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Supercritical Fluid Chromatography Instrumentation
Published in Grinberg Nelu, Rodriguez Sonia, Ewing’s Analytical Instrumentation Handbook, Fourth Edition, 2019
Thomas L. Chester, J. David Pinkston
Chromatography, in its various forms, is the most frequently used analytical technique for tasks such as assays, stability testing, and screening and is often the first step in chemical problem solving. There is tremendous emphasis in industry on performing product development and manufacturing better, faster, and cheaper. Also, when things go awry, the causes of problems must be discovered and fixed as quickly as possible. Faster analyses, especially when combined with the ability to develop analytical methods faster, lead to tremendous savings in research, time- and cost-to-market expenses, manufacturing, and problem solving. There is also much interest and energy in supplementing or replacing traditional chemical processes, including analyses, with green processes to meet ever-changing environmental challenges. The desire to improve speed, lower costs, and greatly lower or eliminate the environmental impact of chemical separations is driving the interest and growth in supercritical fluid chromatography (SFC).
Synthesis of Higher Diamondoids by Pulsed Laser Ablation Plasmas in Supercritical Fluids
Published in James E. Morris, Kris Iniewski, Graphene, Carbon Nanotubes, and Nanostructures, 2017
Sven Stauss, Sho Nakahara, Toru Kato, Takehiko Sasaki, Kazuo Terashima
Because of their high dissolving power, SCFs have also shown excellent potential for chemical analysis applications. Supercritical fluid chromatography (SFC), using scCO2 as a mobile phase, is especially suited for the separation of compounds that are sensitive to organic solvents commonly used in HPLC [47,48]. SFC often shows superior performance compared to conventional HPLC because, besides avoiding the use of organic mobile phases such as acetonitrile, the diffusion coefficients are an order of magnitude higher than in liquids (cf. Table 9.1). Consequently, the transfer of solutes through the separation column encounters less resistance, with the result that separations may be realized more rapidly or with higher resolution in comparison to HPLC.
The generation and reactions of sulfenate anions. An update
Published in Journal of Sulfur Chemistry, 2022
Adam B. Riddell, Matthew R. A. Smith, Adrian L. Schwan
Having already made significant contributions to the palladium catalyzed arylation of alkyl and aryl sulfenate anions, Walsh and coworkers [62] expanded their success to the palladium catalyzed enantioselective alkenylation of sulfenate anions. This work was primarily performed as a means of expanding the scope of sulfoxides available by enantioselective cross-coupling sulfenate reactions [62]. The optimal conditions involved mixing a 2-trimethylsilylethyl sulfoxide with a vinyl bromide (2 equiv.) in the presence of [Pd(allyl)Cl]2 (2.5 mol%), JosiPhos 10 (5 mol%) and CsF (3 equiv.) at 40 °C in THF [62]. With these conditions, the researchers synthesized 15 enantioenriched alkenyl aryl sulfoxides (41) in yields ranging from 41 to 91% and e.e.’s ranging from 63 to 92% (Scheme 25) [62]. The mechanism for this reaction is very similar to that described for arylation of sulfenate anions illustrated in Scheme 7. As explained in the previous section, these conditions were extended to the synthesis of diaryl and alkyl aryl sulfoxides in good enantioselectivities [62]. The enantioenriched products were synthesized with a preference for the (S)-configuration which was confirmed by chiral supercritical fluid chromatography and optical rotation [62].
The separations using pure water as a mobile phase in liquid chromatography using polar-embedded stationary phases
Published in Green Chemistry Letters and Reviews, 2019
Szymon Bocian, Katarzyna Krzemińska
Over the recent years, green analytical chemistry has been developed to reduce or remove the use of environmentally hazardous organic solvents and reagents (1–6). The well-known principles of green chemistry (1), three Rs (Reduce, Replace, Recycle) are commonly used in the field of analytical chemistry methods, including chromatographic analyses. The most important direction to make analytical chromatography more environmentally friendly is the replacement of hazardous solvents. It may be done using more green alternatives of solvents or by the reduction of the amount of generated organic waste (2, 7). As an example, ethanol may be used instead of acetonitrile in RP LC. Unfortunately, such greener solvent is usually less effective (8). The most interesting idea is to use pure water as a mobile phase (9, 10). This idea may be realized at a normal, elevated and subcritical temperature (11–20). An alternative to purely aqueous HPLC may be the supercritical fluid chromatography with pure water (21–23). However, the application of pure water in typical reversed-phase chromatography is usually associated with phase collapse, non-repeatable retention times, peak tailing. In this case using an apolar stationary phase such as C18 does not ensure enough retention towards polar compounds (24, 25).
Paraffin wax precipitation/deposition and mitigating measures in oil and gas industry: a review
Published in Petroleum Science and Technology, 2020
Current progresses in laboratory expertise have empowered the study of a stretched variety of constituents existing in pipeline deposits. For instance, High temperature gas chromatography (HTGC) and Supercritical fluid chromatography (SFC) support the detection of paraffin waxes of 100 carbon atoms and above, although hitherto C40 was near to the frontier of the technique. Supercritical fluid chromatography technique avoids employing the usual very high temperatures of HTGC and thereby suffers less hazard of sample dissolution. The procedure is exclusively suitable as a feed for biological tracer study using Gas Chromatography-Mass Spectrophotometry (GC-MS) (Wenda and Qiyu 2014).