SOP/PD/312 01 STANDARD OPERATING PROCEDURE · PDF fileuniversity of malta faculty of medicine & surgery pharmacy department ref. no. sop/pd/312_01 standard operating procedure hanna®

UNIVERSITY OF MALTA

FACULTY OF MEDICINE & SURGERY

PHARMACY DEPARTMENT Ref. No. SOP/PD/312_01

STANDARD OPERATING PROCEDURE

HANNA® BENCH-TOP PH METER HI 8521

Valid for:

2 years from

approval

Page 1 of 14

Table of Contents

Page

1. Scope 2

2. Objective 2

3. Definitions 2

4. Responsibility 3

5. Procedure 3

6. Precautions 13

7. References 13

8. Appendices 13

9. Revision History 14

Original

Authorised Copy

for:

Reading Copy

Written by: Signature/Date:

Reviewed by: Signature/Date:

Approved by: Signature/Date:

UNIVERSITY OF MALTA





Valid for:

2 years from

approval

Page 2 of 14

1. Scope

This Standard Operating Procedure (SOP) applies to the staff and students

using the Hanna® Bench-Top pH Meter HI 8521 in the laboratories of the

Pharmacy Department, University of Malta.

2. Objective

To describe the procedure for installation, operation, calibration, maintenance

and troubleshooting of the Hanna® Bench-Top pH Meter HI 8521.

3. Definitions

3.1. ↑ oC and ↓

oC Keys: To set the temperature for Manual Temperature

Compensation.

3.2. Automatic Temperature Compensation (ATC): A feature in which

the temperature probe is able to detect the temperature of the solution

in which it is immersed in.

3.3. Bayonet Neill-Concelman (BNC) Electrode connector (1): A cable

connector used to connect the pH or an ORP electrode to the meter.

3.4. CAL Key: To enter the calibration mode.

3.5. CON Key: To confirm the calibration data.

3.6. Display: Digitally displays the pH, temperature and millivolt (mV)

results.

3.7. DC Power Socket (5): To connect the meter with the mains power

supply.

3.8. Manual Temperature Compensation (MTC): A feature in which the

temperature of the sample solution is manually inputted when this is

already known.

3.9. On/Off Key: To turn the meter on or off.

3.10. RANGE Key: To select between pH, millivolt or temperature results.

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Page 3 of 14

3.11. Reference Jack Socket (2): To connect a reference electrode to the

meter.

3.12. Reset Button (3): To be pressed whenever erroneous messages are

displayed due to strong electrical interference or when the meter is

disconnected from its power supply before being switched off properly.

3.13. Temperature Probe Socket (4): The socket at which the temperature

probe is connected to the meter.

4. Responsibility

4.1. The members of the Department of Pharmacy (staff and students) are

responsible for following this SOP.

4.2. The designated Laboratory Officer or Laboratory Assistant is

responsible for ensuring that this SOP is followed.

5. Procedure

5.1. Diagram of Front Panel

5.2. Diagram of Rear Panel

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Page 4 of 14

5.3. Installation

5.3.1. Connect the power cable to the DC Power Socket and to the

mains supply.

5.3.2. Connect the pH electrode and the temperature probe to the

BNC and temperature sockets respectively.

5.4. Operation

5.4.1. Measuring pH

5.4.1.1. Before use, ensure that the meter is being calibrated,

to obtain more accurate measurements (see section

5.5).

5.4.1.2. Press the On/Off Key to switch on the meter, which

will automatically enter into pH mode.

5.4.1.3. Submerge the pH electrode and the temperature

probe into the sample to be tested and keep them

close together, if automatic temperature

compensation is desired.

5.4.1.4. Disconnect the temperature probe from the meter if

manual temperature compensation is desired

whenever the temperature of the sample to be tested

is already known.

5.4.1.4.1. Press the RANGE Key until the display

changes to temperature mode.

5.4.1.4.2. Adjust the displayed temperature by

using the Up and Down Keys

respectively.

5.4.1.4.3. Press the RANGE Key again until the

display changes back to pH mode.

5.4.1.4.4. Submerge pH electrode into the sample

to be tested.

5.4.1.5. Shake the sample briefly and wait for reading to

stabilise before taking the reading.

5.4.1.6. Read off the displayed stable pH reading

compensated for temperature.

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5.4.1.7. Rinse off the pH electrode with some solution from

the next sample if more than one sample is to be

successively tested.

5.4.2. Measuring Temperature

5.4.2.1. Press the On/Off Key to switch on the meter.

5.4.2.2. Press the RANGE Key until the display changes to

temperature mode.

5.4.2.3. Dip the temperature probe into the sample.

5.4.2.4. Allow 1-2 minutes for the reading to stabilise.

5.4.2.5. Read off the displayed stable temperature reading.

5.5. Calibration

5.5.1. Pour small quantities of pH 7.01 and pH 4.01 or pH 10.01

buffer solutions into two separate clean beakers and use another

two separate beakers for rinsing.

5.5.2. Press the On/Off Key to switch on the meter.

5.5.3. Rinse the pH electrode with some pH 7.01 buffer solution.

5.5.4. Immerse the pH electrode into the pH 7.01 buffer solution and

stir gently.

5.5.5. Ensure that the pH electrode is kept submerged approximately

4cm into the solution.

5.5.6. Ensure that the temperature probe is located as close to the pH

electrode as possible.

5.5.7. Press the CAL Key.

5.5.8. Wait until the pH symbol, next to the pH buffer value, stops

flashing to indicate that reading is stable.

5.5.9. Press the CON Key to confirm the calibration.

5.5.10. If [E 4] is flashing, ensure that the correct buffer solution is

being used.

5.5.11. Wait until [E 5] is displayed to indicate that the electrode is still

in the pH 7.01 buffer, but expecting a pH 4.01 or 10.01 buffer.

5.5.12. Rinse the pH electrode with distilled water followed by the

second buffer solution to be used.

5.5.13. Immerse the pH electrode into the second buffer solution (pH

4.01 or pH 10.01) and stir gently.

5.5.14. Wait until the pH symbol, next to the pH buffer value, stops

flashing to indicate that the reading is stable.

5.5.15. Press the CON Key to confirm the calibration.

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5.5.16. If [E 4] is flashing, ensure that the correct buffer solution is

being used.

5.5.17. Wait until the meter returns to the normal operating mode to

ensure that the calibration process was successful.

5.6. Maintenance

5.6.1. Inspect the cables of the electrodes for any signs of broken

insulation.

5.6.2. Inspect the pH electrode for any cracks in its stem or bulb.

5.6.3. Rinse off any salt desposits with water.

5.6.4. Soak the pH electrode in Hanna HI 7061 or HI 8061 General

Cleaning Solution for approximately ½ hour to perform general

cleaning.

5.6.5. Soak the pH electrode in Hanna HI 7073 or HI 8073 Protein

Cleaning Solution for 15 minutes if protein deposits are present

on the membrane and/or junction of the electrode.

5.6.6. Soak the pH electrode in Hanna HI 7074 or HI 8074 Inorganic

Cleaning Solution for 15 minutes if inorganic deposits are

present on the membrane and/or junction of the electrode.

5.6.7. Rinse the pH electrode with Hanna HI 7077 or HI 8077 Oil and

Fat Cleaning Solution if oil films or deposits are present on the

membrane and/or junction of the electrode.

5.6.8. Rinse the pH electrode thoroughly with distilled water after

performing any of these cleaning procedures.

5.6.9. Refill the reference chamber with fresh electrolyte and soak it

in HI 70300 or HI 80300 Storage Solution for at least 1 hour

before taking any measurements.

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Page 7 of 14

5.7. Trouble Shooting

Fault Possible Cause/s Solution

Meter fails to calibrate or

gives erroneous results pH electrode is defective

Replace the electrode and repeat the

calibration

Meter is slow in responding

or gives erroneous readouts

Electrode not working or

diaphragm is clogged

- Leave electrode in storage

solution after performing

diaphragm cleaning

- If problem is not solved,

replace electrode and

recalibrate pH scale

Meter does not accept 2nd

buffer solution

pH electrode defective or

bad buffer solution

- Clean the electrode

- Replace electrode and re-

calibrate

- Use fresh buffer solution

Reading is drifting

Temperature not stable

Wait longer since thermal

equilibrium is still not reached

Display shows [E 1] pH scale is out of range

- Ensure pH electrode is

connected

- Ensure pH of sample is

between 0-14

- Check the state of the electrode

and the level of its filling

electrolyte

Display shows [E 2] Temperature scale is out

of range

- Ensure T probe is properly

connected

- Ensure that T of sample lies

between -10oC and 100

oC

Display shows [E 3] mV scale is out of range

- Ensure that ORP probe is

properly connected

- Ensure mV is within +/- 1999

range

Display shows [E 4]

- Erroneous buffer

solution used for first

part of calibration

- Defective electrode

- Ensure that buffer solution used

is of pH 7 and replace if

necessary

- Replace electrode and re-

calibrate pH scale

Display shows [E 5]

- Erroneous buffer

solution used for

second part of

calibration

- Defective electrode

- Ensure that correct pH buffer

solution is being used (pH 4.01

or pH 10.01)

- Check electrode and replace if

necessary

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5.8. Average time taken to carry out Procedure

Procedure Section Average Time (mins)

Installation N/A

Measuring pH with Automatic

Temperature Compensation

1 (for one pH reading)

Measuring pH with Manual

Temperature Compensation

2 (for one pH reading)

Measuring Temperature 2 (for one T reading)

Calibration 3 ( for two-point calibration)

Maintenance N/A

Troubleshooting N/A

5.9. Flow Charts

5.9.1. Installation

Start

Connect power cable to DC power

socket and to mains supply

Connect pH electrode and T probe to

BNC and T sockets respectively

End

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Page 9 of 14

5.9.2. Operation

before

Start

Measuring pH

Meter being

calibrated

Perform calibration before

use (see section 5.8.3)

Press On/Off Key

to switch on meter

Use ATC feature MTC

Submerge pH electrode and T probe into sample and keep

them close together

Press RANGE Key until display

changes to T mode

Disconnect T probe from meter

Adjust displayed T by using the

Up and Down keys respectively

Press RANGE Key again until

display changes back to pH mode

Submerge pH electrode into

sample to be tested

Shake sample briefly and wait

for reading to stabilise

Read off stable pH reading

Test another

sample

Rinse off electrode with next

sample before further use

1

Measuring T

Press On/Off key to

switch on meter

Dip T probe

Allow 1-2 minutes for

reading to stabilise

Read off displayed

stable T reading

End

2

1

Yes

No Yes

Yes Yes

Yes

Yes

No

No

No

No

No

Display in

T mode

Press RANGE Key

until display changes to T mode

Yes

No

2

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Page 10 of 14

5.9.3. Calibration

Start

Pour small quantities of pH 7.01 and pH 4.01 or pH 10.01 buffer

solutions into 2 separate beakers

Use another 2 separate

beakers for rinsing

Press On/Off Key to

switch on meter

Immerse pH electrode into

pH 7.01 buffer and stir gently

Submerged 4cm

into solution

Meter in pH

mode

Press CAL Key

[pH] symbol

stopped flashing

Press CON Key

[E 4] seen

flashing

1

Submerge accordingly

Place T probe as close to pH

electrode as possible

Press RANGE Key until display

changes to pH mode

Wait until it stops flashing

Using correct

buffer solution

Replace electrode

Use appropriate

buffer solution

1

Wait until [E 5] is displayed

2

Yes

Yes

Yes

Yes

Yes

No

No

No

No

No

Rinse pH electrode with some

pH 7.01 buffer solution

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2

Rinse pH electrode

with distilled water

Rinse pH electrode with second buffer solution

Immerse pH electrode into

second buffer and stir gently

[E 4] seen

flashing [pH] symbol

stopped flashing

Press CON Key

Wait until meter returns to

normal operating mode

before further use

End

Wait until it stops flashing

Using correct

buffer solution Use appropriate

buffer solution

Replace electrode

1

1

No No

No

Yes

Yes

Yes

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5.9.4. Maintenance

Start

Inspect cables of electrodes for any

signs of broken insulation

Inspect pH electrode for any

cracks in stem or bulb

Rinse off any salt deposits with water

General cleaning

Soak pH electrode in Hanna HI 7062

or HI 8061 General Cleaning Solution for ½ hour

Protein deposits

present


or HI 8073 Protein Cleaning Solution for 15 minutes

Inorganic deposits present


or HI 8074 Inorganic Cleaning

Solution for 15 minutes

Oil films / deposits present


or HI 8074 Inorganic Cleaning

Solution for 15 minutes

Rinse pH electrode thoroughly

with distilled water

Refill reference chamber

with fresh electrolyte

Soak in HI 70300 or HI 80300 Storage

Solution for at least 1 hr before use

1 1 1

1

2

2

No No No

No

Yes Yes

Yes

Yes

End

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Page 13 of 14

6. Precautions

6.1. Always keep the pH electrode wet and rinse it thoroughly with the

sample to be measured before use.

6.2. In order to measure the pH accurately, the temperature factor must

always be taken into consideration.

6.3. If the sample temperature is quite different from the temperature at

which the pH electrode is kept, allow a few minutes for thermal

equilibrium to take place.

6.4. When performing a two-point calibration, use pH 7.01 and pH 4.01

when measuring acidic samples and pH 7.01 and pH 10.01 for alkaline

measurements. This provides more accurate readings to be taken.

6.5. Do not be alarmed when salt deposits are present on the electrode since

these normally form and can easily be rinsed off with water.

6.6. If any air bubbles form inside the glass bulb, “shake it down” firmly to

remove them.

6.7. Always store the electrode in its appropriate storage solution and never

store it in distilled or deionised water.

6.8. Avoid high humidity environments and static discharges since these are

detrimental for a stable pH reading.

6.9. Perform a calibration:

6.9.1. When pH electrode or temperature probe is replaced

6.9.2. When reference electrode is changed

6.9.3. At least once a month

6.9.4. After testing aggressive chemicals

6.9.5. When greater accuracy is required

6.9.6. After any cleaning procedure

7. References

Hanna® Instruments. Instruction Manual HI 8417 – HI 8519 – HI 8520 – HI

8521 Microprocessor Bench-Top pH Meters;1998.

8. Appendices

N/A

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Page 14 of 14

9. Revision History

Version Number Amendments/ Reasons for change

01 Initial Release

Documents

SOP/PD/312 01 STANDARD OPERATING PROCEDURE · PDF fileuniversity of malta faculty of medicine & surgery pharmacy department ref. no. sop/pd/312_01 standard operating procedure hanna®