Hydrogels can be used for localized and non-destructive extractions in a number of fields. Marco et. al. used hydrogels to aid them in art conservation, extracting dyes from the surface of art and identifying them using Surface Enhanced Raman Spectroscopy (SERS). A strong interference band at 1330 cm-1 was present from an unknown source, thought to be from extractables leaching out of the gel and possibly onto the surface of the art. For strong Raman scatterers, such as dyes, the interference does not impede identification but that would not be true for weak Raman scatterers, such as drugs, limiting the versatility of hydrogel-SERS as an extraction-identification technique. In this study, hydrogels were brought through an aqueous- methanol washing pretreatment sequence, to remove these extractables. Absorbance of the solutions used to hydrate the gels was monitored over time, indicating negligible concentrations of extractables after a week of pretreatment. SERS data was collected on a pretreated hydrogel, showing no interference band. To illustrate the selectivity of the hydrogel extraction, hydrophilic species in cosmetics were extracted off of different surfaces, such as napkins, textiles, and glass and detected using SERS. The Normal Raman and SERS spectra of multiple types of lipstick were obtained, generating a fingerprint spectrum by color and manufacturer. Matrix interferences from hydrophobic species (e.g. waxes, oils) observed in normal Raman spectra were removed or minimized after hydrogel extraction.

Extraction of hydrophilic cosmetic components using hydrogels and surface enhanced Raman spectroscopy (SERS) detection

255th National Meeting (2018)

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