Preconcentration and determination of Pb at ultra-trace levels in bee products by magnetic ionic liquid based dispersive liquid-liquid microextraction coupled to electrothermal atomic absorption spectrometry

RODOLFO G. WUILLOUD; EMILIANO F. FIORENTINI; MARÍA B. BOTELLA

Santiago de Chile

Congreso; 6th Iberoamerican Meeting on Ionic Liquids; 2021

Universidad de Santiago de Chile

Lead is considered a highly toxic contaminant because the absorption of small amounts causes adverse health effects, such as respiratory, renal, cardiovascular and reproductive dysfunction1. The Mercosur Technical Regulation establishes a maximum permissible limit of 0.3 µg g-1 of Pb in honey, 0.1 mg L-1 of Pb in alcoholic beverages in general (like honey beer and honey vinegar) and 0.2 mg L-1 of Pb in wine (like mead)2. Therefore, considering the low concentrations at which Pb can be found in bee products, as well as the low limits established by regulatory authorities, sensitive and precise analytical methods are a constant demand in food industry.Several microextraction analytical methods based on ionic liquids (ILs) have been reported for the preconcentration of Pb in samples of different complexity, using electrothermal atomic absorption spectrometry (ETAAS) for detection. However, most of the microextraction methods demand the separation of the extraction phase by centrifugation3. Likewise, ILs with higher density than water are required for efficient separation of the extraction phase and analytes, which demands extensive time, or the addition of magnetite in order to magnetize the extractant phase and speed-up the process. Alternatively, magnetic ionic liquids (MILs) have started to be used because they avoid the use of centrifugation and the addition of magnetite, and in turn can be easily separated with a magnet4.In this work, a highly efficient dispersive liquid-liquid microextraction method based on MIL (MIL-DLLME) and detection by ETAAS was developed to determine Pb at ultra-trace levels in bee products. The analyte was chelated with 1,5-diphenylcarbazide in acidic medium (2 mol L-1 HCl) and was extracted by 150 µL of trihexyl(tetradecyl)phosphonium tetrachloromanganate (II) ([P6,6,6,14]2MnCl4). Subsequently, the extractant phase was separated by a magnet and an aliquot was injected into ETAAS. The optimal extraction conditions were established by multivariate optimization. Under optimal experimental conditions, a 97.0% extraction efficiency and a sensitivity enhancement factor of 107 were obtained. Detection limit (LOD) of 3 ng L-1 with a relative standard deviation of 3.6% (at 30 ng L-1 Pb, n=10) and a linear range of 10-3000 ng L-1 were obtained. This work reports the first application of the MIL [P6,6,6,14]2MnCl4 along with the DLLME technique for the determination of Pb at trace levels in different bee products, including honey, mead, honey vinegar and honey beer.