title: Quantitative determination of ochratoxin A by liquid chromatography/electrospray tandem mass spectrometry.
abstract: Mass spectrometry of ochratoxin A (OTA) and B (OTB) under electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) was studied. ESI offers higher sensitivities and less fragmentation than APCI. A sensitive LC/MS/MS method for the determination of ochratoxin A (OTA) in human plasma samples was developed. The absolute minimum detection limit was around 10-20 pg per injection, corresponding to 0.5 ppb in an injection equivalent to 20-40microg of human plasma. Ochratoxin B (OTB) was used as an internal standard and its absence in real-life samples was carefully checked before samples were spiked with the internal standard. It was found that these two ochratoxins are susceptible to sodium adduct formation. Fragment ions from the [M + H](+) and [M + Na](+) ions of both OTA and OTB were monitored in the multiple reaction monitoring mode. Three quantitative approaches, standard addition method, internal standard method (using ochratoxin B as an internal standard) and external standard method, were compared in the analysis of human blood plasma. Results from the mass spectrometric method were comparable to those from a conventional LC/fluorescence method. The LC/MS/MS method was also applied to the analysis of contaminated coffee samples.
authors.affiliation: Health Canada, Health Protection Branch, Food Research Division, Address Locator 2203D, Tunney's Pasture, Ottawa, Ontario, Canada K1A 0L2.
authors.forename: B P
authors.initials: BP
authors.lastname: Lau
authors.forename: P M
authors.initials: PM
authors.lastname: Scott
authors.forename: D A
authors.initials: DA
authors.lastname: Lewis
authors.forename: S R
authors.initials: SR
authors.lastname: Kanhere
mesh_terms: D001274:Atmospheric Pressure; D002273:Carcinogens / Q000032:analysis*; D002853:Chromatography, Liquid / Q000379:methods*; D005504:Food Analysis; D005506:Food Contamination; D006801:Humans; D013058:Mass Spectrometry / Q000379:methods*; D009793:Ochratoxins / Q000032:analysis / Q000097:blood*
chemical_list: D002273:Carcinogens; D009793:Ochratoxins; C025589:ochratoxin A