Using Infrared Spectroscopy to Identify Legal Highs and Scheduled Narcotics

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Image Credit: Syda Productions/

Legal highs are drugs that consist of a complex mixture of different chemical 'ingredients', precisely manufactured to ensure that they remain off the list of controlled substances. In some cases, a few of the drugs present in the mixture are illegal and a few are not, making it difficult to categorize these drugs.

Legal highs are also known as New Psychoactive Substances (NPS)1. These “highs” are designed to create similar effects to drugs like ecstasy, cocaine, and cannabis. They can be addictive and are a serious threat to public health. Sometimes they are even fatal2.

Since the ingredients have not been examined, users cannot be certain of their effect. Time and again, the drugs themselves do not match their label claim3, so the identity of the active ingredient(s) is dubious. Furthermore, the online availability of legal highs has grown, thus making them a lot more of a threat than before.

Law Enforcement and Hospitals need a Fast and Effective Identification Method

It is crucial to quickly identify new synthetic compounds as the distribution of these substances increases. It is vital for law enforcement4 to be able to identify the exact composition of legal highs, for use as evidence in a courtroom. Likewise, hospital staff need a reliable method to analyze these substances to prescribe accurate overdose treatment.

However, identifying and testing these drugs can be hard. This is because of their varying chemical make-up – they do not match their label claim - and the fact that they comprise of an extensive range of impurities and additives. In addition, the laboratories that prepare these drugs modify them whenever they are declared illegal, rendering them hard to track and legislate.

The appearance of drugs cannot be used to identify them, making a rapid and accurate method of drug identifcation a necessity for law enforcement and hospitals.

The appearance of drugs cannot be used to identify them, making a rapid and accurate method of drug identification a necessity for law enforcement and hospitals. Image Credit: sumire8/

Using FT-IR Spectroscopy to Identify Legal Highs

Legal highs contain novel psychoactive substances that are chemically similar to illegal drugs, like ecstasy and cocaine. Their composition is modified just enough to circumvent the law, which raises legal issues with prosecution4. The list of illegal substances is continuously evolving in response to the introduction and consequent gains in popularity, of various legal highs.

This means that the legal high scenario and legal frameworks connected with it, are constantly changing. Due to this, accurate chemical identification becomes important; either to establish if a confiscated substance is illegal or, in a clinical setting, to determine the cause of an overdose.

The analytical techniques used to identify legal highs have to be non-destructive (so samples can be presented as evidence), as well as quick and easy-to-use by a non-expert. They also have to be easily deployable in the field and not just limited to a laboratory. Besides this, the specific method needs to provide precise information on the structural properties of the chemicals, such as isomeric and stereo-chemical specificity.

Fourier Transform – Infrared Spectroscopy (FT-IR) is considered a “Category A” method by the Scientific Working Group for the Analysis of Seized Drugs (SWGDRUG), because of its high discriminating power5.

This is because FT-IR is a very rapid method which is fully non-destructive4,6. It enables the user to easily identify and differentiate between, a variety of compounds within a drug sample. This makes it perfect for hospital staff and law enforcement officers, who do not have the time or skill to use complicated equipment.

Shutterstock | Thomas Morris

Image Credit: Thomas Morris/

Comparison of Molecular Fingerprints for Accurate Substance Identification

Numerous studies have shown that FT-IR is a suitable method for the identification of unfamiliar substances. When used together with reference libraries, FTIR can be used to compare a substance’s molecular fingerprint against numerous others to quickly identify drugs in seized materials4,7.

Using an innovative Attenuated Total Reflectance (ATR, a technique of FT-IR analysis) correction algorithm, the Researchers have properly identified samples with a probability of 93%.

Research has also demonstrated how FTIR spectroscopy can be rapidly and easily used in the field by non-specialists. In one study, handheld instruments were used to conduct analysis on a white powder found at a secret laboratory. The results of searching the external ATR reference library threw up a best match to 3-methylmethcathinone (3-MMC) hydrochloride with a probability of 93%. The result: “A very good match was obtained for a spectrum acquired in the field from a sample of questionable purity.”

The Authors established the effectiveness of FT-IR spectroscopy for analyzing legal highs, stating: “ATR spectroscopy is becoming the technique of choice for rapid infrared spectral analysis.”

The Ideal FT-IR System for the Analysis of Legal Highs

The Golden Gate Diamond and Quest ATR systems, provided by Specac, can be used to quickly and accurately examine legal highs.

The Golden Gate and Quest from Specac

The Golden Gate and Quest from Specac

As the most versatile infrared sampling system in the world, the Golden Gate ATR accessory is suitable for high-throughput qualitative and quantitative analysis. This means it can be used for both quick drug identification and for more comprehensive analyses following the capture of the illegal substance.

The Quest ATR accessory is both simple and easy to use, making it the preferred choice of a number of non-expert users. The simple design of the ATR accessory means it can be used quickly by hospital officials or law enforcement officers without any training.

Both accessories are economical, user-friendly, non-destructive and need little or no sample preparation.

References and Further Reading

  1. “What exactly are legal highs?” BBC News
  2. “The Human Cost of Cheap Highs: A Journey into Britain's Most Addicted City”, 2016
  3. M. Baron, M. Elie and L. Elie “An Analysis of Legal Highs: Do They Contain What It Says on the Tin?” Drug Test Anal. 2011, 3(9):576-81. DOI: 10.1002/dta.274.
  4. S. Lowry, M. Bradley, and W. Jalenak, “Identifying Synthetic Designer Drugs Using FT-IR, Raman, and GC–IR” Spectroscopy, 2014, 29, 8
  5. SWGDRUG Recommendations Edition 6.1 (2013-11-01),
  6. V.M. Zancajo, J. Brito, M.P. Carrasco, M.R. Bronze, R. Moreira and A. Lopes, “Analytical Profiles of "Legal Highs" Containing Cathinones Available in the Area of Lisbon, Portugal”, Forensic Sci Int. 2014, Nov; 244:102-10. DOI: 10.1016/j.forsciint.2014.08.010
  7. S. Angelos and M. Garry, Forensics Magazine, 2011, 08, 5


This information has been sourced, reviewed and adapted from materials provided by Specac.

For more information on this source, please visit Specac.


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