Funding for this research was provided by:
Center for Human Health and the Environment (NIH P30ES025128)
Text and Data Mining valid from 2018-02-17
Received: 4 December 2017
Revised: 18 January 2018
Accepted: 30 January 2018
First Online: 17 February 2018
Compliance with ethical standards
: This research did not involve human participants or animals.
: David C. Muddiman is named on a patent that is pending for which Cambridge Isotope Laboratories pays royalties to NC State University. None of the remaining authors have any conflicts of interest.