What considerations should I take when handling cuvettes?
Proper use of cuvettes can help to avoid measurement errors. For example, cuvettes always should be used in the same orientation. Most cuvettes have index marks as a guide. Also, it’s important not to touch the optical surfaces of the cuvette. Oils from your skin, particles from wiping tissues and other contaminants can affect the readings.
For open-top square cuvettes, perhaps the most effective approach is to use a slender transfer or Pasteur pipette to add and remove fluids. The tiny tip allows for suction of fluid from the corners, minimizing the carry-over volume. The typical procedure is to rinse the cuvette with the next sample to be analyzed at least three times. If the residual fluid is less than 10% of the wash fluid (it’s more likely to be 1% or less), the carry-over is reduced to 1/1000. It is important that the pipettes also be washed with the sample and not allowed to touch or scratch the inside optical surfaces.