UPLC-MS/MS determination of ptaquiloside and pterosin B in preserved natural water

• Published in: Analytical and bioanalytical chemistry 2016-11, Vol.408 (28), p.7981-7990
• Main Authors: Clauson-Kaas, Frederik, Hansen, Hans Christian Bruun, Strobel, Bjarne W.
• Format: Article
• Language: English
• Subjects: Ammonium; Analytical Chemistry; Biochemistry; Buffers; Carcinogens; Characterization and Evaluation of Materials; Chemical analysis; Chemical properties; Chemistry; Chemistry and Materials Science; Chromatography; Detection limits; Extraction; Food Science; Groundwater; High performance liquid chromatography; Laboratory Medicine; Leaching; Liquid chromatography; Mass spectrometry; Mathematical analysis; Methods; Monitoring/Environmental Analysis; Protozoa; Purity; Raw water; Reference materials; Research Paper; Sample preparation; Sample preservation; Shallow water; Stands; Supports; Surface water; Water analysis; Water sampling; Water table
• ISSN: 1618-2642; 1618-2650
• DOI: 10.1007/s00216-016-9895-z

The naturally occurring carcinogen ptaquiloside and its degradation product pterosin B are found in water leaching from bracken stands. The objective of this work is to present a new sample preservation method and a fast UPLC-MS/MS method for quantification of ptaquiloside and pterosin B in environmental water samples, employing a novel internal standard. A faster, reliable, and efficient method was developed for isolation of high purity ptaquiloside and pterosin B from plant material for use as analytical standards, with purity verified by 1 H-NMR. The chemical analysis was performed by cleanup and preconcentration of samples with solid phase extraction, before analyte quantification with UPLC-MS/MS. By including gradient elution and optimizing the liquid chromatography mobile phase buffer system, a total run cycle of 5 min was achieved, with method detection limits, including preconcentration, of 8 and 4 ng/L for ptaquiloside and pterosin B, respectively. The use of loganin as internal standard improved repeatability of the determination of both analytes, though it could not be employed for sample preparation. Buffering raw water samples in situ with ammonium acetate to pH ∼5.5 decisively increased sample integrity at realistic transportation and storing conditions prior to extraction. Groundwater samples collected in November 2015 at the shallow water table below a Danish bracken stand were preserved and analyzed using the above methods, and PTA concentrations of 3.8 ± 0.24 μg/L (±sd, n  = 3) were found, much higher than previously reported. Graphical abstract Workflow overview of ptaquiloside determination