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PHO
TOMETER
7. PHOTOMETER
7.1. PROPER USE OF SYRINGE
1. Push the plunger completely into the syringe and insert the tip into the solution.
2. Pull the plunger up until the lower edge of the seal is exactly on the mark for the
desired volume.
3. Take out the syringe and clean the outside of the syringe tip, be sure that no
drops are hanging on the tip of the syringe. Then, keeping the syringe in vertical
position above the cuvette, push the plunger down into the syringe, the desired
volume has been delivered into the cuvette.
7.2. CUVETTE PREPARATION
Proper mixing is very important for reproducibility of the measurements. The proper
mixing technique is listed in the method procedure.
Invert the cuvette a couple of times or for a specified time: hold the cuvette in the
vertical position. Turn the cuvette upside-down and wait for all of the solution to flow
to the cap end, then return the cuvette to the upright vertical position and wait for all
of the solution to flow to the cuvette bottom. This is one inversion. The correct speed
for this mixing technique is 10-15 complete inversions in 30 seconds. This mixing
technique is indicated with “invert to mix” and the following icon:
