Arnicas Solidago microglossa DC. and Arnica montana L.Arnica, are a natural medicine with analgesic, anti-inflammatory and antiseptic action, is easily accessible by the Brazilian population. These products are susceptible to contamination by elemental impurities that are harmful to the human health. In 2017, the United States Pharmacopeia (USP) has published two new chapters for heavy metal determination. The classical method was replaced by advanced analytical techniques such as optical emission spectrometry or inductively coupled plasma mass spectrometry (ICP OES and ICP-MS, respectively). However, these are high cost techniques to implement in small laboratories. Dispersive liquid-liquid microextraction (DLLME) involves the rapid injection of a mixture of extractor and dispersant solvents into the sample. The use of ionic liquids (IL-DLLME) and / or complexing agents (cDLLME) to extract metals from samples is an interesting alternative in the determinination of metals normally present in trace levels in pharmaceutical samples. This procedure contributes to improve limits of quantification (LOQ), allowing the use of alternative analytical techniques to ICP such as capillary electrophoresis, atomic absorption and UV-Vis spectrophotometry. Therefore, this work aimed to use a design of experiment (DOE) for the optimization of DLLME for determination of metallic impurities in arnica infusion. The replacement of chlorinated or toxic solvents, such as chloroform and methanol, with a combination of organic carbonates and ionic liquids, proved to be a promising alternative, thus allowing the development of an analytical methodology that follows the precepts of green chemistry. Initially, the matrix effect was proven due to the difference in extraction efficiency between water and infusion in addition to the absence of parallelism between curves. This problem was solved by changing the form of quantification by performing the analytical curve in infusion of arnica. The enrichment factor in tea was between 89 - 127. The method was validated according to RDC 166 where the parameters selectivity, linearity, precision, accuracy, limit of detection (LOD) and limit of quantification (LOQ) were evaluated. The defined range was 5.0– 100.0 ppb for cadmium and lead, and 1.5 – 30.0 ppb for mercury, with accuracy was between 94% and 107% and DPR 1.77% and 8.51%. The technique proved to be applicable for the analysis of elemental impurities in other infusions such as Passiflora incarnata.

Evaluation of dispersive liquid-liquid microextraction in the determination of metallic impurities in arnica

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