Aspirating High Density Liquids; Recalibration - HTL DISCOVERY PRO Manual Del Usuario

4.4 ASPIRATING HIGH DENSITY LIQUIDS

The accuracy errors provided in Table 1 have been
determined using distilled water. When pipetting liquids
whose properties (density, viscosity, surface tension)
differ from the properties of water, it may be necessary to
compensate for volume settings.
CAUTION: Aspiration differences can be avoided if the
pipetting operation is conducted slowly, so that the liquid
can slowly adjust to the changing pressure. Wait for
about 2 seconds after each aspirating and dispensing,
without changing the position of the pipette.
If the above procedure does not provide accurate
results, pipette recalibration is required according to sec-
tion 5.
After calibration, it is recommended to record recalibration
and the adjustment value, which will facilitate return cali-
bration to the standard liquid.

5. RECALIBRATION

DISCOVERY PRO pipettes are calibrated by gravimetric
method, using HTL tips and distilled water, at the tem-
perature 20°±1°C, according to EN ISO 8655 standard.
It is recommended to conduct periodic inspection of the
pipette operation, with the interval between inspections
being dependent on the type of load (aspirated liquids)
and other conditions (load intensity and autoclave sterili-
zation, replacement of subassemblies) in which the
pipette is used.
The pipette recalibration procedure should be carried out
if during the pipette operation you find that the accuracy
error (the difference between the real aspirated volume
and the preset volume) exceeds the permissible value
given in Table 1.
Aspiration efficiency of the pipette is determined e.g. by:
applied tips, properties of pipetted liquid (density, visco -
sity) and operation conditions (ambient temperature,
pressure).
Checking the pipette parameters
To determine accuracy error of the pipette, the following
requirements must be fulfilled:
• The ambient temperature of the pipette, tips and the
test liquid (typically distilled water) should be within the
range of 20-25°C and stabilized during weighing within
the range ±0.5°C,
9
• The balance sensitivity should be appropriate to the
tested volume (Table 2),
• Table 3 shows the values of the [mg/μl] conversion rates
for distilled water or another liquid of comparable density.
Volume [μl]
Balance sensitivity [mg]
Table 2
Temperature [°C]
20
21
22
23
24
25
Table 3
CAUTION: The pipetting procedure should be conducted
in accordance with the rules described in sections 3 and 4.
Recalibration procedure:
• Set the dose volume depending on the pipetted volume
according to Table 4.
Model
volumes [μl]
DP8-10, DP12-10
DP8-50, DP12-50
DP8-200, DP12-200
DP8-300, DP12-300
Table 4
• Perform 5 aspirations, weigh each one and calculate
the average value of the aspirations.
• Calculate average aspirated volume in [μl] by multiplying
the average aspiration amount [mg] by the distilled
water density coefficient [μl/mg], which depends on
temperature and pressure (Table 3).
• If the average aspirated volume exceeds the permissi-
ble values, pipette recalibration should be conducted.
ENGLISH
0.1 - 10 10 - 100 > 100
0.001 0.01 0.1
Pressure [kPa]
95 101.3 105
1.0028 1.0029 1.0029
1.0030 1.0031 1.0031
1.0032 1.0033 1.0033
1.0034 1.0035 1.0036
1.0037 1.0038 1.0038
1.0039 1.0040 1.0040
Range
Preset Permissible
of the
volume volumes
pipettes
[μl] [μl]
0.5-10 0.5 0.45-0.55
5-50 5 4.8-5.2
20-200 20 19.4-20.6
50-300 50 49.2-50.8
10