Reproducibility measurements for ESR signal intensity and dose determination: high precision but doubtful accuracy

Reproducibility measurements on fossil tooth enamel show that the intensity of the main signal can be measured with high precision (<1%). Dose response curves based on conventional peak-to-peak measurements yield doses with errors in the range of 1-3.5%. The most appropriate weighting model for exponential regression is the experimentally determined variance; a model using weights inversely proportional to intensity squared also gives sensible results. Dose versus magnetic field plots on derivative and absorption spectra yield dose values with similar high precisions. However, these plots cast doubt on the general validity of ESR dose assessments from complex ESR spectra such as fossil tooth enamel. Meaningful spectrum deconvolution is urgently required for the estimation of reliable dose values