For additional deconjugation experiments in breast milk samples, 100 µL of buffered βglucuronidase/arylsulfatase (from Helix pomatia; activity = 2000 U/mL (glucuronidase) and 21 U/mL (sulfatase)) were added to 100 µL of breast milk and incubated at 37°C for 17 h. For the neonate cohort, selected plasma samples were adjusted to the remaining plasma (40 µL sample + 40 µL enzyme solution) as sample volumes were limited and only available for three neonate samples.