Abstract
GC with nitrogen phosphorus detection and HPLC with UV detection were used to determine midazolam levels in rabbit plasma following ocular and nasal administration. For GC with nitrogen phosphorus detection, the analyte was extracted from the plasma using a three-step liquid-liquid extraction including extraction with an isopropanol/butyl chloride mixture in an alkaline solution, followed by extractions with 1 M HCl and finally with an alkaline solution of butyl chloride.
The recovery of midazolam was very dependent on the sample alkalization time prior to the final extraction. The procedure increased the recovery of midazolam up to 99.6%.
Improved sample preparation led to a significant increase in the sensitivity of the determination by GC with nitrogen phosphorus detection. The achieved detection limit was 0.34 ng/ml, which is ten times lower than that obtained using HPLC with UV detection.
The small plasma volume was another advantage of the GC with nitrogen phosphorus detection method (200 μl per assay). Both administration routes of the anesthetic (nasal and ocular) resulted in comparable plasma midazolam levels.
Kinetic simulation of the midazolam plasma was performed for both administration routes.