HPLC-APCI-MS with calibration based on stable isotope-labelled internal standards for the quantification of carbonyls in air samples

A method for the selective determination of formaldehyde and acetaldehyde i n air samples based on HPLC-APCI-MS with calibration using stable isotope-l abelled standards was developed. d(2)-Formaldehyde-2,4-dinitrophenylhydrazo ne and d(4)-acetaldehyde-2,4-dinitrophenylhydrazone were synthesized from 2 ,4-dinitrophenylhydrazine and the respective deuterated aldehydes. The labe lled derivatives were used as internal calibration standards in the quantif ication of formaldehyde and acetaldehyde in complex matrices, including aut omobile exhaust. Co-elution of the labelled and non-labelled derivatives in HPLC provides for identical mass spectrometric conditions, thus significan tly reducing the relative standard deviation of the internal calibration ap proach compared with external calibration with non-labelled derivatives.