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CBD Isolation by Crystallization SOP

Last Updated: February 1, 2018 (SOP-003 V1.0). This guide outlines how to isolate chemically pure CBD from distilled oil using pentane as a crystallization solvent. It covers required materials, PPE, safety considerations, and a step-by-step procedure for preparing the solution, forming crystals, rinsing, pulverizing, and drying the final CBD isolate.

Link to CBD Isolation by Crystallization SOP

Quick Facts

  • Process Name: CBD Isolation by Crystallization
  • Category: SOP / Post-Processing
  • Primary Solvent: Pentane (non-polar, flash temp ~57°F / 14°C; boil ~97°F / 36°C)
  • Feedstock: Distilled oil (winterized, decarboxylated, distilled, ≥70% CBD by weight)
  • Key Outputs:
    • CBD isolate (crystalline solid)
    • Mother liquor (cannabinoid-rich residual oil)
  • Skill Level: Intermediate lab technician
  • Core Objectives:
    • Maintain personnel safety
    • Produce a consistent, quality-controlled isolate product

Safety & PPE

This process involves flammable solvent (pentane) and cold temperatures. Follow your lab’s Chemical Hygiene Plan and pentane-specific SOPs at all times.

Required PPE (worn for the full procedure):

  • Gloves
  • Lab coat
  • Safety glasses
  • Shoe covers
  • Hairnet or lab hat
  • Beard cover (if applicable)

Training Requirements:

  • “SOP – Chemical Hygiene Plan”
  • “SOP – Pentane Use” (must be completed before working with pentane)

General Safety Notes:

  • Do not mix pentane outside of a properly ventilated environment.
  • Do not work with pentane without full PPE.
  • Keep ignition sources away from pentane handling and storage areas.

Key Definitions

  • Personal Protective Equipment (PPE): Specialized clothing or equipment worn to protect against health and safety hazards.
  • Standard Operating Procedures (SOP): Established methods to be followed routinely for defined operations or situations.
  • CBD Isolate: Purified CBD in crystalline form.
  • Mother Liquor: The liquid mixture remaining after crystal filtration.
  • Pentane: Non-polar solvent with a flash temperature of ~57°F (14°C) and boiling temperature of ~97°F (36°C).
  • Distilled Oil: Winterized, decarboxylated, and distilled oleoresin containing ≥70% CBD by weight.

Responsibilities

According to the SOP, responsibility for this process lies with:

  • Director of Extraction
  • Extraction Technician

These roles are accountable for following the procedure, maintaining records, and ensuring safety and quality.

Materials & Equipment

Materials:

  • Distilled oil (≥70% CBD by weight)
  • Chemically pure pentane

Equipment:

  • Stainless steel mixing vessel
  • Stainless steel overhead or hand mixer/homogenizer
  • Stainless steel mesh screen basket (as large as vessel opening)
  • Mortar & pestle or stainless grinder (manual, pneumatic, or appropriately rated electric motor)
  • Dry ice/alcohol slurry & storage bucket (sized to hold the mixing vessel)
  • Vacuum oven
  • Appropriately rated, solvent-safe freezer

Before You Begin / Preparation

  1. Verify that the distilled oil is fully winterized, decarboxylated, and distilled, with CBD content ≥70% by weight.
  2. Confirm all PPE is available and worn.
  3. Ensure the work area is ventilated and approved for pentane handling.
  4. Pre-check:
    • Freezer is operating and capable of –31°F / –35°C
    • Dry ice/alcohol slurry is prepared if using a bath
    • Vacuum oven is clean and ready at ambient temperature

Step-by-Step Procedure

1. Prepare the Distilled Oil
  • Add distilled oil to a clean stainless steel vessel, filling no more than half full.
  • Warm the oil to 90°F / 32°C while stirring constantly with an overhead mixer or homogenizer set to low speed.
    • Do not exceed 90°F / 32°C.

2. Mix Pentane with Distilled Oil
  • With the mixer running on low, slowly introduce room-temperature pentane into the warm distilled oil.
  • Maintain mixing at the lowest effective setting.
  • Do not allow the mixture temperature to exceed 90°F / 32°C.
  • Do not mix pentane outside of a properly ventilated environment or without full PPE.
  • Continue mixing until the distilled oil is uniformly distributed within the pentane (homogeneous solution).

3. Chill the Solution and Form Crystals
  • Place the vessel into a solvent-safe freezer or a dry ice/alcohol slurry.
  • Slowly bring the solution temperature down to –31°F / –35°C.
    • Slow cooling is important for clean, well-defined crystal formation.
  • Hold the solution at this temperature until substantial crystal formation is visible at the bottom of the vessel.

4. Remove the Mother Liquor
  • Once crystals have formed, pour the chilled solution from the original stainless vessel into another stainless vessel through a fine stainless steel mesh screen.
  • The mesh screen separates the solid crystals from the liquid (mother liquor).
  • Recover the pentane from the mother liquor using an appropriate solvent recovery system.
  • Set the remaining oil aside to be refined later, according to your lab’s procedures.

5. Rinse the Crystals
  • Chill fresh pentane to –31°F / –35°C using an appropriate freezer or dry ice slurry.
  • Remove the CBD crystals from the bottom of the original mixing vessel and place them into a stainless steel mesh screen basket positioned securely over the mother liquor or a suitable catch vessel.
  • Pour the chilled pentane over the crystals, agitating/stirring as little as possible—just enough to rinse away impurities.
  • Use the minimum volume of pentane needed to fully rinse the crystals.
  • A wash bottle with a nozzle can be used to maximize efficiency and control rinsing.
  • Ensure the pentane remains at –31°F / –35°C throughout the rinse process.

6. Pulverize the Crystals
  • Chill the rinsed CBD crystals again in a freezer or dry ice slurry to –31°F / –35°C.
  • Remove from the cold environment and filter any remaining liquid pentane through a stainless steel mesh screen.
  • Return the crystals to a stainless steel vessel.
  • Pulverize into a uniform powder using:
    • A mortar and pestle, or
    • A manual, pneumatic, or appropriately rated electric grinder.
  • Evenly spread the CBD powder over a large flat surface area, such as:
    • Stainless steel trays lined with parchment, or
    • Shallow Pyrex dishes.
  • Aim for a layer thickness of approximately 1 inch / 2.5 cm.

7. Final Drying in Vacuum Oven
  • Place the trays or dishes of CBD powder into a vacuum oven at ambient/room temperature.
  • Pull vacuum in one- or two-hour intervals to remove residual pentane.
  • Periodically break vacuum only to stir and redistribute the powder to promote even drying.
  • Continue until residual pentane is removed to the lab’s specification for final product.

Documentation & Change Control

The original SOP includes a Change Log and Document Release section for internal QA/QC:

  • Version: 1.0
  • Status: Initial release
  • Fields for date, revision, modified by, and description of changes
  • Signature lines for document release

In your KB, you can mirror this by:

  • Tracking revision dates and editors in the “Last Updated” line
  • Linking back to your internal SOP system for full change history
  • even layer.

Contact & Support

For questions about equipment or process optimization:

📞 734-855-4890
📧 support@usalabequipment.com