatography. II. Reflectance spectroscopy.

Various factors affecting the fluorescence quenching properties ofs-triazines on fluorescing silicagel layers have been investigated. An analytical method has been developed which permits the quantitative analysis of these triazines, after Chromatographic separation, with an accuracy of ±5%. The instrumental detection limit for atrazine, based on a 2∶1 signal to background ratio, ranges from 0.40 to 0.25μg per spot depending on the type of silicagel used. The method compares favourably with three other techniques used for the determination of identical samples.

Beitrag zur trennung von seltenerden durch extraktionschromatographie mit di(2-äthylhexyl)phosphorsäure (HDEHP) I. Silicagel als trägermaterial für die stationäre phase

Hydrophobised silica gel was used as support material for extraction chromatographic separations of rare earths with di(2-ethylhexyl)phosphoric acid (HDEHP). Columns with a capacity of 0.8 mequiv, per ml of column and a “height equivalent of one theoretical plate” of H ≤ 0.1 mm for europium and gadolinium were obtained. H is independent of the type of silica gel when its mean pore diameter is ≥ 35 Å, and is also nearly independent of the amount of HDEHP used, as long as the silica gel only absorbs the dialkylphosphoric acid so that a dry powder is produced again after absorption. Examples of separation show the efficiency of the columns obtained.

Infrared adsorption spectrum of microporous adsorbents of the silica gel type : Yaroslavskii, N. G.; Zhur. Fiz. Khim. 1950 24 64-81

Infrared adsorption spectrum of microporous adsorbents of the silica gel type : Yaroslavskii, N. G.; Zhur. Fiz. Khim. 1950 24 64-81

SORPTION OF GAS BY MINERAL. VI

Abstract (1) The sorptions of ammonia and carbon dioxide under one atmospheric pressure at 25°C. by the dehydrated samples of sepiolite, talc, serpentine, asbestos, acid clay, bentonite, and vivianite have been measured. (2) Sepiolite sorbs either ammonia or carbon dioxide in a considerable amount. It is already known that this mineral sorbs various kinds of gases and that this is a sorbent of silica gel type. (3) Acid clay and bentonite sorb ammonia but no carbon dioxide. Asbestos sorbs some amount of ammonia. (4) Talc, serpentine, and vivianite sorb neither ammonia nor carbon dioxide.

The sorption of methyl and ethyl alcohol by silica gels

The original object of the present research was to investigate the sorption of methyl alcohol by silica gel, in order to compare the isothermals with those of water and ethyl alcohol, which had been determined by Lambert and Foster. Owing to the fact that the supply of gel used for this earlier work had been exhausted, it as necessary to examine a number of other specimens. One of these, which like the original gel, was a commercial product, was found to take up a larger amount at saturation, and also to exhibit hysteresis phenomena which were not observed with the original gel. Unfortunately it was impossible to find a sample giving exactly the same shape of isothermal as the original gel, although some specimens known to belong to the same batch gave very similar curves. One of these was selected for the present work, and an examination has been made of the isothermals of methyl and ethyl alcohols on these two types of silica gel at 25° C. The fact that one specimen showed hysteresis provided a suitable occasion further to confirm the view, always maintained by Lambert and the author, that these phenomena are in no way due to incomplete removal of permanent gases or other impurities from the systems. In previous work with silica and ferric oxide gels, evacuation was carried out at 150° C, which is actually the optimum temperatures of activation for the latter gel, the adsorptive capacity of which decreases rapidly when higher temperatures are employed. Silica gels, however, will withstand a much higher temperature with comparatively little diminution in capacity, and in the present work it has been shown that the hysteresis phenomena are not affected by raising the temperature of the initial evacuation to 250° C or even to 350° C. It has also been shown that the phenomena persist after continued "flushing out" of the gel with methyl or ethyl alcohol vapour. (McBain suggested that the hysteresis observed by Lambert and Clark with benzene on ferric oxide gel would not have ocucrred if the gel had been flushed out with benzene before the isothermals were determined.)

A New Type of Silica Gel.

A New Type of Silica Gel.