The broad-spectrum organophosphorus insecticide, phosmet (N–(mercaptomethyl) phthalimide–S–(O,O-dimethylphosphorodithioate)) is used worldwide in farming and horticulture. When used properly, it does not pose a risk to humans and animals. Improper usage of phosmet however, has the potential to cause serious illnesses and environmental concerns for local wildlife. Because of these effects, phosmet pesticide is carefully regulated and monitored to ensure it is not misused or that too much phosmet residue remains on vegetable produce. Previous studies have indicated surface-enhanced raman spectroscopy (SERS) has the potential to determine the amount of phosmet reside on produce. Interested in determining the range of phosmet detection using SERS, Fan et al.1 analyzed Fuji apples that were pureed and spiked with a known concentration of phosmet (0.5 to 10 µg/g).To be sure the SERS analysis was correctly identifying the phosmet and not any other organic compounds present. After extraction from the spiked samples, the extracts were analyzed using a Nicolet DXR microscopy Raman spectrometer (Thermo Scientific) equipped with a 780 nm diode laser source and gold-coated Klarite substrate (Renishaw Diagnostics). The linear relationship of the measured phosmet concentrations and SERS spectra peaks indicated that SERS was correctly detecting phosmet, and it was identified at concentrations as low as 1 µg/mL in standard solution and 1 µg/g in apple extracts, with a calculated limit of detection of 1 µg/mL and 1.5 µg/g standard solution and in apple extracts respectively. In this carefully controlled experiment, SERS was sensitive enough to identify phosmet in apples; however, under more natural conditions, other organic compounds present in the produce have the potential to cause too much interference in the SERS spectra and would make it difficult to differentiate between phosmet and other compounds. The authors remain encouraged that improved sampling and preparation methods may be able to make SERS a more feasible method for complex samples. Reference
- Analyses of phosmet residues in apples with surface-enhanced Raman spectroscopy”, Food Control, Epub ahead of print, March 2014 (37), (pp. 153-157)
Leave a Reply