Quality assessment for tramadol in pharmaceutical preparations with thin layer chromatography and densitometry

Research studies have been carried out to develop a chromatographic and densitometric method suitable for identification and determination of tramadol and impurities. In addition, the stability of tramadol in solutions was investigated, including an effect of solution pH, temperature and incubation time. In the first instance the conditions for identification and quantitative determination of tramadol and impurities in pharmaceutical preparations were established. The separation was performed on silica gel-coated chromatographic plates (HPTLC) using two mobile phases: (I) chloroform-methanol-glacial acetic acid (9:2:0.1, v/v/v); (II) chloroform-toluene-ethanol (9:8:1, v/v/v). The UV densitometry was carried out at lambda = 270 nm. The developed method is of high sensitivity and low detection and determination limits ranging from 0.044 to 0.35 microg. For individual constituents the recovery ranges from 93.23 to 99.66%. The next step was to evaluate the stability of tramadol and determine a method of decomposition under various experimental conditions. It was found that tramadol decomposes in various ways in acidic and basic environments producing (1RS)-2-(3-methoxyphenyl)cyclohex-2-enyl]-N,N-dimethylmethanamine (imp. B) and (1RS, 2RS)-2-(dimethylamino)methyl]-1-(3-methoxyphenyl)cyclohexanol (imp. cis-T) or imp. cis-T, respectively.