Manual and semi-automated procedures for measurements of triglycerides in serum

We describe manual and semi-automated procedures for serum triglyceride determinations, in which lipids are partitioned between a water/isopropanol phase and a nonane phase. More than 99% of the triglyceride is extracted into the nonane phase, as determined by recovery of 3H-labeled triolein. Studies with 14C-labeled lecithin demonstrate that less than 1.3% is extracted into the nonane phase at concentrations up to 2.5 g/liter. A novel feature of the method is that glycerol can be liberated from triglyceride by sodium hydroxide at room temperature in less than 5 min. Glycerol is oxidized by periodate in 1-2 min at 25 degrees C; the formaldehyde produced is reacted with 2,4-pentanedione to yield 3,5-diacetyl-1,3-dihydrolutidine. The manual procedure requires less than 20 min; the semi-automated method requires 7 min from sampling to readout. The procedure may be run at 30-40 samples/h, with stable baseline and less than 2.0% carryover. Both methods are linear to 0.50 g (5.6 mol) of triolein per liter. Analytical recoveries at several concentrations ranged from 97-101% (mean, 100%).