| 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 wasisolated from Western poison oak according to the method of Elsohly et al. () (J. Nat. Prod.1982,45, 532−538)the purified preparation contained C17- and C15-substituted urushiols with zero, one,two, and three double bonds as determined from GC-MS analysis of trimethylsilyl derivatives. Urushiolmixtures were separated on a C18 reversed phase HPLC column with a methanol−water gradientwith urushiols eluting in 100% methanol. Atmospheric pressure chemical ionization (APCI) producedprimarily [M − H]- and MH+ molecule ions. Electrospray ionization (ESI) yielded [M − H]- and adductions including [M + Cl]-. Daughter ions of [M − H]- included quinoid radical anions ([M − H − H2]-and m/z 122-) and a benzofuran phenate (m/z 135-). A suite of hydrocarbon fragments were producedby collision-induced dissociation of MH+ directly or via an intermediate [MH − H2O]+ daughter ion.Six urushiol congeners, one not previously reported in poison oak, were determined by negative ionAPI-LC-MS-MS with detection limits of ∼8 pg/μL (ESI) and ∼800 pg/μL (APCI). API-LC-MS-MS wasused to determine urushiol in surface wipes, air samples, and plant materials. Keywords: Urushiol congeners; poison oak allergens; API-LC-MS-MS analysis
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