Heller Test

Heller Test for protein (Heller), based on the precipitation of protein by nitric acid. If several cubic centimeters of concentrated (fuming) nitric acid are poured into a test tube and the liquid being tested is carefully layered on top of it so that the two layers do not mix, then in case the tested liquid contains protein, a ring-shaped whitish turbidity appears at the boundary of the two layers. The sensitivity limit of the test is very high (0.03%_e). The Heller test forms the basis of one of the most common methods for quantitative determination of protein in urine—the Roberts-Stol'nikov method. Based on the fact that with a protein content of 0.033%, a white ring appears in the Heller test after 3 minutes, it is determined how many times the urine must be diluted so that it contains 0.033%_o protein. For this, a series of increasing dilutions of urine are prepared and from them the last one is found in which, with the Heller test, a white ring appears after 3 minutes. Protein content = 0.033 × a %₀, where a is the degree of urine dilution. For protein amounts above 0.3%_o, the test is unsuitable, and it is necessary to use the Esbach's albuminometer. In urine containing a large amount of uric acid, a turbid ring from the precipitation of uric acid sometimes appears with the Heller test. Unlike the protein ring, it forms not at the boundary of the two layers, but higher, and when the Heller test is repeated with diluted urine, it does not appear.