A spectrophotometer measures the transmittance or the absorbance, or both, of a

Question

A spectrophotometer measures the transmittance or the absorbance, or both, of a particular wavelength of light after it has passed through a liquid sample. Before the transmittance or absorbance of the sample Is measured, a cuvette filled only with solvent, called the blank, is placed in the spectrophotometer. Select the following step that Is NOT necessary to complete before a cuvette is placed into the spectrophotometer. Make sure the cuvette is oriented in the spectrophotometer in the same way each time it is used. Make sure the cuvette has exactly the same amount of solution so the readings are consistent. Wipe off the outside of the cuvette with a cleaning tissue to remove any debris or fingerprints. Rinse the cuvette with the sample solution, after washing, to remove residual solvent.

Explanation / Answer

Before placing the cuvette in the spectrometer, it should be cleaned well so as to remove the debris.

The clear faces of the cuvette should face towards the front, that is, the orientation of the cuvette in the spectrometer should be same.

The cuvettes have to be rinsed well to remove the residual solvent in order to obtain concurrent values.

The solution in the cuvette need not be exactly the same as the previous one but ensure that the light from the spectrometer passes through the solution.

Therefore, the correct option that need not be necessarily done before the cuvette is placed in the instrument is, Make sure the cuvette has exactly the same amount of solution so the readings are consistent.

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