Fast screening of trace multiresidue pesticides on fruit and vegetable surfaces using ambient ionization tandem mass spectrometry.

An ambient ionization tandem mass spectrometric approach was developed to rapidly screen multiresidue pesticides on fruits and vegetables without sample preparation and chromatographic separation. The residual pesticides on fruits and vegetables were collected by sweeping a metallic probe across the sample surface for 2 cm. The analytes collected on the probe were desorbed and ionized in a thermal desorption electrospray ionization (TD-ESI) source, after which analyte ions were detected by a triple quadruple mass analyzer (QqQ) operated in multiple reaction monitoring (MRM) mode. With this TD-ESI/MS/MS approach, 308 pesticides were monitored, where a mixture containing 15 pesticide standards was successfully identified to demonstrate the capability of this approach to screen trace multiresidue pesticides. The approach had reasonable detection limits (<50 ppb) and reproducibility (RSD: 8.43%, n = 9) from the analysis of a benthiazole standard solution. Real samples including a tomato and bell pepper were analyzed using this TD-ESI/MS/MS approach. After TD-ESI/MS/MS analysis, the organic solvent extracts from the same samples were subjected to TD-ESI/MS/MS, gas chromatography mass spectrometry (GC-MS), and liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis for validation.

Point-of-care identification of organophosphates in gastric juice by ambient mass spectrometry in emergency settings.

BACKGROUND: For emergency management, it is important to promptly identify the organophosphate ingested by self-poisoning patients since different organophosphates cause intoxication through different mechanisms and require different therapeutic strategies. This study aimed at the development of a point-of-care ambient mass spectrometric approach for rapid identification of organophosphate(s) in gastric juice for emergency management. METHODS: Six organophosphate insecticides that are commonly ingested by self-poisoning patients in Taiwan were examined. The sample solutions were prepared and diluted with human gastric juice. A direct metallic probe was dipped and removed immediately from the sample solution. The probe was then inserted into the thermal desorption-electrospray ionization/mass spectrometry (TD-ESI/MS) to detect the analyte on the probe. RESULTS: Since no pretreatment of the specimen was required, the sampling processes followed by thermal desorption-electrospray ionization and mass spectrometric analysis of the organophosphate in the gastric juice were completed within 30 s. The detection limit of the organophosphates is at the 10-100 parts per billion level. Good linearity was observed between the corresponding changes in mass spectrometric signal intensities and the changes of organophosphate concentrations within the range of 5-1000 parts per billion. The high efficiency of this ambient mass spectrometric platform was further confirmed when a real sample of the drained gastric lavage fluid of a patient who suffered from ingestion of chlorpyrifos was collected in the emergency room and tested with this cutting-edge technique. CONCLUSIONS: The results suggested that TD-ESI/MS is promising in promptly providing toxicological information to assist succeeding medical management in an emergency room.