Stable isotope dilution method for measurement of palmitate content and labeled palmitate tracer enrichment in microliter plasma samples.

In studies where [1-13C]palmitic acid is employed as isotopic tracer in vivo, we have described a selected ion monitoring gas-liquid chromatography-mass spectrometry micro-method which allows plasma tracer enrichment as well as plasma palmitate content to be determined in the same 100-microliter sample through the use of [5,5,6,6-2H4]palmitic acid as assay internal standard. For standard solutions in the range equivalent to plasma palmitic acid concentrations of 10--2500 microM, assay precision was +/- 5%. For plasma samples in the physiologic range (approximately 30--200 microM palmitate) assay precision averaged better than +/- 2%. The use of the method is illustrated by measuring palmitate turnover in a 12-hr-old human infant.