BP-A1, Page i



### Balance Protocol for Gravimetric Determination of S ample Weight

Using a Precision Analytical Balance

BP-A1

Adoption Date: July 20, 2009 As Last Amended: January 5, 2010

NOTE: This document, approved by the Air Resources Board at its January 22, 2009 hearing for incorporation by reference in California Code o f Regulations (CCR), title 17, sections 95360 through 95370, was originally shown without underli ne as permitted by California Code of Regulations, title 1, section 8. The modifications are indicated in underline to indicate additions and in strikeout to indicate deletions.BP-A1, Page ii Table of Contents

1. SCOPE AND APPLICATION ..............................

................................................... .............................. 1

2. SUMMARY OF METHOD ..................................

................................................... ............................... 1

3. DEFINITIONS........................................

................................................... ............................................ 1

4. INTERFERENCES ......................................

................................................... ...................................... 1

5. PERSONNEL HEALTH AND SAFETY........................

................................................... ..................... 2

6. EQUIPMENT AND SUPPLIES.............................

................................................... ............................. 2

7. REAGENTS AND STANDARDS.............................

................................................... .......................... 2

8. SAMPLE COLLECTION, PRESERVATION, AND STORAGE .......

................................................... . 2

9. QUALITY CONTROL....................................

................................................... .................................... 2

10. CALIBRATION AND STANDARDIZATION....................

................................................... .............. 3

11. PROCEDURE ..........................................

................................................... ..................................... 3

11.1 O VERVIEW OF W EIGHING S EQUENCE

................................................... ......................................... 3

11.2 H ANDLING

................................................... ................................................... .................................. 3

11.3 R EADING THE B ALANCE

................................................... ................................................... ............. 3

11.4 I NITIAL A DJUSTMENT

................................................... ................................................... ................. 4

11.5 Z ERO C HECK

................................................... ................................................... .............................. 4

11.6 C ALIBRATION C HECK

................................................... ................................................... ................. 5

11.7 R EPLICATE W EIGHING C HECK

................................................... ................................................... .. 5

12. DATA ANALYSIS AND CALCULATIONS.....................

................................................... ............... 7

13. METHOD PERFORMANCE .................................

................................................... ........................ 8

14. POLLUTION PREVENTION...............................

................................................... .......................... 8

15. WASTE MANAGEMENT ...................................

................................................... ........................... 8

16. REFERENCES.........................................

................................................... ..................................... 8BP-A1, Page 1

1. SCOPE AND APPLICATION

This Protocol summarizes a set of procedures and to lerances for weighing objects in the range of 0 to 1,000g with a resolution of 0.001 g. This protocol only addresses balance operations, it does not address project req uirements for equilibration, sample hold time limits, sample collection etc.

2. SUMMARY OF METHOD

The balance is zeroed and calibrated using procedur es defined herein. Object weight determinations are conducted along with control obj ect weight determinations, zero checks, calibration checks, sensitivity checks, and replicate weightings in a defined sequence designed to control and quantitatively cha racterize precision and accuracy.

3. DEFINITIONS

N/A.

4. INTERFERENCES

Object weights can be affected by temperature and r elative humidity of their environment, air currents, static electricity, gain and loss of water vapor, gain or loss of and loss of volatile compounds directly from the sa mple or from contaminants such as finger prints, marker ink, and adhesive tape.

Contamination, transfer of material to or from the samples, is controlled by conducting operations inside a clean area dedicated to the pur pose and having a filtered laminar air flow where possible; by wearing gloves while ha ndling all samples and related balance equipment; by using forceps to handle small objects, and by keeping the balance and all related equipment inside the clean area.

Air currents are controlled by conducting weighing operations inside a closed chamber or glove box and by allowing the substrates to reac h temperature and relative humidity equilibrium. The chamber is maintained at 40% rela tive humidity and 25 o C by a continuous humidity and temperature control system. The temperature and RH conditions are recorded at least once per weighing sessions. Equilibration times for samples that are particularly sensitive to humidity or to loss of semi-volatiles species are specified by project requirements.

Static electric charges on the walls of the balance and the weighed objects, including samples, controls, and calibration weights, can sig nificantly affect balance readings. Static is avoided by the operator ground himself an d test objects as described in the balance manual.BP-A1, Page 2

5. PERSONNEL HEALTH AND SAFETY

N/A

6. EQUIPMENT AND SUPPLIES

• Filtered, temperature and humidity controlled weig hing chamber.

• Precision Balance

• Plastic forceps

• Nylon fabric gloves.

• Working calibration weights: ANSI Class 2, 1000g a nd 500 g

• Working sensitivity weight: 50 mg

• Reference objects: references are one or more obje cts that are typical of the objects to be weighed during a project, but that ar e stored permanently inside the balance glove box. Reference objects are labeled T est1, Test2, Test3, etc.

7. REAGENTS AND STANDARDS

N/A

8. SAMPLE COLLECTION, PRESERVATION, AND STORAGE

N/A. See relevant project requirements and SOPs.

9. QUALITY CONTROL

Data quality is controlled by specifying frequencie s and tolerances for Zero, Calibration, Linearity, and Sensitivity checks. If checks do no t meet tolerance criteria, then samples must be re-weighed. In addition, the procedures sp ecify frequencies for Control Object Checks.

Data quality is quantitatively characterized using Zero Check, Calibration Check, and Control Check data. These data are summarized mont hly in statistics and QC charts.

See Section 11 for procedures, frequencies, and tol erances.BP-A1, Page 3

10. CALIBRATION AND STANDARDIZATION

The absolute accuracy of the balance is established by calibration against an ANSI Class 2, stainless steel working weight: 1000.000 g +/- 0.0025 g. Linearity is established checking the midpoint against an ANSI C lass 2 stainless steel working weight: 500.000 +/- 0.0012 g. Sensitivity is estab lished using and ANSI Class 2 stainless steel or aluminum working weight: 50 mg. Precision is checked by periodically checking zero, calibration, and reference object we ights.

See Section 11 for procedure.

11. PROCEDURE

11.1 Overview of Weighing Sequence
Weighing a series of substrates consists of perform ing the following procedures in sequence, while observing the procedures for handli ng and the procedures for reading the balance:

1. Initial Adjustment 2. Weigh 8 samples
3. Zero Check 4. Weigh 8 samples
5. Zero Check 6. Weigh 8 samples
7. Calibration Check 8. Return to step 2. 9. If less than 24 cans are weighed, perform a fina l Calibration Check at the end of weighing.

This sequence is interrupted and samples are reweig hed if QC check tolerances are not met. Each of these procedures along with procedure s for handling and reading the balance are described below. The QC tolerances ref erred to in these procedures are listed in Table 1. The QC codes described in these procedures are summarized in Table 2. The data are recorded in the Precision Ba lance Data Log, a sample is shown in Table 3.

11.2 Handling
1. Never touch samples, weights, balance pans, etc. with bare hands. Wear powder free gloves to handle the weights, controls, and sa mples.

11.3 Reading the Balance

1. Close the door. Wait for the balance stabilizat ion light to come on, and note the reading.BP-A1, Page 4

2. Watch the balance reading for 30 sec (use a cloc k). If the reading has not changed by more than 0.001 g from the reading noted in step 1, then record the reading observed at the end of the 30 sec period. 3. If the reading has drifted more than 0.001 g not e the new balance reading and go to step 2. 4. If the balance reading is flickering back and fo rth between two consecutive values choose the value that is displayed more often than the other. 5. If the balance reading is flickering equally bac k and forth between two consecutive values choose the higher value.

11.4 Initial Adjustment
1. Empty the sample pan Close the door. Select Ran ge 1000 g 2. Wait for a stable reading 3. Record the reading with QC code IZC (initial zer o check)
4. Press the Tare button 5. Record the reading in the logbook with QC code I ZA (initial zero adjust) 6. Place the 1,000 g working calibration weight on the balance pan 7. Wait for a stable reading. 8. Record the reading with QC code ICC (initial cal check)
9. Press the Calibrate button 10. Record the reading with QC code ICA (initial ca l adjust) 11. Remove the calibration weight. 12. Wait for a stable reading. 13. Record the reading with QC code IZC. 14. If the zero reading exceeds +/- 0.002 g, go to step 4. 15. Place the 500 g calibration weight on the balan ce pan 16. After a stable reading, record the reading with QC code C500. Do not adjust the balance. 17. Add the 0.050 g weight to 500 g weight on the b alance pan. 18. After a stable reading, record the reading wit h QC code C0.05. Do not adjust the balance. 19. Weigh reference object TEST1, record reading wi th QC code T1. 20. Weigh the reference object TEST2, TEST3, etc. t hat is similar in weight to the samples that you will be weighing. Record with QC code T2, T3, etc.

11.5 Zero Check
1. Empty the sample pan. Close the door. 2. Wait for a stable reading 3. Record the reading with QC code ZCBP-A1, Page 5

4. If the ZC reading is less than or equal to the z ero adjustment tolerance shown in Table 1, return to weighing and do not adjust the z ero

. If the ZC reading exceeded the zero adjustment tolerance, proceed with steps 5 through 7.
5. Press the Tare button 6. Record the reading in the logbook with QC code Z A. 7. If the ZC reading exceeded the zero re-weigh tol erance, change the QC code recorded in step 3 from ZC to FZC. Then enter a QC code of FZ into the QC code column of all samples weights obtained after t he last valid zero check. Reweigh all of those samples, recording new data in n ew rows of the logbook.

11.6 Calibration Check
1. First, follow procedures for Zero Check. If the ZC was within tolerance, tare the balance anyway (i.e. follow steps 5 and 6 of the Ze ro Check method) 2. Place the 1,000 g working calibration weight on the sample pan, wait for a stable reading. 3. Record the reading with QC code C1000 4. If the C1000 reading is less than or equal to th e calibration adjustment tolerances, skip steps 5 through 8 and proceed to step 9. Do n ot adjust the calibration. 5. If the C100 reading exceeded the calibration adj ust tolerance, press the Calibrate button. 6. Record the reading in the logbook with QC code C A 7. Perform a Zero Check (follow the Zero Check meth od) 8. If the C1000 reading exceeded the calibration re -weigh tolerance, change the code recorded in step 3 from C1000 to FC1000. Ente r FC into the QC column for all sample weights obtained after the last vali d calibration check. Re-weigh all of those samples, recording new data in new row s of the logbook.

11.7 Replicate Weighing Check
1. This protocol does not include reweigh samples t o obtain replicates. The projects for which this protocol is intended already include procedures multiple weightings of each sample.BP-A1, Page 6

Table 1. QC Tolerances and Frequencies for Balance Protocol A1 Reading tolerance: 0.001 g, stable for 30 sec

Adjustment Tolerances: Zero: - 0.003 to +0.003 g. Calibration: 999.997 to 1000.003 g Controls: none Replicates: none

Re-weigh Tolerances: Zero: - 0.005 to +0.005 g. Calibration: 999.995 to 1000.005 g Controls: none Replicates: none

Reference Objects: Test 1 – A reference object weighing about 400 g Test 2 – A refernce object weighing about 200 g Test 3 – A reference object weighin about 700 g.

QC Frequencies: Zero Checks: once per 8 samples Calibration Checks: once per 24 samples Repeat weighings: none (test method includes rep licate determinations) Control objects: once per weighing session

Table 2. QC Codes For Balance Protocol A1

IZC Initial Zero Check IZA Initial Zero Adjust ICC Initial Calibration Check ICA Initial Calibration Adjust

ZC Zero Check ZA Zero Adjust

CC Calibration Check CA Calibration Adjust

R Replicate Filter Weighing

FZ Sample Failed Zero Check FC Sample Failed Calibration Check

T1 Test Object 1: empty can of automotive refriger ant T2 Test Object 2: T3 Test Object 3:BP-A1, Page 7

12. DATA ANALYSIS AND CALCULATIONS

For Zero Checks, let Z equal the recorded Zero Chec k value. For control checks let T1, T2, etc. equal the recorded value for control objec t Test 1, Test 2, etc. For Calibration Checks, let C1000 equal C1000 reading minus 1000, M = C500 – 500, S = .C.050 – C500 - .050. For Replicate Checks, let D equal the loss that occurred between the first and second measurements. In summary:

T1 = T1 T2 = T2 T3 = T3 Z = ZC - 0 C = C1000 - 1000 M = C500 – 500 G = C.050 – C500 - .050

Tabulate the mean and standard deviation for each o f the following: Z, C, M, G. T1, T2, T3. Depending on the number of operators using the balance and the number of protocols in use, analyze the data by subcategories to determine the effects of balance operator and protocol. Each of these standard devi ations, S Z , S C , etc. is an estimate of the precision of single weight measurement.

For Z, C, M, and G, check the mean value for statis tical difference from 0. If the means are statistically different than zero, troubleshoot ing to eliminate bias may be called for. For Z, C, M, G, T1, T2, T3, check that the standard deviations are all comparable. If there are systematic differences, then troubleshoot ing to eliminate the problem may be called for.

Note that the precision of a weight gain , involves two weight determinations, and therefore is larger than S by a factor of sqrt(2). On the other hand replicates weighings improves the precision of the determinations by a f actor of sqrt(N). If N= 2, i.e. duplicates, then the factors cancel each other.

To estimate the overall uncertainty in a weight det ermination, a conservative estimate might be to combine the imprecision contributed by the zero with the imprecision contributed by the calibration.

U

. = sqrt( S Z 2 + S C 2 )

The uncertainty in a weight gain from N replicates is then given by:

U gain. = sqrt(2) * sqrt( S Z 2 + S C 2 ) / Sqrt(N)

But due to the balance adjustment and reweigh toler ances, we expect S Z to approximately equal S C , to approximately equal S M , etc. tolerances, so that the equation above becomes:

U gain. = 2 * S / Sqrt(N)BP-A1, Page 8

Where S is any individual standard deviation; or be tter, a pooled standard deviation.

13. METHOD PERFORMANCE

The data necessary to characterize the accuracy and precision of this method are still being collected. The method is used primarily to w eigh objects before and after a period of soaking to determine weight loss by subtr action. Given the reweigh tolerances, we expect the that the precision of wei ght gain determinations will be on the order of 0.006 g at the 1-sigma level. Bias in the weight gain determination, due to inaccuracy of the calibration weight and to fixed n on-linearity of the balance response is on the order 0.005% of the gain.

14. POLLUTION PREVENTION

When discharging half the can contents during can p reparation, do not vent the contents to f the small can to the atmosphere. Use an automotive recovery machine to transfer small can contest to a recovery cylinder.

15. WASTE MANAGEMENT

Return full and half full cans to the place of purc hase for a refund of the purchase deposit. Dispose of the contents of the recycle cyl inder through a service that consolidates waste for shipment to EPA certified fa cilities for reclaiming or destruction.

16. REFERENCES

Precision Balance Instruction Manual. Company, Cit y, StateBP-A1, Page 9Table 3. Precision Balance Data LogQC Can Can RecordedRec # Date Time Proj. Prot. Tech. Code Type ID# grams Comment12345678910111213141516171819202122232425