Dissipation behavior, residue distribution and dietary risk assessment of field-incurred boscalid and pyraclostrobin in grape and grape field soil via MWCNTs-based QuEChERS using an RRLC-QqQ-MS/MS technique.

A QuEChERS technique employing multi-walled carbon nanotubes was developed and validated for the simultaneous quantitation of boscalid and pyraclostrobin in grape field samples using rapid resolution liquid chromatography triple- quadrupole tandem mass spectrometry. The validated method was successfully applied to determine the levels of residual boscalid and pyraclostrobin in soil and grapes. The dissipation behavior of each fungicide followed first-order kinetics, with a linear correlation coefficient of 0.995-0.998 at 95% confidence. The highest levels of boscalid and pyraclostrobin in grape, with a pre-harvest interval of 14 days and doses of 380-570 mg a.i. kg-1 in three or four applications, were 3.99 mg kg-1 and 0.792 mg kg-1, respectively. These are below the maximum residue limits for boscalid and pyraclostrobin in grape, as recommended by the Chinese Ministry of Agriculture. Risk quotients (RQs) of these pesticides were evaluated by comparing national estimated daily intake with acceptable daily intake. The results yielded RQs for boscalid and pyraclostrobin in grape of 54% and 31.7%, respectively, which suggest a low health risk to consumers.