Background: Identification and quantitative determination of analytes released from the packaging material is undoubtedly a difficult and tricky task, requiring the chemical analyst to develop an individual approach to obtain reliable analytical information. Unfortunately, it is still challenging for scientists to determine bisphenols at trace or even ultra-trace levels in samples characterized by a very complex, and often variable, matrix composition. Objective: Optimization and application of QuEChERS/d-SPE coupled with HPLC-DAD (and LC-QqQ-MS) method for the simultaneous determination of bisphenols (A, S, F, B, BADGE and derivatives) in milk samples from a can and breast milk samples have been performed. Methods: Concerning the analysis of unconjugated analytes, after the thawing and shaking the sample (5 mL breast milk or 10 mL milk samples from a can), it was transferred into a 50 mL polypropylene centrifuge tube. For the analysis of the total amount of analytes, prior to the extraction with acetonitrile, a deconjugation step was implemented in a tube by adding to sample, the an Isotopically Labelled Internal Standard (IS) solution (50 ng/mL) and 1 mL of the enzymatic solution with the β-Glucuronidase (3500 U/mL). The mix was homogenized and incubated for 16–18 h at 37 °C. Next, 10 mL of acetonitrile, and a QuEChERS salt packet (4 g anhydrous MgSO4, 1 g NaCl) were added. After shaking and centrifugation, the total acetonitrile layer was isolated in a polypropylene tube evaporate to dryness, and reconstitute in 1.2 mL acetonitrile. During d-SPE step the extract was transferred into a 15 mL polypropylene tube with Z-Sep and primary secondary amine (PSA). Next, shake the tube, store in fridge, and centrifuge for 15 min. The acetonitrile supernatant was obtained with a pipette and evaporated to dryness. Mixture MeOH: water (20:80, v/v) were added to the dry residue and the extract was reconstitute in 200 μL and analyzed by HPLC-DAD and HPLC–QqQ-MS equipment. Conclusion: Six different salts during d-SPE step were evaluated such as: zirconium dioxide-based sorbent (Z-Sep, Z-Sep Plus), primary secondary amine (PSA), octadecyl (C18), EMR-Lipid, Chitin and also their mixtures. Negligible matrix interference was observed for most of the analytes due to application of Z-Sep and PSA in dispersive-solid phase extraction clean-up step. Extraction of target analytes was performed using QuEChERS/d-SPE cleanup, and presents good performance for selected analytes with recoveries in the range of 15–103% and relative standard deviations (RSD) less than 10% in breast milk samples.
Recent advances and prospects in the Zn-catalysed Mannich reaction
