The best voltammetric parameters have been obtained for the 0.5 mg mL\({}^{-1}\) dispersion of CeO\({}_{2}\):Fe\({}_{2}\)O\({}_{3}\) nanoparticles. Scanning electron microscopy confirms the presence of spherical nanoparticles of 25-60 nm and their aggregates evenly distributed on the electrode surface and formed porous coverage. This leads to the 4.4-fold increase in the effective surface area vs. bare glassy carbon electrode. Electrode modification provides significant increase in the electron transfer rate as electrochemical impedance spectroscopy data indicate. Electrooxidation of lipoic acid on CeO\({}_{2}\):Fe\({}_{2}\)O\({}_{3}\) nanoparticles modified GCE is an irreversible, diffusion-controlled, pH independent process occurring with the participation of two electrons. Direct differential pulse voltammetric method of lipoic acid determination in phosphate buffer pH 7.0 medium has been developed. The linear dynamic ranges of 0.075-7.5 and 7.5-100 uM with the detection limit of 0.053 uM have been obtained. These characteristics are the best ones reported for electrochemical methods, including other modified electrodes. Another advantage of the method is high selectivity of the electrode response towards lipoic acid in the presence of inorganic ions, ascorbic acid, and saccharides, as well as other S-containing compounds (cysteine, cystine, and methionine). The developed approach has been applied to the pharmaceutical dosage forms of lipoic acid (tablets and concentrate for the infusion preparation). voltammetric results have been validated with coulometric titration data. Figure 44: Determination of chloride anions in sweat as a biomarker of cystic fibrosis. Thus, a simple, sensitive, selective, cost-effective, and reliable approach has been developed for the lipoic acid quantification that can be applied for the pharmaceutical quality control. ## References  
* Ziyatdinova et al. (2017) Ziyatdinova, G.K.; Ziganshina, E.; Romashkina, S.; Budnikov, H. Highly sensitive amperometric sensor for eugenol quantification based on CeO\({}_{2}\) nanoparticles and surfactants. _Electroanalysis_**2017**, _29_, 1197-1204. * Pwavodi et al. (2021) Pwavodi, P.C. ; Ozyurt, V.H. ; Asir, S.; Ozsoz, M. Electrochemical sensor for determination of various phenolic compounds in wine samples using Fe\({}_{3}\)O\({}_{4}\) nanoparticles modified carbon paste electrode. _Micromachines_**2021**, _12_, 312. * Vinay and Nayaka (2019) Vinay, M.M. ; Nayaka, Y.A. Iron oxide (Fe\({}_{2}\)O\({}_{3}\)) nanoparticles modified carbon paste electrode as an advanced material for electrochemical investigation of paracetamol and dopamine. _J. Sci. Adv. Mater. Devices_**2019**, \(4\), 442-450. * Fayemi and Adekunle and Ebenso (2017) Fayemi, O.E. ; Adekunle, A.S.; Ebenso, E.E. Electrochemical determination of serotonin in urine samples based on metal oxide nanoparticles/MWCNT on modified glassy carbon electrode. _Sens. Biol. Sens. Res._**2017**, _13_, 17-27. * de Carvalho et al. (2020) de Carvalho, R.C. ; Betts, A.J. ; Cassidy, J.F. Diclofenac determination using CeO\({}_{2}\) nanoparticle modified screen-printed electrodes--A study of background correction. _Microchem. J._**2020**, _158_, 105258. * Patil et al. (2019) Patil, D.S. ; Shetti, N.P. ; Nayak, D.S. ; Revankar, R.S. Fabrication of multi-walled carbon nanotubes and ZnO nanoparticles composite electrode as a sensor for paracetamol. _Mater. Today Proc._**2019**, _18_, 1124-1131. * _Adapting Surface Enhanced Raman Spectroscopy for Organic Residue Analysis in Archaeological Artifacts_**M. E. Konstantinou 1,2,*, A. Philippidis 1 and D. Anglos 1**
* Institute of Electronic Structure and Laser, Foundation for Research and Technology-Hellas (IESL-FORTH), 70013 Heraklion, Greece
* Department of Materials Science and Technology, University of Crete, 70013 Heraklion, Greece
* Correspondence: mek@iesl.forth.gr  
Organic archaeological residues analysis is a highly challenging in archaeometry.