Hach ISENH4181 User manual

DOC022.53.80029
ISENH4181
05/2021, Edition 5
User Manual

Table of Contents
Section 1 Product overview................................................................................. 3
Section 2 Specifications ...................................................................................... 3
Section 3 Safety information............................................................................... 4
3.1 Intended use ....................................................................................................... 4
3.2 Use of hazard information..................................................................................... 4
3.3 Precautionary labels............................................................................................. 5
3.4 Product hazards.................................................................................................... 5
Section 4 Preparation for use.............................................................................. 5
Section 5 Calibration............................................................................................... 5
5.1 Calibration notes ................................................................................................. 5
5.2 Calibration procedure........................................................................................... 6
Section 6 Sample measurement....................................................................... 7
6.1 Sample measurement notes ............................................................................... 7
6.2 Sample measurement procedure......................................................................... 7
6.3 Low-level measurements...................................................................................... 8
6.4 Interferences ....................................................................................................... 8
Section 7 Verify the calibration.......................................................................... 9
7.1 Verification procedure........................................................................................... 9
Section 8 Maintenance........................................................................................ 10
8.1 Clean the probe.................................................................................................. 10
8.2 Storage............................................................................................................... 10
Section 9 Troubleshooting ............................................................................... 10
9.1 Slope check........................................................................................................ 11
9.2 Standard additions check................................................................................... 11
Section 10 Consumables..................................................................................... 12
10.1 Accessories...................................................................................................... 13
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Table of Contents
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Section 1 Product overview
The Intellical ISENH4181 series probes are digital, combination ion-selective electrodes (ISE) that
measure the concentration of ammonium in water samples. The Ammonium Ionic Strength Adjuster
(ISA) does not adjust the pH of the sample. Thus, the probes measure the ammonium ion (NH4+) but
not unionized ammonia (NH3). The probes have a built-in temperature sensor, a non-refillable gel
reference and non-replaceable membranes. Refer to Figure 1.
Figure 1 Probe overview
1 Sensing element 3 Sensor protection cap
2 Reference junction 4 Cable
Section 2 Specifications
Specifications are subject to change without notice.
Specifications Details
Probe type Digital combination probe with a non-refillable reference junction
and a built-in temperature sensor
Measurement range 0.018 mg/L (10–6 M) to 9,000 mg/L (0.5 M) as ammonium
(NH4+–N)
Accuracy ±0.02 mV or 0.05% (the larger value)
Sample pH range pH 0 to 8.5
Reference type Ag/AgCl
Reference junction Double junction (ceramic porous pin and annular porous PTFE)
Slope –58 mV/decade (90 to 110% at 25 °C (77 °F) in linear range per
Nernstian theoretical value)
Linear region 0.9 mg/L to 9,000 mg/L as ammonium
Temperature accuracy ±0.3 °C (±0.54 °F)
Temperature sensor type 30 kΩ NTC thermistor
Operating temperature 5 to 50 °C (41 to 122 °F)
Storage temperature 5 to 35 °C (41 to 95 °F)
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Specifications Details
Response time in linear region < 60 seconds (application dependent)
Minimum sample volume 25 mL
Minimum immersion depth 25.4 mm (1 in.)
Body material (standard) Epoxy
Membrane Solid-state PVC membrane
Reference electrolyte Non-refillable Dritek gel reference element
Cable connection M12 digital output and connector
Dimensions Diameter: 12 mm (0.47 in.)
Length: 175 mm (6.9 in.) total; 103 mm (4.1 in.) below head
Cable length: ISENH418101: 1 m (3.3 ft); ISENH418103: 3 m
(9.8 ft)
Warranty 1 year on the probe. This warranty covers manufacturing defects,
but not improper use or wear.
Certifications CE, FCC/ISED
Section 3 Safety information
3.1 Intended use
The Intellical probes are intended for use by individuals who measure water quality parameters in the
laboratory. The Intellical probes do not treat or alter water.
3.2 Use of hazard information
D A N G E R
Indicates a potentially or imminently hazardous situation which, if not avoided, will result in death or
serious injury.
WARNING
Indicates a potentially or imminently hazardous situation which, if not avoided, could result in death
or serious injury.
CAUTION
Indicates a potentially hazardous situation that may result in minor or moderate injury.
N O T I C E
Indicates a situation which, if not avoided, may cause damage to the instrument. Information that
requires special emphasis.
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3.3 Precautionary labels
Read all labels and tags attached to the instrument. Personal injury or damage to the instrument
could occur if not observed. A symbol on the instrument is referenced in the manual with a
precautionary statement.
Electrical equipment marked with this symbol may not be disposed of in European
domestic or public disposal systems. Return old or end-of-life equipment to the
manufacturer for disposal at no charge to the user.
3.4 Product hazards
CAUTION
Chemical exposure hazard. Obey laboratory safety procedures and wear all of the
personal protective equipment appropriate to the chemicals that are handled. Refer to
the current safety data sheets (MSDS/SDS) for safety protocols.
CAUTION
Chemical exposure hazard. Dispose of chemicals and wastes in accordance with local,
regional and national regulations.
Section 4 Preparation for use
Prepare the probe for calibration and measurement as follows.
1. Remove the sensor protection cap from the probe.
2. Rinse the probe with deionized water. Blot dry with a lint-free cloth. Do not wipe the tip of the
probe.
3. Condition the probe before use. To condition the probe, soak the probe in approximately 25 mL of
the lowest concentration standard solution used for calibration for 30 to 60 minutes. Do not add
the ISA to the standard solution.
Note: Condition the probe each day for 15 to 30 minutes or for 30 to 60 minutes after long-term storage.
4. Make sure that the meter has the correct date and time settings. The service-life time stamp in
the probe comes from the date and time settings in the meter.
Note: Some meters automatically open the date and time settings when the meter starts for the first time, or
after battery replacement.
5. Connect the probe to the meter.
Section 5 Calibration
The procedure that follows is applicable to meters that can connect to Intellical ISE probes. Refer to
the applicable meter documentation for meter operation and probe-specific settings.
5.1 Calibration notes
Read the notes that follow before calibration.
• Measure the standard solutions from lowest to highest concentration for best results.
• Keep all of the solutions (standard solutions and samples) at the same temperature (± 2 °C
(± 3.6 °F)) for best results.
• Stir the standards and samples at a slow and constant rate to prevent the formation of a vortex.
• Use the default calibration options or change the options in the probe settings menu.
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• Use the single display mode for calibration when more than one probe is connected to the meter (if
applicable).
• Calibrate the probes and verify the calibration regularly for best results. Use the meter to set
calibration reminders.
• The calibration data is stored in the probe. When a calibrated probe is connected to a different
meter with the same calibration options, a new calibration is not necessary.
• Air bubbles below the sensor when in solution can cause a slow response or error in the
calibration. Make sure to remove air bubbles during calibration.
5.2 Calibration procedure
1. Go to the
calibrate menu.
Select the probe, if
applicable. The
display shows the
standard solutions to
use for calibration.
2. Add 25 mL of
each standard
solution to different
beakers.
3. Add one
Ammonium Ionic
Strength Adjustor
(ISA) Solution Pillow
to each 25 mL of
standard solution.
4. Add a stir bar to
the first standard
solution. Put the
standard solution on
an electromagnetic
stirrer. Stir at a
moderate rate.
5. Rinse the probe
with deionized water.
Dry the probe with a
lint-free cloth.
6. Put the probe in
the standard solution
with the sensor fully
submerged. Do not
put the probe on the
bottom or sides of
the beaker.
7. Shake the probe
from side to side to
remove air bubbles.
8. Stir for 30 to
60 seconds, then
read the ammonium
concentration of the
standard solution.
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9. Do steps 3
through 8 to read the
value of the
remaining standard
solutions.
10. Save the
calibration.
Section 6 Sample measurement
The procedure that follows is applicable to meters that can connect to Intellical ISE probes. Refer to
the applicable meter documentation for meter operation and probe-specific settings.
6.1 Sample measurement notes
Read the notes that follow before sample measurements.
• Rinse the probe with deionized water and dry with a lint-free cloth between measurements to
prevent contamination.
• If the stabilization time is long, try a different stir rate and make sure to condition the probe.
• Keep all of the solutions (standard solutions and samples) at the same temperature (± 2 °C
(± 3.6 °F)) for best results.
• If complete traceability is necessary, enter a sample ID and operator ID before measurement.
Refer to the meter manual for instructions.
• Stir the standards and samples at a slow and constant rate to prevent the formation of a vortex.
• The meter automatically saves the measurement data when the user manually reads each data
point and when the meter is set to read at regular intervals. The user must manually save each
data point when the meter is set to read continuously.
• Air bubbles below the sensor can cause a slow response or error in the measurement. Make sure
to remove air bubbles before and during measurements.
6.2 Sample measurement procedure
1. Pour 25 mL of
fresh sample into a
50‑mL beaker.
2. Add one
Ammonium Ionic
Strength Adjustor
(ISA) Solution Pillow.
3. Add a stir bar.
Put the beaker on an
electromagnetic
stirrer. Stir at a
moderate rate.
4. Rinse the probe
with deionized water.
Dry the probe with a
lint-free cloth.
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5. Put the probe in
the sample with the
sensor fully in the
sample. Do not put
the probe on the
bottom or sides of
the beaker.
6. Shake the probe
from side to side to
refresh the reference
junction and remove
air bubbles.
7. Stir for 30 to
60 seconds, then
read the ammonium
concentration of the
sample. The display
shows the value
when the reading is
stable.
6.3 Low-level measurements
Use the guidelines that follow for measurements at low concentrations (<1 mg/L NH4+–N).
• Fully rinse the probe with deionized water and blot dry between measurements.
• Soak the probe in the lowest concentration standard solution for 1 hour maximum before
calibration and measurement.
• Use the meter to set the stability criteria for the probe to a low value.
• Stir the standards and samples at a slow and steady rate to prevent the formation of a vortex.
• Use a dilute ionic strength adjustor (ISA) solution for calibration and measurements:
1. Dissolve the contents of one ionic strength adjustor powder pillow in 50 mL of deionized water.
2. Add 5 mL of the dilute (ISA) solution to each 25 mL of standard solution or sample.
Note: The ISA is not necessary when all of the conditions that follow apply:
• The sample does not contain interferences.
• The sample pH is within the range given in the specifications.
• Omission of the ISA is accepted by the regulatory reporting agency (if the measurement is for regulatory
reporting).
6.4 Interferences
The sensing element will measure some other ions that are known to interfere with the method. The
probe response to other ions usually increases the mV potential and causes a positive error. The
response to other ions can be semi-quantitatively calculated through the Nikolsky equation, an
extended Nernst equation:
E = Eº + (RT/(zF))ln[aNa + KNax × ax]
Where
• ax = the activity of the interfering ion
• KNax = the selectivity coefficient for the interfering ion relative to the primary ion
The primary interferences for ammonium ion-selective electrodes are perchlorate (ClO4–), chlorate
(ClO3–) and iodide (I–). There is no procedure to remove the interference from these ions. Other
interferences are shown in Table 1. Addition of the Ammonium ISA adjusts the pH and prevents most
of the interferences from Table 1.
The selectivity coefficient is the approximate apparent increase in the measured concentration that is
caused by one unit of the interfering ion (e.g., 1 unit of K+ increases the ammonium concentration by
0.1). The approximate selectivity coefficients for some ions with the Intellical Ammonium ISE are
shown in Table 1.
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Table 1 Interferences
Interference Selectivity coefficient
Potassium (K+) 0.1 (interferes more)
Sodium (Na+) 0.002
Magnesium (Mg2+) 0.00002
Lithium (Li+) 0.00003
Calcium (Ca2+) 0.00006 (interferes less)
Section 7 Verify the calibration
Measure the value of a fresh standard solution at regular intervals to make sure the result is
accurate. The meter compares the expected standard solution value to the measured value and
accepts or rejects the measurement. The user can change the standard solution and acceptance
criteria for verification in the probe-specific settings.
Note: Password protection may prevent access to the acceptance criteria.
7.1 Verification procedure
1. Go to the
verification menu.
The display shows
the standard solution
to use for
verification.
Note: Menu name for
HQd meters: Run check
standard.
2. Pour 25 mL of the
standard solution
into a 50‑mL beaker.
3. Add one
Ammonium Ionic
Strength Adjustor
(ISA) Solution Pillow.
4. Add a stir bar.
Put the beaker on an
electromagnetic
stirrer. Stir at a
moderate rate.
5. Rinse the probe
with deionized water.
Dry the probe with a
lint-free cloth.
6. Put the probe in
the standard solution
with the sensor fully
in the solution. Do
not put the probe on
the bottom or sides
of the beaker.
7. Shake the probe
from side to side to
remove air bubbles.
8. Stir for 30 to
60 seconds, then
read the value of the
standard solution.
The meter accepts
or rejects the result.
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Section 8 Maintenance
Regular maintenance is necessary for the best accuracy, stabilization time and life of the probe. Fully
rinse the probe with deionized water between measurements to keep the probe clean.
8.1 Clean the probe
Rinse the probe with deionized water regularly to remove mineral or sample buildup on the sensing
element. Symptoms of contamination:
• Incorrect or irregular readings
• Slow stabilization times
• Calibration errors
• Sample material stays on the probe
1. Rinse the probe with deionized water. Blot dry with a lint-free cloth. Do not touch the tip of the
probe.
2. Polish the white reference junction on the probe tip with a soft cloth or cotton swab. Refer to
Product overview on page 3. Do not polish the PVC sensing element in the center of the probe
tip. Do not use cleaning solutions. Make sure to fully rinse the probe with deionized water
between sample measurements to prevent mineral or sample buildup on the sensing element.
3. Soak the probe for 30 minutes in a 100-mg/L ammonium standard solution.
8.2 Storage
Keep the sensor protection cap on the probe during storage to prevent damage to the sensing
element.
Note: Make sure to condition the probe after long-term storage. Refer to Preparation for use on page 5.
1. Rinse the probe with deionized water. Dry the probe with a lint-free cloth.
2. Make sure that the probe sensor is dry, then install the sensor protection cap. Refer to Product
overview on page 3.
Section 9 Troubleshooting
Refer to Table 2 for general troubleshooting information. To check the probe performance, refer to
Slope check on page 11. To check the accuracy of sample measurements, refer to Standard
additions check on page 11.
Table 2 Troubleshooting information
Problem Possible cause Solution
Decreased probe performance
causes slow stabilization and
prevents accurate calibrations or
measurements.
The probe has contamination
on the sensing element.
Rinse and condition the probe.
Refer to Clean the probe
on page 10.
The reference junction is
clogged.
Fully rinse the reference junction
with deionized water. Shake the
probe down to remove air
bubbles.
The probe is not conditioned
to the sample sufficiently.
Condition the probe. Refer to
Preparation for use on page 5.
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Table 2 Troubleshooting information (continued)
Problem Possible cause Solution
Sample properties cause slow
stabilization or inaccurate
measurements.
The sample pH with ISA is
incorrect.
Make sure that the sample pH
after the ISA is added is less
than pH 8.5. Make sure to add
one ISA pillow to each 25 mL of
sample.
The sample temperature is
low, or there is a large
temperature difference
between samples.
Increase the sample temperature
or adjust the temperature of
different samples to be the same
(within 2 °C (3.6 °F)).
Procedure problem causes slow
stabilization and prevents
accurate calibrations or
measurements.
Air bubbles are around or
below the probe tip.
Carefully tap or shake the probe
to remove air bubbles.
The ISA was not added. Add one ISA powder pillow to
each 25 mL of sample and
standard solution.
The stir speed is too slow or
too fast.
Try a different stir speed.
Magnetic stirrers can
become warm and increase
the solution temperature.
Put a piece of insulating material
between the stirrer and beaker.
An incorrect standard
solution was used or the
standard solution has
contamination.
Use the specified standard
solution of good quality.
Too much time passed after
the ISA was added.
Measure the sample or standard
solutions immediately after the
ISA is added.
9.1 Slope check
Use the mV value of two standard solutions to make sure the probe gives the correct slope.
1. Prepare two standard solutions that are ten times apart in concentration (e.g., 10 mg/L and
100 mg/L NH3—N). Select standard solutions with a concentration above and below the typical
sample concentration. Use a minimum concentration of 1.8 mg/L.
2. Use the measurement procedure to add the ISA and measure the mV value of each standard
solution.
3. Calculate the difference in the mV value of the two standard solutions to find the slope. If the
probe is in good condition, the slope will be 58 mV (within the ± slope limits of the method) at
25 °C (77 °F).
9.2 Standard additions check
To make sure that the sample measurement is accurate, add a small volume of a standard solution
to the sample and calculate the percent recovery. The sample with the known volume of standard
solution is known as a spiked sample.
1. Use the measurement procedure to measure the concentration of a 25-mL sample.
2. Use a pipet to add the applicable volume of standard solution to the sample. Refer to Table 3.
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Table 3 Standard solution volumes and concentrations
Measured sample
concentration
Volume of standard to
add
Concentration of standard solution
1 to 2 mg/L 0.5 mL 100 mg/L NH3—N
3 to 6 mg/L 1.0 mL 100 mg/L NH3—N
7 to 15 mg/L 0.3 mL 1000 mg/L NH3—N
15 to 30 mg/L 0.5 mL 1000 mg/L NH3—N
30 to 60 mg/L 1.0 mL 1000 mg/L NH3—N
3. Measure the concentration of the spiked sample.
4. Calculate the expected (theoretical) concentration of the spiked sample:
CE = (CS x VS/VT) + (CSS x VSS/VT)
Where:
• CE = expected (theoretical) concentration of the spiked sample
• CS = concentration of the sample (mg/L) before the standard solution was added
• CSS = concentration of the standard solution (mg/L)
• VS = sample volume (mL) before the standard solution was added
• VSS = volume of the standard solution (mL)
• VT = total volume (standard solution volume (mL) + sample volume)
5. Calculate the percent recovery of the standard addition. A percent recovery of 100 (±5)% is an
indication that the sample measurements are accurate.
Percent recovery = CM/CE x 100
Where:
• CM = measured concentration of the sample after the addition of the standard solution
• CE = expected (theoretical) concentration of the sample after the addition of the standard
solution
Section 10 Consumables
Note: Product and Article numbers may vary for some selling regions. Contact the appropriate distributor or refer to
the company website for contact information.
Description Quantity Item no.
Ammonium Ionic Strength Adjustor (ISA) Powder Pillows 100/pkg 2980699
Ammonia standard solution, 1 mg/L as NH3–N 500 mL 189149
Ammonia standard solution, 10 mg/L as NH3–N 500 mL 15349
Ammonia standard solution, 100 mg/L as NH3–N 500 mL 2406549
Ammonia standard solution, 1000 mg/L as NH3–N 1 L 2354153
Wash bottle, polyethylene, 500 mL 1 62011
Disposable wipes, 11 x 22 cm 280/pkg 2097000
Beaker, 30 mL, plastic, colorless 80/pkg SM5010
Beaker, 100 mL, polypropylene 1 108042
Probe stand for standard Intellical probes 1 8508850
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10.1 Accessories
Description Quantity Item no.
Beaker, polypropylene, 50 mL, low form 1 108041
Disposable wipes, 11 x 22 cm 280/pkg 2097000
Wash bottle, polyethylene, 500 mL 1 62011
Probe stand for standard Intellical probes 1 8508850
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*DOC022.53.80029*
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