No abstract

Cholesterol determination has been hampered by the lack of suitable means to prepare lyophilized serum control materials with an appropriate range of values. We prepared a water-soluble cholesterol derivative by first esterifying cholesterol with adipic acid and then reacting the cholesterol hemiadipate with Polyethylene Glycol 600 to form polyethoxyethanyl-cholesteryl adipate. The compound reacts quantitatively in several commonly used methods, including enzymic, extraction, and direct-assay procedures. When the additive is directly mixed with human serum that has been depleted of beta- and pre-beta-lipoproteins, an optically clear solution results for which cholesterol values are stable. The clarity is retained upon lyophilization and reconstitution. Addition of this cholesterol compound to partially delipidized serum appeared to have no significant effect on results of assay of 18 other commonly measured serum constituents.

An automated method is described for determining alkaline phosphatase activity in serum, with use of sodium thymolphthalein monophosphate as the substrate. The system makes use of standard AutoAnalyzer components, has a simple flow diagram, and does not involve dialysis. The method has good precision, and the results correlate well with those from the manual method of which it is an adaptation