Application of dried urine spots (DUS) for non-targeted quadrupole time-of-flight drug screening.

The use of dried urine spots (DUS) can simplify sample handling, shipment, and storage when compared to liquid urine samples. To prepare DUS, a small amount of urine is pipetted on a filter paper card. The subsequent drying of the specimen can prevent the post-sampling formation or degradation of substances (e.g. caused by bacteria). To evaluate the potential of DUS screening, 17 authentic urine samples, containing a broad range of substances, were extracted and analyzed on a Sciex 5600 TOF instrument using a non-targeted screening and library searching approach. The screening results were compared to the analysis of the same urine sample in liquid form, using the same high resolution liquid chromatography quadrupole time-of-flight mass spectrometry method. More than 65 different legal and illegal drugs were successfully identified within the investigated 17 urine samples using the DUS screening approach. When compared to the analysis of liquid urine, the following compounds could not be identified: 1x ecgonine methyl ester, 1x nicotine, 1x promazine, 1x 11-Nor-9-carboxy-Δ9-tetrahydrocannabinol. Overall, 95.2% of the target substances that have been detected in liquid urine were identified correctly using the DUS approach. In conclusion, DUS screening offers a simple, cost-effective, and easier sample handling alternative to the traditional use of liquid urine and provides detection of the most important substances for forensic requirements. Furthermore, the DUS sample preparation can be fully automated (sample documentation, internal standard application, and extraction).