Monitoring of chlorsulfuron in biological fluids and water samples by molecular fluorescence using rhodamine B as fluorophore.

A new simple methodology is proposed for chlorsufuron (CS) traces quantification based upon enhancement of rhodamine B (RhB) fluorescent signal. Experimental variables that influence fluorimetric sensitivity have been studied and optimized. The zeroth order regression calibration was linear from 0.866 to 35.800µgL(-1) CS, with a correlation coefficient of 0.99. At optimal experimental conditions, a limit of detection of 0.259µgL(-1) and a limit of quantification of 0.866µgL(-1) were obtained. The method showed good sensitivity and adequate selectivity and was applied to the determination of trace amounts of CS in plasma, serum and water samples with satisfactory results analyzed by ANOVA test. The proposed methodology represents an alternative to traditional chromatographic techniques for CS monitoring in complex samples, using an accessible instrument in control laboratories.

Determination of rosuvastatin in urine by spectrofluorimetry after liquid-liquid extraction and derivatization in acidic medium.

Statins are a class of drugs mostly used for treating hyperlipidemia, and rosuvastatin is the newest drug in the market belonging to this class. In this present work, a method was developed based on the molecular fluorescence technique, with the objective to quantify rosuvastatin in urine samples. For this purpose, the study of several parameters was made to achieve the maximum analytical signal (under reaction with sulfuric acid during 40 min). Also, a previous step to avoid matrix interference was carried out (liquid-liquid extraction). The limit of detection (LOD) and the limit of quantification (LOQ) were 0.38 and 1.28 mg L(-1), respectively. Linear relationship between rosuvastatin concentration and it's fluorescence intensity was found until 5.0 mg L(-1). The proposed method was tested in several samples spiked with rosuvastatin and recovery was found in the range of 90 ± 10%.

Liquid chromatography with amperometric detection of some sulphonamides and their N4-acetyl-metabolites in serum and urine.

Sulphonamides separated on a C18 LC column were detected at lower levels using amperometric detection at a glassy carbon electrode in comparison with UV detection at 258 nm. Whereas sulphonamides are detectable at a potential of +1.00 V, their N4-acetyl-metabolites required a potential of +1.25 V to be detected after their separation by LC. An interference commonly present in serum and urine, which co-eluted with one of the analytes, was detected at 1.25 V. This was overcome with an appropriate sample preparation in which 150 microliters of serum or 75 microliters of urine were first diluted to 1.5 ml with phosphate buffer (pH 3.0; 0.2 M). A 1.0 ml volume of this solution was then passed through an Extrelut 1 column. The analytes were eluted with dichloromethane, which was evaporated under vacuum, and redissolving the analytes in an appropriate volume of mobile phase, i.e. methanol-phosphate buffer (pH 6.7; 0.067 M) (25:75, v/v). For sulphamethoxazole (SMX) and sulfamethoxypyridazine (SMP) and their N4-acetyl-metabolites the calibration curves were linear between 1.5 x 10(-7) and 8 x 10(-6) M. The recovery ranged between 92.6 and 97.6% in serum and between 80.5 and 99.4% in urine. Detection limits were 10 times lower with amperometric detection than with UV detection. The method has been applied to the quantitation of SMX and SMP and their N4-acetyl-metabolites in serum and urine after their oral administration.