This paper describes and reports on the testing of a simple microfluidic device (MFD) that has been developed to perform multiple color and crystal presumptive field and lab tests for controlled substances.
In testing for cocaine, methamphetamine, amphetamine, and oxycodone (opiate representative), the crystal tests proved more sensitive than the color tests. Only two mixtures, complex combinations of amphetamine/starch/dextrose and oxycodone/lidocaine/starch failed to yield crystals in the microfluidic devices across all operators. The concentrations needed for positive color tests varied from 10 percent to 25 percent or approximately 50-125 pg of the drug. This compares favorably with reported detection limits of color tests performed in spot plates, which range from 5 to 100 mg. Amphetamine and oxycodone both yielded the same result using the MFD or spot plates; however, at the lowest concentrations, both amphetamine and oxycodone mixtures failed to produce positive crystal formation inside the MFD. Cocaine results proved to be most similar between the spot plate and MFD techniques, providing similar results at the lowest level of concentration. The microfluidic protocol used significantly less reagents and produced far less waste than the same sequences of tests using spot plate and ASTM methods. If these devices were mass produced and disposable, a significant cost savings for lab and field applications could be realized. The current generation MFD is the size of a microscope slide with four analytical channels: one for microcrystal tests and three for color tests. The final design allows for three color tests and one crystal test to be performed simultaneously. 3 tables, 4 figures, and 11 references