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D2913-20 – Standard Test Method Technical Guide
ASTM D2913-20 provides a standardized methodology for quantifying the concentration of total mercaptans (organic thiols) in the atmosphere. It is primarily intended for integrated sampling over a selected time span in applications such as ambient air monitoring, industrial hygiene assessments, and odor control, where these sulfur compounds are detectable at trace levels.
📋 Scope and Application
This test method is specifically designed for the measurement of mercaptans in the atmosphere at concentrations below 100 parts per billion (ppb(v)), equivalent to 195 µg/m³. For concentrations exceeding this threshold, the sampling period can be adjusted or the volume of the trapping liquid modified.
💡 Method Specificity: This procedure determines total mercaptans and does not differentiate between individual thiol species. However, the test is most sensitive to lower molecular weight alkanethiols.
Under standard reference conditions (101.3 kPa and 25°C), the minimum detectable concentration of methyl mercaptan is 1.0 ppb(v) (1.95 µg/m³). This is achieved when sampling air at a maximum recommended rate of 2 L/min for 2 hours, with a minimum detectable amount of 0.04 µg/mL in a final liquid volume of 25 mL.
⚠️ Safety Responsibility: This standard does not purport to address all safety concerns. The user is responsible for establishing appropriate safety, health, and environmental practices. Specific precautionary statements are provided in Sections 8.7, 8.8, and 9 of the full document.
⚙️ Sampling and Test Procedure
The procedure utilizes a bubbler containing 10 mL of absorption liquid to capture the mercaptan sample. Sampling can be performed either manually or via an automatic sequential sampler. Following collection, the absorption liquid is delivered to a laboratory for colorimetric analysis using N,N-dimethyl-p-phenylenediamine. For accurate calibration and quality control, practitioners should refer to Practice D1357 for sampling guidance and Practice D3609 for calibration techniques using permeation tubes.
| 🟦 Parameter | 📏 Specification | 🎯 Units |
|---|---|---|
| Maximum Sampling Rate | 2 | L/min |
| Standard Sampling Period | 2 | hours |
| Absorption Liquid Volume | 10 | mL |
| Final Analysis Volume | 25 | mL |
📊 Key Performance Metrics and Data
The following table summarizes the critical detection limits and reference conditions specified in D2913-20. The values stated in SI units are to be regarded as the standard.
| 🎯 Metric | ⚡ Value | 📐 Notes |
|---|---|---|
| Minimum Detectable Conc. | 1.0 ppb(v) | 1.95 µg methyl mercaptan/m³ |
| Minimum Detectable Amount | 0.04 µg/mL | In final liquid volume of 25 mL |
| Standard Concentration Range | < 100 ppb(v) | Procedure can be modified for higher conc. |
| Reference Conditions | 101.3 kPa (760 mm Hg), 25°C | Standard temperature and pressure |
The standard is issued under the fixed designation D2913 and is under the jurisdiction of ASTM Committee D22 on Air Quality. It was developed in accordance with internationally recognized principles on standardization established by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
❓ Frequently Asked Questions
🔍 What is the primary purpose of ASTM D2913-20?
This standard specifies a test method for measuring the total concentration of mercaptans (organic thiols) in the atmosphere, primarily targeting concentrations below 100 ppb(v).
💡 How does the detection mechanism work?
The collected mercaptan sample undergoes a colorimetric analysis via a chemical reaction with N,N-dimethyl-p-phenylenediamine in a laboratory setting.
⚡ What are the minimum detection limits?
When sampling at 2 L/min for 2 hours, the minimum detectable concentration is 1.0 ppb(v), which corresponds to 0.04 µg/mL in a final 25 mL liquid volume.
📌 Can this standard differentiate between specific mercaptans?
No. The test method is designed to determine the total mercaptan content. While it is most sensitive to lower molecular weight alkanethiols, it does not differentiate among individual mercaptan species.