Determination of theophylline in plasma ultrafiltrate by reversed phase high pressure liquid chromatography

Direct injection determination of theophylline and caffeine in blood serum by high-performance liquid chromatography using an ODS column coated with a zwitterionic bile acid derivative

“…Therapeutic drug monitoring is necessary to establish effective therapy because drugs have a narrow therapeutic range. [1][2][3] A variety of high-performance liquid chromatographic (HPLC) methods have been proposed with the increasing demand for simple, fast and automated determinations of drugs in biological fluids. Under general mobile phase conditions, however, most proteins are denatured and irreversibly adsorbed on conventional reversed-phase columns, resulting in a drastic deterioriation of chromatographic efficiency and easy clogging of the columns.…”

Determination of theophylline in plasma by electron capture gas chromatography

“…Recent modifications in high pressure liquid chromatography, e.g., the use of molecular filtration or precipitation to remove proteins prior to chromatographic analysis, have considerably improved the usefulness of the method (9,13-15). Problems associated with column packing instability have been largely eliminated (9); however, the retention times needed to adequately resolve theophylline and the internal standard from coextractable material are long (10 to 30 min compared to 3 min reported here). Sample requirements vary from 10 µ\ to 1 ml (9, 13-15) which is well within the limits of the electron capture gas chromatographic method.…”

“…Temperature programming is required in several of the methods (6,7) and a lack of a proper internal standard has led, in many instances, to high relative standard deviations. A high pressure liquid chromatographic method offering several improvements over current methods has recently been published (9).…”

Simultaneous and Specific Determination of Proxyphylline, Theophylline and other Xanthine Derivatives in Serum by High Pressure Liquid Chromatography

“…Several methods have been described for the determination of theophylline in serum by means of reverse-phase high pressure liquid chromatography using 7-10% acetonitrile in 0.01 M acetate buffer adjusted to pH 4 (Franconi et al 1976;Orcutt et a/. 1977) or a 0.01 M phosphate buffer with similar pH (Nelson et al 1977) as the mobile phase.…”

“…Direct injection on the column of smaller, untreated serum samples (about 5 pl), which has been advocated by some investigators, will in our experience lead to a rapid deterioration of the column. Molecular filtration is a means of removing the plasma proteins prior to the chromatographic analysis (Franconi et al 1976), but the protein precipitation with trichloroacetic acid used in the present method is a fast and efficient procedure, which is also a relevant fact in comparison with ethanol (Nielsen-Kudsk et al 1978) Experimental addition of the following compounds to serum samples in amounts yielding therapeutic concentration did not reveal any analytical interference : aspirin, salicylic acid, indomethacin, acetaminophen, diazepam, oxazepam, chlorpromazine, amitriptyline, nortriptyline, imipramine, desipramine, clomipramine, lofepramine, phenprocoumon, furosemide, papa-verine, alprenolol, metoprolol, ajmaline, orphenadrine and phenylephrine. In the analyses of serum samples from patients under treatment with the drugs subsequently mentioned, no interference with the determination of the xanthine derivatives in question was observed.…”