Determination of theophylline in blood serum by UV spectrophotometry and partial least-squares (PLS-1) calibration Original Research Article

Partial least-squares (PLS-1) multivariate calibration of spectrophotometric data have been applied to the determination of theophylline in blood serum. After sample deproteinization and alkalinization, the electronic absorption spectrum (in the 265–302 nm region) is processed using a calibration design which includes a series of serum pools spiked with theophylline. The concentrations lay within the therapeutic range (0.0–35.0 μg ml−1). All statistical indicators (prediction in validation sets, precision and accuracy) are reasonably good. A comparison of this method with an immunofluorescent polarization technique revealed no significant differences in their prediction abilities. Studies in the presence of triglycerides, bilirubin, hemoglobin and caffeine showed that only the latter was able to interfere, as with other theophylline monitoring techniques.