Studies on the gravimetric determination of serum lipids

Gravimetric methods for determination of serum total lipids were studied to establish the validity of estimation of neutral fats by difference between total lipid concentration and the sum of the cholesterol, cholesterol ester and phospholipid fractions. Total lipid procedures tested were: (A) extraction with Bloor's solvent, evaporation to dryness and re-extraction into petroleum ether, (B) as in (A) but with evaporation of Bloor's solvent extract to 1–2-ml volume, (C) as in (B) but with water wash of the final petroleum ether extract, and (D) a modification of the method of sperry and brand involving chloroform-methanol extraction followed by purification of the extract with water. Large concentrations of chloride were found in petroleum ether extracts from method B which were in sufficient amount to account largely for discrepancies in apparent total lipid concentrations determined by this method as compared to the other three, all of which agreed well. Comparison of triglyceride results by the method of carlson and wadström with neutral fat calculated by difference from the four total lipid methods showed large discrepancies only with method B, a reflection of erroneous total lipid estimation.