Voltammetric determination of traces of 4-chloroaniline in antiseptic samples on a cathodically-treated boron-doped diamond electrode

A Novel Polymeric Membrane Sensor for Chlorhexidine Determination

In the present work, potentiometric sensors with polymer membranes used for chlorhexidine (CHXD) determination were developed. The polymer membranes were plasticized with bis(2-ethylheksyl)sebacate (DOS) or 2-nitrophenyloctyl ether (o-NPOE). The active compounds used in the membrane were cyclodextrins, crown ethers, and ion exchangers. The best-constructed electrode was based on neutral heptakis(2,3,6-tri-O-benzoyl)-β-cyclodextrin with lipophilic salt (KTpClBP)-potassium tetrakis(4-chlorophenyl) borate-dissolved in plasticizer, DOS. The presented electrode is characterized by an average cationic slope of 30.9 ± 2.9 mV decade-1 within a linear range of 1 × 10-6 to 1 × 10-3 mol × L-1, while the value of the correlation coefficient is 0.9970 ± 0.0026. The response time was about 5 s when increasing the sample concentration and about 10 s when diluting the sample. The electrode potential is independent of the pH within a range of 4.0-9.5. The polymeric membrane sensor was successfully applied for assays of chlorhexidine digluconate in pure samples and pharmaceutical samples. The relative error from three replicate measurements was determined to be 1.1%. and the accuracy was RSD = 0.3-1.1%.

A novel electrochemical micro-titration method for quantitative evaluation of the DPPH free radical scavenging capacity of caffeic acid

In this report, the stoichiometric ratio (R) for the interaction of diphenylpicrylhydrazyl (DPPH) radicals with the antioxidant was employed as an evaluation index for the DPPH radical scavenging activity of antioxidants. This evaluation index was related only to the stoichiometric relationship of DPPH radicals with the antioxidant and had no relationship with the initial DPPH amount and the sample volume, which could offer a solution to the problem of poor comparability of EC50 values under different conditions. A novel electrochemical micro-titration method was proposed for the determination of the stoichiometric ratio (R) for the interaction of DPPH radicals with the antioxidant. This electrochemical micro-titration model was verified using caffeic acid as the DPPH radical scavenger, with the stoichiometric ratio (R) of DPPH radicals to caffeic acid determined to be in the range of 2.003–2.046. The calculated EC50 values were 0.513, 1.011, and 1.981 × 10–5 mol/L for 2.10, 4.05, and 8.02 × 10–7 moL of added DPPH radicals, respectively. The proposed method showed no differences from the conventional method, but had better precision and reliability, and used a smaller amount of sample.

Chromatographic Separation of Aromatic Amine Isomers: A Solved Issue by a New Amphiphilic Pillar[6]arene Stationary Phase

In this work, the fabrication, synthesis, and characterization of a new stationary phase based on an amphiphilic pillar[6]arene (P6A-C10-2NH₂) for gas chromatographic analyses are reported. The gas chromatography (GC) column prepared with P6A-C10-2NH₂ stationary phase exhibited a medium polarity, an efficiency of 3219 plates/m, and unmatched resolving capabilities toward chloroaniline, bromoaniline, iodoaniline, and toluidine isomers. Furthermore, the P6A-C10-2NH₂ column showed excellent repeatability with maximum relative standard deviations equal to 0.02, 0.07, and 2.56% for run-to-run, day-to-day, and column-to-column, respectively, demonstrating a great potential as a new stationary phase in separation science.