Direct determination of naftopidil by non-protected fluid room temperature phosphorescence.
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%.
Murillo Pulgarín
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JA
Department of Analytical Chemistry and Food Technology, University of Castilla-La Mancha, 13071, Ciudad Real, Spain. jamurill@qata-cr.uclm
Alañón Molina
A
A
Alañón Pardo
M T
MT
D000317:Adrenergic alpha-Antagonists / Q000652:urine*; D000959:Antihypertensive Agents / Q000652:urine*; D002121:Calcium Channel Blockers / Q000652:urine*; D006801:Humans; D049449:Luminescence; D009281:Naphthalenes / Q000652:urine*; D010879:Piperazines / Q000652:urine*
D000317:Adrenergic alpha-Antagonists; D000959:Antihypertensive Agents; D002121:Calcium Channel Blockers; D009281:Naphthalenes; D010879:Piperazines; C064357:naftopidil