Rj. Caimi et Jt. Brenna, HIGH-SENSITIVITY LIQUID-CHROMATOGRAPHY COMBUSTION ISOTOPE RATIO MASS-SPECTROMETRY OF FAT-SOLUBLE VITAMINS, Journal of mass spectrometry., 30(3), 1995, pp. 466-472
The sensitivity of high-precision liquid chromatography/combustion iso
tope ratio mass spectrometry (LC/C-IRMS) was improved by more than two
orders of magnitude by modifications which permit optimization of flo
ws, The lower limits for high precision are about 3 mu g of analyte on
-column for flow injection and LC modes. Pneumatic aerosol spray coati
ng was implemented and compared with simple dip coating. The signal en
hancement for aerosol compared with dip coating is up fourfold at high
er levels but drops to less than twofold at lower levels, while the dy
namic range is extended at higher levels by fourfold at high sample lo
ad levels. LC separations for underivatized tocopherols, retinyl aceta
te and ergocalciferol are demonstrated with precision and accuracy of
about delta(13)C < 2.5 parts per thousand for replicates. This work de
monstrates sensitivity useful for a wide range of LC analyses and exte
nds high-precision LC/C-IRMS to the determination of several fat-solub
le vitamins.