An automated sample changer for Bruker ESR spectrometers

Abstract

We have developed an automated sample changer which allows the measurement of up to 40 samples without operator attendance. It had not been possible to adapt commercially available robotic arms or autoloaders. A performance test on enamel samples from a single tooth showed that (i) the changer worked reliably and was not an additional source of error and (ii) when using Fourier transformation to eliminate high frequency noise of the spectra, the unvertainty in the measurement of the ESR intensity was in the range of 1%. Furthermore, there was no difference in the unvertainty of an ESR measurement between aliquots that were weighed as precisely as possible to 40 mg before measurement and subsamples (ranging between about 33 and 50 mg) whose weight was used after measurement for spectrum weight normalisation.