Development of a spectrofluorimetric method for the determination of ofloxacin in urine.

A simple, accurate, rapid, and sensitive spectrofluorimetric method for the determination of ofloxacin in urine was developed by means of first derivative matrix isopotential synchronous fluorescence spectrometry (MISF). The calibration curve was found to be linear in the concentration range 40-320 ng/mL. The method allows the determination of compound in samples with unknown background fluorescence without the need for tedious pre-separation. Synchronous scans are performed along a trajectory that connects points of identical intensity in a three-dimensional fluorescence spectrum. The unknown analytical signal of the urine is suppressed from the MISF spectrum by calculating its first derivative at λex = 319.2 and λem = 465 nm. In order to ensure maximum sensitivity and adequate selectivity, the experimental variables affecting fluorescence intensity were studied in the ofloxacin band centered at λex = 333 and λem = 460 nm. As result, the determination was performed in a water medium at pH 7.2, adjusted by using sodium dihydrogen phosphate as a buffer solution. Calibration graphs were subjected to a comprehensive statistical analysis. The detection limit according to Long and Winefordner was 8.4 ng/mL, and the detection limit proposed by Clayton was 13.9 ng/mL.

Automatic chemiluminescence-based determination of carbaryl in various types of matrices.

Carbaryl, a modern pesticide widely used for both agricultural and non-agricultural purposes, was determined from the chemiluminescence produced in its reaction with Ce(IV) in a nitric acid medium containing rhodamine 6G as sensitizer, using flow-injection techniques. A straightforward automatic method based on measurements peak height and peak area, which are directly proportional to the carbaryl concentration, was thus developed. Calibration graphs are linear over the concentration range from 50 to 2000 ng mL(-1). The limit of detection, as determined according to Clayton, is 45.6 and 28.7 ng mL(-1) for peak height and peak area measurements, respectively. The relative standard deviation for 10 samples was less than 1.4% with both types of measurements. Two commercial formulations containing carbaryl were analysed using both types of measurements, which provided acceptable recovery values. Solid-phase extraction was used to concentrate and separate the analyte from the matrix. The method was successfully applied to the analysis of spiked water samples as well as in soil and grain samples. The proposed method exhibited a high selectivity no other pesticide containing the naphthalene group such as antu, napropamide or naftalam, etc., was found to interfere with the determination of carbaryl.