Foxcroft FX-300-F, Инструкция по эксплуатации, Страница: 31 / 45

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15.
5.5 How to prepare a fluoride standard solution
We do not recommend 2-point slope field calibration for new sensor installations; for most if not all
applications the factory set slope will provide the best results.
The 2-point calibration should only be done when the sensor begins to lose response or sensitivity. The
1-point offset is the only calibration required on a regular basis.
Performing calibration with fluoride standards will not get the inline installation dialed-in. This can only be done with a
proper grab sample offset calibration.
Materials
•
Sodium fluoride (Analytical or ACS Reagent Grade or better, brand new sealed dry bottle preferred)
•
TISABII (Total Ionic Strength Adjustor Buffer) USE TISAB II ONLY
•
1L volumetric flask (one each minimum, four each recommended)
•
5L volumetric flask (one each) or 2L volumetric flask (two each)
•
1ml volumetric pipette
•
10ml volumetric pipette
•
1L opaque plastic bottles with air-tight sealing cap (five each)
•
DI water (15mΩ or higher resistivity grade recommended but not critical)
NOTES : Ensure that all glassware is clean and dry before proceeding.

Thoroughly clean volumetric flasks after preparing any solution with distilled or deionized
water.

Solution prepared from this procedure will stay good for 1 year from date of manufacture if
stored in a sealed, opaque plastic bottle in a cool, dry location.
 Always use the more stable TISAB II rather than TISAB III total ionic strength adjusting
buffer for both self prepared and premixed solutions purchased from a lab supply
company.
 Since the fluoride transmitter has a 3-digit display, a 1,000 mg/L (ppm) calibration solution
will only display as “999”. It’s suggested to use a “non-standard” solution of lower
concentration in order to display 3 significant digits during calibration.
Stock solution preparation procedures
Preparation of diluted TISAB II background stock solution (DO THIS FIRST)
1.
Measure out 2L of TISAB II solution and pour into a 5L volumetric flask.
2.
Dilute with distilled or deionized water to 5L mark. Mix solution well until all the two solutions are
completely miscible and the resulting solution is homogenous.
3.
Seal 5L volumetric flask with glass stopper.
Preparation of 10,000ppm fluoride stock solution (DO THIS FIRST)
1.
Measure out 22.101g of sodium fluoride salt.
2.
Place this sodium chloride salt into 1L volumetric flask.
3.
Dilute with distilled or deionized water to 1L mark. Mix solution well until it is completely homogenous
(dissolved).
4.
Transfer this 10,000ppm fluoride stock solution to a 1L plastic bottle and label appropriately.
5 Calibration