Gas chromatographic determination of iodinated compounds

The qualitative and quantitative gas chromatographic evaluation of a large variety of iodinated substances (iodoamino acids and their side chain and position analogs, intermediates in the synthesis or degradation of the thyroid hormones, and related compounds) is described. As little as a few hundred picograms can be determined accurately in most cases by means of an electron capture detector. Nonvolatile compounds have been converted to their volatile trimethylsilyl derivatives by treatment with N,O-bis(trimethylsilyl)acetamide at room temperature or at 80°. Various characteristics of these derivatives as well as precautions which must be taken for the determination of picogram and nanogram amounts are described. Mass spectrometry shows that the gas chromatographically determined derivatives of the iodoamino acids contain three trimethylsilyl groups.