Ion: Direct Reading Methods - Fisher Scientific accumet XL150 accumet XL200 accumet XL250 accumet XL500 accumet XL600 Reference Manual

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ION: DIRECT READING METHODS

There are two direct reading methods – Direct Reading with Standards and Direct Reading with Blank
Offset. These types of measurements allow you to directly read the concentration of your sample after
standardizing the meter with ion standards of known values or blank values.
Direct Reading With Standards:
This is the most common method of ion measurement. You can directly read the concentration of
the sample after standardizing the meter with known ion standard solutions. An ionic strength adjuster
(ISA) is added to both the standards and the sample. The standards should bracket the expected value of
the sample.
You must use a minimum of two standards to standardize the meter. For best results always begin with
your lowest calibration standard value, followed by the next lowest, and so on.
1. Rinse and immerse your clean Ion selective electrode which has been prepared according to the
electrode instruction manual into a known standard solution and stir gently.
2. Select the Standardize icon. "Clear" will delete the previous standardization values and "Cancel" will
return to measurement mode.
3. A keypad will open after one scanning cycle. Using the displayed keypad, input the value of the known
standard solution you are using and press "ENTER".
4. The meter will show the value which can be seen blinking on the display.
5. Wait for the reading to stabilize (Tip: observe the millivolt value). When stable, select "Confirm" to
accept the standardization.
6. Repeat steps 1-5 with additional ion standards.
Tip: The STABLE indicator will only appear upon completion of a successful two
point standardization. If the meter has not been standardized with at least two
standards, a series of dashes will appear in place of a measurement value.
Direct Reading With Blank Offset:
This method is useful for measuring samples with low level concentrations of selected ion of interest.
It eliminates background interference by subtracting the value of a blank concentration from the value of
the sample. You must use a minimum of one blank and two standards for this method. For best results
always begin with your blank, followed by your lowest calibration standard value, followed by the next
lowest, and so on.
1. Add ionic strength adjuster as needed to the calibration standards and the blank.
2. Rinse and immerse your clean Ion selective electrode which has been prepared according to the
electrode instruction manual into your solution blank or lowest calibration standard value and stir gently.
3. Select the Standardize icon. "Clear" will delete the previous standardization values and "Cancel" will
return to measurement mode.
Ion Operation: Incremental Methods
XL25, 50 and 60 meters
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