Determination of chlorine ions in raw milk by pulsed amperometric detection in a flow injection system

Abstract

Chloride ion concentration in milk was determined by pulsed amperometric detection in a flow injection system. Results showed that the Au electrode lost 3 electrons at 1.10 V and formed chloroaurate ions (AuCl) by combining with chloride ions, after which AuCl was partly reduced to Au at 0.6 V. Based on the electrochemical process, a triple waveform with detection potential of 1.15 V, detection time of 150 ms, oxidation potential of 1.4 V, oxidation time of 550 ms, reduction potential of 0 V, and reduction time of 400 ms was applied to the Au electrode for detecting chloride ion concentration in milk. The approach is rapid and automatic and features a detection limit of 0.005 g/L. The relative standard deviation obtained by 60 repetitive injections reached 1.48% at 2 g/L of NaCl. The method developed using the Au electrode without modification was used to analyze the chloride ion concentration in raw milk without preprocessing. The method showed good agreement with potentiometric titration.

Electrochemical Determination of Capsaicinoids Content in Soy Sauce and Pot-Roast Meat Products Based on Glassy Carbon Electrode Modified with Β-Cyclodextrin/Carboxylated Multi-Wall Carbon Nanotubes

“…Meanwhile, the redox peak current of [Fe(CN) 6 ] 3−/4− on β-GCNT increased significantly as the scanning rate increased and featured a good linear relationship with the square root of the scanning rate (Figure 1J,K). These findings demonstrated that the composites composed of β-CD and MWCNT could efficiently promote electron transfer with a diffusion-controlled process [10]. It was worth noting that the peak current of β-GCNT was obviously enhanced in comparison to GCNT and the peak current of β-GCE showed little increase in comparison to GCE.…”

“…470 mV were controlled by diffusion [31]. Meanwhile, the electron transfer number of the above reversible peak was calculated to be about two, according to Laviron's theory [10,33]. Figure 2C illustrated the CV curves of capsaicin under different pH values.…”

“…The static contact angles of GCE, GCNT, β-GCE, and β-GCNT were obtained by static contact angle measuring instrument (SDC-200). The electrochemical characterization of GCE, GCNT, β-GCE, and β-GCNT was obtained by scanning 10 mmol/L of [Fe(CN) 6 ] 3−/4− solution using cyclic voltammetry (CV) method [10,31]. The initial parameter of CV for scanning [Fe(CN) 6 ] 3−/4− solution: the potential range was −200~600 mV and the scanning rate was 100 mV/s.…”

“…In order to obtain the number of electrons involved in the electrochemical reaction, 50 µmol/L capsaicin solution was scanned under different CV scanning rates (20,100,200, and 300 mV/s) [10]. To obtain the number of protons involved in the electrochemical reaction, 50 µmol/L capsaicin solution was scanned under different pH (1, 2, 3, 4, 5, 6, 7, and 8) using the CV method [10]. A total of 0.1 mol/L of HCl solution was used for the supporting electrolyte of pH = 1, and PBS solution was used for supporting electrolytes of pH = 2-8.…”

“…In recent years, with the development of analytical techniques, many new analytical methods of capsaicinoids have been developed, including ELISA [7], infrared spectroscopy [8], electrochemical methods, etc. Compared with ELISA and infrared spectroscopy, electrochemical detection is recognized as a more economical and easier to miniaturize method [9][10][11][12][13]. To meet the determination of capsaicinoids content, electrochemical sensors based on carbon nanotubes (CNTs) [14,15], graphene [16,17], and nanoparticles [18] have been developed.…”