Uniformly sized, polymer-based packing materials affording excellent chromatographic performance in semimicro HPLC were prepared from mixtures of alkyl methacrylate and glycerol dimethacrylate by a copolymerization technique using a multistep swelling and polymerization method. A column efficiency of up to 13000 plates was obtained for a 2-mm-i.d. x 150-mm column with beads prepared from a 1:1 (v:v) mixture of an alkyl methacrylate and glycerol dimethacrylate. The packing materials exhibit a considerable improvement in column efficiency, as demonstrated on the separation of polyaromatic hydrocarbons (PAHs) having a relatively long retention time, which thus far has been a serious problem of polymer-based packing materials. Detailed studies suggested a rather limited optimum pore size, and its distribution was depicted to get the excellent column efficiency on polymer-based packing materials.
Abstract. The construction and performance of dual-and triple-column systems for the analysis of dilute drug samples are described. The systems are based on the following two separation processes: (1) deproteinization and analyte fractionation using a short polymer-coated mixed-function (PCMF) phase (10 mm x 4.0 mm i.d. column) and, (2) final separation using a C18 semi-microcolumn (1.5 to 2.0 mm i.d.). The surface structure of the MF phase and the geometry of the packed column for the primary separation made it possible to inject hundreds of microliters of serum samples into the system. Analytes separated in the primary chromatography are transferred to the main column with or without an intermediate column (35 mm x 1 .O mm i.d.). A system using an intermediate column was designed to save time of analysis when a 1.5-mm i.d.(and smaller) main column was used. The systems showed an increased concentration sensitivity for drug molecules, such as diazepam, carbamazepine, and phenobarbital, without any loss in chromatographic efficiency. Carbamazepine and phenobarbital at 12.5 ppb and 50 ppb, respectively, in human serum were detected with good S/N ratio.
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