[Determination of the serum protein concentration based on the measurement of density by the mechanical oscillator technique (author's transl)].

: A linear relation is well established between the density and protein concentration of the serum. The measurement of protein concentration by a new technique for the determination of the absolute density, the mechanical oscillator technique, was investigated. The method is based on the determination of the resonant frequency of a mechanical bending-type, U-shaped glass tube oscillator filled with the sample. The shift in the resonant frequency of the oscillator caused by the mass of the defined volume of the sample taking part in the vibration can be used to calculate the density or protein concentration of the sample. In spite of the low specificity of the method, the interference of substances like glucose, urea or triglycerides is small. Simplicity and rapid results of high accuracy recommend the mechanical oscillator technique for the routine laboratory.