Surface swabbing technique for the rapid screening for pesticides using ambient pressure desorption ionization with high‐resolution mass spectrometry

Abstract

A rapid screening method for pesticides has been developed to promote more efficient processing of produce entering the United States. Foam swabs were used to recover a multiclass mixture of 132 pesticides from the surfaces of grapes, apples, and oranges. The swabs were analyzed using direct analysis in real time (DART) ionization coupled with a high-resolution Exactive Orbitrap™ mass spectrometer. By using a DART helium temperature gradient from 100-350°C over 3 min, a minimal separation of analytes based on volatility differences was achieved. This, combined with the Exactive's mass resolution of 100,00, allowed the chromatographic step, along with the typical compositing and extraction steps associated with gas chromatography/mass spectrometry (GC/MS) or liquid chromatography/mass spectrometry (LC/MS) approaches, to be eliminated. Detection of 86% of the analytes present was consistently achieved at levels of 2 ng/g (per each apple or orange) and 10 ng/g (per grape). A resolution study was conducted with four pairs of isobaric compounds analyzed at a mass resolution of 100 000. Baseline separation was achieved with analyte ions differing in mass by 25 ppm and analyte ions with a mass difference of 10 ppm were partially resolved. In addition, field samples that had undergone traditional sample preparation using QuEChERS (quick, easy, cheap, rugged, and safe) were analyzed using both LC/MS and DART-MS and the results from the two techniques were found to be comparable in terms of identification of the pesticides present. The use of swabs greatly increased sample throughput by reducing sample preparation and analysis time.

Determination of Dicyandiamide in Powdered Milk Using Direct Analysis in Real Time Quadrupole Time-of-Flight Tandem Mass Spectrometry

“…The wire screen was positioned in the DART TM, which has 10 holes designed to orient the screen such that the heated He carrier gas passes directly through the center of each hole [30]. Individual 10 μL aliquots of each of the six working solutions were pipetted onto the center region of each wire screen.…”

The role of direct high-resolution mass spectrometry in foodomics

“…If no specimen pretreatment is carried out to the surface, it might result in poor sensitivity. Thus, effective contaminant detection was possible by applying swabbing methods on the surfaces of fruits and vegetables [104,105]. Thus, by spiking different pieces of fruits with a complex mixture of pesticides, it was demonstrated that swabs increased sample throughput by reducing sample preparation and analysis time [104].…”

Rapid Identification of Psychoactive Drugs in Drained Gastric Lavage Fluid and Whole Blood Specimens of Drug Overdose Patients Using Ambient Mass Spectrometry

“…e thermally desorbed analytes are subsequently carried by a nitrogen stream into an electrospray plume and ionized via ion-molecule reactions with the charged solvent species to form analyte ions. Even though sampling, desorption, ionization, and detection are separate events, a typical TD-ESI/ MS analysis takes less than 30 s. Compared to other ambient ionization sources such as desorption electrospray ionization (DESI), [9][10][11] direct analysis in real time (DART), 12,13) and electrospray-assisted laser desorption ionization (ELDI), 14) where samples must meet the ion source, the use of a direct sampling probe in TD-ESI/MS makes the technique suitable to analyze pesticides and drugs on oversized or immovable objects and in viscous biological solutions. 7,8,15,16) During early rescue, gastric lavage is a common practice for removing sustained-release medications and ingested substances.…”