How to remove Pesticide from distillate

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How to remove Pesticide from distillate

It is very unfortunate to detect pesticide in your distillate, but there are way to remove them.

Currently, we have two popular methods for refining THC distillate:

1: Liquid Phase Extraction (LPE)

2: Solid Phase Extraction

The LPE is performed with the distillate suspended in a non polar alkane, then washed with a range of pH balanced saline. This both extracts the water solubles and buffers the solution for proper adsorption during the SPE. The solution is then passed over a chromatography column loaded with MagSil-PR. The alkane is then recovered and the distillate is distilled a second time. The resulting distillate passes PPB residual testing for most common pesticides, specifically Myclobutanil.

1 Introduction:

With the introduction of Cannabis regulations, comes stringent testing requirements. One of these requirements is maximum pesticide contamination in extracts and concentrates. While the best course of action would be to avoid the use of pesticides and pesticide contaminated material while growing and processing, this is not always possible. In California, a state with a large viticulture industry, aerial application of systemic pesticides such as Myclobutanil can drift into nearby watersheds, soil, and cannabis farms. These systemic pesticides, while sometimes undetectable in the flower, have been found to concentrate to test failing amounts after extraction and concentration of THC. A solution was needed to remediate pesticide contaminated distillate. After multiple combinations of experiments were performed, a successful, repeatable, and simple procedure was formed.

2 Materials and Methods:

2.1 Chemicals and Materials

75% THC distillate (500g) was produced in house. Distilled water, pH 6, sodium chloride, sodium bicarbonate, and citric acid were purchased from the local grocery store. MagSil-PR and CBleach were purchased from Lab Society via ColumboLabs. Heptane and Isopropyl were purchased from Lab Society via Imperial Gas.

2.2 Base Distillate

The starting first pass distillate tested at 75.39% d9- THC and 4,269 PPB myclobutanil.

2.3 Purification and Buffering with Liquid Phase Extraction

Mixing and separation occurred in a 50L glass reactor with overhead stirring. This reactor was used to prepare 60L of saline (distilled water with 3% sodium chloride dissolved in). This 60L of saline was then split into 3 even parts of 20L each. One of these parts was brought to a pH of 4 using citric acid. The second of these parts was brought to a pH of 9 with the sodium bicarbonate. The final part was left at its neutral pH of 6. All mixing and separation occurred at room temperature. 1L of heptane and 500g of distillate were separately heated to 35c, and then combined. Once fully homogenized, this solution was added to the reactor. The 20L of saline with a pH of 9 was added to the reactor. The stir paddle was turned on to a medium rpm, and let stir for 10 minutes. After 10 minutes the stirring was stopped and the solution was left alone to settle. After a few minutes the saline had separated from the heptane solution, and being more dense, settled in the bottom of the reactor. In between the saline and the heptane solution existed an emulsion layer. Both the saline and the emulsion were drained to waste. This process was repeated with both of the remaining two parts of the saline.

2.4 CBleach Scrub

Now that the heptane distillate solution has had the water solubles extracted, and has been pH buffered for effective adsorption, a cheap bulk color scrubbing adsorbent was applied. CBleach, a ColumboLabs product, is a combination of acid activated carbon, clay, and alumina. This media was used to remove as much remaining impurities as possible before exposing the solution to the expensive MagSil-PR. The heptane distillate solution was heated to 35c and 5% v/v CBleach was added, and thoroughly mixed together for 10 minutes.

2.5 MagSil-PR Chromotography

A 3” by 24” chromatography column was wet loaded with MagSil-PR in a heptane slurry. On top of this the heptane distillate CBLeach solution was poured. Four equal fractions were collected, the last requiring an additional 250ml heptane to elute. The column was then loaded with Isopropyl and a final fraction was collected.

2.6 Heptane Recovery and Second Pass Distillation

The heptane fractions were combined and the heptane was recovered via rotary evaporator. The resulting oil was distilled for a second time in a short path distillation apparatus. The resulting distillate was colorless, odorless, and had 0 PPB myclobutanil (Fig. 3).

3. Results and Discussions

3.1 LPE Salt % and pH Multiple different combinations of salt concentrations, pH extremes, and order of pH solution applications were tested. We found that minimal salt was required to achieve the desired pesticide remediation, only 3%. However high concentrations of salt often yields greater a extraction of undesirable water soluble. At the extreme ends of the pH scale, the polarity of H20 changes. While having other potential benefits, for the purpose of our experiment, a pH range of 4 – 9 was suitable. While playing an important role in the stability of the THC, it did not effect the ability of the MagSil-PR to adsorb myclobutanil no matter which order we used the different pH salines.

3.2 Citric Acid

We found that while citric acid alone has the ability to modify myclobutanil to the point it becomes undetectable, the method also causes degradation and isomerization of the d9- THC.

3.2 SPE “Chromatography”

While none of the first four fractions collected had any detectable amounts of myclobutanil, there was a definite difference in color. The first fraction was completely colorless, the second and third a pale yellow, and the fourth a muddy brown. The final Isopropyl fraction contained significant amounts of myclobutanil, and trace amounts of THC.

4. Conclusions

The described procedure was quick, simple, effective, and scalable. Processors now have a method for remediating their distillate of most pesticides. As a side bonus, the also get a potency increase and a water clear product.

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