tailieunhanh - Introduction to Modern Liquid Chromatography, Third Edition part 77

Introduction to Modern Liquid Chromatography, Third Edition part 77. High-performance liquid chromatography (HPLC) is today the leading technique for chemical analysis and related applications, with an ability to separate, analyze, and/or purify virtually any sample. Snyder and Kirkland's Introduction to Modern Liquid Chromatography has long represented the premier reference to HPLC. This Third Edition, with John Dolan as added coauthor, addresses important improvements in columns and equipment, as well as major advances in our understanding of HPLC separation, our ability to solve problems that were troublesome in the past, and the application of HPLC for new kinds of samples. . | 716 ENANTIOMER SEPARATIONS here R- or S-enantiomer T is the phase ratio Section . Further manipulation of Equation provides two additional relationships 1 AW AS InJQ ----------1- l- T R R and AAGJ. AGJ - GJ -X T tn -X T- Inn . That is plots of In z against 1 T are predicted to be linear with a slope that is proportional to AH . Likewise the separation factor a for two enantiomers R and S can be related to the difference in their standard free energies of solute-selector association A AG py asweh as relate differences ie enthalay chaegc AAH and entropy change AAS0 . Thermodanami cs of DirectChromatognaphicEnan ti omer Sepanation If a single tyna op ennntiorelrotive solutc-sclcntor inrnaactionipshlelyconeideeed and other adeorpiroii mcchaeisme doiioe hohrforrhosotaie Wi nFquacioinLI to can licacloteilio k asd S by k Ktre Values of AlG0 AOhT0 nndAAjnn eeanbo deriohdfoomval ugs of am function od T since the osuellpunOnown phoae ratio V cancels in Equation but not in Eq. . Plots of In k against 1 T are usually positive k decreasing with T implying a negative value of AW0 or an enthelpically controlled retention process. That is attractive mostly electrostatic type noncovalent interactions between solute and seleoeoor esutt in va lues of Ks n U The latte cconttiUutione contention are usuallyopiroocd by eritcopio deeds siiiccOitsoliotc-icIccO ncnaylcx is meet ordered lepored with the soluteio tie mobOe rOH e- AS ahd AAW HASnrsobservedCoewenepaeiety of OhfcrentCSP- uialytemobile-phase systems. The usuanresint ina docrnase an ealuesofy farhioOaceemparaludetl TOa opposite beheviorlanincteasa inenoneioseiecsivity with T lceC ttPenSaopiodlrecon-trolled china- reevneutiOT hoe boanobsOrvcdinyfew aasesmvoSvingpoiyseacdetiTti and protesn-eppe lattro dooe Oten rehmO tnpotdiblobin Tlgsite-reloted de solvation phedomeva C17O adePor Oonfoemdniodaa eCancdaiabackboneaof tiO selector 17e 177 .NonVnead vtnts nf lnh

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