A study on determination of theophylline in plasma and urine sample using electromembrane extraction combined with high-performance liquid chromatography-ultraviolet

The main focus of this study is to introduce and validate an electromembrane extraction (EME) method along with HPLC-UV analysis to determine theophylline in the plasma and urine. The main parameters affecting the extraction process such as type of supported liquid membrane organic solvent, donor and acceptor pH, extraction time and voltage were examined. Under optimal conditions, theophylline was extracted from the sample solution at pH=9 to the acceptor solution at pH=13, and as the extraction driving force, a voltage of 50 V was used for 10 min. Considering the main phenomena in EME, a computational model was used to predict the recovery ratio of EME systems. At this voltage and extraction time, the simulation was performed for various pH of the sample and acceptor solutions. Results revealed that the optimum working condition was computed to be when the sample and acceptor solution pH is around 9.5-10 and, 12.5-13, respectively, which are in acceptable agreement with experimental results. Under these conditions, the calibration curve is linear in the range of 50-500 ng/ml with a relative standard deviation of less than 7.0%. The limit of detection and limit of quantitation were 15 and 50 ng/ml, respectively. The enrichment factor and extraction recovery calculated for this method were 42 and 28%, respectively. The developed method was used for the plasma and urine with relative recovery of 95.1% and 69.2%, respectively. Moreover, the relative standard deviation of the biological samples was 4.4% and 3.9% for the plasma and urine, respectively.

Automated summary

This study introduces and validates an electromembrane extraction (EME) method for determining theophylline in plasma and urine using HPLC-UV analysis. Optimal conditions for extraction were determined through examination of various parameters, and a computational model was used to predict extraction recovery. Experimental results agreed with simulated results, showing a linear calibration curve in the range of 50-500 ng/ml with low relative standard deviation.