1. Choose a cuvette that is free from scratches.

2. Always use the same cuvette for all your measurements.

3. When handling the cuvette, avoid touching the surfaces the light will pass

through. Many cuvettes will have frosted sides and clear sides. Handle the

cuvette on the frosted sides and make sure the light goes through the clear

sides.

4. When cleaning, rinse the cuvette a few times with the solution you are about

to fill it with. This minimizes the impact of residual solution left in the cuvette.

5. Only use non-abrasive materials when cleaning the cuvette (tissues and other

items that don’t scratch are the best to use for cleaning).

6. Make sure to fill the cuvette so that the light is going through the solution.

Typically filling to three-quarters full is sufficient.

7. Wipe any drips or liquid from the outside of the cuvette using a soft tissue.

8. Always put the cuvette into the instrument with the same orientation.

Typically, there is a mark on the cuvette, and you can always ensure that the

mark is facing the same direction.

Blanking the Instrument

The entire technique is built on measuring how much light makes it through the

sample. This requires us to know how much light would make it to the detector if

our sample were not present. To accomplish this, we set a reference point that

we will call the “blank,” which is how much light reaches the detector when a

cuvette contains everything except the compound of interest. Often pure water is

sufficient to be used as a blank for simple measurements.

When blanking the instrument, we measure how much light reaches the detector

and then set that amount of light to 100% transmission. That means if the

detector measures that specific amount of light, then we can assume all of the

light made it through at that particular wavelength. If the sample absorbs some

of the light at that wavelength, then we should measure a smaller amount of

light reaching the detector.

It is important to note that a separate blank measurement is required for each

wavelength because the light source gives off different amounts of light at each

wavelength.

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