Simultaneous quantitation of morphine and codeine in biological samples by electron impact mass fragmentography

A method was developed for the quantitative determination of free morphine and codeine utilizing multiple ion detection mass fragmentography. Samples were spiked with nalorphine (internal standard), extracted and converted to pentafluoropropionyl (PFP) derivatives prior to GC/MS analysis. The PFP derivatives were separated chromatographically on a 5% OV-1 column. The base peak and molecular ion of the El mass spectra were at m/e 414 and 577; 282 and 445; and 440 and 603, for morphine-PFP, codeine-PFP and nalorphine-PFP, respectively. These multiple ions were monitored and the peak area ratio relative to nalorphine-PFP was used as the basis for quantitation. Other drugs studied were found not to interfere with this method.