China
Africa
Explore chapters and articles related to this topic
Chemistry and Isotopes of Iodine
Published in Erwin Regoeczi, Iodine-Labeled Plasma Proteins, 2019
For a limited period in 1973, the NaI25I supplied by one of the distributors ceased to give good yields of labeled proteins by the solid-phase lactoperoxidase method in the absence of carrier KI. The cause of this temporary setback has never been resolved,30 but one may assume that the radioactivity could have been in a chemical form from which the enzyme was unable to generate a substituting species. Situations like this require trouble shooting and the method of choice is paper chromatography.
Planar Chromatography
Published in Joseph Chamberlain, The Analysis of Drugs in Biological Fluids, 2018
Although Tswett’s original column method proved very useful for preparative separations in natural product and organic chemistry, it did not find extensive favor as an analytical method. Paper chromatography was probably the earliest type of chromatography that was enthusiastically developed for analytical purposes. Its advantage over the classical column technique was that the components could be readily detected by viewing the paper after development of the chromatogram. The general method of paper chromatography consists of spotting a solution of the sample to be analyzed directly on the paper. The solvent is allowed to evaporate and the paper is then subjected to a migrating mobile phase using either an ascending or descending technique (Figure 5.1). For descending chromatography, the end of the paper is held in a trough of mobile phase, usually by the weight of a glass rod, and the mobile phase flows down the paper by a combination of capillary attraction and gravity. This process makes for relatively rapid chromatography. Due to the wetting of the paper as the chromatography proceeds, the solvent front will be clearly visible in this type of chromatography. It is usual to allow the solvent front to flow to within a few centimeters of the end of the paper before terminating the chromatography, so as to characterize the components of the sample by relating their distance from the origin to that of the solvent front — the Rf value. In some applications, the solvent may be allowed to run off the end of the paper, but this raises questions as to when to stop the chromatography before analytes are lost by elution, and how to characterize unknown components.
Current Perspectives and Methods for the Characterization of Natural Medicines
Published in Rohit Dutt, Anil K. Sharma, Raj K. Keservani, Vandana Garg, Promising Drug Molecules of Natural Origin, 2020
Muthusamy Ramesh, Arunachalam Muthuraman, Nallapilai Paramakrishnan, Balasubramanyam I. Vishwanathan
Paper chromatography is the simplest and widely used chromatography technique for the isolation, identification, and quantification of natural compounds. In paper chromatography, solvent flow is occurring on a filter paper. Two major principles are involved in paper chromatography, i.e., (i) paper adsorption chromatography: A paper impregnated in silica media, and it acts as a stationary phase. The organic solvent acts as the mobile phase; and (ii) paper partition chromatography-moisture present in the pores of filter paper acts as a stable phase and organic solvent acts as a mobile phase. The separation of particles in paper chromatography is based on partition than adsorption. What man filter papers No. 1, 2, 3, 4, 20, and 40 are used for stationary medium. It consists of 98–99% α-cellulose and 0.3–1% β-cellulose. In addition, the modified papers (acid/base washed papers), hydrophilic papers, and hydrophobic papers are also used as the stationary phase. To run a paper chromatogram, the sample is dissolved in a solvent and spotted at the base of the paper. The paper is dried and allows developing the spots on a paper. Two types of mobile phase composition are used: (i) hydrophilic mobile phase, i.e., isopropanol:ammonia:water; methanol:water; and n-butanol:glacial acetic acid:water; and (ii) hydrophobic mobile phase, i.e., dimethyl ether:cyclohexane. While running paper chromatography, the atmosphere must be saturated with the solvent vapor. The chromatogram is developed in different ways: (i) ascending; (ii) descending; (iii) ascending and descending; (iv) circular/radial; and (v) two dimensional. After developing the chromatogram, the components are detected visually if it is colored. Alternatively, iodine chamber, UV chamber, reagents are used for the detection of a specific class of components. The Rf (distance traveled by sample/distance traveled by the solvent) and Rx values (distance traveled by sample/distance traveled by the standard) are used as an indicator of sample class with the reference sample. Paper chromatography is employed for the separation of compounds from mixtures, carbohydrates, proteins, amino acid sand impurities (Block et al., 2016). A systematic assembly of paper chromatography is illustrated in Figure 2.4.
Drug dependence as a split object: Trajectories of neuroscientification and behavioralization at the Max Planck Institute of Psychiatry
Published in Journal of the History of the Neurosciences, 2023
In addition, a new chemical-diagnostic approach was devised within the biochemical group. In the early 1950s, Jatzkewitz developed a diagnostic testing method for addictive substances in urine (Jatzkewitz 1954, 1953). His test was based on the new, broadly applicable biochemical method of paper chromatography adopted by several research groups for the intention of developing drug tests (Schmidt 1959). With Jatzkewitz’s test, not only nicotine, morphine, and methadone but also synthetic drugs such as amphetamines (especially Pervitin®) could be detected in urine. It took only half an hour to complete the test, and the new chromatographic tests changed the repertoire of medical treatments for addicted patients. For the first time, it became possible to monitor abstinent patients in an uncomplicated and spontaneous way. Some clinicians expressed the hope that the tests would now allow them to carry out the lengthy inpatient withdrawal and rehabilitation treatment on an outpatient basis (Max-Planck-Gesellschaft 1959, 241–42).
Bioactive compounds and therapeutic role of Brassica oleracea L. seeds in rheumatoid arthritis rats via regulating inflammatory signalling pathways and antagonizing interleukin-1 receptor action
Published in Biomarkers, 2021
Manal A. Hamed, Asmaa F. Aboul Naser, Mona E. Aboutabl, Abeer F. Osman, Entesar E. S. Hassan, Wessam M. Aziz, Wagdy K. B. Khalil, Ayman A. Farghaly, Ali M. El-Hagrassi
The UV spectra were recorded on Shimadzu model UV-240 and 2401 PC spectrophotometer (Shimadzu Inc., Tokyo, Japan). EI/MS thermo scientific (Italy). Buchi apparatus was used to determine the melting points of the isolated pure compounds in open capillaries. NMR experiments were recorded on Bruker spectrometer (Switzerland) 500 (1H NMR spectra: 500 MHz; 13C NMR spectra: 125 MHz). The chemical shifts are given in δ (ppm) relative to tetramethylsilane (Me4Si). Column chromatography (CC) was carried out on Polyamide S6: (Ridel-De-Haen AG, Seelze Haen AG, Seelze Hanver, Germany) and Sephadex LH-20 (Pharmazia, Uppsala, Sweden). Paper chromatography (PC, descending) Whattman No. 1 and 3 mm papers, using solvent systems (1) H2O, (2) 15% HOAc (H2O: HOAc, 85:15), (3) BAW (n-BuOH: HOAc: H2O, 4:1:5, upper layer) and (4) BBPW (C6H6:n-BuOH:Pyridine:H2O, 1:5:3:3, upper layer.
Radiosynthesis, molecular modeling studies and biological evaluation of 99mTc-Ifosfamide complex as a novel probe for solid tumor imaging
Published in International Journal of Radiation Biology, 2018
Mohamed A. Motaleb, Dina M. El-Safoury, Walaa H. Abd-Alla, Gehanne A. S. Awad, Tamer M. Sakr
Quality control of 99mTc-ifosfamide complex was assessed by ascending paper chromatography and HPLC to evaluate the percent of 99mTc-ifosfamide, free 99mTcO4−, and reduced hydrolyzed-99mTc colloid species. In case of paper chromatography, acetone was used to check the percent of 99mTcO4−, which moved with the solvent front (Rf = 0.9), while other species remained at the point of spotting (Rf = 0.0). Saline was used as a developing solvent for another paper strip to determine the percent of reduced hydrolyzed-99mTc colloid species, which stayed at the start point (Rf = 0.0), while 99mTc-ifosfamide complex and 99mTcO4− moved at the top of the paper (Rf = 0.9).