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6.3.2.3  Methods  for  Pentachlorophenol  and  Trichloropyridinol
PCP  and  TCPy  are  susceptible  to  adsorption  in  the  GC  system  because  of  their  polar
phenolic  substructure.  Direct  GC  analysis  was  only  possible  at  high  concentrations
(>lng).  Therefore,  two  alternative  approaches  were  applied  during  the  study.
First,  an  HPLC-MS  method  was  developed  in  order  to  overcome  thermal  stress  during
the  analysis.  This  was  successful  in  principle.  A  reversed  phase  HPLC  gradient
separation  yielded  well-defined,  non-tailing  peaks  both  for  PCP  and  TCPy,  and  ESI  MS
showed  M-l  ions  in  the  negative  ionisation  mode  with  a  good  ion  yield  (Figure  52,
Appendix  6.6.6.1).  Unfortunately,  it  was  not  possible  to  fragment  the  pseudo-molecular
ion;  the  high  selectivity  of  MS-MS  thus  could  not  be  used,  but  only  the  less  selective
single-stage  MS  in  SIM  mode.  Consequently,  this  method  was  applicable  only  to  water
samples,  where  matrix  disturbances  are  much  less  pronounced  than  in  sediment  or  biota
samples.  But  even  with  water  samples  only  a  moderate  sensitivity  could  be  obtained.
The  second  approach  used  a  derivatisation  step  with  heptafluorobutyric  acid  anhydrate
(HFBAA)  to  form  the  HFBA  esters  and  a  GC-MS  analysis  in  the  NCI  mode.  This
technique  was  used  for  sediments  and  biota.  Only  PCP  could  be  derivatised  and
analysed  by  this  method.