# Induced Effect of Gold Nanoparticles (AuNPs) and Halide Ions on Pyridoxine Molecule Stability
## 1 Introduction
Some studies involved vitamin B6 separation and determination in food, dietary supplements and pharmaceutical tablets using various spectrometric techniques [11; 12; 13; 14; 15; 16]. UV-Vis spectrophotometry applied in the analysis of samples containing vitamin B6, showed an increase in sensitivity followed by a decrease in detection limits to values of about 60 ng \(\times\) mL\({}^{-1}\)[11], 5-25 ug \(\times\) mL\({}^{-1}\)[12] and 2-21 ug \(\times\) mL\({}^{-1}\)[13]. The use of fluorescence spectrophotometry, without or with a CdSe quantum dot sensor, also led to detection limits of 33-450 ug \(\times\) mL\({}^{-1}\)[14; 15]. UV-Vis spectrophotometry, fluorescence spectrophotometry and FTIR spectroscopy allowed the individual physicochemical study of pyridoxine as well as its interactions with bovine serum albumin [16]. Although these methods have advantages such as selectivity and sensitivity, they also have certain limitations, such as high costs, elaborate sample preparation processes and long analysis time. Compared to these methods, electrochemical sensors have been introduced and developed as a modern alternative for determining vitamins [17; 18; 19; 20]. Electrochemical sensors have a much greater simplicity, miniaturization, reproducibility, low cost and high sensitivity, and among them, vitamin sensors based on carbonaceous materials, namely glassy carbon electrodes [18; 19; 20; 21], carbon ceramic electrodes [22], graphite, [23; 24], screen printed carbon [25], multiwalled carbon nanotubes [26; 27], graphene [28] and boron-doped diamond [29; 30] have been used. The performance of the electrochemical sensors for detecting water-soluble vitamins (B1, B2, B6, B9, B12, C) and fat-soluble vitamins (A, D, E, K) varies from the nano to micro scale and takes into account the electrochemical processes of vitamins on the electrode surface [17; 18; 19; 20; 21; 22; 23; 24; 25; 26; 27; 28; 29; 30; 31; 32; 33; 34]. Sensitive hybrid heterostructures such as SnO\({}_{2}\) nanoparticles supported mesoporous TiO\({}_{2}\) over glassy carbon electrodes [31], Au-CuO core-shell/multiwalled carbon nanotubes [32], calix-8-arene/phosphotungstic acid/di isooctyl phthalate [33] and \(\beta\)-cyclodextrinruf/carboxylated poly(vinyl chloride) [34] are reported for pyridoxine determination. Nanomaterials incorporating electrochemical sensors for vitamin B6 determination are an excellent class of materials due to their unique multifunctionality [35]. Synthesis, characterization and application of gold and silver nanoparticles are revolutionizing all the fields to which they are applied [36; 37; 38; 39]. Probably the most important applications are the detection, diagnosis and therapy of cancer with gold nanoparticles [40; 41]. Despite their valuable properties and bio-applications, gold and silver nanoparticles also have negative aspects, such as toxicity [42; 43; 44]. The synthesis and use of gold and silver nanoparticles and even gold-silver bimetallic nanoparticles in the removal of pollutants from polluted waters have been reported [45; 46; 47; 48; 49]. Simultaneously with pyridoxine, the halide ions can be ingested from food or by administering sodium halide-containing drugs. In particular cases, the gold nanoparticles can be an option for antiviral treatment, inducing immunostimulatory activity. In this context, it is important to study the concerted action of these biologically active compounds. Various interactions between halide ions and vitamin molecules or AuNPs can occur, leading to the inhibition or stimulation of vitamin degradation reaction. Consequently, the present study aimed to highlight the induced effects by gold nanoparticles on the decomposition/transformation reaction of B\({}_{6}\) vitamin molecules. Concomitantly, the influence of B\({}_{6}\) vitamin molecules and halide ions on the on the activity of gold nanoparticles was investigated.