D-828

Use of Balances in the QC Laboratory

Section D — Laboratory Operations and Specifications Revision 8 9 pages

Original Document

Scanned document (image-only PDF)

Extracted Text

Searchable text extracted from PDF

1.0 Purpose

This procedure provides internal guidelines for the calibration and use of balances in the QC

Laboratory.

2.0 Scope

This procedure generally applies to all analytical and micro balances installed at Jon Labs with a

scale interval between 0.001 mg and 1 mg. This procedure utilizes guidance from USP <1251>

Weighing on an Analytical Balance and USP <41> Weights and Balances.

3.0 Responsibility

3.1. ‘It is the responsibility of QC Laboratory Analysts to comply with this procedure.

3.2 ‘It is the responsibility of QC Laboratory Management to implement this procedure and

to ensure compliance.

3.3 ——‘It is the responsibility of QC Laboratory Management and/or Analytical Development
personnel to keep this procedure aligned with current practices.

4.0 Definitions

4.1 QC — Quality Control

4.2 Hysteresis — In a balance, is caused by excessive stretching of the springs and is primarily
due to overloading or dropping an object on the pan (excessive stretching of springs is

cause for major repair)

5.0 References

5.1 D-828-F1, Form, QC Laboratory Balance Log

[SOP

Standard Operating Procedure SOP No | Rev
Use of Balances in the QC Laboratory D-828 8 panecens

5.2. USP <1251> Weighing on an Analytical Balance

5.3. USP <41> Weights and Balances

5.4 ANSI/ASTM E617, American National Standard, Laboratory Weights and Precision

Mass Standards

5.5 G-201, SOP, Calibration Program

5.6 C-501, SOP, Document Control Procedure

5.7 C-502, SOP, Record Storage, Retention, and Destruction

6.0 Location and Setup

6.1 Laboratory balances will be located on a solid, level, nonmagnetic surface.

6.2 Laboratory balances will be isolated from vibrations and air currents. A granite weigh
bench is ideal to minimize vibrations.

6.3 Laboratory balances will be isolated from excessive temperature or humidity variations.

6.4 Laboratory balances will be isolated from sources of electromagnetic radiation and

magnetic fields.

6.5 After powering up, the balance should be allowed to equilibrate according to the

manufacturer’s instructions (typically 1-24 hours) before use. Some balances use a
standby mode and are ready for operation immediately after being changed out of

standby.

7.0 General Use

7.1 Ensure that the weekly precision check has been performed within the last week. If not,

perform the weekly precision check as outlined in section 10.0.

tae Ensure that the daily accuracy check has been performed on the day of use. If not, perform
the daily accuracy check as outlined in section 11.0.

7.3 Note the current minimum net sample weight. Ensure that the desired sample weight is

not less than the specified minimum weight.

[SOP

Standard Operating Procedure SOP No | Rev
Page 3 of 8
Use of Balances in the QC Laboratory D-828 8

7.4 Record the Ion number of the balance, the next calibration due date, and the specified

minimum weight in the laboratory notebook.

7.5 Wear powder free gloves or use forceps to handle any material being weighed.

7.6 Inspect balance pan for loose debris and remove as necessary before weighing. A camel

hair brush or equivalent can be used to clean the balance pan of loose debris before each
use.

7.7 The level of the balance should be verified each day prior to the balance check and before

each use. Leveling can be accomplished by rotating clockwise or counterclockwise the

adjustable feet on the balance until the bubble is inside of the circle.

7.8 Use a weigh boat or weigh paper of the appropriate size to hold all of the material being
measured and never measure directly on the balance pan.

1g Take extra precautions when weighing liquids as not to spill on the balance pan or inside

the weigh chamber, as serious damage could result.

7.10 Take extra precautions when weighing materials that are potentially corrosive to the
analytical balance as not to spill on to balance surfaces. Immediate cleanup is required if

material falls outside the weigh boat.

7.11 Weigh the material either by quantitative transfer or by difference as outlined in section

13.0.

Tel2 Print the weigh result and affix the weigh tape in the laboratory notebook.

73 Clean the balance pan and immediate area after use.

8.0 Calibration Weights

8.1 Traceable calibration weights spanning the range of the balance and conforming to

ASTM E617 standards should be used for the Weekly Precision Check and Daily
Accuracy Check.

8.2 Calibration weights should be calibrated at the frequency specified in SOP G-201

Calibration Program.

[SOP

Standard Operating Procedure SOP No | Rev
Use of Balances in the QC Laboratory D-828 8 Po s 4 astof 8

9.0 Annual Calibration

9.1 Laboratory balances should be calibrated by an external entity at the frequency specified
in SOP G-201 Calibration Program.

10.0 Weekly Precision Check

10.1 An evaluation of precision should be conducted on a weekly basis or after the balance
has been moved. The result of the precision check is used to determine the minimum

weight that can be accurately measured.

10.2 Because the standard deviation of measurement is virtually independent of sample mass

within the balance’s capacity, the use of a small test weight, which may be difficult to
handle, is not required.

10.3. The analyst performing the precision check should record his or her initials and date on

the Weekly Precision check form.

10.4 Document the Ion number, nominal mass, and next calibration due date of the calibration
weight used for the Weekly Precision Check.

10.5 Ensure that the balance is level as outlined in section 7.7.

10.6 Perform ten replicate measurements of the calibration weight

10.6.1 On the balance keypad, print the header for documentation of the date and time
of precision check.

10.6.2 Remove all objects from the balance pan, allow the reading to stabilize, and tare

the balance.

10.6.3 Transfer the calibration weight to the balance pan using forceps or static free

gloves.
10.6.4 Allow the balance reading to stabilize.

10.6.5 On the balance keypad, press print to record the weight.

10.6.6 Repeat steps 10.6.2 - 10.6.5 for a total of ten replicate measurements.

[SOP

Standard Operating Procedure SOP No Rev
Page 5 of 8
Use of Balances in the QC Laboratory D-828

10.6.7 Affix the weigh tape to the Weekly Precision Check form.

10.7 Calculate the minimum net sample weight.

10.7.1 Calculate the standard deviation of the ten replicate measurements.

10.7.2 If the standard deviation is less than 0.41 times the scale interval, replace the
standard deviation by 0.41 times the scale interval in step 10.7.3.

10.7.3 The minimum net sample weight is equal to 2000 times the standard deviation.

Example 1: The balance capacity is 220 g and the scale interval is 0.00001 g

(0.01 mg). Ten replicate measurements of a 2 g weight are

performed, and the standard deviation of the measurements is
0.0000096 g. The standard deviation is greater than 0.41 times the

scale interval (0.41 X 0.00001 g = 0.0000041 g). The minimum
weight is 2000 X 0.0000096 g = 0.0192 g, or 19.20 mg.

Example 2: The balance capacity is 220 g and the scale interval is 0.00001 g

(0.01 mg). Ten replicate measurements of a 2 g weight are

performed, and the standard deviation of the measurements is
0.0000029 g. The standard deviation is less than 0.41 times the

scale interval (0.41 X 0.00001 g = 0.0000041 g). The minimum
weight is 2000 X 0.0000041 g = 0.0082 g, or 8.20 mg.

10.8 Enter the minimum net sample weight on the Weekly Precision check form.

10.9 Have a second person review the data and calculations.

10.10 Clearly post the minimum net sample weight on the balance. In practice, a minimum

sample weight that is greater than the weight calculated in section 10.7 may be used as a

convenience so that the minimum weight does not change frequently.

11.0 Daily Accuracy Check

11.1. An evaluation of balance accuracy will be conducted on a daily basis.

[SOP

Standard Operating Procedure SOP No | Rev
Use of Balances in the QC Laboratory D-828 8 P as6 of 8

11.2 Two calibration weights spanning the range of the balance capacity should be used for

the accuracy check.

11.3. The analyst performing the accuracy check will record his or her initials and date on the

Daily Accuracy Check form.

11.4 Document the Ion number and weight specifications (+ 0.1%) of the calibration weights
used for the Daily Accuracy Check. As an example of weight specification for a

calibration weight with a mass of 2.00001 g, the weight specification would be 1.99801

g—2.00201 g.

11.5 Ensure that the balance is level as outlined in section 7.7.

11.6 Perform the balance internal calibration. Consult the manual for the specific balance for
internal calibration procedure. Be very careful not to subject the balance to air currents

or vibration while the internal calibration is being performed.

11.7. On the balance keypad, print the header for documentation of the date and time of the

accuracy check.
11.8 Remove all objects from the balance pan, allow the reading to stabilize, and tare the

balance.

11.9 Transfer the calibration weight to the balance pan using forceps or static free gloves.

11.10 Allow the balance reading to stabilize.

11.11 On the balance keypad, press print to record the weight.

11.12 Repeat steps 11.8 - 11.11 for the second weight used for the accuracy check.

11.13 Affix the weigh tape to Form D-828-F1 QC Laboratory Balance Log.

11.14 The measurements should be within 0.1% of the weights listed on the Certificate of

Analysis. On Form D-828-F1 QC Laboratory Balance Log, indicate pass or fail for the

accuracy check.
11.15 Have a second person review the accuracy check.

[SOP

Use o S f t B a a n l d a a n rd c e O s p e i r n a t t h i e n g Q P C r o L c a e b d o u r re a tory S D O - P 82 N 8 o | Re 8 v P age 7 of 8

12.0 Troubleshooting: Causes of Drift

12.1 A balance door is open.

12.2 Temperature of the balance and material to be weighed are not the same.

12.3. The sample is actively loosing or gaining weight.

12.4 The balance has been moved and is not equilibrated to the new environment.

12.5 Air currents are present in the laboratory.

12.6 The balance is not properly leveled.

12.7. The balance is subjected to vibration, electromagnetic radiation, or magnetic field.

12.8 Hysteresis of the mechanical parts occurs during weighing.

13.0 Weighing Methods

13.1 Quantitative Transfer

13.1.1 Center the weigh container on the balance pan, and tare the balance.

13.1.2 Load the material to the desired weight specification.

13.1.3 After the balance has equilibrated print out the result and log in notebook.

13.1.4 Transfer the weighed material to the sample container. Liquid may be used to
wash any residue from the weigh container into the sample container to ensure

quantitative transfer.

13.2 Weight by Difference

Note: Weighing by difference does not remove the need to meet the minimum weight
calculated for the balance in use. The amount weighed is required to be at or

above the balance minimum.

13.2.1 Tare the balance with the weigh container centered on the balance pan.

13.2.2 Load the material to the desired weight specification.

13.2.3 After the balance has equilibrated print out the result.

[SOP

Standard Operating Procedure SOP No Rev
Page 8 of 8
Use of Balances in the QC Laboratory D-828

13.2.4 Transfer the weighed material to the test vessel.

13.2.5 Reweigh the weigh boat.

13.2.6 Subtract the weigh boat final weight from the initial material weight to get the
transferred weight.

13.2.7 Record the results on Form D-828-F1 QC Laboratory Balance Log and attach

printouts.

14.0 Documentation Requirements

14.1 Documents will be distributed and maintained as outlined in SOP C-501 Document

Control and SOP C-502 Record Storage, Retention, and Destruction.

15.0 Revision History

| Rev | Date | Description of Changes | CCR # | By |
|-----|----------|------------------------|-------|----|
| 0 | 05/06/10 | New - - | - | - |
| 1 | 01/24/12 | Updated Original Format - - | - | - |
| 2 | 02/14/13 | Added more troubleshooting information, reformatted for easier interpretation, added more good practice information. Biennial review. Added specific instruction for the daily | 13-090 | B. Johns |
| 3 | 02/04/15 | calibration of the Adam PW-124 and Mettler Toledo X5204 scales. * aclilall s B p i e e c n i n f i i a c l a t r i e o v n i s e . w. M o U d p i d f a i t e e d p Ti r t o l c e. e du U r p e d a t t o e m d e e c t h e c c u k r r w e e n i t g p h r t actices. diiiaain B, Jenne Update for compliance with USP general chapter. Added | 15-0136 | B. Johns |
| 5 | 02/22/19 | weekly precision check. Remove instructions for specific balances. Added log. | 19-0159 | S. Sassman |
| 6 | 08/05/21 | Added micro balance to scope of SOP. Other minor changes. CC- | 21-0276 | J. Sassman |
| 7 | 03/23/22 | Review to ensure SOP matches current practices. CC- | 22-0114 | S. Sassman |
| 8 | 11/04/23 | Add references to document control procedures. Add document CC- maintenance requirements. Change SOP number. | 23-0544 | K. Burris |

[SOP

ION QC Laboratory Balance Log
tabs Form: D-828-F1 CCRNo. CC-23-0544 Revision:

Logbook Number: Logbook Page:

Weight Ion Weight ‘ Entered | Reviewed
ee Number Specification Pass! Fall by by

By
e
|
oe
Ls)
<
Zz
‘S
fam)