immunofixation on Thin-Layer Agarose

Na2CO3. After 1 mm, 1.0mL of alkaline picrate reagent (500 mL saturated picric acid, 100 mL of 1 mol/L NaOH, and 1 mL of Triton X-100 per liter) is added. The absorbance change at 505 nm and 37 #{176}C is measured between 48 s and 7 mm after adding the picrate reagent. Under these conditions, samples of pooled sera from jaundiced patients showed negative interference, 35 mg of total bilirubin per liter being sufficient to depress the creatinine result by 10 mgIL. For individual specimens, however, it was not possible to correlate the amount of interference with either total, conjugated, or unconjugated bilirubin concentrations. Further investigation revealed that the interference was almost never found with specimens that displayed only the yellow color of bilirubin, but was to be expected when the specimens were brown or green. Evidently, development of a kinetic creatinine assay that works well for icteric specimens will require attention to the other bile and heme pigments sometimes associated with bilirubin. It will not sufficeto test such an assay only with pools containing added unconjugated bilirubin, inasmuch as my experience has shown that it is possible to stumble on a set of conditions in which pigments other than bilirubin are the major interfering materials in jaundiced specimens. I expect that the solution of the problem will lie along the lines already indicated by Osberg and Hammondisolation of the pigment oxidation step from the Jaff#{233} reaction step. I would like to know how the Beckman system used by Osberg and Hammond responds to icteric specimens of unusual color.