Dimethylisopropylsilyl ether derivative in gas chromatography/mass spectrometry of 2,3-dinor-6-keto-prostaglandin F1a.

2, 3-Dinor-6-keto-prostaglandin F (I), extracted from its acidic aqueous solution, was converted to its 1-m__--propylamide-6-methyloxime-9, 11, 15-tris-dimethylisopropylsilyl (DMIPS)-ether derivative by treating it with n__-propylamine. O-methylhydroxylamine-HCI and then with DMIPS-imidazole. The chromatogram of the reaction product showed a single broad peak accompanying a shoulder, which was considered to be the unresolved structural syn- and anti-isomer pair. The methylene unit value of this derivative was 34.28, being about 7.5 higher than that of the trimethylsilyl ether derivative of I methyl ester-methyloxime. The reaction product gave a mass spectrum with the ion of [M-43]+ at m/z 669 as a base peak. The molecular ion was observed at m/z 712 with low intensity, and many characteristic ions reflecting the structure with moderate or low intensity. The present I derivative concentrated more than 5% of the total ion current (above m/z 100) into the base peak ion. When Gas chromatography/high resolution selected ion monitoring was carried out at the resolution of 10000 monitoring the ion at m/z 669.4512, specific for the structural integrity of I, the selected ion recording showed a single broad peak with signal-to-noise ratio of more than 10 : 1 after injection of 2 picograms of the derivative.