YSI 9300 Photometer - Manual (Page 122)

PHOTOMETER TEST INSTRUCTIONS
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Turbidity is an important parameter for characterizing water quality. Turbidity is
aused by the scattering of light by suspended matter such as clay, silt, finely
divided organic, and inorganic matter. A knowledge of turbidity facilitates
estimation of the concentration of undissolved substances.
Method
The turbidity of the water is determined photoelectrically using the YSI Photometer.
In many samples both color and turbidity will be present. In order to separate the
effect of turbidity and color, the sample is compared against a filtered portion of the
same water.
The YSI method has been calibrated against the widely recognised formazin
turbidity solutions. Turbidity is expressed in terms of Formazin Turbidity Units
(FTU). These units are broadly equivalent to Jackson Turbidity Units (JTU) and
Nephelometric Turbidity Units (NTU).
Reagents and Equipment
YSI Color/Turbidity Set (PM 269)
YSI 9300 or 9500 Photometer
Test Procedure
1 Filter a portion of the sample through a GF/B filter paper.
2 Fill a test tube with filtered sample and retain for use as the BLANK tube.
3 Fill a test tube with unfiltered sample to the 10 ml mark.
4 Select Phot 48 on photometer.
5 Take photometer reading in usual manner (see photometer instructions)
using the filtered sample as the blank.
Note
An optional light shield is available for use with the photometer. This shield fits
over the test chamber and reduces stray light reaching the photocell. It is not
necessary to use the light shield when carrying out this test indoors or under
shaded outdoor light. The use of the light shield is however recommended when
testing for turbidity under bright or variable lighting conditions.
Photometer Method
AUTOMATIC
WAVELENGTH
SELECTION
5 – 400 Turbidity Units
PHOT.48.AUTO