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

Arnica, 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. 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 for extracting and pre-concentrating metals in 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. It shows improvements achieved over the traditionally used DLLME. The replacement of chlorinated or toxic solvents such as chloroform and methanol with a combination of carbonates and ionic liquids contributed for the green chemistry.In water, it was obtained recoveries between 70% and 92% for the metals Cd, Hg and Pb. However in arnicas infusions the recoveries were from 43% to 64% showing presence of matrix effect. This issue will be solved by using the standard addition method in future studies.