Calibration Standard to Check the Spectral Resolution

Spectral resolution is a measure of the ability of an instrument to differentiate between two adjacent wavelengths. Two peaks usually are considered resolved if the minimum of the absorption between the two peaks is lower than 80% of the peak maxima. Resolution of a modern spectrophotometer is closely related to its slit width. The smaller the slit width and associated instrumental spectral bandwidth, the higher is the spectral resolution.

For wavelength and absorbance measurements the dispersive power of the monochromator has to be considered, too. At the same time a small spectral bandwidth leads to a reduction of energy throughput and so the signal-to-noise ratio will fall.

When measuring in a high-resolution spectrophotometer, it is recommended that the spectral bandwidth should not exceed 10% of the natural bandwidth of the peak that is to be analysed.

Regularly checks of the resolution power of an instrument assure that, for example adjacent peaks will be fully resolved and not blended into a combined peak with the associated wavelength. Additionally absorbance errors will be avoided.