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A procedure for spectrophotometric statistical error calibration is described, in which estimates of the variance (sigmaA2) in the absorbance A are derived as a function of A and the wavelength
lambda, directly from recorded spectra. Spectra are obtained over the desired wavelength range for a number of neutral-density filters, and are then least-squares fitted piecemeal to low-order polynomials.
The variances from these fits constitute the estimates of the instrumental variance sigma 2 for the lambda and A of the respective fitted segments. These values are in turn expressed as functions of lambda
and A, by means of a small number of parameters. In the present case a representation in terms of A and I0, the ''effective'' source intensity, is even more compact, requiring only five parameters
to cover the 200-850nm region for absorbances up to and exceeding 2. For the instrument studied here, the high-A precision is limited by digitization error, the error being independent of lambda and I.
Index Headings: UV-visible spectrophotometry; Statistical errors; Calibration; Least-squares weights; Spectral fitting.
The Society publishes the internationally recognized, peer reviewed journal, Applied Spectroscopy, which is available both in print and online. Subscriptions are included with membership or can be purchased by institutional or corporate organizations. Abstracts may be viewed free of charge. Previously published as Bulletin (Society for Applied Spectroscopy)