6
PRINCIPLE OF OPERATION
Absorption of Light is a typical phenomenon of interaction between electromagnetic radiation and
matter. When a light beam crosses a substance, some of the radiation may be absorbed by atoms,
molecules or crystal lattices.
If pure absorption occurs, the fraction of light absorbed depends both on the optical path length
through the matter and on the
physical
-chemical characteristics of the substance according to the
Lambert-Beer Law:
-log
I
/
I
o
=
ε
λ
c d
or
A
=
ε
λ
c d
Where:
-log
I
/
I
o
= Absorbance (A)
I
o
= intensity of incident light beam
I
= intensity of light beam after absorption
ε
λ
= molar extinction coefficient at wavelength
λ
c
= molar concentration of the substance
d
= optical path through the substance
Therefore, the concentration "c" can be calculated from the absorbance of the substance as the
other factors are known.
Photometric chemical analysis is based on the possibility to develop an absorbing compound from
a specific chemical reaction between sample and reagents. Given that the absorption of a
compound strictly depends on the wavelength of the incident light beam, a narrow spectral
bandwidth should be selected as well as a proper central wavelength to optimize measurements.
The optical system of Hanna's
HI 83000
series colorimeters is based on special subminiature
tungsten lamps and narrow-band interference filters to guarantee both high performance and
reliable results.
Block diagram (optical layout)
15
• After a few seconds the display will show “-0.0-”. The
meter is now zeroed and ready for measurement. Remove
the Blank Vial.
• Insert the Sample Vial into the instrument.
Note
: Do not shake or invert the Sample Vial
anymore otherwise the samples may become turbid.
• Press READ and the display will show “----” during
measurement.
• The instrument directly displays concentration in g/L (ppt)
of Reducing Sugars on the Liquid Crystal Display.
• If the concentration in g/L (ppt) of Reducing Sugars is
less than 5 g/L it is recommended to repeat analysis
following the instructions on page 16.
The concentration displayed on the LCD must then be
divided by 4
by 4
by 4
by 4
by 4 to obtain the correct value in g/L (ppt) of
Reducing Sugar.
Sample
Note
To convert the Reducing Sugars concentration from g/L to %, multiply the reading by 0.1.
e.g. 12.5 g/L x 0.1=1.25%.
When you analyse the must before alcoholic fermentation, to calculate the potential alcohol
degree multiply the read sugar concentration (g/L) by 0.06.
e.g. 175 g/L x 0.06=10.5% vol (potential alcohol degree)