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

Walash et al. Chemistry Central Journal 2011, 5:65 http://journal.chemistrycentral.com/content/5/1/65 RESEARCH ARTICLE Open Access Spectrophotometric determination of certain CNS stimulants in dosage forms and spiked human urine via derivatization with 2,4-Dinitrofluorobenzene Mohamed I Walash, Nahed M El-Enany* and Samar Saad Abstract 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 yellow colored product peaking at 370 nm for PPA and 380 nm for EPH and PSE, respectively. The absorbance concentration plots were rectilinear over the range of 2-20 for PPA and 1-14 μg/mL for both of 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 of 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 percentage recoveries. The proposed method was further applied for the determination of PSE in spiked human urine with a mean percentage recovery of 108.17 ± 1.60 for (n = 3). Statistical comparison of the results obtained with those of the comparison methods showed good agreement and proved that there was no significant difference in the accuracy and precision between the two methods. The mechanism of the reaction pathway was postulated. 1. Introduction Phenylpropanolamine hydrochloride, (PPA) is (1RS, 2SR)2-amino-1-phenylpropanol hydrochloride [1] (Figure 1). It is a largely indirect acting sympathomimetic with an action similar to ephedrine; it is orally administered for the treatment of nasal congestion. It is frequently used in mixture preparations for the relief of cough and cold symptoms. Other uses of phenylpropanolamine include; the control of the urinary incontinence in some patients. It has also been used to suppress appetite in the management of obesity [1]. The United States Pharmacopoeia (USP) [2] and the British Pharmacopoeia (BP) [3] recommended non-aqueous titrimetric method for the determination of PPA in the pure form in presence of mercuric acetate, using perchloric acid as a titrant and crystal violet as indicator. On the other hand, USP [2] recommended HPLC method for its determination in dosage forms using * Correspondence: Department of Analytical Chemistry, Faculty of Pharmacy, University of Mansoura, 35516, Mansoura, Egypt © 2011 Walash et al a mixture of (1-hexanesulfonate, monobasic sodium phosphate and triethylammonium phosphate) and methanol as a mobile phase with UV detection at 210 nm. Due to its clinical advantages, PPA received a great interest. A good guide to the work published is found as comprehensive monograph in analytical profiles for drugs [4]. Several analytical techniques have been reported for PPA determination either perse or in pharmaceutical preparations and biological fluids including; titrimetry [5], spectrophotometry [6], fluorimetry [7], HPLC [8], capillary electrophoresis [9], flow injection [10] and gas chromatography [11]. Ephedrine hydrochloride (EPH) is (1R, 2S)-2-(Methylamino)-1-phenylpropan-1-ol hydrochloride [1] (Figure 1). It is a sympathomimetic drug with direct and indirect effects on adrenergic receptors. It has alpha and beta-adrenergic activity and has pronounced stimulating effects on the central nervous system [1]. It is reported to reduce the viscosity of tenacious sputum and is used as an expectorant. The USP [2] recommended a non aqueous titration method for its determination in pure form in presence of mercuric Walash et al. Chemistry Central Journal 2011, 5:65 http://journal.chemistrycentral.com/content/5/1/65 Page 2 of 13 OH H CH3 H .HCl NH2 A) Phenylpropanolamine HCl H OH NH H CH3 CH3 .HCl B) Ephedrine HCl H OH H N H CH3 . CH3 HCl C) Pseudoephedrine HCl Figure 1 Structural formulae of the three studied drugs. acetate and titration with 0.1N perchloric acid using crystal violet as indicator. The BP [12] favored a potentiometric titration method for its determination in pure form using 0.1 M NaOH as a titrant. Both of USP and BP recommended HPLC method with UV detection at 263 nm for its determination in dosage forms. Various reports have been described for the analysis of EPH A good guide to the work published for EPH is found as comprehensive monograph in analytical profiles for drug substances [13]. Several techniques were reported for its determination including; titrimetry [14], spectrophotometry [15], fluorimetry [16], flow injection [17], capillary electrophoresis [18], TLC [19], HPLC [20], and gas chromatography [21]. Pseudoephedrine HCl (PSE) is (1S, 2S)-2-(Methylamino)-1-phenylpropan-1-ol hydrochloride [1] (Figure 1) is a direct and indirect sympathomimetic. It is a stereoisomer of ephedrine and has a similar action, but has been stated to have less pressor activity and fewer CNS effects. It is given orally for the relief of nasal congestion. They are commonly combined with other ingredients for the relief of cough and cold symptoms [1]. Also the USP [2] recommended a non aqueous titration method for the determination of PSE in its pure form in presence of mercuric acetate and titration with 0.1 M perchloric acid using crystal violet as indicator. The BP [12] preferred a potentiometric titration for its determination in pure form using 0.1 M NaOH as a titrant. Both USP and BP recommended HPLC method with UV detection at 254 nm and 258 nm, respectively, for its determination in dosage forms. A good guide to the work published for PSE is found as comprehensive monograph in analytical profiles for drugs [22]. The literature revealed that the analysis of PSE was through techniques such as; spectrophotometry [23], flow injection [24], capillary electrophoresis [25], HPTLC [26] and HPLC [27]. Walash et al. Chemistry Central Journal 2011, 5:65 http://journal.chemistrycentral.com/content/5/1/65 Sanger’s reagent (DNFB), on the other hand, has been utilized as a chromogen for the spectrophotometric estimation of many compounds of pharmaceutical interest such as desloratadine [28], enalapril [29], lisinopril [30] and gabapentin [31]. Page 3 of 13 and 200 mg of propyphenazone, product of Egyptian Int. Pharmaceutical Industries CO. E.P.I.CO,10th of Ramadan City, Egypt. -Ephedrine ampoule, batch # 11, each ampoule (1 mL) labeled to contain 30 mg of EPH, product of Chemical industries Development(CID)-Giza-A.R.E. 2. Experimental 2.1. Instruments 2.3. Standard solutions - A shimadzu UV-Visible 1601 PC spectrophotometer (...truncated)