System Performance

Sensitivity

CW Performance

Bruker BioSpin is dedicated to consistently delivering the world's top spectrometer performance.  Through constant hardware development, the ELEXSYS and EMX CW-EPR spectrometers offer the highest sensitivity and highest resolution available.

Spectrometer Sensitivity

WP_SN
The Super High Sensitivity Resonator has a Weak Pitch Signal to Noise of at least 3000 at a modulation frequency of 100 kHz. This signal to noise corresponds to a spin sensitivity of 1×109 spins. Signal trace (red) and noise trace (green).

Weak Pitch Signal to Noise - The sensitivity of the spectrometer is the most important feature in CW-EPR measurements.  To assess the spectrometer sensitivity, the internationally recognized Weak Pitch Protocol is utilized.  A standard Weak Pitch sample is measured at a microwave power of 1 mW and a noise trace is measured at the full output power of the microwave bridge.  The signal to noise from this measurement is used as a means to evaluate both the resonator's performance and the spectrometer's sensitivity.

Utilizing the Weak Pitch Protocol, the ELEXSYS E500 routinely achieves a sensitivity of at least 3000:1 and the EMXplus a sensitivity of 2000:1.
 

Tempol Sensitivity
CW-EPR Spectrum of an aqueous solution of TEMPOL. The sample volume was 6 μL at a concentration of 0.888 μM TEMPOL giving a total number of spins of 3×1012.

Another demonstration of the spectrometer sensitivity is illustrated using an aqueous free-radical solution in the Super High Sensitivity Resonator.  To minimize the interaction with the electric field, the sample was contained in a 50 μL capillary.  The CW-EPR spectrum was measured under non-saturating conditions with a microwave power of 2 mW and a modulation amplitude of 1 G at 100 kHz.