title: Atmospheric pressure ionization LC-MS-MS determination of urushiol congeners.
abstract: This paper describes atmospheric pressure ionization (API) LC-MS-MS determination of urushiols, 3-n-alkenyl- and -alkyl-substituted catechols responsible for poison oak dermatitis. Urushiol was isolated from Western poison oak according to the method of Elsohly et al. (1) (J. Nat. Prod. 1982, 45, 532-538)-the purified preparation contained C(17)- and C(15)-substituted urushiols with zero, one, two, and three double bonds as determined from GC-MS analysis of trimethylsilyl derivatives. Urushiol mixtures were separated on a C(18) reversed phase HPLC column with a methanol-water gradient with urushiols eluting in 100% methanol. Atmospheric pressure chemical ionization (APCI) produced primarily [M - H](-) and MH(+) molecule ions. Electrospray ionization (ESI) yielded [M - H](-) and adduct ions including [M + Cl](-). Daughter ions of [M - H](-) included quinoid radical anions ([M - H - H(2)](-) and m/z 122(-)) and a benzofuran phenate (m/z 135(-)). A suite of hydrocarbon fragments were produced by collision-induced dissociation of MH(+) directly or via an intermediate [MH - H(2)O](+) daughter ion. Six urushiol congeners, one not previously reported in poison oak, were determined by negative ion API-LC-MS-MS with detection limits of approximately 8 pg/microL (ESI) and approximately 800 pg/microL (APCI). API-LC-MS-MS was used to determine urushiol in surface wipes, air samples, and plant materials.
authors.affiliation: Sanitation and Radiation Laboratory Branch and Environmental Health Laboratory Branch, California Department of Health Services, Berkeley, California 94704, USA. wdraper@dhs.ca.gov
authors.forename: William M
authors.initials: WM
authors.lastname: Draper
authors.forename: Donald
authors.initials: D
authors.lastname: Wijekoon
authors.forename: Michael
authors.initials: M
authors.lastname: McKinney
authors.forename: Paramjit
authors.initials: P
authors.lastname: Behniwal
authors.forename: S Kusum
authors.initials: SK
authors.lastname: Perera
authors.forename: C Peter
authors.initials: CP
authors.lastname: Flessel
mesh_terms: D001274:Atmospheric Pressure; D002396:Catechols / Q000032:analysis*; D002851:Chromatography, High Pressure Liquid; D002853:Chromatography, Liquid / Q000379:methods*; D008401:Gas Chromatography-Mass Spectrometry; D013058:Mass Spectrometry / Q000379:methods*; D010936:Plant Extracts / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization; D012251:Toxicodendron / Q000737:chemistry*; D014297:Trimethylsilyl Compounds / Q000737:chemistry
chemical_list: D002396:Catechols; D010936:Plant Extracts; D014297:Trimethylsilyl Compounds; C003747:urushiol; C047270:N,N-bis(trimethylsilyl)-2,2,2-trifluoroacetamide; C039293:trimethylchlorosilane