Comparison of fluorocarbon and hydrocarbon weak anion exchange columns for the separation of surfactants with indirect detection

Abstract

Short Communications ~~ ~~ separations are performed between 60 and 140 "C, the temperature limitations of these connectors do not seem too restrictive.Deactivation of the quartz couplings was essential for obtaining reproducible performance: this applied not only from the standpoint of inertness, but also to their ability to withstand high pressures. Untreated couplings regularly burst upon introduction of carbon dioxide a t moderate pressures because of the formation of fissures along the inner wall which grew until failure occurred.The deactivation layer formed a stabilizing bridge which prevented the growth of fissures and enabled the use of the couplings at pressures a s high as 10,000 psi. Similar observations of the embrittlement of raw and deactivated fused silica tubing over a wide range of dimensions have also been made in our laboratory.The epoxy adhesive used to bind the quartz coupling assembly cures to form a very hard glassy solid. Its point of contact with the fused silica tubing of the column and restrictor produces high stress which can lead to spontaneous breakage. A short piece of thin walled polyimide tubing inserted over the column or restrictor tubing at the interface to the coupling provides strain relief and produces a more robust connection. Strain relief is especially important with thin walled fused silica tubing (wall thickness <75 pm) but is not necessary with thick walled tubing (wall thickness >75 pm).In addition to coupling columns and restrictors, these quartz unions can also be used for efficient coupling of two columns coated with similar or different stationary phases in order to furnish higher resolution, or for selectivity tuning, respectively.They also provide an excellent interface between columns and retention gaps Hundreds of connections with fused quartz couplings have been made with success in our laboratories and fewer than 10 % resulted in poor connections The latter were usually a result of leaks in the assembly or breakage of the coupling References [ l ] M. Novotny, HRC & CC 9 (1986) 137.

Preparation of branched-polyfluoroalkylsilane-coated silica gel columns and their HPLC separation characteristics

“…More detailed comparisons of HFD columns with C18 (ODS) columns have been conducted [12][13][14][15][16][17][18][19][20]. The pentafluorophenyl (PFP) phase [21][22][23] and other fluorinated silica gel packings, perfluoroethoxyethanol [24], pentafluoroanilinopropyl [25], pentafluorobenzamidopropyl [26], chiral R-N-(pentafluorobenzoyl) phenylglycine [27], heneicosafluorodecyl (HFDo) [19], and trifluoroacetamido [28], have been synthesized and characterized. Recently, a dual-zone material (DZM) has been developed by use of a mixed fluorocarbon-hydrocarbon phase [29].…”

Multimodal liquid chromatography of small molecules

“…The uorocarbon-amine anion exchange column showed a better separation of long chain compounds. 78 The separation of longer chain sulfate and sulfonate surfactants (C6-C18) from alkyl phosphates in 30 minutes was possible by using an Alltech silica multimodal RP/phenyl-anion exchange column. 79 Detection limits in the nanogram range were attained using indirect photometric and conductimetric detection.…”