Electro-Chemical Devices (ECD) SMS22 - Manual (Page 26)

4. ENTER the Cal1 line and adjust the calibration value to pH 7.00. When the mV value has
stabilized accept the value by pressing the down MENU key (MENU SELECT ▼). An Acceptable
mV value is < ±60 mV zero point offset.
5. Rinse the sensor and place it in a beaker of pH 4.01 or 10.0 Calibration buffer for the second
point calibration.
6. Scroll down and ENTER the Cal2 Line. Enter the value of the Calibration Solution and accept the
calibration when the mV/pH value has stabilized. An Acceptable value is > 54 mV/pH.
7. Rinse the sensor and return it to the SMS-22 flow cell.
4.2.3 SULFIDE SENSOR
The MVS10 Sulfide Ion Sensor was calibrated in 5 ppm and 50 ppm sulfide solutions at the factory.
Calibrations should always be two point calibrations. The pH sensor must be in the sulfide ion calibration
solution during calibration since the sulfide ion measurement is pH compensated. The Calibration is not
pH compensated and the compensation must be done manually.
The MVS10 sulfide ion sensor has a linear range from 0.3 ppm to 30,000 ppm. Measurements outside of
this range are difficult to impossible with the SMS-22 analyzer. It is possible to set the range of the
instrument to as low as 20 ppb but the accuracy of the measurement is severely degraded above 1 ppm.
Consult with the factory for more information about low level measurements,
[email protected] .
1. Switch the SMS-22 Analyzer to CALIBRATE Mode
2. Remove the PHS10 pH sensor and MVS10 Sulfide sensor from the flow cell, clean them (see
Section 5.1.3 below) and place them in a beaker of 5.0 ppm Sulfide Solution. Swirl sensors
through the calibration solution for at least 30 seconds. Wait for the sensors to stabilize.
3. Scroll down (MENU SELECT key) to the Channel 1 Set Up menu, Enter the menu by pressing both
horizontal CALIBRATE keys, then scroll down (MENU SELECT key) to the TC Screen. The
dissociation factor on the bottom line of the screen is the pH correction factor. Record the
factor and exit the screen. Calculate the Calibration Value.
Dissociation Factor x ppm value of the Calibration Solution = Calibration Value
Example: 0.958 x 5.00 ppm = 4.79 ppm
4. Scroll down to the Channel 1 Buffer Menu and ENTER the menu by pressing both horizontal
CALIBRATE keys, (See section 3.3.3 above)
5. ENTER the Cal1 line and adjust the calibration value to 1 S-- 4.79 ppm. When the mV value has
stabilized accept the value by pressing the down MENU key. An Acceptable mV value is -720 mV
± 20 mV for a new electrode, the readings will trend more negative as the electrode ages.
6. Rinse the sensors and place them in a beaker of 50.0 ppm Sulfide Solution for the second point
calibration.
7. Exit the Cal 1 screen and scroll down to the TC Screen, Record the dissociation factor for the 50
ppm Calibration Solution and exit the screen. The factor is usually different for different strength
solutions so check the value and do not assume it is the same as the 5 ppm solution. Calculate
the 50 ppm Calibration Value. Example: 0.977 x 50 ppm = 48.85 ppm
8. Scroll down and ENTER the Cal2 Line. Enter 2 S-- 48.85 ppm and accept the calibration when
the mV/dec value has stabilized. An acceptable value is -29 mV/dec ± 3 mV.
SMS-22 Page 17