Naslov
Determination of chiral metabolites of styrene in biological material

Autori
Jakaša, Ivone

Vrsta, podvrsta i kategorija rada
Ocjenski radovi, magistarski rad

Fakultet
Prirodoslovno-matematički fakultet

Mjesto
Zagreb

Datum
09.02

Godina
2000

Stranica
103

Mentor
Kezic, Sanja ; Drevenkar, Vlasta

Ključne riječi
gas chromatography ; enantiomer separation ; styrene-7 ; 8-oxide ; styrene glycol ;

Sažetak
The aim of this work was to develop sensitive and stereospecific gas chromatographic methods for determination of chiral metabolites of styrene in biological material using the chiral CP Chirasil- Dex CB and CP Cyclo-Dex B 236 M columns. The following metabolites were analysed: styrene-7, 8- oxide (SO) and styrene glycol (SG) in the human and rat liver and brain microsomes, and mandelic acid (MA) in human urine. The method for the determination of SO is based on a highly stereospecific, base-catalysed ring opening of the SO using a strong nucleophile (NaOMe/MeOH). As confirmed by proton nuclear magnetic resonance and mass spectrometry, the opening of the epoxide ring led to the formation of two regional stereomers for each enantiomer: 2-methoxy-2-phenylethanol and 2-methoxy-1-phenylethanol. In order to improve the sensitivity of the determination, the formed methoxy alcohols were subsequently derivatized using pentafluoropropionic anhydride (PFPA) making it suitable for the electron capture detection (ECD). The derivatization proceeded stereospecifically for both enantiomers. The repeatability (within-day precision) of the method, assessed at the SO concentration levels of 0.3 and 3.0  g mg-1 of protein by analyzing 10 aliquots of microsome samples was 9.1 and 6.0 %, for the R-SO and 8.0 and 6.1 % for the S-SO, respectively. For both SO enantiomers the limit of quantitation was 0.016  g mg-1 of protein. The determination of SG enantiomers is based on the extraction with ethyl acetate and subsequent derivatization with PFPA enabling a very sensitive ECD detection. The derivatization step proceeded without enantiomeric excess (<1 %). The repeatability (within-day precision) of the method, assessed at the SG concentration levels 0.45 and 4.5  g mg-1 of protein by analyzing of 10 aliquots of microsome samples was 4.1 and 7.5 %, for the R-SG and 4.8 and 4.5 % for the S-SG, respectively. The limit of quantitation was 0.045 and 0.067  g mg-1 of protein for R- and S-SG respectively. The method for the determination of the MA enantiomers is based on esterification with isopropanol. The corresponding isopropyl esters could be determined either directly with a flame ionization detecton (FID) or, after subsequent derivatization of a hydroxyl group with PFPA with ECD. Both derivatization steps proceeded with negligible inversion of enantiomers (<1 %). The limit of detection of the GC-FID determination was 8 and 5 mg L-1 for R-MA and S-MA, respectively, and of GC-ECD determination 1 mg L-1 for both enantiomers. For both enantiomers repeatability (within-day precision) and reproducibility (day- to-day precision) were below 7.5 % for GC-FID and below 5.8 % for the GC-ECD analysis. The method was applied for determination of MA enantiomers in urines of volunteers exposed to 105 and 420 mg m-3 styrene.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

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