A kit for citrate in foodstuffs adapted for assay of serum and urine.

A kit method for rapid analysis of citrate in foodstuffs, based on use of citrate lyase (EC 4.1.3.6), has been adapted and evaluated for use with clinical samples. Membrane filters removed serum proteins, which interfere with the analysis, and reagent and sample volumes were decreased from those in the manufacturer's protocol, thereby decreasing the cost of the assay. Using gravimetrically prepared citrate standards, we determined that assay results varied linearly with concentration up to sixfold the upper reference limit for serum citrate. Intra- and interassay variation were within acceptable limits (CVs less than 3% and less than 8.5%, respectively). Kit reagents were stable for four weeks at -20 degrees C. Assay results were unaffected by hemolysis or other biochemical interferences. The method evidently provides a rapid, convenient microassay for citrate in clinical samples.