Direct immersion solid-phase microextraction combined with ambient ionization tandem mass spectrometry to rapidly distinguish pesticides in serum for emergency diagnostics

Abstract

Despite the fact that carbamates and organophosphates cause acute poisoning via different mechanisms and require disparate management, they are indistinguishable by current clinical assays. Herein, direct immersion solid-phase microextraction (DI-SPME) plus thermal desorption-electrospray ionization tandem mass spectrometry (TD-ESI/MS/MS) was developed to discern them. Both pesticides spiked in human serum were extracted by SPME and analyzed by TD-ESI/MS/MS. This is a promising emergency care platform as rapid analyses could be done in tiny sample volumes with satisfactory recovery (89.46%-116.32%), precision (covariance <20%), sensitivity (LOD <0.1 μg/mL), turnaround time (<5 minutes), and linearity (R² = 0.9827-0.9992) within 0.1-100 μg/mL.

Fig. 1

Schematic diagram of the analytical processes in this study: (a) pesticides were spiked in human serum, (b) an SPME fiber was used to extract pesticides from diluted human serum, (c) the SPME fiber was attached to the sampling probe and rinsed with pure water, (d) TD-ESI/MS/MS analysis was performed, (e) acquired MS data were compared with data in pesticide databases to identify analytes.

Fig. 2

DI-SPME-TD-ESI/MS mass spectra of (a) diluted human serum, (b) diluted human serum from (a) spiked with six carbamate (■) and organophosphate (●) insecticides (5 μg/mL each), and (c) diluted human serum spiked with six insecticides (0.5 μg/mL each).

Fig. 3

Carbaryl ion intensity vs. SPME adsorption time for 5 μg/mL of carbaryl spiked in diluted human serum. Six replicates were performed for each adsorption duration.

Fig. 4

Triplicate DI-SPME-TD-ESI/MS/MS analyses of diluted human serum spiked with a mixture of 6 pesticide standards (0.5 μg/mL each), where two ion pairs were monitored for each pesticide in MRM mode (a–f). Pesticide ion signals detected in the sample: a) carbaryl, b) methiocarb, c) methomyl, d) chlorpyrifos, e) ethion, and f) fenthion. (g–l) Six randomly selected pesticide ion signals which were absent in the sample: g) acephate, h) carbofuran, i) isoprocarb, j) methidatihion, k) terbufos, and l) thiobencarb.