Fabrics are common materials that can easily be contaminated with trace drugs and serve as physical evidence at crime scenes. However, relatively few approaches have been researched for measurement of trace drugs on fabrics. In the present work, two approaches for the inexpensive, sensitive measurement of trace drugs on fabrics were investigated. In the first approach, a piece of fabric, possibly containing traces of drugs, was placed over a commercially available multi-drug rapid immunoassay test normally used to test for drugs in a saliva or urine sample. Elution of traces of drug from the fabric onto the rapid test strip was accomplished by addition of a small volume of surfactant-water solution (100-200 µL) onto the fabric using a rectangular hole punch to match the wetted fabric area to the sample addition area of the rapid test. Low levels of methamphetamine (0.01 mg), cocaine (0.05 mg) and THC (0.05 mg) on swatches of five fabrics (nylon, rayon, two types of cotton, and polyester) were prepared by addition of 100 µL of drug solution followed by drying. Subsequent testing of the fabric swatches gave positive results for all drug substances on all fabrics demonstrating the feasibility of the approach.
The second approach involves addition of a small amount of surfactant-water solution to the fabric in order to dissolve traces of drug, followed by application of an absorbent material, in the form of a disk, to collect the drug solution. The disks were subsequently analyzed using a commercially available microtiter plate immunoassay. The feasibility of this approach was demonstrated by testing the ability of a glass fiber disk to absorb surfactant-water (45 uL) added to 18 different fabric types commonly found in clothing or furniture: cotton, polyester, rayon, nylon and select others. Recovery of 50% or more of the added solution was found for 16 of the 18 fabrics tested; high recoveries were found with fairly heavy-weight fabrics (leather, felt, and denim). An ELISA cocaine immunoassay kit was used in combination with the glass microfiber discs and low absorbance values were obtained for theoretical drug concentrations of 2.88 μg/mL (0.003 mg). These results show that the use of rapid immunoassay tests and microtiter plate immunoassay tests have the potential for inexpensive and sensitive trace drug testing of fabrics when laboratories do not possess expensive instruments (i.e. mass spectrometer) and provide options for specialty cases where evidence cannot be transported to the laboratory.
Semester/Year of Award
David D. Cunningham
Restricted Access Thesis
Lindsey, Nicole R., "Fabric Wicking with Microfluidics and Immunoassay" (2016). Honors Theses. 372.