Rapid determination of serum theophylline levels using the MPLC short column concept

Many procedures are currently available demonstrating the feasibility of the analysis of serum theophylline concentrations by high performance, high pressure liquid chromatography utilizing chromatographic columns which can only be described by the term "expensive" in terms of column life and cost. We have developed and evaluated a rapid "medium pressure, medium performance" liquid chromatographic (MPLC) method for theophylline in serum utilizing a chromatographic column that costs up to 1/3 the cost of current HPLC columns. Less than 0.2 ml of serum is required for each determination, yet the sensitivity of the method is easily less than 1 mg/liter. The method involves liquid extractive isolation, chromatography on a micro column (4.6mm x 10cm) of RP-18 and provides adequate selectivity, accuracy and precision for routine and non-routine (neonatal) theophylline determinations. We have found no endogenous or exogenous interferences. Reproducibility for the microscale method is controlled through the use of hydroxypropyl theophylline as an internal standard.