Hach-Lange HQD - Sodium (Na+) Ion Selective Electrode ISENa - Manual (Page 5)

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Run check standard
The run check standard feature validates instrument performance between sample
measurements. Use the run check standard feature for periodic or user-defined interval
measurement of a traceable standard solution. Set the criteria for check standards from
the ISENa381 settings menu.
Note: Access control must be off or a valid password entered before any of the check standard
method options can be changed.
1. Select Run Check Standard from the Meter Options menu.
Note: Select the appropriate sensor if two probes are connected to the meter.
2. Obtain the buffer solution specified in the display.
3. Place the electrode in the buffer solution and select READ . The display will show
Stabilizing... and a progress bar as the electrode stabilizes in the standard. The
display shows the value of the check standard and either Check Standard Passed or
Check Standard Failed.
If the display reads Check Standard Passed, the check standard measurement is within
the accepted limits defined by the administrative user. Select Done to proceed with
sample measurement.
If the display reads Check Standard Failed, the measurement is outside of accepted
limits defined by the administrative user and a recalibration is suggested. If the
acceptance criteria is set to Cal Expires on Failure: Yes, the display will show the
calibrate icon with a question mark until the electrode is recalibrated. Recalibrate the
electrode to correct the status indicator (refer to
Calibration on page 3 ).
Measurement (Direct Method)
Measurement notes
• Data is stored automatically in the data log when PRESS TO READ or INTERVAL is
selected in the Setup Measurement Mode. If Continuous is selected, data will be
stored only when the
STORE key is pushed.
• Always rinse the electrode with a ISA rinse solution between measurements and blot
dry. Never use only deionized water. Refer to
ISA rinse solution preparation .
• Response times with smaller concentration changes generally will be longer and can
be minimized by proper stirring and conditioning. Experiment to determine the proper
stir rate if necessary.
• Note the temperatures of the samples during measurement. Temperatures between
calibration standards and samples should be kept within ±2 ºC for optimal results.
Before measurement
The electrode must have the correct service-life time stamp. Set the date and time in the meter before attaching the
electrode.
The probe is factory calibrated in the range of 10 to 100 mg/L as Sodium (Na + ) and ready for use. For applications that
require greater accuracy, precision and/or different calibration points for different Na + concentration ranges, perform a user
calibration. Routine calibrations are required.
If complete traceability is required, enter a sample ID and operator ID before measurement.
For measurement errors, refer to Troubleshooting on page 12 .
Use an electromagnetic stirrer and stir samples at a moderate rate. Avoid resting the electrode on the bottom or sides of the
container.
The filling-hole must be open during measurement for the proper flow of the filling solution.
The filling solution must be above the sample level during measurement. Refer to Figure 2 .