title: Enhanced detection of the algal toxin PbTx-2 in marine waters by atmospheric pressure chemical ionization mass spectrometry.
abstract: BACKGROUND
  Karenia brevis, a marine dinoflagellate, biosynthesizes a unique class of polyether toxins called brevetoxins that produce significant health, environmental and economic impacts in and along coastal waters. Previous application of liquid chromatography/mass spectrometry for detection of the most common brevetoxin, PbTx-2, has relied almost exclusively upon electrospray ionization (ESI). A different ionization source is proposed in this study with improved sensitivity ultimately leading to lower limit of detection compared to (+) ESI.
  
  
  METHODS
  Brevetoxin standards and samples (PbTx-2) were analyzed by liquid chromatography/mass spectrometry using both (+) atmospheric pressure chemical ionization and (+) electrospray ionization sources.
  
  
  RESULTS
  LC/MS with (+) APCI exhibited an order of magnitude improvement in the limit of detection (7.7 × 10(-4) pg mass on-column) compared to the same method using (+) ESI (7.5 × 10(-3) pg mass on-column). The calibration sensitivity of (+) APCI (1.3 × 10(3)) was also five times higher than positive mode (+) ESI (0.26 × 10(3)).
  
  
  CONCLUSIONS
  Positive mode APCI represents a significant improvement in detection and quantification of PbTx-2 by LC/MS allowing for smaller sample sizes compared to previous studies using (+) ESI. This in turn leads to higher throughput of samples during and after bloom events giving stakeholders detailed information on the fate of this potent marine toxin.
authors.affiliation: Marine and Atmospheric Chemistry Research Laboratory, Department of Chemistry and Biochemistry, University of North Carolina Wilmington, Wilmington, NC, 28403, USA.
authors.forename: Ralph N
authors.initials: RN
authors.lastname: Mead
authors.forename: Emily E
authors.initials: EE
authors.lastname: Probst
authors.forename: John R
authors.initials: JR
authors.lastname: Helms
authors.forename: G Brooks
authors.initials: GB
authors.lastname: Avery
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Kieber
authors.forename: Stephen A
authors.initials: SA
authors.lastname: Skrabal