A Simple Approach for Fe Determination in Beer by using Dispersive Liquid-Liquid Microextraction and Flame Atomic Absorption Spectrometry

Abstract

In this work, a new method for Fe extraction and preconcentration from beer by using dispersive liquid-liquid microextraction (DLLME) and determination by flame atomic absorption spectrometry (F AAS) was developed. Although in DLLME the use of an extraction solvent is mandatory (at least in theory), which is combined with a disperser solvent, in this work only the extraction solvent was used. For Fe extraction by DLLME, the type and volume of extraction solvent, sample volume, type of complexing agent, sample pH, salting out effect, and the number of washing cycles after extraction were evaluated. Thus, after optimization, 10 mL of beer, 75 µL of 1,2-dichlorobenzene of extraction solvent, 500 µL of 0.5% (w/v) pyrrolidine ammonium dithiocarbamate (APDC) as complexing agent were used. It is important to mention that pH adjustment, salt addition or washing cycles were no required. For Fe determination after DLLME, an external calibration curve was performed (R2 > 0.99) by direct extracts (reference solutions through DLLME) introduction in the conventional nebulization system of F AAS instrument. The accuracy evaluation was performed by results comparison with those obtained after microwave-assisted digestion (MAD) and Fe determination by inductively coupled plasma optical emission spectrometry (ICP-OES). The Fe concentration in the studied samples ranged from 59.7 to 68.2 µg L-1 and the limit of quantification for DLLME/F AAS method was 9.0 µg L-1. Finally, the proposed method DLLME/F AAS was applied for Fe determination in several beer samples showing simplicity, low operational costs, suitable accuracy (104 to 119%) and precision (better than 13%), opening the possibility for its use in routine analysis for Fe determination in beer.