Determination of tramadol in various dosage forms by capillary isotachophoresis

Cationic capillary isotachophoresis (ITP) with conductometric detection has been used for separating and determining milligram amounts of tramadol [2- dimethylaminomethyl-1-(3-methoxyphenyl)-cyclohexanol hydrochloride] (I) in seven commercial mass-produced pharmaceutical preparations. The optimised I TP electrolyte system consisted of 5 mM potassium picolinate + 5 mM picolin ic acid (PI-I 5.25) as the leading electrolyte and 10 mM formic acid as the terminating electrolyte. The driving and detection currents ware 50 mu A ( for 320 s) and 10 mu A, respectively (a single analysis took 12-15 min). Un der such conditions the effective mobility of I was determined as 24.26 x 1 0(-9) m(2) V-1 s(-1) (with tetraethylammonium ion as standard); thermodynam ic pK(a) value of I was 9.44 +/- 0.03 (n = 8) as determined by UV spectroph otometry at 25 degrees C and I = 0.01 (NaCl). The calibration graph relatin g the ITP zone length to the concentration of I was rectilinear (r = 0.9999 7) in the range 15-180 mg l(-1) of I. The relative standard deviation (RSD) was 0.21% (n = 6) when determining 60 mg l(-1) of I in pure test solution. Sample pre-treatment of the dosage forms involved dilution or extraction o f I with water (for suppositories the extraction was carried out in an ultr asonic bath at 40 degrees C for 10 min). The method was suitable for determ ining 50 or 100 mg ml(-1) of I in injections and drops, 50 mg of I in capsu les, and 100 mg of I in suppositories with I;:SD values 0.4 to 1% (n = 6). According to the validation procedure based on the standard addition techni que the recoveries were 97.2-100.1% of I. (C) 1998 Elsevier Science B.V. Al l rights reserved.