O-TRIMETHYLSILYLQUINOXALINOL DERIVATIVES OF AROMATIC ALPHA-KETO ACIDS - MASS-SPECTRA AND QUANTITATIVE GAS-CHROMATOGRAPHY

As an extension of earlier work on aliphatic α-keto acids, a method is described for the quantitative gas chromatographic determination of urinary aromatic α-keto acids. The keto acids are derivatized with o-phenylenediamine to yield the quinoxalinols. These compounds are chromatographed after trimethylsilyation. The aromatic keto acids are stabilized by sodium dithionite (4 mg/ml urine) and storage below 0°. The final derivatives are stable for weeks at room temperature. Low resolution mass spectra are reported. The fragmentation mechanims are elucidated by analysis of O-trimethylsilyl-(TMS)-quinoxalinols, O-(TMS-d9)-quinoxalinols and O-TMS-6(7)-chloroquinoxalinols. © 1978.