12
• In order to measure exactly 5 mL of reagent with the 5 mL syringe:
(a) push the plunger completely into the syringe and insert the tip into the reagent bottle.
(b) pull the plunger up until the lower edge of the seal is exactly on the 5 mL mark.
(c) 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, if so eliminate them. Then, keeping the syringe in
vertical position above the cuvet, push the plunger completely down into the syringe. Now
the exact amount of 5 mL has been added to the cuvet.
The instructions listed below should be carefully followed during testing to ensure best accuracy.
• For a correct filling of the cuvet: the liquid in the
cuvet forms a convexity on the top; the bottom of
this convexity must be at the same level of the 10
mL mark.
• It is important that the sample does not contain
any debris. This would corrupt the reading.
• Each time the cuvet is used, the cap must be
tightened to the same degree.
• Whenever the cuvet is placed into the measurement
cell, it must be dry outside, and completely free of
fingerprints, oil or dirt. Wipe it thoroughly with
HI 731318
(tissue for wiping cuvets, see chapter
ACCESSORIES) or a lint-free cloth prior to insertion.
GENERAL TIPS FOR AN ACCURATE MEASUREMENT
(a)
(b)
(c)
13
• Proper use of the dropper:
(a) to get good reproducible results, tap the dropper on the table for several times and wipe the
outside of the dropper tip with a cloth.
(b) always keep the dropper bottle in a vertical position while dosing the reagent.
• Proper use of the powder reagent packet:
(a) use scissors to open the powder packet;
(b) push the edges of the packet to form a spout;
(c) pour out the content of the packet.
• Shaking the cuvet can generate bubbles in the sample, causing higher readings. To obtain accurate
measurements, remove such bubbles by swirling or by gently tapping the vial.
• Do not let the reacted sample stand too long after reagent is added, or accuracy will be lost.
• It is possible to take multiple readings in a row, but it is recommended to take a new zero
reading for each sample and to use the same cuvet for zeroing and measurement.
• After the reading it is important to discard immediately the sample, otherwise the glass might
become permanently stained.
• All the reaction times reported in this manual are referred to 20°C (68°F). As a general rule of
thumb, they should be doubled at 10°C (50°F) and halved at 30°C (86°F).
• In order to maximize accuracy, prior to a measurement follow the
validation procedure
to be
sure that the instrument is properly calibrated. If necessary, calibrate the instrument.
(a)
(b)
(c)
(a)
(b)