Evaluation of electrosprayed graphene oxide coatings for elemental analysis by thin film microextraction followed by Laser-induced Breakdown Spectroscopy detection

Abstract

In this work, a solid phase microextraction procedure, denoted as Thin Film Microextraction (TFME), was combined with Laser-induced Breakdown Spectroscopy for the detection of several analytes in aqueous solutions (Cu, Cr, Ni and Pb). The adsorbent films, consisting of a thin layer of graphene oxide deposited on glass substrates, were generated by using the electrospray deposition technique (ESD). Several parameters affecting the quality and shape of the films resulting from the ESD process were studied, and the morphology and adsorption capacity of the films were evaluated. The generated films were used for extraction of the target analytes from aqueous solutions and, after extraction, the analytes-enriched adsorbents were analysed by LIBS without the need of any desorption or elution step. In order to assess the analytical capability of the TFME-LIBS procedure, different analytical figures of merit of the proposed TFME-LIBS methodology were evaluated. The obtained limits of detection were 14 μg kg−1 for Pb and 15 μg kg−1 for the rest of the tested analytes. Measurement repeatability was better than 4% RSD at low concentration level (20 μg kg−1) but deteriorated by increasing the concentration level at 100 μg kg−1, with %RSD ranging from 3.6% (Cr) to 24% (Pb). Method trueness, evaluated from the analysis of a real sample of bottled water, led to recovery values in the range 85%–106%.