Two chromatographic methods were developed for the assay of the FDA approved lozenges containing dextromethorphan hydrobromide (DXT) and menthol (MNT). The first was a green HPTLC method which depends on using Merck HPTLC aluminum sheets of silica gel 60 F254 and methanol-ammonia (10:0.1, v/v) as mobile phase. This was followed by densitometric measurements of the spots which were retained at 0.28 ± 0.01 for DXT and 0.76 ± 0.02 for MNT scanned at 210 nm. The method was found linear over the concentration ranges of 0.1 – 1 μg.band−1 for both DXT and MNT with values of correlation coefficients exceeding 0.999. The other method was RP-HPLC method with stability indicating merits at which Agilent 5 HC-C18 (2) 150 x 4.6mm was used as stationary
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Several methods have been described in the literature for the determination of MNT in its pharmaceutical dosage forms or in biological samples. Examples of these methods in biological samples are gas chromatography – mass spectrometry (GC-MS) [18] in plasma and urine of rats and human while GC-FID [19] was used for MNT analysis in human urine. Also, MNT in mixture with other drugs have been assayed in human plasma using GC-FID [20]. In pharmaceutical preparations, MNT has been assayed using HPLC with refractive index detector [21], with ultra-violet (UV) detection [22], with UV detection after chromogenic derivatization [23] and with polarized photometric detection [24]. Other methods used for analysis of MNT are HPTLC [25] and spectrophotometric color reactions …show more content…
Usually MNT is used as a flavoring agent in most pharmaceutical preparations, but in the lozenges under study MNT is one of the active ingredients with a pharmacological action in relieving oral pain in patients suffering from common cold. Moreover, the challenge in the work was to separate MNT (which is a very polar compound with very weak absorbing character due to its simple cyclic aliphatic structure) with reasonable RF and tR values, symmetrical peak shapes, and good resolution with high purity
Several methods have been described in the literature for the determination of MNT in its pharmaceutical dosage forms or in biological samples. Examples of these methods in biological samples are gas chromatography – mass spectrometry (GC-MS) [18] in plasma and urine of rats and human while GC-FID [19] was used for MNT analysis in human urine. Also, MNT in mixture with other drugs have been assayed in human plasma using GC-FID [20]. In pharmaceutical preparations, MNT has been assayed using HPLC with refractive index detector [21], with ultra-violet (UV) detection [22], with UV detection after chromogenic derivatization [23] and with polarized photometric detection [24]. Other methods used for analysis of MNT are HPTLC [25] and spectrophotometric color reactions …show more content…
Usually MNT is used as a flavoring agent in most pharmaceutical preparations, but in the lozenges under study MNT is one of the active ingredients with a pharmacological action in relieving oral pain in patients suffering from common cold. Moreover, the challenge in the work was to separate MNT (which is a very polar compound with very weak absorbing character due to its simple cyclic aliphatic structure) with reasonable RF and tR values, symmetrical peak shapes, and good resolution with high purity