Reversed-phase capillary electrochromatography for the simultaneous determination of acetylsalicylic acid, paracetamol and caffeine in tablet formulations

The separation and simultaneous determination of caffeine, paracetamol and acetylsalicylic acid in two analgesic tablet formulations was investigated by capillary electrochromatography (CEC). The effect of mobile phase composition on the separation and peak efficiency of the three analytes was studied and evaluated; in particular, the influence of buffer type, buffer pH, and acetonitrile content of the mobile phase was investigated. The analyses were carried out under optimised separation conditions, using a full packed silica capillary (75 µm I.D.; 30.0 cm and 21.5 cm total and effective lengths, respectively) with a 5 µm C8 stationary phase. A mixture of 25 mM ammonium formate at pH 3.0 and acetonitrile (30:70 v/v) was used as the mobile phase. UV detection was at 210 nm. Good linearity was found in the range of 50-200, 20-160, and 4-20 µg/mL for acetylsalicylic acid, paracetamol and caffeine, respectively. Intermediate precision (RSD interday) as low as 0.1-0.8% was found for retention times, while the RSD values for the peak area ratios (Aanalyte / AIS) were in the range of 1.9-2.9%. The CEC optimised method was applied to the analysis of the studied compounds present in commercial tablets.