RESUMEN

The stopped-flow mixing technique has been used to study the kinetic determination of propranolol by means of micellar-stabilized room-temperature phosphorescence. This mixing system diminishes the time required for the deoxygenation of micellar medium by sodium sulfite, allowing a kinetic curve that levels off within only 7s to be obtained. The phosphorescence enhancers thallium (I) nitrate, sodium dodecyl sulfate, and sodium sulfite were optimized to obtain maximum sensitivity and selectivity. A pH value of 6.54 was selected as adequate for phosphorescence development. The kinetic curves of propranolol phosphorescence were scanned at lambda(ex)=290 nm and lambda(em)=524 nm. The calibration graphs were linear for the concentration range from 25 to 400 ng mL(-1). The phosphorescence lifetime of propranolol is approximately 1210 micros. The detection limit calculated as proposed clayton was 13.53 ng mL(-1) and by applying the error propagation theory, the detection limit was 8.37 ng mL(-1). The repeatability was studied using 10 solutions of 200 ng mL(-1) of propranolol; if error propagation theory is assumed, the relative error is 1.94%. The standard deviation for a replicate sample was 4.0 ng mL(-1). This method was successfully applied to the determination of propranolol in commercial formulations and in urine. Suitable recovery values were obtained.

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A direct and simple procedure for the determination of 4-methylpropranolol, a specific beta-adrenergic receptor blocking agent, in biological fluids was developed. The method was based on the measurement of the nonprotected fluid room-temperature phosphorescence of the drug. This technique enables us to determine analytes in complex matrices without the need for a tedious prior separation process. The appropriate experimental conditions to obtain suitable reproducibility and maximum phosphorescence signal, when sodium sulfite is used to eliminate the oxygen from the solution and when potassium iodide is used as heavy atom, were studied. The optimum concentration of KI was 3.2 M. The optimization of Na(2)SO(3) (7.0 x 10(-3) M) and the accurate value of pH (10.88) were determined using a simplex as the method of optimization. A sodium carbonate-hydrogen carbonate buffer solution (5.0 x 10(-2) M) was used to adjust the value of pH. The delay time (124 micros), gate time (206 micros), and time between flashes (5 ms) were also optimized using a simplex. Under the above conditions, the maximum signal of phosphorescence appears instantly once the sample has been prepared, and the intensity was measured at lambda(ex) = 300 nm and lambda(em) = 537 nm, in the concentration range 25-500 ng/ml. Overall least-squares regression was used to find the straight line that fit the experimental data. The detection limit according to the error propagation theory was 6.2 ng/ml and the detection limit calculated as proposed by C. A. Clayton et al. (1987, Anal. Chem. 59, 2506) was 11.7 ng/ml. The repeatability was studied using 10 solutions of 200 ng/ml 4-methylpropranolol; if error propagation theory was assumed, the relative error was 1.78% and the standard deviation for replicate samples was 3.5 ng/ml. This method was successfully applied to the determination of 4-methylpropranolol in urine, serum, and cerebrospinal fluid, with recoveries of 99.3 +/- 0.5% in the case of urine, 99.8 +/- 0.2% for serum, and 101.5 +/- 1.5% for cerebrospinal fluid.

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In the present paper, the modified simplex method (MSM) has been applied, for the first time, to determine compounds by a luminescence technique. The method was based on the optimization of chemical and instrumental variables affecting phosphorescence using a geometric simplex in two and three dimensions of space, respectively. As application, we have determined a novel antihypertensive drug, naftopidil, in urine and serum, by heavy atom induced room temperature phosphorescence (HAI-RTP); this technique enables us to determine analytes in complex matrices, biological fluids, without the need for a tedious prior separation process. With the proposed method, the maximum signal of phosphorescence appears instantly once the sample has been prepared and the intensity was measured at lambda(ex)=287 nm and lambda(em)=525 nm. Overall least-squares regression was used to find the straight line that fitted the experimental data. The detection limit, as well as the repeatability and the standard deviation (S.D.) for replicate sample, were also determined.

RESUMEN

A selective and sensitive room temperature phosphorimetric method for the direct determination of naftopidil in biological fluids is described. The method is based on obtaining a phosphorescence signal from this antihypertensive drug using TlNO3 as a heavy atom perturber and Na2SO3 as a deoxygenator agent without a protective medium. This technique is named non-protected room temperature phosphorescence (NP-RTP), and enables us to determine analytes in complex matrices without the need for a tedious prior separation process. The optimization of Na2SO3 (8.5 x 10(-3) M) and the accurate value of pH (9.0) were determined using a simplex as a method of optimization. Sodium carbonate-hydrogencarbonate buffer solution (5.0 x 10(-2) M) was used to adjust the suitable pH. The optimum concentration of Tl+ (8.5 x 10(-2) M) was also determined. The delay time, gate time and time between flashes selected were 200 microseconds, 200 microseconds and 5 ms, respectively. Under the above conditions we propose a method to determine naftopidil by direct measurement of phosphorescence intensity with an emission wavelength of 526 nm and an excitation wavelength of 296 nm in the concentration range 0.05-1.00 mg L-1. Under these conditions the phosphorescence signal appears in 3 min once the sample has been prepared. Optimization of the various conditions permitted the establishment of an NP-RTP method for the determination with a detection limit, according to the error propagation theory, of 21.0 ng mL-1. The repeatability was studied using 10 solutions of 0.20 mg L-1 of naftopidil; if error propagation is assumed, the relative error is 1.39%. The standard deviation for replicate samples was 1.1 x 10(-2) mg L-1. This method was successfully applied to the determination of naftopidil, in human urine with recoveries between 106 and 112%.

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RESUMEN

Non-protected fluid room temperature phosphorescence, NPRTP, has been applied to the determination of naftopidil in biological fluids. The proposed method is based on obtaining a phosphorescence signal from naftopidil using potassium iodide as heavy atom perturber and sodium sulfite as a deoxygenating reagent without a protected medium. Optimized conditions for the determination were 1.4 mol L= KI, 5.0 x l0(-3) mol L(-1) sodium sulfite, pH 6.5 (adjusted with sodium hydrogen phosphate-dihydrogen phosphate buffer solution, 5.0 x 10(-2) mol L(-1). The delay time, gate time, and time between flashes were 70 micros, 400 micros, and 5 ms, respectively. The maximum phosphorescence signal appeared instantly and the intensity was measured at lambda(ex)=287 nm and lambda(em)=525 nm. The response obtained was linearly dependent on concentration in the range 50 to 600 ng mL(-1). The detection limit, according to error-propagation theory, was 7.93 ng mL(-1) and the detection limit as proposed by Clayton was 11.12 ng mL(-1). The repeatability was studied by using ten solutions of 400 ng mL(-1) naftopidil; if the theory of error propagation is assumed the relative error is 0.88%. The standard deviation of replicates was found to be 3.5 ng mL(-1). This method was successfully applied to the analysis of naftopidil in human serum and urine with recoveries of 104.0 +/- 0.6% for serum and 106.0 +/- 1.0% for urine.

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