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Ion Setup:
Ion Method
XL25, 50 and 60 meters
The Ion Method window lets you select from a variety of ion measurement methods.
Direct Reading with Standards:
The most common method of ion measurement. When using
this method, you will use standards of known values to standardize the meter with ion standards.
An ionic strength adjuster (ISA) is added to both the standards and the sample. Two to five
standards are used. The standards should bracket the expected value of the sample. The ion
specific electrode is immersed in a stirring sample and the ion concentration is read directly from
the meter.
Direct Reading with Blank Offset:
Commonly used for determining ion concentration in a
sample with a very low level of ions. Due to background interference at low concentration levels,
a blank is used and the value of the ion concentration in the blank is subtracted from the value of
the measured sample.
Known Addition Method:
An incremental method used for samples with a complex matrix. A
standard with a known concentration of the ion species of interest is added to the sample. The
difference in mV potential is then used to calculate ion concentration.
Known Subtraction Method:
An incremental method where the ion of interest in the sample is
not identical to the ion in the standard solution. The standard of known ion concentration that is
added to the sample quantitatively reacts in the sample with the ion of interest. This reaction
removes a fixed amount of the ion of interest from the sample solutions. The ion concentration is
then calculated based upon the difference in the mV potential.
Analate Addition:
A modification of the known addition method. The initial mV measurement is
recorded in a standard solution. The ion in the standard solution is the ion of interest and is
detected by the ion selective electrode in use. A sample containing the ion of interest is then
added to the standard solution. The difference in the mV potential is then used in the calculation
of the concentration of the ion of interest. This method is useful if the sample temperature is
significantly different than that of the standard. When the small volume of hot sample is added to
the larger volume, the temperature impact becomes negligible.
Analate Subtraction:
Useful when there is no ion specific electrode available to directly measure
the concentration of the ion of interest. This method employs the addition of a sample of the ion of
interest to a standard containing a different ion of known concentration. The ion of interest will
quantitatively react with the ion in the standard, creating a complex and removing the ion from the
standard solution. The ion specific electrode is specific for the ion in the standard solution and not
for the ion of interest. The difference in mV potential is used to calculate the concentration of the
ion of interest based upon this quantitative reaction.
To select Ion Method:
1. Touch the Arrow key to the right of Ion Method
2. Touch the desired method.
Summary of Contents for XL 20
Page 1: ......
Page 138: ...127 Ion Operation Known Addition Method XL25 50 and 60 meters...
Page 140: ...129 Ion Operation Known Subtraction Method XL25 50 and 60 meters...
Page 142: ...131 Ion Operation Analate Addition Method XL25 50 and 60 meters...
Page 144: ...133 Ion Operation Analate Subtraction Method XL25 50 and 60 meters...