Abstract :
[en] Surface-enhanced Raman chemical imaging (SER-CI) is a highly sensitive analytical tool recently used in the
pharmaceutical field owing to the possibility to obtain high sensitivity along with spatial information. However,
the covering method of the pharmaceutical samples such as tablets with metallic nanoparticles is a major issue
for SER-CI analyses due to the difficulty to obtain a homogeneous covering of tablet surface with the SERS
substrates. In this context, a spray-coating method was proposed in order to fully exploit the potential of SER-CI.
A homemade apparatus has been developed from an electrospray ionization (ESI) probe in order to cover the
pharmaceutical tablets with the colloidal suspension in a homogeneous way. The silver substrate was pulled
through the airbrush by a syringe pump which was then nebulized into small droplets due to the contact of the
solution with the gas flow turbulence. A robust optimization of the process was carried out by adjusting experimental
parameters such as the liquid flow rate and the spraying time. Besides, the performances of this
spraying technique were compared with two others covering methods found in the literature which are drop
casting and absorption coating. A homogeneity study, conducted by SER-CI and matrix assisted laser desorption/
ionization mass spectrometry imaging (MALDI-MSI) applied to the different covering techniques was performed.
The influence of the metallic nanoparticles deposit on soluble compounds was also investigated in order to
highlight the advantages of using this new spray coating approach.
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