Polycyclic aromatic hydrocarbons analysis in tea infusions and tea beverages using membrane assisted solvent extraction

Abstract

Membrane Assisted Solvent Extraction (MASE) was applied as an extraction and enrichment technique of polycyclic aromatic hydrocarbons (PAHs) from tea infusions and fruit/herbal-tea beverages. PAHs have been separated and detected by high performance liquid chromatography coupled to a fluorescence detector (HPLC-FLD). Variables affecting MASE comprising extraction temperature and time, stirring rate, acceptor solvent (hexane) volume, organic modifier in the donor phase (methanol) volume, aqueous donor phase pH and ionic strength were simultaneously studied by applying a Plackett–Burman design (PBD) as screening method. Results showed statistical significance for acceptor solvent volume, extraction time and stirring rate, which were optimised by an orthogonal 23 + star central composite design (CCD). Quantitative recoveries for all PAHs (within 78–116%) were obtained by using the optimized extraction conditions: 350 µL of hexane, extraction time of 70 min and stirring rate of 175 rpm. Extraction temperature, ionic strength and donor phase pH were statistically non-significant, which simplify the procedure. The MASE method has been found sensitive (LOQs < 43 ng L−1) and precise (RSDs of < 13%). Finally, the method has been applied to assess PAHs levels in several tea infusions and fruit/herbal-tea beverages in the presence of surrogate standards. The total mean Σ16PAHs in tea infusions were from 1.2 ng L−1 (white tea) to 151.7 ng L−1 (black tea), while total mean Σ16PAHs was lower than 11.5 ng L−1 regarding tea fruit/herbal beverages. Furthermore, benzo(a)pyrene (BaP) concentrations were from < 1.5 ng L−1 (white tea) to 4.6 ng L−1 (green tea). Nevertheless, BaP concentrations obtained as well as the summation of BaA, Chry, BbF and BaP concentrations (4.6 ng L−1 for tea beverages to 7.5 ng L−1 for green tea infusions) did not exceeded the maximum levels according with European Union (EU) standards. Finally, BaP carcinogenic equivalent concentration (BaPeq) and BaP mutagenic equivalent concentration (BaPMeq) were estimated, ranging from 0.01 ng L−1 to 19.8 ng L−1 and 0.23 ng L−1 to 6.9 ng L−1, respectively.