Troubleshooting
VI-9
Thermo Scientific Orion 2117HL High Level Chloride Analyzer User Guide
Slope less than -45 mV/decade
• Check the electrode function, clean the electrode, recalibrate the
analyzer, and if the analyzer continues to read low, replace the electrode.
• Check electronics to read mV input correctly. Use electronic test kit
(Cat. No. 180029) procedure for checking electronics function.
Ion-selective electrodes (ISE) can be shown as DC-voltage sources
with 50 to 1000 Megohm; a very high output impedance. ISEs respond
to ion concentration changes with a voltage change of approximately
-59 mV/decade for monovalent anions such as chloride. Knowing
electrode and analyzers parameters like offset potential, slope, etc allows
testing of various instruments by applying a known mV voltage.
Input Signal
Expected Reading: ± (0.5 mV + 0.1%)
0 mV
- 0.5 mV to + 0.5 mV
- 1000 mV
-1001.5 mV to – 998.5 mV
+ 1000 mV
+ 998.5 mV to + 1001.5 mV
• Background concentration too high for the standards used.
• Standards contaminated or incorrectly made – verify calibration with
fresh standards.
• Standard 1 and standard 2 interchanged – check the volume of the
standard added during calibration (add 0.5 mL for standard 1 and
add 1.5 mL for standard 2) and repeat the calibration. If using custom
standards, verify the values for each standard.
• Standard 1 and standard 2 added in wrong sequence – check the
sequence of the standards and repeat the calibration.
Slope Problems
Low Slope
