title: Dicationic ion-pairing of phosphoric acid diesters post-liquid chromatography and subsequent determination by electrospray positive ionization-tandem mass spectrometry.
abstract: Several organophosphate triesters are widely used as flame retardants and can be metabolized to dibutyl (DBP), diphenyl (DPhP), di(2-ethylhexyl) (DEHP) and di(1,3-dichloro-2-propyl) (or bis(1,3-dichloro-2-propyl); DDCPP) phosphoric acid, respectively. A highly sensitive liquid chromatography-electrospray ionization(+)-triple quadrupole mass spectrometry (LC-ESI(+)-QQQ-MS/MS) based analysis method was presently developed. In this method the target compounds were separated with a C(18)-based reversed phase LC column, and decamethonium hydroxide (dicatonic reagent) was introduced post-LC to form ion-pairs, which were subsequently detected by ESI(+). For the phosphate acid diester ion-pairs, the mass spectra showed the most abundant ion to be [(CH(3))(2)N(CH(2))(10)N(CH(3))(3)](+), with lesser abundances of [[M-H](-)[(CH(3))(3)N(CH(2))(9)CH(2)](2+)](+) and [CH(2)CH(CH(2))(8)N(CH(3))(3)](+). For DDCPP, the fragment ions of [[Cl](-)[(CH(3))(3)N(CH(2))(10)N(CH(3))(3)](2+)](+) and [[Cl](-)[(CH(3))(3)N(CH(2))(9)CH(2)](2+)](+) could also be observed. The limits of quantitation (LOQs) by LC-ESI(+)-MS/MS (based on multiple reaction monitoring) were 0.14, 0.03, 0.14 and 0.02 ng/mL for DPhP, DBP, DDCPP and DEHP, respectively. The response was highly linearly correlated (r>0.995) with concentration over the range of the LOD to 1000 ng/mL. The matrix effect on ESI+ was negligible for the samples in experiment of in vitro metabolism using rat liver microsomes.
authors.affiliation: Ecotoxicology and Wildlife Health Division, Science and Technology Branch, Environment Canada, National Wildlife Research Centre, Carleton University, Ottawa, Ontario K1A 0H3, Canada.
authors.forename: Shaogang
authors.initials: S
authors.lastname: Chu
authors.forename: Da
authors.initials: D
authors.lastname: Chen
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Letcher
mesh_terms: D000818:Animals; D002412:Cations / Q000737:chemistry; D056148:Chromatography, Reverse-Phase / Q000379:methods*; D003650:Decamethonium Compounds / Q000737:chemistry; D005411:Flame Retardants; D008297:Male; D008862:Microsomes, Liver / Q000737:chemistry / Q000378:metabolism; D010755:Organophosphates / Q000032:analysis / Q000737:chemistry* / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D053719:Tandem Mass Spectrometry / Q000379:methods
chemical_list: D002412:Cations; D003650:Decamethonium Compounds; D005411:Flame Retardants; D010755:Organophosphates; C033019:decamethonium