Gold nanorods for in-drop colorimetric determination of thiomersal after photochemical decomposition
This work reports on the implementation of gold nanorods (AuNRs) in headspace solvent microextraction for colorimetric determination of volatile analyte derivatives in a single drop. The exposure of AuNRs to both H2Se and elemental mercury (Hg0) results in a shift of the longitudinal plasmonic band, unlike a number of volatiles. Accordingly, a method is reported for the determination of Hg0 with potential applicability to the determination of thiomersal (sodium ethylmercurithiosalicylate). It is based on the photochemical decomposition of thiomersal into Hg(II) and subsequent exposure of AuNRs-containing microdrop to in situ generated Hg0. Colorimetric analysis of the enriched drop was carried out without dilution by means of a cuvetteless microvolume UV-vis spectrometer. Under optimal conditions, the limit of detection was 0.5 ng mL−1 (as Hg). The repeatability, expressed as relative standard deviation, was 8.4% (for n = 10). AuNRs exposed to increasing concentrations of the analyte were characterized by means of transmission electron microscopy and UV-vis spectrophotometry to ascertain the mechanism of detection. The method was finally applied to the determination of thiomersal in various pharmaceutical samples and showed quantitative recoveries.
KeywordsCentral composite design Mercury Microextraction Microvolume spectrometry Miniaturization Nanoparticles Pharmaceuticals Plackett-Burman design Sample preparation Thiomersal
Financial support from the Spanish Ministry of Economy and Competitiveness (Project CTQ2015-68146-P) (MINECO/FEDER) is gratefully acknowledged. F. Pena-Pereira thanks Xunta de Galicia for financial support as a post-doctoral researcher of the I2C program. The CACTI facilities (University of Vigo) are also acknowledged for obtaining TEM and SEM images and performing EDS analyses.
Compliance with ethical standards
The author(s) declare that they have no competing interests.
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