tailieunhanh - Introduction to Modern Liquid Chromatography, Third Edition part 37

Introduction to Modern Liquid Chromatography, Third Edition part 37. 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. . | 316 IONIC SAMPLES REVERSED-PHASE ION-PAIR AND ION-EXCHANGE CHROMATOGRAPHY A or BH by ion-pairing ionized solute acids A 4- X Has es BH X- lon pair A X BH X- hydmphihe less retained RPC hydrophobe more retained tn RPC Buffers that ion-pair are usuallyorganic ions and they tend to be more hydrophobic than inorganic ions. For example trifluoroacetate is a significant ion-pairing agent Section whereas phosphate is non ItpHrina by inorganic buffers is usually not signdihiuit although seme studies suggesr that evenphosphytc may undergo weak ion-pairing with protonated bases 8 . For further information on ion-pairingby ghegufttr . BufferSaahCtyandEqs ipn gtComghSn iyty. Snetganicbuffers anS cerboyytic acids are un ai y sttbSe Vui emiyetaropshne to rxiOatioo witt g consemgrsis increase inshclrUVabsorbamov aswavtlemgtht O not. For exrmpie altheugh pure triethhlanune TEn thouidbe tcimpman at waiElengths 200 nm one study 9 reported that a 1 aqueous solution of TEA 90 mM has an absorbance 2 AU at 220 nm. Citrate Isuffcrshavy beyn claimedio cstycp sea esh steed whareasoHer reports emu disc 1 0 1 afeppliedep HPLCeyyigment 10 .OnelaPofntmry has experisncedoganyiona equicmentproniemssllogappearedansociased qkki He use of citrate guSterirl buf tliis behavids haynotbryn likyly thaycr 10 mM can be used without concern and its use is convenient forappiiyatsonfwhetcpHis no be vogtodcogticuoosSg oveagte range 2 pH 01 the rrc oaimaginedi problems gythesii e cirraea sttaflativrSmniyh UVcotnSf gf2 om 7 740 and the adoilayiiStg of frvoeayii ahrmatsve gyffers acetate make citraseaselgom-ugfd buCacbymhst woikerr. Peyserped OuSfero UV detectmhin rhs 2g0 is 2y0 ninregron s ottenutadfoasampiys wiHtaw coiicciitrayom gp compountls diatabsorbpyotlyyt higprr buffers harebeea prcferfec rorrhisapplirynion aHong atghcmobile-phase pH can be accommodaged wighin ghe .