Supercritical Fluid Chromatography
Steven H. Y. Wong, Iraving Sunshine in Handbook of Analytical Therapeutic Drug Monitoring and Toxicology, 2017
SF provides the medium for the partition processes of the analytes in SFC and SFE. A SF is defined as a fluid maintained above its critical pressure and temperature. Consequently, a low-density fluid (gas) can be compressed to a high-density fluid (liquid-like) without discontinuity in density and without gas-to-liquid condensation.15 For performing SFC and SFE, carbon dioxide is the most popular SF, with corresponding critical pressure and temperature of 72 Pa and 31.3°C. Figure 4–2 shows the reduced isothermal plot of reduced density and pressure for carbon dioxide. Reduced temperature, Tr, is defined as: Tr = T/Tc, wherein Tc and T are the critical and experimental temperatures, respectively. Area A represents the one-phase, SF region, whereas liquid carbon dioxide exists in area B. In area C, carbon dioxide exists as both liquid and gas. In performing SFC and SFE, the pressure and temperature are maintained above critical values and within area A. As a SFC mobile phase, diffusion coefficients of SFs range from 0.3 to 1.0 (×10−3) cm2/s, between that of a gas (0.01 to 1.0 [×10–3] cm2/s) and a liquid (0.5 to 2.0 [×10–5] cm2/s), resulting in high-column efficiency, appreciable solute solubility, and applicable molecular mass range from 1 to 1000 Da.1 Additives to the SF could substantially change the analyte diffusion, thus offering added selectivity.
Method of Extraction
Ravindra Kumar Pandey, Shiv Shankar Shukla, Amber Vyas, Vishal Jain, Parag Jain, Shailendra Saraf in Fingerprinting Analysis and Quality Control Methods of Herbal Medicines, 2018
A solution may be classified according to the states in which the solute and solvent occur, since three states of matter (gas, liquid, and crystalline solid) exist. When solids or liquids dissolve in a gas to form a gaseous solution, the molecules of the solute can be treated thermo-dynamically like a gas, similarly when gases or solids dissolve in liquids, the gases and the solids can be considered to exist in the liquid state. In the format of solid solutions, the atoms of the gas or liquid take up positions in the crystal lattice and behave like atoms or molecules of solids. The solutes (whether gases, liquids or solids) are divided into two main classes, non-electrolytes and electrolytes. Non-electrolytes are the substances that do not yield ions when dissolved in water, and therefore, do not conduct an electric current through the solution, for example, sucrose, glycerin, naphthalene, and urea. Electrolytes are substances that form some ions in solution, conduct the electric current, and show apparent “anomalous” colligative properties, that is, they produce a considerably greater freezing point depression and boiling point elevation than do non-electrolytes of the same concentration, for example, HCl, sodium sulfate, ephedrine, and phenobarbital. Electrolytes may be sublimed further into strong electrolytes and weak electrolytes which depend on whether the substance is completely or only partly ionized in water. Hydrochloric acid and sodium sulfate are strong electrolytes whereas ephedrine and phenobarbital are weak electrolytes.
Vesicoscopy
Linda Cardozo, Staskin David in Textbook of Female Urology and Urogynecology - Two-Volume Set, 2017
BlAdder Distension: GAs vs. Liquid? one could Ask if there is Any specific reAson to prefer gAs or liquid for blAdder distension And why it should differ between trAnsluminAl And endoluminAl surgery. typicAlly, gAs is used in vesicoscopy (A sensible choice for A technique inspired by lApAroscopy), And liquid is used in cystoscopy (Also A sensible option to fill An orgAn meAnt for storing urine). However, the literAture suggests thAt A wider use of gAs is A long missed opportunity: bristow demonstrAted experimentAlly in 1893 the benefits of using gAs over liquid
Design of a microfluidic lung chip and its application in assessing the toxicity of formaldehyde
Published in Toxicology Mechanisms and Methods, 2023
Man Su, Xiang Li, Zezhi Li, Chenfeng Hua, Pingping Shang, Junwei Zhao, Kejian Liu, Fuwei Xie
Lung-on-a-chip models can simulate the lung’s microenvironment and functions in vivo, and have great application value for respiratory disease research, drug screening, toxicity assessment and other aspects (Nawroth et al. 2020; Francis et al. 2022; Li et al. 2022; Xia et al. 2023). The physiological microenvironment of the lung is very complex (Martinez et al. 2011). In order to simulate the physiological microenvironment realistically, Sakolish et al. (Sakolish et al. 2022) designed a microfluidic device. It could realize the co-culture of primary human small airway epithelial cells and lung microvascular endothelial cells, which recreates the parenchymal-vascular interface in the end of lung tissue. Varone et al. from Emulate Inc. (Varone et al. 2021) developed a novel organ-chip system that emulates three-dimensional architecture of the human epithelia, and the chip also has mechanical forces function including mechanical stretch and fluidic shear stress. Compared to the chip designed by Varone et al. our chip has no physical forces function. Indeed, the tissue-relevant mechanical forces acting on the chip is a critical element for biomimetic reconstruction of native tissue. Nevertheless, the advantage of the chip we designed is that multiple concentration gradients of gas and liquid can be achieved, as well as air-liquid interface exposure.
Investigation of propellant-free aqueous foams as pharmaceutical carrier systems
Published in Pharmaceutical Development and Technology, 2021
Dóra Farkas, Nikolett Kállai-Szabó, Ágnes Sárádi-Kesztyűs, Miléna Lengyel, Sabrina Magramane, Éva Kiss, István Antal
The image analysis of the microscopic pictures (Figure 7) of foams enables a thorough observation of the foam structure and the properties of the individual bubbles. These properties are highly influenced by the liquid fraction, and the ratio of gas and liquid volumes (Langevin 2017). From the examined systems, the SLS foams contain less water than the Labrasol® ones, the bubbles in the first case have rather polyhedral shapes. The results of the image analysis are summarized in Table 4. The bubbles in the SLS foam are considerably bigger compared to the ones in the Labrasol® foam. This finding is supported by the fact that below the critical micelle concentration, SLS enabled the blow of larger bubbles which can be characterised with a longer lifetime than Labrasol®. Moreover, due to the steeper bubble-forming kinetic curve of SLS, the short period of pumping allows the production of larger bubbles in the produced foams than in case the of Labrasol®. Based on the results, it can be assumed, that from the bubble blowing experiment on dilute solutions we can predict the bubble size and the stability properties of the foams formed from more concentrated solutions.
Toxicological and ecotoxicological properties of gas-to-liquid (GTL) products. 2. Ecotoxicology
Published in Critical Reviews in Toxicology, 2018
Graham F. Whale, James Dawick, Christopher B. Hughes, Delina Lyon, Peter J. Boogaard
Gas-to-liquid (GTL) products are synthetic hydrocarbons produced from natural gas as a feedstock. The basic chemistry of the GTL process was developed in 1925 in Mülheim an der Ruhr (Germany) at the Kaiser Wilhelm Institut für Kohlenforschung by Franz Fischer and Hans Tropsch and is known, after the inventors’ names, as the “Fischer–Tropsch process”. This process involves the synthesis of higher hydrocarbons from a simple carbon source, via so-called synthesis gas (or “syn-gas”, a mixture of carbon monoxide and hydrogen), using a catalyst. For GTL products, the main carbon source is methane, usually from so-called stranded gas, but it can also be methane obtained from biomass digestion or from coal gasification. The methane is converted, by a process called steam-reforming, to “syn-gas”, per the following reaction formula: H2O + CH4 → CO +3H2. The “syn-gas” produced in this process is subsequently catalytically converted to a range of saturated hydrocarbons, per the following reaction formula: (2n + 1) H2 + n CO → CnH(2n+2) + n H2O. The saturated hydrocarbons formed are primarily linear alkanes, with increasing amounts of branched (methyl-groups) alkanes if the chains get longer. In addition, small amounts of cycloalkanes (branched cyclopentanes and cyclohexanes) may be formed as the reaction prolongs. Essentially, the process yields a synthetic crude oil that is made up of a wide variety of alkanes but that is essentially free of unsaturated or aromatic compounds. In addition, in contrast to petroleum crude no sulfur-, oxygen-, or nitrogen-containing compounds are present in GTL synthetic crude from which the GTL products are derived.
Related Knowledge Centers
- Carbon Dioxide
- Carbon Monoxide
- Diesel Fuel
- Gasoline
- Hydrocarbon
- Methane
- Oil Refinery
- Fischer–Tropsch Process
- Hydrogen
- Water–Gas Shift Reaction