Results for a monoaromatics fraction from the 535-675 °C distillate of a Wilmington, CA, crude oil demonstrate the efficacy of probe mlcrodlstlllation/mass spectrometry for the qualitative and quantitative analysis of mixtures containing relatively nonvolatile substances. The probe temperature was controlled by a programmer either linearly or to maintain a constant ion current by feedback of the voltage from the Ion current monitor to the programmer. Ions were produced by 70-eV and 10-eV electrons and by field Ionization. Qualitatively, all three methods of Ionization produced the same spectral patterns. Detectable compounds are distributed in

For molecules over 5OOOu, abundances of multiply-charged molecular ions in the fast atom bombardment mass spectra reflect changes in the pH of the sample. This result follows from the production of stable multiply-charged ions with desorption rates comparable to that of singly-charged ions.

No abstract

A high pressure liquid chromatographic (HPLC) method is described for determining ethopabate in poultry feeds. Feed samples containing ethopabate are finely ground, extracted 30 min by sonification with methanol-water (80+20), and filtered. The extract is cleaned up on an alumina column, and the first 4 ml eluate collected is analyzed. The drug is eluted through a μBondapak C18 column with acetonitrile-water (30+70) at a flow rate of 1.4 ml/min and detected by ultraviolet absorption at 280 nm. Chromatography is complete in 7 min, and detector response is linear. The drug is quantitated by peak height ratios. The procedure described is reproducible and shows good agreement with the official AOAC colorimetric method. The lower limit of detection is 2 ng by HPLC, making the method applicable to residue analyses.