Analytical standards were purchased from Riedel de Haën: 1-naphthol (1N; purity 99.9%) and 3,5,6-trichloro-2-pyridinol (TCPY; purity 98.8%). Labeled analog of 3,5,6-trichloro-2-pyridinol (4,5,6-13C, 99%, 100 µg/ml in acetonitrile, CP97%) was obtained from Cambridge Isotope Labaratories (CIL) and was used as the internal standard.
Hexane (HEX, ⩾99%), tert-butyl methyl ether (MTBE, ⩾99%), and a mixture of N,O-bis(trimethylsilyl)trifluoroacetamide and trimethylchlorosilane (BSTFA:TMCS, 99:1, BSTFA 99.5%, TMCS 99.2%) were purchased from Sigma-Aldrich. Formic acid (80%), magnesium sulfate anhydrous (98.5%), sodium acetate (99%), and primary secondary amine sorbent (PSA) were obtained from POCH (Gliwice, Poland) and Scharlab (Barcelona, Spain), respectively. β-Glucuronidase (Type HP-2 from Helix pomatia, activity 184973 U/ml) was obtained from Supelco.
Standard stock solutions were prepared in acetonitrile at a concentration of 10 mg/ml and then were used to prepare working solutions of 100 and 10 µg/ml. Working solutions were applied to prepare sequential dilutions for method calibration. Mixed internal standard solutions were prepared in acetonitrile at a final concentration level of 1 µg/ml. All solutions were stored at −20°C. Acetate buffer solution (1 M, pH 5.0) containing 230 U of β-glucuronidase per 750 µl was prepared freshly for each analytical batch.
Hexane (HEX, ⩾99%), tert-butyl methyl ether (MTBE, ⩾99%), and a mixture of N,O-bis(trimethylsilyl)trifluoroacetamide and trimethylchlorosilane (BSTFA:TMCS, 99:1, BSTFA 99.5%, TMCS 99.2%) were purchased from Sigma-Aldrich. Formic acid (80%), magnesium sulfate anhydrous (98.5%), sodium acetate (99%), and primary secondary amine sorbent (PSA) were obtained from POCH (Gliwice, Poland) and Scharlab (Barcelona, Spain), respectively. β-Glucuronidase (Type HP-2 from Helix pomatia, activity 184973 U/ml) was obtained from Supelco.
Standard stock solutions were prepared in acetonitrile at a concentration of 10 mg/ml and then were used to prepare working solutions of 100 and 10 µg/ml. Working solutions were applied to prepare sequential dilutions for method calibration. Mixed internal standard solutions were prepared in acetonitrile at a final concentration level of 1 µg/ml. All solutions were stored at −20°C. Acetate buffer solution (1 M, pH 5.0) containing 230 U of β-glucuronidase per 750 µl was prepared freshly for each analytical batch.