An electron paramagnetic resonant (EPR) instrument able to determine chemical properties of a sample using paramagnetic resonance is provided. In one embodiment, the instrument is able to measure the paramagnetic concentration of a wide variety of practical substances, ranging from food and beverages to biological specimens and solid-state electronic materials. The disclosed device can be portable and perform a measurement faster than commonly used techniques to quantify this parameter, including methods that use vibrating sample magnetometers and currently available electron paramagnetic resonance spectrometers.