title: Automated solid-phase extraction and quantitative analysis of 14 phthalate metabolites in human serum using isotope dilution-high-performance liquid chromatography-tandem mass spectrometry.
abstract: Phthalates are industrial chemicals with many commercial applications. Because of their common usage, the general population is exposed to phthalates. A sensitive and selective analytical method is necessary to accurately determine the phthalate levels in serum. We improved our previously developed analytical method to measure nine phthalate metabolites in human serum by automating the solid-phase extraction (SPE) procedure and by including five additional phthalate metabolites: phthalic acid; mono-isobutyl phthalate, a metabolite of di-isobutyl phthalate; mono-(3-carboxypropyl) phthalate, a major oxidative metabolite of di-n-octyl phthalate; and mono-(2-ethyl-5-oxohexyl) phthalate and mono-(2-ethyl-5-hydroxyhexyl) phthalate, two oxidative metabolites of di-(2-ethylhexyl) phthalate. Automation of the SPE eliminated the human variation associated with the manual SPE, thus improving the reproducibility of the measurements. Additional wash steps during SPE produced cleaner extracts and resulted in higher recoveries (80-99%) than the manual SPE method. Furthermore, the automated SPE method allowed for the unattended extraction of samples, with a concomitant increase in sample throughput compared to the manual SPE method. The method is accurate, precise, and sensitive, with limits of detection in the low nanogram-per-milliliter range.
authors.affiliation: Division of Laboratory Sciences, National Center for Environmental Health, Centers for Disease Control and Prevention, Atlanta, Georgia 30341, USA. zca2@cdc.gov
authors.forename: Manori J
authors.initials: MJ
authors.lastname: Silva
authors.forename: Ella
authors.initials: E
authors.lastname: Samandar
authors.forename: James L
authors.initials: JL
authors.lastname: Preau
authors.forename: John A
authors.initials: JA
authors.lastname: Reidy
authors.forename: Larry L
authors.initials: LL
authors.lastname: Needham
authors.forename: Antonia
authors.initials: A
authors.lastname: Calafat
mesh_terms: D002247:Carbon Isotopes; D002851:Chromatography, High Pressure Liquid; D006801:Humans; D006863:Hydrogen-Ion Concentration; D013058:Mass Spectrometry; D010795:Phthalic Acids / Q000378:metabolism*
chemical_list: D002247:Carbon Isotopes; D010795:Phthalic Acids; C032279:phthalic acid