Biosan BS-050102-AAF, Инструкция пользователя

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6
3. General information
DEN-1 & DEN-1B densitometers are designed for solution turbidity measurement in
the range of 0.0 - 6.0 McFarland units or 0 cells/ml - 18x10
8
cells/ml. DEN-1 & DEN-1B are
capable of measuring solution turbidity in a wider range, up to 15.0 McFarland units, how-
ever, it is necessary to remember that in this case the standard deviation values increase.
DEN-1 & DEN-1B densitometers are used for 1) determining concentration of cells
(bacterial, yeast cells) in the fermentation process, 2) detection of susceptibility of microor-
ganisms against antibiotics, 3) identification of microorganisms with various test systems, 4)
measuring optical density at fixed wavelength and 5) quantitative evaluation of concentration
of dyed solutions that absorb green light.
The operation principle is based on optical density measurement with digital result
representation in McFarland units.
The unit is calibrated at the factory and saves calibration data when being switched
off. However, it can be recalibrated by multiple points in 0.0
–6.0 McF range if necessary. We
reccommend using our Biosan standards for opyimal results, but both commercial standards
and the cell suspensions prepared in the laboratory (e.g., BaSO
4
) can be used for calibration.
Table 1. Interpretation of McFarland Standard results into corresponding numeric values of
bacterial suspension concentration and their optical density at 550 nm.
McFarland
Standard
Composition Interpretation
Concentration of
BaSO
4
Bacterial concentration
1
Theoretical optical
density
2
at 550 nm
0.5 2.40 x 10
-5
mol/L 150 x 10
6
cells/mL 0.125
1 4.80 x 10
-5
mol/L 300 x 10
6
cells/mL 0.25
2 9.60 x 10
-5
mol/L 600 x 10
6
cells/mL 0.50
3 1.44 x 10
-4
mol/L 900 x 10
6
cells/mL 0.75
4 1.92 x 10
-4
mol/L 1200 x 10
6
cells/mL 1.00
5 2.40 x 10
-4
mol/L 1500 x 10
6
cells/mL 1.25
6 2.88 x 10
-4
mol/L 1800 x 10
6
cells/mL 1.50
1
Bacterial concentration depends on microorganism size. The numbers represent an average value
valid for bacteria. For yeasts, which are larger, these numbers should be divided by about 30.
2
Values correspond to optical densities of bacterial suspensions. The BaSO
4
solutions optical density
values differ, because the particle size and form differ from those of bacteria and light is diffracted dif-
ferently