Article pubs.acs.org/est
Part I. A Temporal Study of PFCAs and Their Precursors in Human Plasma from Two German Cities 1982−2009 Leo W. Y. Yeung,† Shona J. Robinson,† Jan Koschorreck,‡ and Scott A. Mabury*,† †
Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, M5S 3H6, ON, Canada Umweltbundesamt, Wörlitzer Platz 1, 06844 Dessau-Roßlau, Germany
‡
S Supporting Information *
ABSTRACT: A total of 420 human plasma samples from two cities (Halle and Münster, Germany), collected between 1982 and 2009, were analyzed for a suite of PFCAs (C6−C12) and selected PFCA precursors (4:2-, 4:2/6:2-, 6:2-, 6:2/8:2-, 8:2-, 8:2/10:2-, and 10:2-diPAPs). PFCAs (C7−C11 and C13) were detected in over 80% of the samples (99%), and ammonia (NH3, 30%) were obtained from Sigma-Aldrich. Methanol (MeOH, LCMS grade) and methyl-tert-butyl ether (MTBE, Omnisolv, >99%) were acquired from EMD Chemicals Inc. (Mississauga, ON). Standard reference material (SRM1957, Organic Contaminants in Non-Fortified Human Serum) was purchased from the National Institute of Standards and Technology (NIST); the SRM1957 are certified with C7−C12 PFCAs and C6 and C8 PFSAs (SI Table S1). All plasma samples were stored at −20 °C. 3866
dx.doi.org/10.1021/es303716k | Environ. Sci. Technol. 2013, 47, 3865−3874
Environmental Science & Technology
Article
significant problem. We have no similar line of comfort for assessing PFCA contamination. With respect to diPAP stability during sample storage, two reports have discussed the stability of phosphate esters; they suggest that phosphate esters are resistant to hydrolysis;33 although enzymatic hydrolysis of phosphate esters has been demonstrated at 22 °C, this mechanism would not be expected at the storage temperatures of −80 °C or −150 °C in the GSB.25 To lower detection limits for LC-MS/MS and avoid potential interference during instrumental analysis, all accessible polytetrafluoroethylene (PTFE) and other fluoropolymer materials were removed from the instruments to minimize background signal due to contamination. An extra column (PFC isolator, Waters Corporation) was inserted between the pump and injector to trap contaminants originating from the LC system (SI Figure S3). DiPAP contamination was found in solvent/sample handling materials, such as transfer pipets, pipet tips, and even on their containing boxes (SI Figure S4). More importantly, diPAPs were also found in high purity methanol after a 40-fold concentration. DiPAP-free consumables were used for the project, however, no diPAP-free methanol was commercially available. Therefore, no further cleanup procedures involving concentration of methanol could be performed on the samples before instrumental analysis. Falcon tubes and septa were selected after a thorough checking of blanks (
