Abstract
Contaminants such as pesticides for controlling pests and weeds (herbicides bentazone and picloram, fungicide thiram) or food additives (melamine) can be both life and environment threatening. Pesticides use in agricultural areas can result in the unintended release into groundwater contamination.
It is of high importance to detect these substances at biologically and environmentally relevant concentrations by fast, simple and highly sensitive methods. Raman spectroscopy is a powerful analytical tool providing unique information about the vibrational motion of molecules.
However, the conventional Raman spectroscopy approach to solutions is generally limited to highly concentrated samples. To study solutions or suspensions in low concentration (~µM) and small volumes (~2 µl), a special method, drop coating deposition Raman spectroscopy (DCDR), was introduced.
DCDR technique is based on the deposition of a small droplet of liquid sample on the hydrophobic substrate where subsequent evaporation of solvent leads to the preconcentration of analyte into a dried pattern from which Raman spectra can be acquired. Compared to conventional Raman spectra from the solution, the sensitivity of DCDR can be significantly improved, often by several magnitudes.
Raman spectra of selected contaminant solutions were acquired by DCDR technique employing the commercial hydrophobic substrate with an attempt to detect low concentrations [1]. The Raman fingerprint spectral bands of studied contaminants were distinguished at relevant concentrations and assigned to specific molecular vibrations.
For the food additive, the real sample was prepared, where the commercial powder infant formula was contaminated by melamine and successfully detected by DCDR.