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Methods and Equipment for Quality Control of Radiopharmaceuticals
Published in Michael Ljungberg, Handbook of Nuclear Medicine and Molecular Imaging for Physicists, 2022
Rolf Zijlma, Danique Giesen, Yvette Kruiter, Philip H. Elsinga, Gert Luurtsema
Thin Layer Chromatography (TLC) is a chromatography technique based on a solid phase, like paper or silica-coated plates (stationary phase) and a mobile phase (liquid). The analysis is run by putting the TLC plate with the sample on the origin spot in a glass container containing a small layer of mobile phase. The mobile phase is moving upwards along the TLC plate until the liquid has reached the top. The compound and its impurities have different affinities and absorption to the stationary and the mobile phases. The technique is easy to perform and does not require dedicated equipment and, if combined with a reader or scanner (Figure 6.8a), the readout of the plate of paper is simple to determine the per cent of radiochemical purity and the radionuclide purity of the radiopharmaceutical. Typically, TLC takes only a few minutes. (See Figure 6.8b for a typical chromatogram.)
Thin-Layer Chromatography
Published in James P. Lodge, Methods of Air Sampling and Analysis, 2017
TLC is a versatile technique that can be used to separate inorganic or organic materials, and low-molecular weight species up to high chain-length polymers. There are few volatility restrictions, as opposed to gas chromatography; however, highly volatile materials may require special adaptations as they are difficult to migrate and recover without loss of sample. There are virtually no polarity restrictions on materials to be separated. If a solvent is available for the material, generally a TLC separation system can be found to resolve it. The extensive use of relatively stable sorbents makes TLC separations feasible for many reactive species that are difficult to separate by other means. The inexpensiveness of HPTLC plates when compared to the cost of capillary columns for GC or HPLC columns provides a medium that is forgiving in terms of incomplete sample clean-up. Injection of a dirty sample may render a column valued at hundreds of dollars useless for further analysis, while application of the same sample onto a TLC plate may provide adequate separation (thereby ending the process). At worst, such an error requires disposal of a plate worth several dollars.
Thin-Layer Chromatography of the Skin Secretions of Vertebrates
Published in Bernard Fried, Joseph Sherma, Practical Thin-Layer Chromatography, 2017
The materials and methods for the photodensitometry described here are adapted primarily from Downing105–108 and Downing and Stewart.55 TLC plates are coated with a 0.25-mm layer of silica gel G or H and dried by heating at 120°C for 2 h immediately after setting. Plates are cooled and then predeveloped in diethyl ether or chloroform–methanol (2:1) to wash contaminants to the top. After drying, vertical 5- to 7-mm lanes are scored on the plates with the tip of a dissecting needle; the development of chromatograms on scored lanes prevents spots from expanding beyond the width of the densitometer light beam. A line also is scored at the top of the plate to restrict the ascent of the solvent. The need to score plates disqualifies from use some commercially prepared plates carrying a hard layer of adsorbent because they may crack. Plates impregnated with a binding material or packaged in some paper or plastics also may be unusable because organic compounds incorporated or transferred onto the adsorbent may interfere with visualization.
A semi-industrial reactor for producing biodiesel from waste cooking oil
Published in Biofuels, 2023
Said M. A. Ibrahim, K. A. Abed, M. S. Gad, H. M. Abu Hashish
TLC is a widely used technique for determining the number of different compounds present in a sample. This test determines how many different compounds are present in a mixture on a qualitative level. It also allows one to determine whether different materials are present in two samples. Very small samples are placed on a TLC plate made of a plastic sheet and coated with a thin layer of white powdered silica gel for this analysis technique. The plate is placed in a solvent or solvent mixture container. The solvent flows through the plate to separate the various types of molecules based on polarity and size differences. The biodiesel sample and a control sample of FFAs, methyl oleate, and mono-di-, and triglycerides were spotted on 60 g silica gel thin-layer plates that had been activated at 110 °C for 1 h. Afterwards, the plates were placed in a jar containing the eluting solvent.
Synthesis of cholesterol containing unsymmetrical dimers: a new series of liquid crystals
Published in Liquid Crystals, 2022
Tiago E. A. Frizon, André A. Vieira, Fernando C. Giacomelli, Rodrigo Cercená, Alexandre Dal Bó, Eduardo Zapp, Eduardo Junca, Antônio A. Chepluki, Cassiano D. Tomasi, Luiz B. Ribeiro, Sumbal Saba, Jamal Rafique
All reagents and solvents were obtained from commercial sources and used without any further purification. Column chromatography was performed using Silica Gel (230–400 mesh). Thin-layer chromatography (TLC) was performed using Merck Silica Gel GF254, 0.25 mm thickness. TLC plates were either placed under ultraviolet light or stained with iodine vapour and acidic vanillin for visualisation. TLC monitored most reactions for the disappearance of starting material. Fourier transform infrared (FTIR) spectra (4000–600 cm−1) were recorded on a Bruker Alpha using KBr pellets. Proton and Carbon nuclear magnetic resonance spectra (1H and 13C NMR) were recorded in CDCl3 (with TMS as reference) at 400 and 100 MHz, respectively, on a Varian AS-400. Data are reported as follows: chemical shift (δ), multiplicity, coupling constant (J) in Hertz, and integrated intensity. Abbreviations to denote the multiplicity of a particular signal are: s (singlet), d (doublet), t (triplet), q (quartet), quint (quintet), sext (sextet), and m (multiplet). High-resolution mass spectra (HRMS) were recorded on a Bruker micrOTOF-Q-II (APPI+ mode) mass spectrometer equipped with an automatic syringe pump for sample injection. Melting points were determined on a Microquimica MQRPF-301 digital model apparatus. The phase transitions were investigated by an Olympus BH2 polarised light microscope (POM) equipped with a Mettler hot stage FP-82, and the temperature scanning rates were determined at the rate of 10°Cmin−1. Elemental analysis was carried out using a PerkinElmer 2400Series II CHNS/O Elemental Analyser System.
Fermentative production of rhamnolipid and purification by adsorption chromatography
Published in Preparative Biochemistry and Biotechnology, 2018
Jagurti Jadhav, Sruba Dutta, Sandeep Kale, Amit Pratap
The formation of mono- and di-rhamnolipid was analyzed by thin-layer chromatography (TLC) using silica gel plates (Merck DC Kieselgel 60 F254) and chloroform/methanol/water (65:15:2, v/v/v) as mobile phase.[22] The sample was applied on the TLC plate using glass capillary and the plate was placed vertically in a TLC chamber containing the mobile phase. After plate development, the spots were visualized by spraying the methanol/H2SO4 (50:50, v/v) on plate and were heated at 140°C. The Rf values of the various spots were calculated as the ratio of distance run from the spot and solvent front.