Final answer:
The spectral purity of a spectrophotometer is indicated by its bandwidth or spectral resolution, with a narrower bandwidth or higher resolution being preferable for precise measurements.
Step-by-step explanation:
The spectral purity of a spectrophotometer refers to its ability to isolate and measure specific wavelengths of light, which is essential for accurate spectrophotometric analyses. The specifications that reflect the spectral purity might be listed as the bandwidth or the spectral resolution of the instrument. A narrower bandwidth or higher spectral resolution generally indicates better spectral purity, allowing for more precise measurements. Instruments such as monochromators and spectral analyzers are key to achieving high spectral purity as they can isolate small wavelength bands of light, providing detailed information on the chemical composition of samples. In purchasing a spectrophotometer, it's important to consider its spectral purity to ensure it meets the requirements of the experiments and analyses you plan to conduct.