Spectrophotometric determination of certain CNS stimulants in dosage forms and spiked human urine via derivatization with 2,4-dinitrofluorobenzene

Author(s): Mohamed I.Walash, N.El.Enany, Samar Saad

A new spectrophotometric method is developed for the determination of phenylpropanolamine HCl (PPA), ephedrine HCl (EPH) and pseudoephedrine HCl (PSE) in pharmaceutical preparations and spiked human urine. The method involved heat-catalyzed derivatization of the three drugs with 2,4-dinitrofluorobenzene (DNFB) producing a yellowcoloured product peaking at 370 nmfor phenylpropanolamine HCl and 380 nmfor ephedrine HCl and pseudoephedrineHCl, respectively. The absorbance concentration plots were rectilinear over the range of 2-20, 1-14 and 1-14 µg/mL, for PPA, EPH and PSE, respectively. The limit of detection (LOD) values were 0.20, 0.13 and 0.20 µg/mL for PPA, EPH and PSE, respectively and limit of quantitation (LOQ) values were 0.60 and 0.40 and 0.59, µg/mL for PPA, EPH and PSE, respectively. The analytical performance of the method was fully validated and the results were satisfactory. The proposed method was successfully applied to the determination of the three studied drugs in their commercial dosage forms including tablets, capsules and ampoules with good recoveries. The proposed method was further applied for the determination of PSE in spiked human urinewith amean percentage recovery of 108.17±1.60% for n =3. Statistical comparison of the results with those of the comparison methods showed good agreement and proved that there was no significant difference in the accuracy and precision between the comparison and the proposed methods, respectively. The mechanisim of the reaction pathway was postulated.

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