Carbendazim (MBC) is a common fungicide approved for regulated use in agriculture globally, outside of the EU. Most MBC is found on fruits as surface contamination, the result of sprays applied prior to harvest. The US EPA has determined that a concentrations below 80 μg/mL in orange juice are not a health risk, while the EU restricts MBC levels to 10 ng/g (from imported produce) in foods intended for baby food production. Outside of this wide range of acceptance, it is agreed that MBC interrupts hormone production and can damage the testes in males. In the US, strawberries are the most common whole fruit to be contaminated with MBC, as determined by the USDA with GC/MS and LC/MS.

This Application Note describes a very simple test for surface MBC and provides library spectra demonstrating the sensitive detection of MBC with Misa (Metrohm Instant SERS Analyzer).

The most common agricultural use of MBC is a 500 μg/mL spray applied in the field, 2–3 weeks preharvest. Detection of surface contamination is a very quick and easy assay, ideal for on-site testing with Misa.

To establish a reference spectrum for MBC, a pure standard in methanol is analyzed using gold nanoparticles (Au NPs). The unique SERS spectrum presented in Figure 1 can be used to create a library entry for MBC.

A baseline-corrected spectrum acquired from whole strawberries sprayed with a 100 mg/L solution of MBC, then rinsed with ethanol agrees with the obtained MBC standard reference spectrum (Figure 2).

Detection of carbendazim in the field

Place a whole fruit (e.g., strawberry, orange) into a glass beaker just large enough to contain it. Rinse with 4–6 pipettes full of ethanol. Remove fruit and reduce ethanol volume, by means of evaporation on a hot plate, to ~1 mL. Fill a clean vial halfway full with Au NPs. Using pipettes, add 2 drops each of reduced ethanol solution and NaCl solution to Au NPs, cap and shake the vial gently to mix. Insert into vial attachment on Misa for measurement.