Hanna Instruments HI 83742, Instruction Manual, Page: 6 / 14

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)
23
TOTAL PHENOLS, RED WINE
SPECIFICATIONS SPECIFICATIONS SPECIFICATIONS SPECIFICATIONS SPECIFICATIONS
Range 0.00 to 5.00 g/L
Resolution 0.01
Precision ±0.10 @ 2.00 g/L
Light Source Tungsten lamp with narrow band interference filter @ 610 nm
Method The reaction between Phenols and the reagents causes a blue tint in the sample.
REQUIRED REAGENTS REQUIRED REAGENTS REQUIRED REAGENTS REQUIRED REAGENTS REQUIRED REAGENTS
Code Description Quantity/test
HI 83742A-0 Acid Reagent 5 mL
HI 83742B-0 Folin & Ciocalteu’s Reagent 6 drops
HI 83742C-0 Carbonate Buffer 4.5 mL
For reagent set and other accessories see page 26.
SAMPLE PREPARATION SAMPLE PREPARATION SAMPLE PREPARATION SAMPLE PREPARATION SAMPLE PREPARATION
• Use the 2000 µL automatic pipette to add exactly 2
mL of deionized water to an empty cuvet.
For a correct use of the automatic pipette please follow
the related Instruction Sheet.
• Then use the 200 µL automatic pipette to add exactly
0,2 mL of red wine.
• Replace the cap and shake gently to mix. This is the
diluted red wine sample .
• Take another empty cuvet and use the 5 mL syringe
to add exactly 5 mL of HI 83742A-0 reagent to an
empty cuvet.
Note : in order to measure exactly 5 mL of reagent
with the syringe, follow the instructions on page 11.
2 mL
200 µL