Direct determination of quinidine in urine

The determination of quinidine in urine was performed by means of first derivative matrix isopotential synchronous fluorescence spectrometry. This new technique, which consists of performing synchronous scans through a trajectory joining points of equal intensity in a three-dimensional spectrum of fluorescence spectrometry, allows to determine drugs such as quinidine in a fluorescent matrix like urine without the need for tedious pre-separation. In this case the application of first derivative data was necessary. The analyses were performed in aqueous medium at pH 6.2 provided by the addition of phosphate buffer solution. The calibration graph was linear between 0.2 and 1.0 μg/ml of quinidine and the obtained value of repeatability of the method was a standard deviation of 2.9 × 10−3 μg/ml.