Determination of Mexiletine Hydrochloride in Tablets by Visible Absorption Spectrometry with Erythrosin

OBJECTIVE To establish a novel high sensitivity visible absorption spectrometry for rapid determination of mexiletine hydrochloride in drugs. METHODS In acidic Tris-HCl medium, the color reaction occurred between erythrosin with mexiletine hydrochloride to form ion association complex with two strong positive absorption peaks, the single-wavelength visible absorption spectroscopy and double-wavelength visible absorption spectroscopy were used to study the quantitative detection method of mexiletine hydrochloride in the drugs. The detection wavelength were 477 nm and 548 nm. RESULTS In a acidic solution of pH 4.69, erythrosin interacts with mexiletine hydrochloride through electrostatic attraction to form a binary ion association complex, which led to appear two strong positive absorbing peaks on absorption curve and their positive absorbing peaks were located at 477 nm and 548 nm, respectively. The absorbance(A₄₇₇ and A₅₄₈) had a good linear relationship with the mass concentration of mexiletine hydrochloride in the range of 0.03 to 4.30 mg·L^-1, they obeyed Lambert-Beer's law. The apparent molar absorbance coefficient(κ) of the single-wavelength method were 5.56×10⁴ L·mol^-1·cm^-1(477 nm) and 5.04×10⁴ L·mol^-1·cm^-1(548 nm), their detection limits were 0.024 mg·L^-1(477 nm) and 0.020 mg·L^-1(548 nm), respectively. The apparent molar absorption coefficient(κ) of the double-wavelength method could be up to 1.05×10⁵ L·mol^-1·cm^-1, its detection limit was 0.011 mg·L^-1, the recovery rate was 98.4%-102%, and the relative standard deviation was 2.2%-2.6%. CONCLUSION The single-wavelength visible absorption spectrometry or double-wavelength visible absorption spectrometry can be used for the quantitative determination of mexiletine hydrochloride in drugs, they are simple, fast and sensitive.