Electroanalytical sensing of dyes and colorants

Color is an important element of the final product of many industries, including the textile, leather, food, cosmetic, pharmaceutical, plastic, and fuel-marking industries. Dyes are complex organic substances with chromophore and auxochromic groups, which can be electrochemically oxidized and/or reduced; this constitutes the basis of their electroanalytical determination. Despite some controversies, dyes pose risks to living organisms, especially after biotransformation, as the metabolites can be more toxic, mutagenic, or carcinogenic than the original dyes. The present work provides a brief overview of the recent progress in electrochemical sensors used for dye detection in diversified matrices. Sensors developed over the recent years are characterized by high sensitivity and selectivity, besides being economically advantageous once they allow the use of little or no clean-up samples in portable and miniaturized systems.     

Development and validation of a UHPLC‐MS/MS bioanalytical method to quantify in plasma the analgesic candidate PT‐31 following a preliminary pharmacokinetic study in rats

A selective and sensitive UHPLC‐MS/MS bioanalytical method to determine PT‐31, an analgesic drug candidate, in rat plasma was developed and validated. Analyses were performed using a UHPLC‐MS/MS system equipped with an electrospray ionization interface operating in the positive ionization mode using a C₁₈ reversed‐phase column with a mobile phase of water:acetonitrile (68:31, v/v) containing 0.1% acetic acid eluting in a gradient mode with a flow rate of 0.3 mL/min. Plasma samples were deproteinized with cold acetonitrile containing 0.01% TFA (1:2, v/v) and 50 μL of the supernatant were injected into the system. PT‐31 and phenytoin (internal standard) retention times were roughly 1.0 and 1.5 min, respectively. Linear standard curves were plotted for the 0.01–10 µg/mL concentration range, with a coefficient of determination > 0.99. The method's precision was over 88%. Maximum intra‐ and inter‐day relative standard deviations were 14.6% and 11.6%, respectively. Interfering substances were not detected in the chromatogram, indicating that the method was specific. PT‐31 stability was assessed under different temperature and storage settings. The method was used to characterize PT‐31 plasma pharmacokinetics following administration of 5 mg/kg i.v. to Wistar rats. Therefore, the method described is sensitive, linear, precise and specific enough to determine PT‐31 in preclinical pharmacokinetic investigations. Copyright © 2015 John Wiley & Sons, Ltd.     

Variable interval sampling in economical designs for online process control of attributes with misclassification errors

Online process control consists of inspecting a single item at every mth items produced, where m is an integer greater than two. Based on the results of the inspection, one decides if the process is in-control (the fraction of conforming item is p₁—state I) or out-of-control (the fraction of conforming item is p₂—state II). If the inspected item is non-conforming, the process is designated as out-of-control and production is stopped for possible adjustment; otherwise, production goes on. In this paper, a contribution to online process control is presented, where the inspection system is considered to be subject to classification errors. After every adjustment, the sampling interval is L units (L?m), and in the case of non-adjustment, the sampling interval is m units. The expression for the average cost per produced item is calculated, and optimum parameters (the sampling intervals L and m) are obtained by a direct search. The procedure is illustrated by a numerical example.     

A novel sensing platform based on self-doped TiO2 nanotubes for methylene blue dye electrochemical monitoring during its electro-Fenton degradation

Journal of Solid State Electrochemistry - The synthesis of a self-doped TiO2 nanotubes (SD-TNT) electrode and its potential applicability as a sensing platform electrode for voltammetric...