Question

The calibration of absorbance of UV-Visible spectrometer is performed by using _______

• A. \( \text{Potassium chloride} \)
• B. \( \text{Potassium dichromate} \)
• C. \( \text{Holmium perchlorate} \)
• D. \( \text{Potassium permanganate} \)

Hint:

Think of "dichromate" as having reliable colors (absorbance) that a UV-Vis machine should read correctly if it's calibrated.

Answer 1

The Correct Option is B

The calibration of the absorbance scale of a UV-Visible spectrophotometer is commonly performed using standard solutions with known absorbance values at specific wavelengths. Potassium dichromate in acidic solution is often used for this purpose because it exhibits stable and well-defined absorbance peaks at several wavelengths in the UV and visible regions (e.g., 235 nm, 257 nm, 313 nm, 350 nm). These absorbance values are well-documented and can be used to check the accuracy of the instrument's absorbance readings. Holmium perchlorate solutions are primarily used for wavelength calibration due to their sharp and well-defined absorption bands. Potassium chloride does not have significant absorbance in the UV-Visible range and is not used for absorbance calibration. Potassium permanganate has strong absorbance but is less stable and therefore less suitable as a primary absorbance standard compared to potassium dichromate.