Determination of ambroxol of bromhexine in pharmaceuticals by capillary isotachophoresis

Expectorant drugs ambroxol (AX) and bromhexine (BX) were determined by capillary isotachophoresis (ITP) with conductimetric detection. The leading electrolyte (LE) was a buffer solution that contained 5 mM picolinic acid and 5 mM potassium picolinate (pH 5.2). The terminating electrolyte (TE) was 10 mM formic acid. The driving current was 80 muA (for approximate to 200 s) or 50 muA (for approximate to 350 s) and the detection current was 20 muA (a single analysis took about 8 min). The effective mobilities of AX and EX (evaluated with tetraethylammonium as the mobility standard) were 18.8 x 10(-9) m(2) V-1 s(-1) and 14.3 x 10(-9) m(2) V-1 s(-1) respectively. The calibration graphs relating the ITP zone length to the concentration of the analytes were rectilinear (r = 0.9993-0.9999) in the range 10 mg l(-1) (20 mg l(-1) for EX) to 200 mg l(-1) of the drug standard. The relative standard deviations (RSD) were 1.2-1.6% (n = 6) when determining 100 mg l(-1) of the analytes in pure test solutions. The method has been applied to the assay of AX or EX in seven commercial mass-produced pharmaceutical preparations. According to the validation procedure based on the standard addition technique the recoveries were 97.5-102.7% of the drug and the RSD values were 0.11-2.20 (n = 6). (C) 2001 Elsevier Science B.V. All rights reserved.