Electro-Chemical Devices (ECD) HYDRA Ammonium - Manual (Page 31)

HYDRA NH
4
+ -N Page 23
4.2 CALIBRATION
The HYDRA Ammonium Analyzer was calibrated at the factory using the Two Point Calibration described
below. The sensor was assembled and placed beaker of equilibration solution for 8-12 hours before
starting the calibration. The Potassium Ion and Ammonium Ion electrodes sensing membranes require
several hours to properly hydrate/ equilibrate to the measured solution. The calibration sets the zero
potential and slope for each of the sensors into the analyzers memory.
Since the factory calibration characterizes the complete measurement system the initial user calibration
should only require a standardization of the Ammonium Ion Electrode once the HYDRA has equilibrated
to the process solution.
The Factory Calibration and all subsequent calibrations should be performed in the following sequence:
1. Temperature Calibration
2. pH Electrode calibration in pH 4.01 buffer and pH 7.00 buffer (2 point)
3. Potassium Electrode calibration in 1 ppm and 100 ppm solutions (2 point)
4. Ammonium Electrode calibration in 1 ppm and 100 ppm solutions (2 point)
Calibration checks should be performed weekly by comparison to a grab sample or immersing the
HYDRA sensor into a standard solution with known pH, K+ and NH4-N values. Performing a Single Point
Calibration will eliminate any offset found in the calibration check. Continuous drifting of the potassium
or ammonium ion reading may indicate the electrode needs to be replaced. (See Section 6 Trouble
Shooting below)
Two Point Calibration is required whenever an electrode is replaced, pH, Potassium or Ammonium. Two
Point Calibrations are also recommended every two months to verify the response of the electrodes is
greater than 50 mV/decade.
4.2.1 Recommended Materials
pH Calibration Solutions
1. pH 4.01, 500 ml (Part # 2010100)
2. pH 7.00, 500 ml (Part# 2010101)
pIon Calibration Solutions
1. 1 ppm K + , 500 ml (Part# 2010443)
2. 100 ppm K + , 500 ml (part# 2010444)
3. 1 ppm NH
4
+
-N, 500 ml (Part# 2010445)
4. 100 ppm NH
4
+
-N, 500 ml (part# 2010446)
Accessories
1. 1 liter plastic beakers
2. Distilled Water for rinsing
3. Calibrated thermometer with 0.1 °C graduations
4. Stir plate with magnetic stir bars.