Potential of gas chromatography coupled to triple quadrupole mass spectrometry for quantification and confirmation of organohalogen xenoestrogen compounds in human breast tissues.

The potential of gas chromatography coupled to tandem mass spectrometry (GC/MS/MS) with a triple quadrupole analyzer (QqQ) has been investigated for the accurate and sensitive determination of xenoestrogens in human breast tissues. Special emphasis has been given to the confirmation of the identity of compounds detected in the samples analyzed in order to avoid the reporting of false positives. The work has been focused on the determination of approximately 30 organochlorine compounds (PCBs and pesticides) and organobromine compounds (polybrominated diphenyl ethers) in adipose breast tissue and in tumoral fragment. Analytes were extracted by dissolving the samples in hexane, and the extracts were purified by automated normal-phase HPLC prior to GC/MS/MS analysis. Three isotopically labeled standards were added before extraction as surrogates for the quality control of the analyses. Accuracy and precision were evaluated by means of recovery experiments using adipose breast tissue spiked at three concentration levels, with satisfactory results for most analytes. The excellent selectivity and sensitivity of QqQ in selected reaction monitoring mode allowed us satisfactory quantification and confirmation at levels as low as 5-25 ng/g, i.e., the lowest concentration level for which the method was fully validated. Two MS/MS transitions were selected for each analyte, using the concentration ratio obtained from them as a confirmatory parameter. The developed methodology was applied to the analysis of 51 breast samples (26 adipose tissues and 25 tumoral fragments), giving as a result the detection and confirmation of several organochlorine compounds in both types of samples. Due to its adequate analytical characteristics, the optimized method fits with the requirements of accurate quantification and reliable confirmation of the identity of compounds detected according to the most recent European Guidelines. As an ultimate unequivocal confirmation, several selected samples were reanalyzed by gas chromatography coupled to mass spectrometry with a time-of-flight (TOF) analyzer. Confirmation of analytes present at higher concentrations was successful with mass error less than 5 mDa. However, confirmation by TOF MS was not possible al low concentrations (i.e., at the few ng/g level) as a consequence of its lower sensitivity compared with that of triple quadrupole in selected reaction monitoring mode.