Abstract
A spectrophotometric flow injection method for the determination of paracetamol in pharmaceutical formulations is proposed. The procedure was based on the oxidation of paracetamol by sodium hypochloride and the determination of the excess of this oxidant using o-tolidine dichloride as chromogenic reagent at 430 nm. The analytical curve was linear in the paracetamol concentration range from 8.50 x 10-6 to 2.51 x 10-4 mol L-1 with a detection limit of 5.0 x 10-6 mol L-1. The relative standard deviation was smaller than 1.2% for 1.20 x 10-4 mol L-1 paracetamol solution (n = 10). The results obtained for paracetamol in pharmaceutical formulations using the proposed flow injection method and those obtained using a USP Pharmacopoeia method are in agreement at the 95% confidence level.
Highlights
Paracetamol (4-acetoaminophen) has mild analgesic and antipyretic properties and is, along with acetylsalicylic acid, one of the most popular analgesic agents
Paracetamol exhibited significant reactivity with hypochlorite when exposed in large molar excess, leading to the production of multiple products such as 1,4-benzoquinone, N-acetyl-p-benzoquinoneimine and another products with molar mass higher than 300 g mol-1 [12, 35]
The proposed flow injection system is based on the ability of oxidation of paracetamol by hypochlorite in excess at pH 9.0 and the hypochlorite excess was monitored with o-tolidine producing a yellow diiminequinone at pH 9.0 [12, 38]
Summary
Paracetamol (4-acetoaminophen) has mild analgesic and antipyretic properties and is, along with acetylsalicylic acid, one of the most popular analgesic agents. The administration of this drug with caffeine yields analgesic effects significantly greater than that of paracetamol alone [1, 2]. Electroanalytical methods were proposed to paracetamol determination in pharmaceutical formulations using carbon paste electrode [13,14,15]. Flow injection systems are useful tools for the automation, miniaturization and simplification of analytical processes. These procedures permit obtain results faster and accurate than batch procedures [16]
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