Novel Psychoactive Substances (NPSs) are drugs that have been made to have similar effects to common drugs of abuse. For example, synthetic opioids like fentanyl were created to make the user think they were taking heroin. However, these synthetic compounds have potencies that are sometimes much higher than their similar, more common drug of abuse.
Since these compounds are newer, they can pose a problem for laboratories that are trying to develop methods to analyze them. Synthetic opioids are the most widely abused of these NPSs worldwide, which is requiring testing laboratories to quickly develop methods. Fortunately, most of the synthetic opioids have structural and chemical property similarities to other opioid compounds, which means similar methods can be developed for both sets of compounds. Table 1 shows pKa and logP values for the synthetic opioid compounds that we analyzed in our method (values obtained from https://chemicalize.com/welcome).
|
Compounds |
pKa |
logP |
|
Fentanyl |
8.77 |
3.9 |
|
Norfentanyl |
10.03 |
1.42 |
|
Sufentanil |
8.86 |
2.8 |
|
Carfentanil |
8.05 |
3.8 |
|
4-ANPP |
7.50 |
4.5 |
|
Acryl Fentanyl |
8.80 |
4.2 |
|
Alfentanil |
7.50 |
2.81 |
|
Methoxyacetyl Fentanyl |
9.08 |
2.94 |
|
4-fluoro-isobutyryl fentanyl |
8.74 |
4.4 |
|
Furanyl fentanyl |
8.66 |
3.70 |
|
Isobutyryl fentanyl |
8.05 |
4.36 |
|
O-fluorofentanyl |
8.74 |
4.2 |
|
U-47700 |
9.2 |
3.91 |
|
U-51754 |
9.2 |
3.89 |
|
Valeryl fentanyl |
8.77 |
4.7 |
|
Butyryl fentanyl |
8.77 |
4.26 |
Table 1: pKa and logP values of fentanyl compounds
Based on the pKa and logP values for our fentanyl compounds, there are a few extraction mechanisms that we can use. The first is Supported Liquid Extraction. All compounds have logP values above 1, which makes them ideal for ISOLUTE SLE+. Another mechanism that would work well is solid phase extraction (SPE) using cation exchange. Almost all of the compounds have basic pKas between 7 and 10, which makes the strong cation exchange SPE mechanism another great option for extraction. The simplest option for extraction would be using Dual Mode Extraction. This technique is quick and simple, and results in higher recoveries but slightly dirtier extracts. For the exact methods that we used to extract these compounds and a comparison of the recoveries and matrix effects that we saw, download to the application note below!