Analysis of poly(ethyl methacrylate)s by on-line hyphenation of liquid chromatography at the critical adsorption point and nuclear magnetic resonance spectroscopy

Liquid chromatography at the critical adsorption point (LC CAP) with on-line NMR detection (on-line LC CAP NMR) was utilized for analysis of tacticity distribution of stereo-regular poly(ethyl methacrylate)s (PEMAs). The separation of a model PEMA sample composed of four constituents with similar molar masses (Mw = (14-16) x 10(3) g mol-1) differing in their tacticity (rr triad content = 0, 33, 68, and 89%) was achieved by LC CAP with a mixed eluent composed of acetone, acetone-d6, and cyclohexane. The tacticity composition within each peak eluted from the LC CAP column was directly determined by a 750-MHz 1H NMR spectrometer that was used as a real-time detector in the continuous-flow mode. Tacticity distribution in a particular PEMA sample with mm/mr/rr = 2/45/53 and narrow molar mass distribution of Mw/Mn = 1.05 has been revealed by the LC CAP NMR technique.

Use of porous pyrolytic carbon for analytical and microscale high-performance liquid chromatographic bioseparations.

Porous carbonaceous adsorbent was prepared by carbonization of saccharose in silica gel pores followed by leeching out of the silica matrix. The product of pyrolysis was then deactivated by hydrogenation. The resulting adsorbent shows intermediate sorption properties between those of the highly polar pyrolytic glassy carbon and the hydrophobic graphitized carbon. The microparticulate mesoporous carbon was examined for its use in capillary HPLC separations. The separation of selected stereoisomers in a 320 microm I.D. capillary column packed with the porous carbon particles is described and discussed. Additionally, the porous carbon filled with dextran gel was tested as a material for direct HPLC analysis of drugs in human serum.

Study of bilirubin binding in human serum by high-performance liquid chromatography.

We describe a high-performance single-run liquid chromatographic method for the separation of protein-bound and "free" (loosely bound) bilirubin in human serum samples. The procedure is based on both the size-exclusion and the adsorptive properties of the column packing material, LiChrosorb Diol. The elution of all sample constituents is accomplished by means of an aqueous mobile phase containing a phosphate-buffered solution of human serum albumin or adult serum, supplemented by a small amount of bilirubin. The efficacy of the developed method is exemplified by assaying the bilirubin binding to human adult and infant sera.