Dried urine spot and dried blood spot sample collection for rapid and sensitive monitoring of exposure to ricin and abrin by LC-MS/MS analysis of ricinine and L-abrine

Ricin and abrin are protein toxins found in plants. Their extreme toxicity raises concern for their use as bioterrorism agents. Extraction from castor bean seeds yields 1-5% ricin and 0.3-0.8% ricinine. Abrin and L-abrine were extracted from Arbrus precatorius beans in mass ratios of 0.12% and 0.45%, respectively. Hence, ricinine and L-abrine (which are small molecules) may serve as biomarkers for assessing exposure to the corresponding proteins.A new approach was developed for high-throughput rapid identification of ricinine and L-abrine in microsamples of whole blood - dried blood spots (DBSs) and urine - dried urine spots (DUSs). These microsample collection methods are known for their advantages in field- sampling storage and shipping. The new method is based on a rapid sample preparation (extraction in a methanol/water mixture) followed by LC-MS/MS targeted analysis, the total lab time is less than one hour. Therefore, it may serve for preliminary confirmation before a labor-intensive and lengthy verification procedure for the identification of the protein toxin itself is carried out. The detection limit of ricinine was 50 pg/mL in whole blood and 100 pg/mL in urine, and for L-abrine, 100 pg/ mL in whole blood and 300 pg/mL in urine. DUS and DBS samples were highly stable, even after storage for several months at room temperature. This method was successfully implemented in a real forensic case where a limited volume of urine was collected 72 h after self-injection of a castor bean extract in a suicide event.