UV spectrophotometric flow-through multiparameter sensor for the simultaneous determination of acetaminophen, acetylsalicylic acid, and caffeine

A single triparameter flow-through sensor with U.V. detection is described in this study for the simultaneous determination of acetaminophen, acetylsalicylic acid and caffeine. The use of an solid phase (C-18 silica gel) placed in an on-line microcolumn provides the sequential arrival of the analytes to the detection solid zone (also C-18 silica gel beads placed in a flow cell), making possible the determination with only one injection. A flow rate of 1.42mLmin(-1) was pumped and detection wavelength was 272 nm. The linear dynamic ranges were 10-100, 40-500 and 4-50 mug mL(-1), for acetaminophen, acetylsalicylic acid and caffeine, respectively. Limit of detection were from 0.3 to 0.8 mug mL(-1) and limit of quantitation were from 1.0 and 2.7 mug mL(-1) with RSDs from 1.2 to 3.4 (n = 10), respectively. The proposed method was applied to the determination of acetaminophen, acetylsalicylic acid and caffeine in pharmaceutical preparations. The results were compared with those obtained from an HPLC method and they showed a good agreement.