Screening for cocaine on Euro banknotes by a highly sensitive enzyme immunoassay

This study focused on quantitative detection of cocaine on Euro banknotes in Germany. A sensitive direct competitive immunoassay was developed and optimized with a limit of detection (LOD) of 5.6ng/L. Exhaustive cocaine extraction by solvent was tested using different methanol concentrations and buffered solutions. Cross-reactivity studies were performed to determine the degree of interference of cocaine metabolites with the immunoassay. Sixty-five Euro banknotes obtained from different districts in Berlin were evaluated. A 100% contamination frequency with cocaine was detected. A comparison between the amount of cocaine extracted by cotton swabbing of one square centimeter of the banknote showed a good correlation for lower contamination levels. This assay showed high sensitivity of detecting pg of cocaine per 1cm² of one banknote by swabbing 1cm²: 0, 14, and 21pg/cm². Moreover, three notes of different denominations revealed high cocaine concentration; 1.1mg/note, and twice 55µg/note.