Methanol Naphazoline

Figure 4 presents an example of rapid pKa measurement using a pressure-assisted system in combination with a photodiode array (PDA) detector. The migration time of DMSO (EOF marker) was measured at 220 nm, whereas the migration time of the analyte, naphazoline, was measured at 270 nm. The CE run time as well as data analysis time was drastically reduced. Consequently, this system allows the analysis of more than 96 compounds in one day. The limitation of this method is the application to drugs without UV chromophore at more than 250 nm. In some cases, it was effective to remove DMSO by evaporation under vacuum followed by the addition of methanol or acetonitrile as a neutral marker. 

FIGURE 4-9. Comparison of retention of antihistamines on different columns. Sample components 1. phenylephrine 2. phenylpropanolamine 3. naphazoline 4. chlorpheniramine. Columns 4 mm ID x 30 cm /xBondapak phase, (a) Cyano phase. (b) Phenyl phase, (c) C18 phase. Mobile phase methanol/water containing 0.005 M heptane sulfonic acid (PIC-B-7). Flow rate 2 mL/min in a and 3 mL/min in b and c. Detector UV at 254 nm, 0.1 AUFS. 

The USP describes a TLC method for ordinary impurities in naphazoline hydrochloride drug substancel. A sample of the drug substance dissolved in methanol (10 m mL) is spotted on a silica gel TLC plate, eluted with a mobile phase of methanol-glacial acetic acid-water (8 1 1, v/v/v), and visualized with iodoplatinate spray. 

An adaptation of the USP TLC procedure for the determination of ordinary impurities in naphazoline hydrochloride allowed for the detection of 1-naphthylacetylethylenediamine in the presence of naphazoline. Using silica gel 60 high-performance TLC plates (20 X 20 cm) and a mobile ph of methanol-glacial acetic add-purified water (8 1 1, v/v/v), spots were visible after spraying with ninhydrin naphazoline Rf - 0.54 1-naphthylacetyl-ethylenediamine Rf - 0.63. A similar method has been described in the European Pharmacopoeia for 1-naphthylacetylethylenediamine in naphazoline nitrate S. 

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