37
SECTION 3, continued
3.6 Calibration
Calibration of the 2100P Turbidimeter is based on formazin, the
primary standard for turbidity. The instrument's electronic and optical
design provide long-term stability and minimize the need for frequent
calibration. The two-detector ratioing system compensates for most
fluctuations in lamp output. A formazin recalibration should be
performed at least once every three months, more often if experience
indicates the need. When calibration is necessary, use a primary
standard such as StablCal™ Stabilized Standards or formazin
standards.
Hach Company only recommends the use of StablCal
®
Stabilized
Formazin or formazin standards for the calibration of Hach
turbidimeters. Hach Company cannot guarantee the performance
of the turbidimeter if calibrated with co-polymer styrene
divinylbenzene beads or other suspensions.
Important Note: DO NOT calibrate with Gelex® Secondary Standards.
Gelex standards are designed for instrument verification, not calibration.
3.6.1 StablCal Stabilized Formazin Standards*
Most consistent results will be achieved with the use of StablCal
Stabilized Formazin Standards for calibration. Refer to Section 3.6.1.2
and Section 3.6.1.3 for information on preparing the standards for use.
Note: Hach StablCal Stabilized Formazin in 20-, 100-, and 800-NTU values is
packaged in convenient sets for calibration of the 2100P Turbidimeter. The set
may be ordered in 500-mL size bottles by specifying Cat. No. 26594-00, in
100-mL size bottles by specifying Cat. No. 26594-10 or in sealed vials by
ordering Cat. No. 26594-05. (See OPTIONAL ACCESSORIES AND
REAGENTS on page 74.)
3.6.1.1 Storing and Handling StablCal Stabilized Standards
For optimum results when using StablCal Stabilized Standards, adhere
to the following recommendations:
* StablCal Stabilized Formazin is cited as a primary standard in Hach Method
8195, an acceptable version of USEPA Method 180.1.
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