A Colorimetric Membrane-Based Sensor with Improved Selectivity towards Amphetamine

Area of Science:

• Forensic Chemistry
• Analytical Chemistry
• Chemical Sensing

Background:

• Chemical spot tests are vital for presumptive drug identification due to their low cost and speed.
• Current colorimetric methods often lack specificity, identifying only drug classes rather than specific compounds.
• There is a need for chemical tests with enhanced discrimination power for accurate drug analysis.

Purpose of the Study:

• To develop a novel colorimetric assay for the specific identification of amphetamine (AMP).
• To create a method that offers improved selectivity compared to existing drug identification tests.
• To enable both visual and quantitative analysis of amphetamine in various samples.

Main Methods:

• A new colorimetric reaction involving alkaline gold bromide solutions was employed.
• Amphetamine reacts to form an insoluble yellow-orange derivative.
• The precipitate was filtered onto nylon membranes for visual identification and quantified using diffuse reflectance spectroscopy.

Main Results:

• The assay demonstrated high selectivity for amphetamine (AMP).
• Amphetamine was successfully differentiated from methamphetamine (MET), ephedrine (EPH), scopolamine (SCP), and cocaine (COC).
• Diffuse reflectance spectroscopy allowed for rapid and simple quantification of AMP.

Conclusions:

• The proposed colorimetric method provides a highly selective and rapid means for identifying amphetamine.
• This assay has potential applications in point-of-care testing and forensic analysis of illicit substances.
• The developed technique offers a significant improvement over existing drug class-selective spot tests.