Simultaneous determination of dimethadione and trimethadione by infrared-spectrometry: application for mean intracellular pH measurement.

A simple infrared-spectrometric method for the simultaneous determination of dimethadione and trimethadione in plasma is described. The method is based on the absorption band of the carbonyl group for trimethadione at the wavenumber of 1740 cm-1 and for dimethadione at the wavenumber of 1770 cm-1. The accuracy and precision of the method are excellent; at a dimethadione and trimethadione concentration of 0.5 mmol X 1(-1) the coefficient of variation for the determination of both compounds is less than 1%, which is better than that for the ultraviolet spectrometric or gas-liquid chromatographic methods. The method can be used for the determination of the ratio trimethadione/dimethadione in the clinical setting as a sensitive check of the patient's adherence to therapy. It can also be used for the determination of dimethadione as an indicator for the mean body intracellular pH.