A simple, fast, sensitive and selective method for the extraction of Bisphenol A (BPA) from tea samples has been developed. Due to the low concentration of the analyte, sample preparation using Solid Phase Extraction (SPE) with a Molecularly Imprinted Polymer (MIP) as a sorbent was used to preconcentrate BPA from samples. The MIP was synthesized by the precipitation polymerization using BPA as a template, methacrylic acid (MAA) as a monomer, ethylene glycol dimethacrylate (EDMA) as a crosslinking agent, 2,2′-azobisisobutyronitrile (AIBN) as an initiator, and acetonitrile as a solvent. The optimized SPE process was applied loading 100 mL of the sample through the MIP sorbent at a flow rate of 1.0 mL min−1. The retained BPA was then eluted with 4 mL of methanol. Finally, the extract was analysed by High-Performance Liquid Chromatography-Electrospray Ionization Coupled to a Mass Spectrometry (HPLC-ESI-MS) working in negative mode. The method showed good recovery and precision (% RSD of 7.3). The limits of detection and quantification were 0.072 μg L−1 and 0.24 μg L−1, respectively. The optimized method was applied to BPA determination in several commercial tea samples.

A sensitive, precise and selective method for the analysis of butyl benzyl phthalate (BBP), diethyl phthalate (DEP), dibutyl phthalate (DBP), and dimethyl phthalate (DMP) in tea samples has been applied. Molecularly Imprinted Polymer-Solid Phase Extraction (MIP-SPE) has been used for the separation and preconcentration of these compounds. Phthalates extracted by SPE were analysed by high-performance liquid chromatography-electrospray ionisation-mass spectrometry (HPLC-ESI-MS). The method was sensitive (LOD < 2 µg L−1), precise (RSD <10%) and accurate with recovery percentages ranging from 84% to 97%. Finally, the developed method was applied for the analysis of these phthalates in several tea samples marketed in bags. Migration studies were also performed to evaluate the concentration of phthalates released from the bags into the infusions, and teabag filters were analysed by Fourier-transform infrared spectroscopy. The migration study shows that tea filter bags contribute to the total phthalates concentration in tea infusion, and this contribution varies between 1.8 to 93.5 % of the total phthalates’ concentrations. Tea filter bags release higher DBP than BBP, DMP, and DEP.

Bioaccessibility of trace elements (Li, Be, Ti, Ga, Cu, Ag, Hg, Cd, Cs, Pt, Tl, Pb, As, Cr, Co, Ni, V, Se, Sn and Sb) and major elements (Rb, Ba, Al, Fe, Zn, Si, Ca, Mg, Mn, Mo, Sr, P and K) in tea infusions has been assessed using an in vitro dialyzability protocol. Gastric simulation (using pepsin solution) and intestinal simulation (using pancreatin and bile salts) were used to perform the in vitro digestion. ICP-MS, ICP-OES and FAES were used for elements determination in digested tea leaves, their infusions and the dialyzate fractions from tea infusions. Microwaves assisted acid digestion was used for the total element determination in tea leaves, while tea infusions were prepared by brewing tea leaves for 5 min in boiling water. The LODs for elements determined in tea leaves were in the range of 0.11–656 ng g−1 and 0.02–145.6 μg g−1 for trace and major elements, respectively. For elements’ determination in tea infusions, the LODs were ranged between 0.23 and 399.9 ng L−1 for trace elements and 0.2–1248 μg L−1 for major elements. The LODs for the elements in the dialyzable fraction varied from 0.018 to 142 μg L−1. The accuracy of the total element determination was evaluated using certified reference materials (Tea Leaves INCT-TL-1 and Rye Grass). The analytical recoveries were also assessed for analyzed elements in digested tea leaves (95–114%) and their infusions (92–115%), showing good recoveries. Among the studied elements, K was the most abundant element in tea leaves and tea infusions in almost all samples, followed by Ca, Mg, and P. Zn, Cs, and K showed the highest dialyzability percentages up to 84%, 76%, and 54%, respectively, followed by Si and Ca and K that show moderate to high dialyzability percentages. The accuracy of the dialysis process was evaluated using a mass-balance study.