ASTM E958-13(2021)

4.1?These practices should be used by a person who develops an analytical method to ensure that the spectral bandwidths cited in the practice are actually the ones used.

4.2?These practices should be used to determine whether a spectral bandwidth specified in a method can be realized with a given spectrophotometer and thus whether the instrument is suitable for use in this application. If accurate absorbance measurements are to be made on compounds with sharp absorption bands (natural half band widths of less than 15 nm) the spectral bandwidth of the spectrometer used should be better than ¹/_8th?of the natural half band width of the compounds absorption.

4.3?These practices allow the user of a spectrophotometer to estimate the actual spectral bandwidth of the instrument under a given set of conditions and to compare the result to the spectral bandwidth calculated from data given in the manufacturer's literature or indicated by the instrument.

1.1?This practice describes procedures for estimating the spectral bandwidth of a spectrophotometer in the wavelength region of 185 nm to 820 nm.

1.2?These practices are applicable to all modern spectrophotometer designs utilizing computer control and data handling. This includes conventional optical designs, where the sample is irradiated by monochromatic light, and reverse optic designs coupled to photodiode arrays, where the light is separated by a polychromator after passing through the sample. For spectrophotometers that utilize servo-operated slits and maintain a constant period and a constant signal-to-noise ratio as the wavelength is automatically scanned, and/or utilize fixed slits and maintain a constant servo loop gain by automatically varying gain or dynode voltage, refer to the procedure described in Annex A1. This procedure is identical to that described in earlier versions of this practice.

1.3?This practice does not cover the measurement of limiting spectral bandwidth, defined as the minimum spectral bandwidth achievable under optimum experimental conditions.

1.4?The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.5?This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.6?This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.