Attachment_5_-_CARB_Gravimetric_Analysis_Requirements.pdf
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- Solicitation number
- 0000036628
- Issued by
- California
About this file
This document is a State of California Bid Specification for Gravimetric Analysis Requirements for the California Air Resources Board (CARB) Primary Gas Standards. The specification details the precise technical requirements for preparing and certifying gas mixtures with extremely high accuracy, focusing on the methodology for creating gas standards through gravimetric analysis. The document provides a detailed example of creating a gas mixture (2000 ppm CO in N2), demonstrating the step-by-step process of weighing component and balance gases, calculating molar quantities, and determining concentration with an accuracy tolerance of ± 1%.
The specification mandates strict technical requirements for gas mixture preparation, including scale accuracy traceable to the U.S. National Institute of Science and Technology (NIST), component gas purity verification, and certification processes. The blend tolerance table specifies precise concentration ranges and analytical uncertainty requirements for different gas mixtures, such as CH4/Argon, CO2/N2, and NH3/N2, with tolerance ranges between 5-10% and analytical uncertainty of 1-2%. Any gas mixtures not meeting these exacting standards will be returned to the contractor, emphasizing the critical nature of precision in these scientific standards.
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Other files
| File | Type | Posted |
|---|---|---|
| IFB_Event_ID_0000036628.docx | DOCX document | |
| Attachment_1A_-_Loss_of_Use_Worksheet.xlsx | XLSX spreadsheet | |
| APP_Cover_Page.docx | DOCX document | |
| Attachment_1_-_Pricing_Workbook.xlsx | XLSX spreadsheet | |
| Attachment_2_-_CDCR_Special_Provisions.docx | DOCX document | |
| Attachment_5A_-_CARB_Liquid_Nitrogen_Specification.pdf | ||
| Attachment_6_-_Agreement_Cover_Letter.pdf | ||
| Attachment_4_-_BAR_Specification.pdf | ||
| Attachment_3_-_Narrative_Response.docx | DOCX document |
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State of California Bid Specifications
6830-BS-0215676-2RevA Event ID 0000036628
Attachment 5
6/17/2025
Gravimetric Analysis Requirements for California Air Resources Board Primary Gas Standards
1) Scope/Requirements:
The purpose of this procedure is to define the requirements for the California Air Resources Board (CARB) primary gas standards. Gravimetric certification for CARB purposes is defined as adding a carefully measured weight of component as to an evacuated cylinder, followed by the addition of a carefully measured weight of balance gas.
The two (2) weights are converted by appropriate calculations into molar volumes and then given the appropriate gas concentration ratio in units of parts-per-million (ppm).
A sample example is as follows.
Example: Component Gas: 2000 ppm CO, Balance Gas: N2
1. Establish tare weight of cylinder (within + 0.05 grams).
2. Added weight of CO (component gas) = 13.573 g (within + 0.05 grams).
3. Added wt. of N2 (balance gas) = 6617.10 g.
4. Calculated molar quantities.
13.573 g-CO = 0.4846 moles for CO
28.01 g/mole
6617.10 g-N2 = 236.241 moles for N2
28.01 g/mole
Total Moles = 0.4846 + 236.241= 236.73 moles
5. Calculated Concentration (ppm) based on molar quantities.
0.4846 moles CO x 106 = 2051.2 ppm CO (mole/mole)
236.73 moles (Total)
Accuracy (± %)
100 x (twice total weighing error) = 100 x 2 x 0.05 = ± 0.74% (weight of component gas) 13.573
State of California 6830-BS-0215676-2RevA Bid Specifications Event ID 0000033449
Attachment 5
Page 2 of 3 6/17/2025
Mixture Accuracy
The accuracy of the mixture shall be within ± 1% of the calculated value including all weighing tolerances.
Scale Capacity and Accuracy
The scale used to measure the gaseous components, and the treated aluminum and steel cylinders shall be capable of weighing to within ± 0.05 grams, including all hysteresis and readability errors.
Accuracy of the scale must be traceable to the U.S. National Institute of Science and Technology (NIST). The date of the last certification must be included in the data submitted. In addition, the actual accuracy must be included with the analysis.
Balance Gases
The balance gas shall be as specified in Pricing Worksheet.
Component Gas
Component gas purity shall be stated in the analysis. In order to guarantee a ± 1% mixture accuracy, it will be necessary to use a diluted component gas in the preparation of gas mixtures below approximately 2000 ppm. If the component gas is a diluted mixture, it must also have a traceable gravimetric analysis consistent with this procedure.
The final product delivered shall be accompanied by a certificate of analysis of the contents.
Certification
All gravimetric mixtures to be analyzed against an existing gravimetric prior to certification. For zero air and zero nitrogen, the impurities must be verified against analytical standards traceable to NIST by weight and/or analysis. All primary standard gases mixtures must be traceable to NIST weights and/or NIST gas mixture reference materials within 1%, including all measurement tolerances.
State of California 6830-BS-0215676-2RevA Bid Specifications Event ID 0000033449
Attachment 5
Page 3 of 3 6/17/2025
Blend Tolerance Primary gases shall meet the blend tolerances below. If they do not meet the necessary criteria, they will be returned to the contractor.
Target
Concentration Blend Tolerance Analytical
Uncertainty Required
Gas/Bal Gas Range Value Span Gas Conc. Tolerance
+/- Lower Conc. Limit Upper Conc. Limit +/-
CH4/Argon 5% 5% 5% 4.75 5.25 2%
CO2/N2 40% 40.00% 10% 36.00% 44.00% 2%
NH3/N2 1,500ppm 1,425ppm 5% 1353.75 1496.25 1%
10% 10% 5% 9.50% 10.50% 1%
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