Carbaryl, the common name for 1- naphthyl methylcarbamate, is a broad spectrum pesticide used widely in agriculture. In recent years it has gained bad press as a potential carcinogen and toxic compound with some animal tests displaying cancer and toxicity symptoms. The Australian and New Zealand Food Code specifies minimum residue levels (MRL) for Carbaryl in Schedule 20. The MRL is different depending on the food, for example, the MRL for barley is 15 mg/kg while for grapes is 0.01 mg/kg. To be compliant with the food standards code testing must be conducted.
Where once high-performance liquid chromatography HPLC was used, enzyme-linked immunosorbent assay (ELISA) methods are now available for rapid analysis of Carbaryl residue.
ELISA utilises wells with a reagent that binds specifically to the compound being measured (in the case of Carbaryl it binds to carbamate). Samples are pipetted into the wells, and if Carbaryl is present, the binding reagent immobilises it. A second reagent that also binds to the immobilised analyte is added and reacts to cause a colour change. The optical density of the ELISA can then be measured and plotted into a standard curve to quantify the MRL present in the analyte.
The ELISA is not just a rapid method but also allows for duplication or multiple tests to be performed at once. As such it is an effective method for establishing MRL compliance in various food products.