Final answer:
Cleaning the sample tubes in a spectrophotometer is crucial to ensure accurate readings because residues can affect the light path and skew results, a control tube with only broth is necessary when measuring turbidity to account for the medium's inherent turbidity.
Step-by-step explanation:
Yes, it is important to clean the sample tubes when using a spectrophotometer to ensure accurate readings. Cleaning the tubes is essential because any residues on the tube walls can affect the path of light through the sample, leading to inaccurate transmission and absorbance readings. For example, when measuring the turbidity of bacterial cultures, a clean control tube containing only broth is used to measure the transmission of light. This control is critical because the turbidity of the broth alone affects the amount of light that reaches the detector. By comparing the sample with the control, one can account for the inherent turbidity of the broth and obtain a more accurate measurement of bacterial cell density.
Cleaning the tubes is crucial regardless of whether a UV or visible light spectrophotometer is used. In a spectrophotometer's working process, white light from a source is split into a spectrum and then passed through the sample or control medium. Any impurity or residue in the sample tube may scatter the light and skew results. Hence, consistent cleaning protocols are mandatory to maintain the precision of measurements and the reliability of subsequent analyses.