Objective Method for Presumptive Field-Testing of Illicit Drug Possession Using Centrifugal Microdevices and Smartphone Analysis

Abstract

Current colorimetric presumptive identification of illicit drugs for determining illegal possession of controlled substances by law enforcement relies solely on the subjective interpretation of color change using drug- or class-specific reactions. Here, we describe the use of inexpensive polyester-toner, rotation-driven microfluidic devices with a smartphone as a potential alternative for current presumptive colorimetric field-testing of illicit drugs, allowing for an objective and user-friendly image analysis technique for detection. The centrifugal microfluidic platform accommodates simultaneous presumptive testing of material from a single input to multiple reaction chambers, enabling rapid screening. Hue and saturation image analysis parameters are used to define threshold values for the detection of cocaine and methamphetamine as proof-of-principle with 0.25 and 0.75 mg/mL limits of detection, respectively, with nonvolatile reagents stored on-board and smartphone for detection. Reported LODs are lower than those concentrations used in the field. Additionally, the developed objective detection method addresses the testing of drugs with various common cutting agents, including those known to produce false negative and positive results. We demonstrate the effectiveness of the method by successfully identifying the composition of 30 unknown samples.

A review of chemical ‘spot’ tests: A presumptive illicit drug identification technique

“…This “lab‐on‐a‐disc” device can control rotation speed, direction, and time to produce an objective detection method. Authors state this device will be ideal to replace standard colorimetric test kits that require separate test kits for each test …”

“…Authors state this device will be ideal to replace standard colorimetric test kits that require separate test kits for each test. 132…”

Analytical Validation of a Portable Mass Spectrometer Featuring Interchangeable, Ambient Ionization Sources for High Throughput Forensic Evidence Screening

“…Field-based processing of chemical evidence has been mostly relegated to presumptive colorimetric testing [29,30], and while stalwart examples like the Scott (cocaine) and Marquis (opiates, amphetamines) tests are commonly implemented, they have elevated false positive rates due to circumstantial ambiguity in observed color changes [31], and lack of overall chemical specificity [32]. Several portable detection technologies have been recently investigated for forensic analysis, including Raman spectroscopy [33], near infrared spectroscopy (NIR) [34], and X-ray fluorescence microscopy (XRF).…”

Rapid Fabrication of Electrophoretic Microfluidic Devices from Polyester, Adhesives and Gold Leaf

“…It can be argued that no current application necessitates the mass-manufacture of low cost disposable devices more than that of DNA analysis, which is why the marriage of human profiling to the PCL technique holds so much promise. However, while the methodology has inspired this and a multitude of other successful projects [ 10 , 11 , 12 , 13 ], there are concerns regarding the strength and long-term stability of the ink-toner as a binding agent, eliciting caution from those hoping to send their various innovations in to the market. What is required is an alternative to the toner, which would prevent layer delamination and render the devices sufficiently stable for their intended applications, but would not convolute the development and/or add expense to the manufacture of the devices themselves.…”