As a result of the research, ion-selective nitrate electrodes were obtained, which are simple both in construction and operation, and have good analytical parameters. The electrodes obtained as a result of the modification, regardless of the type of MWCNTs, show lower detection limits and wider measuring ranges compared to unmodified electrodes. Figure 43: The response curve of the proposed sensor in glucose solution with different concentrations. ## References  
* Hu et al. (2016) Hu, J.; Stein, A.; Buhlmann, P.; Rational design of all-solid-state ion-selective electrodes and reference electrodes. _Trends Anal. Chem._**2016**, _76_, 102-114. * Yin and Qin (2013) Yin, T.; Qin, W.; Applications of nanomaterials in potentiometric sensors. _Trends Anal. Chem._**2013**, _51_, 79-86. * Hassan et al. (2019) Hassan, S.S.M. ; Eldin, A.G.; Amr, A.E.G.E. ; Al-Omar, M.A. ; Kamel, A.H.; Khalifa, N.M.; Improved Solid-Contact Nitrate Ion Selective Electrodes Based on Multi-Walled Carbon Nanotubes (MWCNTs) as an Ion-to-Electron Transducer. _Sensors_**2019**, _19_, 3891. * _Identification of Degradation Products and New Colouring Components in Shellfish Purple and Indigo by UHPLC-MS/MS_
* _A. Vasileidou_1_, I. Sampsonidis_1,2, S. Kalogiannis_2, G. Theodoridis_1, I. Karapanagiotis_3 and A. Zotou_1,*
* Laboratory of Analytical Chemistry, Department of Chemistry, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece
* Department of Nutritional Sciences and Dietetics, International Hellenic University (IHU), 57400 Thessaloniki, Greece
* Department of Management and Conservation of Ecclesiastical Cultural Heritage Objects, University Ecclesiastical Academy of Thessaloniki, 54250 Thessaloniki, Greece
* Correspondence: azotou@chem.auth.gr  
Degradation products of indigo [1], shellfish purple, and four colourants of shellfish purple which are not often detected [2] were identified (i) in standard solutions of indigotin and 6-monobromo-indigotin, (ii) pigments, and (iii) aged textile samples using a UHPLC-MS/MS method. Chromatographic separation in UHPLC was carried out on ACQUITY UPLC BEH C18 (1.7 \(\upmu\)m, 2.1 \(\times\) 1.8 mm) column thermostated at 40 \({}^{\circ}\)C. The mobile phase consisted of solvent A: water--0.1% (\(v/v\)) formic acid and solvent B: CAN--0.1% (\(v/v\)) formic acid using a gradient elution program during a time course of 38 min. The flow rate was 300 \(\upmu\)L min\({}^{-1}\). MS was performed using an electrospray ionization (ESI) Ion Max source with a HESI-II probe. The ESI was operated in positive mode (ESI+) for the detection of the colouring components and in negative mode (ESI-) for isatin (IS) and the degradation products of indigotin and 6-monobromoindigotin. In order to achieve adequate ionization in ESI for direct infusion analysis of the standard compounds, a novel solution preparation approach had to be developed, as DMSO, the solvent into which the compounds are readily diluted in, is not fully compatible with ESI direct infusion analysis due to its high viscosity and high boiling point. The primary solutions of the colouring components, indigotin and 6-monobromoindigotin, were prepared by diluting with NaOH aqueous solutions for optimisation of detection parameters. To sum up, the four colourants were identified in all shellfish purple samples in small quantities. These components belong to the same structural class with the mono-, di-, and non-brominated indigoids and have one-unit lower masses than indigotin and its mono- and di-brominated derivatives. Two degradation products, isatin and isatoic anhydrite (DP3), were detected in indigotin and 6-monobromoindigotin standard solutions. Isatin and some other indigoid degradation products were identified in both shellfish purple and indigo samples, as well as in the standard solutions of indigotin and 6-monobromoindigotin. This research has been financially supported by the General Secretariat for Research and Technology (GSRT) and the Hellenic Foundation for Research and Innovation (HFRI), Scholarship Code: 1514 (16 th).