Rapid determination of ribonuclease and microanalysis of heparin with a SAW/conductance sensor

A new method using a surface acoustic wave (SAW)/conductance sensor has been described in this paper for rapid determination of ribonuclease (RNase) and microanalysis of heparin. The assay of RNase is based on the change in conductance of the solution caused by enzymatic reaction between ribonucleic acid (RNA) and RNase and the analysis of heparin is based on its inhibitory action on RNase. A linear relationship between frequency response and enzyme concentration is obtained and the detection limit of RNase is evaluated to be 0.17 μg ml −1. The recovery of the sensor system ranges from 95.8 to 105.0%. The inhibition of heparin is a competitive one and the possible inhibition mechanism is discussed. The kinetic parameters and inhibition parameters are estimated. The calibration graph is rectilinear for ≤ 8 μg ml −1 of heparin and the detection limit is 0.1 μg ml −1. The influence of pH value on the inhibition of RNase by heparin has been investigated and the effects of Ca 2+, Mg 2+ are also discussed.