Extraction Grade Butane: Quality Standards, Chain of Custody and ASTM D37 Survey Results

For much of the extraction industry’s history, LP gases—whether labeled high-purity, extraction-grade or industrial-grade—have been incorrectly treated as interchangeable inputs, with insufficient attention paid to the critical differences in purity, handling, and downstream impact. As extraction technology, regulatory scrutiny, and consumer expectations have evolved, that assumption has become increasingly difficult to defend.

The ASTM D37 Compressed Gas Safety and Quality Initiative spearheaded by Solvent Direct conducted a survey which provides a data-driven snapshot of where the industry currently stands. While the results are forward-looking, many of the priorities identified reflect practices already familiar to Solvent Direct which has long treated process gases as critical, consumer-adjacent inputs rather than commodities.

What the Survey Signals

The survey included respondents spanning the full supply chain, including gas users, producers, suppliers, distributors, resellers, and testing laboratories. Despite the diversity of roles, responses showed notable alignment around documentation, traceability, chain of custody and analytical rigor.

When respondents were asked to rank documents required in a standardized chain-of-custody package, the Certificate of Analysis (CoA) for each batch of process gas produced ranked highest overall, with a median score of 5 and the highest cumulative score (59) in the dataset. Closely following was the refinery-level CoA, which ranked second with a median score of 5 and a total score of 54, reinforcing the importance of traceability back to the source.

Other chain-of-custody elements consistently ranked with median scores of 4, including:

• Manufacturer batch numbers (score: 55)

• Transfer fill logs at each responsible party (score: 53)

• Container identification numbers such as DOT registration (score: 51)

• Batch continuity as custody changes (score: 50)

Taken together, these rankings indicate broad agreement that purity claims must remain defensible as gas moves across containers, facilities, and responsible parties.

What the Data Shows About Certificates of Analysis

The survey also examined what information should appear on a standardized CoA. Here again, consensus was strong.

The highest-ranked CoA elements, both receiving median scores of 5 and total scores of 61, were:

• Analytes being tested (including gas concentration, impurities, and contaminants)

• Reported analytical values

Closely behind were quality-control thresholds such as:

• Action limits (median: 5, score: 55)

• Lower Limit of Quantification (LLOQ) (median: 4, score: 55)

• Lower Limit of Detection (LLOD) (median: 4, score: 54)

These results suggest that the industry is moving beyond nominal purity statements toward CoAs that support technical decision-making, particularly in closed-loop extraction systems where small analytical differences can have downstream effects.

Practices That Pre-Date the Conversation

For some suppliers, the survey highlights areas of future implementation. For Solvent Direct, it reflects operating assumptions already in place.

Long before standardized survey language or formal working-group alignment, Solvent Direct adopted practices that now appear repeatedly throughout the ASTM D37 results. These include certified cylinder cleaning prior to refill, managing BTEX compounds within clearly defined conservative limits, conducting routine third-party laboratory analysis, and performing random batch testing to verify consistency over time. Batch identity and container accountability have also been maintained as gas changes custody.

These measures were not adopted in response to compliance pressure. They emerged from operational experience showing that process gas quality is influenced not only by production, but by containers, handling practices, and transfer conditions.

Why Containers, BTEX, and Documentation Matter

BTEX compounds—benzene, toluene, ethylbenzene, and xylenes—are well characterized contaminants with established health and regulatory implications. Managing them effectively requires more than a single test result or a headline purity percentage.

The survey’s emphasis on container ID numbers (median score: 4), custody logs (median score: 4), and CoAs issued at each custody or container change reflects a growing recognition that purity is not static. Even high-grade gas can be compromised without disciplined container management and verification.

Cylinder cleaning, batch traceability, and independent analysis address different risk vectors. Together, they reduce uncertainty for extractors and downstream consumers.

An Industry in Alignment

The ASTM D37 survey suggests the industry is converging on a more consistent definition of quality—one that extends beyond stated purity percentages to include traceability, analytical transparency, and accountability across custody changes.

As expectations continue to mature, these practices are likely to become baseline requirements rather than differentiators. For operators already working within these frameworks, adoption is incremental. For others, it represents a meaningful shift in how process gases are evaluated and supplied.

Closing Perspective

Ultra-high-purity hydrocarbons like butane, propane and isobutane sit upstream of consumer products, and upstream decisions carry downstream consequences. The closer standards move toward full traceability and verifiable analysis, the more resilient the extraction ecosystem becomes.

The ASTM D37 survey does not introduce entirely new concepts so much as it confirms existing ones—and signals that the industry is increasingly prepared to operationalize them.

To learn more visit www.solventdirect.com/compliance