Ligand-free gold nanoparticles as colorimetric probes for the non-destructive determination of total dithiocarbamate pesticides after solid phase extraction

Kyriakos M Giannoulis; Dimosthenis L Giokas; George Z Tsogas; Athanasios G Vlessidis

doi:10.1016/j.talanta.2013.10.063

Ligand-free gold nanoparticles as colorimetric probes for the non-destructive determination of total dithiocarbamate pesticides after solid phase extraction

Talanta. 2014 Feb:119:276-83. doi: 10.1016/j.talanta.2013.10.063. Epub 2013 Nov 9.

Authors

Kyriakos M Giannoulis¹, Dimosthenis L Giokas², George Z Tsogas¹, Athanasios G Vlessidis¹

Affiliations

¹ Laboratory of Analytical Chemistry, Department of Chemistry, University of Ioannina, 45110 Ioannina, Greece.
² Laboratory of Analytical Chemistry, Department of Chemistry, University of Ioannina, 45110 Ioannina, Greece. Electronic address: dgiokas@cc.uoi.gr.

PMID: 24401415
DOI: 10.1016/j.talanta.2013.10.063

Abstract

In this work, we describe a simple and sensitive non-destructive method for the determination of the total concentration of dithiocarbamate fungicides (DTCs) in real samples. The proposed method combines for the first time the benefits of an extraction method for sample clean-up and preconcentration with a sensitive colorimetric assay based on gold nanoparticle probes. In this two-step procedure, the target DTCs are isolated from the matrix and preconcentrated by solid phase extraction onto commercially available C18 sorbents. Following elution, the extract containing the target dithiocarbamates, free from most interferences and matrix components, is delivered into an aqueous dispersion of plain citrate-capped gold nanoparticles (AuNPs) which aggregate in response to DTCs coordination on AuNPs surface through multiple gold thiolate bonds. This aggregation is evidenced by changes in the spectral properties of the solution involving a decrease in the original absorbance of Au nanoparticles at 522 nm and the appearance of a new absorption band above 700 nm. An ensuing chromatic shift of the solution from wine-red to purple-blue is observed which is visual by naked eye at concentrations as low as 50 μg L(-1). Further improvement in the detection limits can be accomplished by scaling-down the method to micro-volume conditions alleviating the need to preconcentrate larger sample volumes. Overall, by combining sample clean-up and preconcentration with the strong affinity of DTC thiol group for the gold surface, the total concentration of dithiocarbamate pesticides was successfully determined in various water samples at the low and ultra-low μg L(-1) levels without resorting to destructive techniques, sophisticated instrumentation or post-synthetic modification of gold nanoparticles. Method application in real samples showed good analytical features in terms of recoveries (81.0-94.0%), precision (5.6-8.9%) and reproducibility (~9%) rendering the method as an attractive alternative to current methodologies for the determination of DTC fungicide residues in samples of environmental interest.

Keywords: Dithiocarbamate pesticides; Gold nanoparticles; Micro-volume assay; Solid phase extraction.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Calibration
Colorimetry / methods*
Gold / chemistry*
Ligands
Limit of Detection
Metal Nanoparticles*
Molecular Probes
Pesticides / analysis*
Solid Phase Extraction / methods*
Spectrophotometry, Ultraviolet
Thiocarbamates / analysis*

Substances

Ligands
Molecular Probes
Pesticides
Thiocarbamates
Gold