A quantitative magnetic analytical method using Curie's law for a mixture of paramagnetic and diamagnetic substances

The principle of quantitative magnetic analytical measurement using Curie's law is proposed as a future candidate for a new potential primary direct method of measurement for amount of substance. The targeted main analyte in a mixture sample is a species-a rare-earth ion or a transition-metal ion-that has a free quantum spin. The matrix of the mixture sample is diamagnetic. The spin number of the analyte can be obtained from the temperature dependence of the sample's magnetic moment. This analytical method uses differences in the temperature dependences of Langevin paramagnetism, which obeys Curie's law, and diamagnetism, which exhibits temperature-independent behaviour. For preliminary validation of this analytical method, powder mixture samples of gadolinium oxide in silicon oxide were prepared by a gravimetric blending method. The mass fractions of the prepared mixture samples were approximately 0.2 to 0.008. The values of the samples' magnetic moments at temperatures below 340 K were measured using a superconducting quantum interference device magnetometer. Each analytical concentration of gadolinium oxide determined by the temperature dependence of the magnetic moment was found to be consistent with the gravimetric concentration within a relative difference of approximately 10%.