Quantitative Densitometry in Situ of Lipids Separated by thin Layer Chromatography

Abstract

Operating parameters are described for a densitometric method to determine in situ eight lipid classes separated by thin layer chromatography. The separated lipids, visualized on the TLC plate by a cupric acetate-phosphoric acid charring method, were quantitatively determined by spectrodensitometry using the Shimadzu CS-910 Dual Wavelength TLC Scanner. Plates were scanned in either a linear scanning mode or in a zigzag scanning mode (flying spot).

Reproducibility of a) sample application (spotting) and b) the lipid separation procedure was determined by scanning. Transmittance measurements yielded response areas that were 2.8 X higher than reflectance measurements. Operating parameters such as scanning direction, wavelength, single and dual-wavelength measurement, scanning speed, and slit geometry were studied. Optimal conditions were established for quantitative densitometry of lipids on thin layer plates.     

Imaging and Quantitation of One and Two Dimensional TLC With a New Radioanalytic Imaging System

Abstract

A new method for the imaging and quantitation of radiolabeled substrates fractionated on one or two dimensional (2D) TLC plates has been developed. The TLC sample is read by a microcomputer-controlled beta- and gamma-sensitive gas proportional counter. The TLC plate is scanned by a 20 × 20 cm array of 952 individual detector elements, and the resulting quantitative image is displayed on a high resolution monitor for analysis. Individual radioactive spots may be quantitated on-screen.     

Liquid chromatographic analysis of sebum lipids and other lipids of medical interest

A technique is described for the high-pressure liquid chromatographic (HPLC) analysis of sebum lipid classes. The lipid present in sebum are separated by gradient elution HPLC from a microparticulate silica column and detected using a moving-wire detector. The system described can be linked to a computer. Quantitation can be carried out by comparing peak areas obtained with those of an internal standard. Peak trapping for further investigations of the separated components, for example by gas chromatography-mass spectrometry, is very easy. Sebum lipids are separated into the following lipid classes: hydrocarbons and squalene, cholesterol esters and wax esters, fatty acids as their methyl esters, triglycerides, 1,3-diglycerides, 1,2-diglycerides, free cholesterol, monoglycerides and other polar materials. Besides to sebum, the method has been successfully applied to other lipid mixtures, such as serum lipids. Examples of other applications are shown.     

SYNTHESIS OF SOME NEW 3-BENZYL-2-ARYLIMINO-4-THIAZOLIDINONE-1,1-DIOXIDES

Abstract

Twenty new 3-benzyl-2-arylimino-4-thiazolidinone-1,1-dioxides (2) were synthesized by oxidising 3-benzyl-2-arylimino-4-thiazolidinones (1) with potassium permanganate in glacial acetic acid. The homogeneity and purity was confirmed by TLC and some of the dioxides were screened for their insecticidal, acaricidal and herbicidal activities.     

Separation of Prostaglandins E1, and E2 and other Major Eicosanoids by Unidimensional Argentation Thin Layer Chromatography

Abstract

Prostaglandins (PG) E₁ and E₂ are important regulators of biologic functions, and can express different biological effects. In thin layer chromatography (TLC) systems which separate these compounds, comigration of other major eicosanoids is a problem. This paper describes a TLC system using a mobile phase of chloroform/methanol/acetic acid/H₂O (90:7.5:5:0.8) that separates PGE₁ and PGE₂, as well as other major eicosanoids, including dihomogammalinolenic acid (DHLA), the immediate fatty acid precursor of PGE₁.     

The Importance of Effective Predevelopment Plate Washing Techniques in Thin-Layer Chromatography

Abstract

Comparative studies were made of the two methods commonly used for predevelopment TLC plate cleaning. In separate studies TLC plates were washed by the two methods: ascending development and dip washing using several solvent and solvent combinations. Residues remaining on the surface of plates after washing were visualized by fluorescence techniques and scanned by densitometry. Evaluation of the two washing methods showed that plate dipping gave superior results in every case over ascending development. The most effective solvent for predevelopment TLC plate washing was found to be methanol.     

Instrumental HPTLC of Aflatoxins: Fluorescence Enhancement by Corn Free Fatty Acids

Abstract

Greater than 100% recoveries using instrumental HPTLC were observed for aflatoxin (AFT) analysis in spiked corn samples. I₂ detection of spots over-laying AFT B₁ and B₂ were identified by GLC as C₁₆ ^?c18 free fatty acids (FFA). These FFA were found to enchance the fluorescence of AFT B₁ from 13.7% to 35.7% greater than controls resulting in >100% recoveries. The inclusion of glacial acetic acid in the TLC mobile phase resulted in an increased mobility of the FFA which eliminated the positive interference on AFT fluorescence. Recoveries using the modified developing solvent then gave values in acceptable ranges.     

Chromatographic Behaviour of Amino Sugars on Metal Salt Impregnated Thin Layers

Abstract

Suitable TLC separation scheme for Amino Sugars on silica gel G plates impregnated with metal salt, using the solvent system methanol-acetone (50:10) has been worked out. The visualization of the spots was done by spraying with ninhydrin in 1 - butanol.     

Thin Layer Chromatography-Laser Mass Spectrometry (TLC-LMS) of Triphenylmethane Dyes: Initial Results

Abstract

Laser mass spectra (LMS) of triphenylmethane dyes were obtained directly from a thin layer chromatographic (TLC) plate using the LAMMA-1000 laser microprobe. Spectra obtained from TLC plates were very similar to those obtained from standard substrates, the only difference being that at threshold power densities spectra from the TLC plates show greater fragmentation. The region below m/z 100 is mostly obscured by peaks due to the chromatographic support; above this range, peaks can be identified corresponding to the molecular cation and simple neutral losses. The inherent lateral rèsolution of the Instrument (～5 μm) was used to resolve multiple components in broad chromatographic spots. The TLC-LMS combination has the advantage that components can be identified even if they are not completely resolved chromatographically.     

胆汁酸的薄层层析——数理统计法用于层析溶剂系统的选择

本文选择氯仿、乙醇、乙酸乙酯、醋酸和水等五种溶剂作为胆汁酸薄层层析的展开剂,采用正交设计法[L_(16)(4~5)]安排实验,对胆固醇、胆酸、脱氧胆酸、甘氨胆酸、甘氨脱氧胆酸、牛磺胆酸、牛磺脱氧胆酸和卵磷脂等八种化合物的R_f值及层析谱斑点的集中情况,用直观分析和方差分析法处理,得到了单向一次薄层层析全部分离胆汁的溶剂系统,较文献报道方法为佳。     

Rapid Separation of Prostaglandins by Linear High Performance Thin Layer Chromatography

Abstract

A continuous development technique using silica gel linear high performance TLC plates is described for the separation of prostaglandins 6-keto-F_1α, F_2α, E₂, 13,14-dihydro-15-keto-F_2α, 13–14-dihydro-15-keto-E₂, and thromboxane B₂. Complete separation of all six prostaglandins was achieved with a solvent system of ethyl acetate/acetone/acetic acid (90:5:1). The method is simple, rapid and provides excellent resolution of plasma prostaglandins prior to quantitation by gas chromatography-mass spectrometry.     

An Improved Copper Reagent for Quantitative Densitometric Thin-Layer Chromatography of Lipids

Abstract

Eleven cupric compounds were screened to determine whether a different cupric anion might give greater and more uniform charring responses with lipid classes on TLC plates than cupric acetate. A procedure was developed which used 10% CuSO₄ in 8% H₃PO₄ as a charring reagent. Improved reproducibility of charring was obtained by temperature-programmed heating of the thin layer plates from 30 to 180°C at 10 degrees per minute in the oven of a commercial gas-liquid chromatograph.     

Comparison of Mobile Phases for Separation and Quantification of Lipids by One-Dimensional TLC on Preadsorbent High Performance Silica Gel Plates

Abstract

Twenty-four solvent systems reported in the literature for the one-dimensional TLC separation of lipids and phospholipids were compared under identical conditions using high performance preadsorbent silica gel plates. The best overall separation of mixtures of neutral lipid and phospholipid standards and compounds extracted from the digestive gland-gonad complex of Biomphalaria glabrata snails was obtained with a system utilizing consecutive development with chloroform-methanol-water (65:25:4), chloroform-hexane (3:1), and carbon tetrachloride. The best system for quantification of neutral lipids was hexane-diethyl ether-formic acid (80:20:2). R_f data are tabulated and results discussed for all systems tested.     

Determination of Biphenyl in Citrus Fruits by Quantitative Thin-Layer Chromatography

Abstract

Residues of the fungicide biphenyl in citrus fruits have been determined by direct scanning of spots on phosphor-impregnated high performance silica gel TLC plates under UV light. Biphenyl was separated from fruit tissue by steam liquid-liquid extraction. Recoveries from spiked samples ranged from 92–99% at 100, 50, and 10 ppm levels. The precision of the TLC determination and overall procedure are shown to be adequate for residue analysis.     

Chromatographic Separation of Some Inorganic Ions on Silica-Gel Pyridinium Tungstoarsenate Impregnated Thin Layer Plates

Abstract

A scheme for the TLC separation of twelve inorganic ions on Silica Gel-Pyridinium Tungstoarsenate impregnated plates by using a mixture of butanol-acetic acid-ethyl alcohol-acetone-water (60:10:30:40:10) or isopropanol acetic acid-acetone (60:5:35) as developing system and employing 0.5% dithizone in chloroform as visualization reagent is described. Examples of separations of binary, ternary and pentnary mixtures are given.     

Lipid classes of in vitro cultivar of Pakistani citrus

The in vitro cultivar of citrus contained 18.0% lipids after 12 weeks of germination of seed. The lipid was analyzed by GC procedure for its fatty acid composition. The oil contained seven major fatty acid constituents which were later identified by GC. The oil was further analyzed for its classes by means of thin layer chromatography and gas chromatography. The major portion of the lipid classes comprised of neutral lipids (93.9%) and polar lipids (6.1%). The identified neutral lipids comprised of hydrocarbon (1.4%), wax esters (1.5%), sterol esters (5.2%), triglycerides (52.3%), free fatty acids (1.3%), 1,3-diglycerides (6.0%), 1,2-diglycerides (5.0%), glycol (15.2%), sterols (6.0%), 2-monoglycerides (6.4%), 1-monoglycerides (5.3%) and the identified polar lipids comprised of phosphatidyl ethanolamine (1.8%) phosphatidyl choline (0.9%) lysophosphatidyl ethanolamine (1.8%) and phosphatidyl inositol (1.1%).     

Analysis of Polydispersity of Oligomers and Polymers by Adsorption Thin-Layer Chromatography

Abstract

Thin-layer chromatography/TLC/ has been widely used for the analysis of virtually all classes of low molecular weight organic substances.     

Separations in Thin Layer and High Performance Liquid Chromatography Using Alkyl Silica Gel Bonded Phases

Abstract

Separations in thin layer (TLC) and high performance liquid chromatography (HPLC) using alkyl bonded phases were carried out under optimum solvent conditions for each of three phases, RP-2, RP-8 and RP-18. The phases were tested for their efficiency and resolving power using three groups of compounds in three binary organic-water mobile phases. The organic solvents were acetonitrile, methanol and tetrahydrofuran, which are widely used as solvent modifiers in reversed phase liquid chromatography.

The results showed that, unlike HPLC, TLC using RP-18 plates was the most, and RP-2 plates the least, efficient. A naphthalene and biphenyl mixture which was resolved by HPLC using any of the three solvents and columns was not resolved by TLC using any plate or solvent combination, unless the plate was prewashed with an organic modifier. The addition of NaCl (1–2% wt/vol) to the solvent for TLC speeded development unless an alcohol was used, but did not greatly affect the separation.     

Thin Layer Chromatography of Pesticides-A Review of Recent Techniques and Applications

Abstract

Recent advances in the techniques and applications of TLC for the separation, detection, and quantitative determination of pesticides are reviewed. Analyses of a variety of samples for residues of pesticides of various classes are considered.     

MALDI-TOF-MS Directly Combined with TLC: A Review of the Current State

Thin-layer chromatography (TLC) is a widely used, fast and inexpensive method for separating complex mixtures. Unfortunately, the quality of achievable separation represents only one side. An additional problem is the unambiguous assignment of the obtained spots to defined compounds. Clear identification of spots is often not possible by common staining methods and comparison with a known reference compound. Therefore, further analytical techniques are mostly required for further structural elucidation. Mass spectrometry (MS) is a suitable method due to its high sensitivity. In particular, matrix-assisted laser desorption and ionization time-of-flight (MALDI-TOF) MS is a modern soft-ionization technique that may be easily combined with TLC. This review summarizes the so far available knowledge about direct TLC–MALDI combination and gives an overview about different molecule classes that have already been successfully analyzed by this approach. This review critically summarizes the capabilities and limitations of the direct MALDI–TLC combination and highlights in particular the problems related to sample preparation and instrumentation.