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D6418-09 – Standard Test Method Technical Guide
🛠️ Overview and Scope of Practice
This standard practice (D6418 – 09) provides a detailed procedure for utilizing the disposable En Core sampler to collect and store soil samples designated for volatile organic analysis (VOA). It is specifically intended for application to soils that may contain volatile waste constituents. The En Core sampler is uniquely designed as an integrated sampling and storage device. The values stated in SI units are to be regarded as standard. It is recommended that this standard be used in conjunction with Guide D4547 and Guide D4687.
| 📏 Sampler Component | 📐 Function |
|---|---|
| Coring Body / Storage Chamber | Collects the soil core and serves as the primary storage vessel during shipment to the laboratory. |
| O-Ring Sealed Plunger | Seals the bottom of the storage chamber to prevent leakage and VOC loss. |
| O-Ring Sealed Cap (Slide-On) | Seals the top of the chamber immediately following sample collection, creating an airtight storage environment. |
| Sample Mass Capacity | Designed to collect either approximately 5 g or 25 g of soil for VOA. |
🌡️ Sample Storage and Holding Times
Proper storage is critical to minimize the loss of volatile organic compounds (VOCs) due to volatilization or biodegradation from the time of collection until laboratory analysis. After the sample is collected, the coring body is immediately sealed with the slide-on cap. This practice does not utilize methanol preservation or other chemical preservatives in the field. The standard specifies the following validated storage options:
| 🟦 Condition | ⚡ Temperature | ⏱️ Maximum Holding Time |
|---|---|---|
| Refrigeration Only | 4 ± 2°C | Up to 48 hours |
| Freezing Only | -7 to -21°C | Up to 14 days |
| Refrigeration then Freezing | 4 ± 2°C, then -7 to -21°C | 48 hours + up to 5 days |
💡 Technical Note: Longer storage at 4 ± 2°C or -7 to -21°C is permitted if it can be demonstrated that the longer storage time does not influence the concentration of the target VOCs, or if the resulting data meet the project’s Data Quality Objectives (DQOs) as defined in Practice D5792.
⚙️ Key Procedural Specifications
The procedure is designed for simplicity and reliability in field conditions. The sampler, consisting of a coring body/storage chamber, an O-ring sealed plunger, and an O-ring sealed cap, is entirely disposable. Once the soil sample is collected, the sealing mechanism is engaged by applying the slide-on cap. The sample is immediately stabilized according to the selected storage option. Operators must refer to Guide D4547 for comprehensive guidance on minimizing VOC loss. Standard sample masses are either approximately 5 g or 25 g, depending on the specific analytical requirements of the laboratory.
⚡ Important Consideration: ASTM officially takes no position respecting the validity of any patent rights asserted in connection with any item mentioned in this standard. Users are expressly advised that determination of the validity of any such patent rights, and the risk of infringement, are entirely their own responsibility.
❓ Frequently Asked Questions
🔍 What types of soil is this practice intended for?
This practice is specifically intended for application to soils that may contain volatile waste constituents requiring volatile organic analysis (VOA).
💡 What are the standard sample sizes for the En Core sampler?
The En Core sampler is designed to collect and store a soil sample of approximately 5 g or 25 g for volatile organic analysis.
⚡ Does this practice allow the use of methanol for field preservation?
No. This practice explicitly states that it does not use methanol preservation or other chemical preservatives in the field. Sample preservation is achieved solely through strict temperature control (refrigeration or freezing) per the specified holding times.
📌 Can I extend the holding time beyond the standard 48 hours?
Yes, storage at 4 ± 2°C or -7 to -21°C for longer holding times is an option, provided it can be shown that the longer storage time does not influence the concentrations of the VOCs of interest in the samples, or that the data generated meet the project’s Data Quality Objectives (DQOs).