AMPEROMETRIC DETERMINATION OF 8-CHLOROTHEOPHYLLINE, CAFFEINE, AND DIPHENHYDRAMINE IN A SINGLE RUN

Abstract

A simple method for simultaneous determination of 8-chlorotheophylline (CTP), caffeine (CAF), and diphenhydramine (DIP) using batch-injection analysis with multiple pulse amperometric detection (BIA-MPA) is reported. A sequence of three potential pulses (+1.10 V, +1.40 V, and +1.70 V) was applied to the boron-doped diamond working electrode with the acquisition of three distinct amperograms. CTP was detected selectively at +1.10 V, both CTP + CAF at +1.40 V and CTP + CAF + DIP at +1.70 V. The subtraction between the currents detected at the three potential pulses (with the use of correction factors) was the strategy used to achieve selectivity for the determination of CAF and DIP. The proposed method is simple, inexpensive, fast (120 injections h-1), presents good precision (RSD < 0.9%; n = 20), and adequate limits of detection (0.31, 0.49, and 0.76 µmol L-1 for CTP, CAF and DIP, respectively). The results obtained by BIA-MPA were similar to those found by high-performance liquid chromatography (95% confidence level).

Keywords

• multielement analysis
• batch injection analysis
• portable method
• amperometric detection