A sequential injection fluorometric procedure for the determination of procaine in human blood and pharmaceuticals

An automated procedure for the assay of procaine hydrochloride in human blood and pharmaceuticals was developed using a sequential injection (SI) technique with fluorometric detection and fluorescamine as the fluorescence probe. A few microliters of fluorescamine and procaine hydrochloride solutions were used in the SI system leading to the formation of a derivative, which was then excited by a 400-nm LED and whose emitted fluorescence was monitored at a wavelength of 494 nm. A linear calibration graph was obtained with 10-200 ng mL(-1) (procaine) by loading 10.0 microL of sample solution and 5.0 microL of fluorescamine solution (both 0.125 % m/v). A detection limit of 2.6 ng mL(-1), defined as 3 times the blank standard deviation (3sigma), was achieved along with a sampling frequency of 25 h(-1) and a precision of 2.1 % RSD at the 50.0 ng mL(-1) level. Procaine contents in injection solutions from various pharmaceutical manufactures were analyzed and reasonable agreement was achieved between the values obtained by using the present procedure and the documented spectrophotometry, and both were coincident with the nominal concentrations. In addition, the degradation of procaine in human blood was investigated. A fast degradation of procaine in human blood was observed for the first 30 min, while afterwards the degradation was retarded.