Simultaneous Flow Injection Analysis of Paracetamol and Ascorbic Acid with Multiple Pulse Amperometric Detection

Abstract

The present work reports a simple and quick strategy for simultaneous determination of paracetamol (PC) and ascorbic acid (AA) in pharmaceutical formulations using flow injection method with multiple pulse amperometric detection. The method allows the resolution of the mixture without chemical pretreatment of the sample or electrode modification or the use of chemometric techniques for data analysis. The compounds are detected by applying four sequential pulses (waveform) in function of time to a three-electrode amperometric system that uses a wall-jet cell with gold as working electrode. AA is direct detected at þ 0.40 V and PC is indirectly detected at 0.0 V by the reduction (desorption) of the oxidation product (N-acetyl-p-benzoquinoneimine) electrochemically generated at þ 0.65 V. The fourth potential pulse (À 0.05 V) is applied for the complete regeneration (cleaning) of the gold electrode surface. The linear response range was optimized between 5 and 24 mg L À1 for AA and 50 and 240 mg L À1for PC. The difference between the two responses ranges (10-fold) present correlation with the concentration of these compounds in two different pharmaceutical formulations available in the Brazilian market. The analytical frequency was calculated in 60 injections per hour. The use of the proposed methodology for PC quantification in the presence of higher AA concentrations was also carried out. Using the standard addition method, it was possible to detect PC in trace levels (LD ¼ 0.2 mg L À1 ) in the presence of 880-fold more of AA (176 mg L À1 ).

Capillary gap flow cell as capillary-end electrochemical detector in flow-based analysis

“…The electroactive species, namely, ascorbic acid, 2,3-dihydroxybenzoic acid, pyrocatechol and dopamine were used as test solutes in this study. These solutes were previously reported in different flow-based analysis systems using EC detectors and therefore allowed direct comparison with previous works [15,[30][31][32]. The analytical application of the gap-FC in LC was also investigated, comparing the detection sensitivity of the gap-FC with EC detectors reported in the literature, as well as with a standard UV detector.…”

“…Table 3 compares the analytical performance of the gap-FC used here with the standard LC and capillary LC formats, with other reported data for flow-through EC detectors [31,32]. The LODs for the gap-FC EC detector in standard LC were at least one order of magnitude lower than those obtained in the capillary LC-EC system for 2,3-DHBA, and pyrocatechol.…”

Boron Doped Diamond Electrodes in Flow-Based Systems

“…In 2010, the simultaneous determination of antioxidants BHA and BHT was carried out in mayonnaise samples (Medeiros et al, 2010a). In this work, for the first time, a BDD electrode was used for simultaneous determination in a FIA system coupled with multiple pulse amperometric detection (FIA-MPA) (dos Santos et al, 2008; Santos et al, 2009). A dual-potential waveform [E det1 = +0.85 V and E det2 = +1.15 V (vs. Ag/AgCl)] was employed with acquisition of two separate amperograms.…”

Prospects of pulsed amperometric detection in flow-based analytical systems - A review

“…Multiplex-pulsed amperometric detection (MPAD, Fig. 3g) [13,38,43] uses multiple potential pulses as a function of time to monitor the current at several applied potentials, which makes it feasible to detect different compounds, both individually and simultaneously [44,45]. It is also used for the introduction of internal standard addition in the…”