Isotachophoretic determination of carboxylic acids in biodegradation samples

In the current study a method of isotachophoretic separation of selected carboxylic acids was developed. The method was used for the determination of carboxylated oligo(ethylene glycol)s and their degradation products in biodegradation tests of PEG 250 DA [a mixture of dicarboxylated oligo(ethylene glycol)s]. Two tests were performed in the studies: the Organization for Economic Cooperation and Development (OECD) screening test and the river water die-away test. Both the biodegradation tests proved relatively fast biodegradation of the studied compounds. In the OECD screening test the biodegradation was faster than in the river water die-away test which can be ascribed to a higher concentration of bacteria in the biodegradation liquor. The minimal sample pretreatment and relatively low cost of analysis by the isotachophoretic method used here make it a good alternative to existing methods of carboxylic acids analysis.     

Photodegradation of pyridylketoximes in methanolic solutions under UV–Vis radiation

Photodegradation of the oximes of alkyl-2-, -3-, and -4-pyridylketones and identification of possible degradation products using LC–MS/MS and GC–MS techniques were performed. The influence of copper(II) and iron(III) ions on the stability of the oxime under UV–Vis radiation exposure were also studied. It was found that the photodegradation of the pyridylketoximes resulted in the photoisomerization, photofragmentation and photosubstitution to a pyridine ring. Based on these results, a hypothetical mechanism of photodegradation of pyridylketoximes was proposed.     

Separation and determination of homogenous fatty alcohol ethoxylates by liquid chromatography with mulitstage mass spectrometry

Alcohol ethoxylates (AEs) are a significant component of a stream of surfactants directed to the aquatic environment. The aim of this work was the investigation of the dependence of the analytical signals of homogeneous AE homologues on liquid chromatography with tandem mass spectrometry conditions, as well as the separation of AEs from the water matrix and, on this basis, the development of an analytical procedure suitable for the determination of AEs in environmental samples. Homogeneous homologues containing dodecyl moiety and 2–9 oxyethylene subunits were investigated. The analytical signals of the investigated homologues were optimized in terms of concentration of ammonium acetate in the mobile phase (optimum 5 mM) and a column temperature (optimum 35°C) of the liquid chromatography with tandem mass spectrometry system. A separation of AEs from the water matrix by liquid–liquid extraction (ethyl acetate, chloroform) or solid‐phase extraction (C₁₈, styrene divinylbenzene, H‐RX) was investigated. In a model investigation, the best recoveries (>90%) were obtained with a styrene divinylbenzene cartridge eluted with a 1:1 mixture of chloroform and methanol. However, much worse recoveries were obtained from the river water sample. Better results were obtained for liquid–liquid extraction with ethyl acetate. Recoveries of 62–80% were obtained for homologues having 4–9 oxyethylene subunits, at the lowest spike.     

Photodegradation and by-products identification of commercial extractant Cyanex 302

The photodegradation of the organothiophosphorous extractant Cyanex 302 and purified bis(2,4,4-trimethylpentyl)monothiophosphinic acid dissolved in toluene was carried out in photoreactor using UV–Vis light irradiation. Possible degradation products were identified with the assistance of FT-IR, LC/MS/MS and GC/MS. The catalytic influence of zinc(II), copper(II) and cobalt(II) ions and the presence of trace values of water and aqueous solutions of sulphuric acids on the photodecomposition of Cyanex 302 were studied. The results demonstrated that the presence of trace amounts of water causes mainly the degradation of bis(2,4,4-trimethylpentyl)monothiophosphinic acid with the simultaneously fourfold increase in bis(2,4,4-trimethylpentyl)phosphinic acid concentration. The shaking with aqueous solution of sulphuric acids results in the decrease in the photodegradation probably by blocking of OH radical. Metal ions also affect the degradation causing the increase in bis(2,4,4-trimethylpentyl)phosphinic acid concentration. The photodegradation was also carried out in open atmosphere under sunlight and the obtained results were compared with those obtained in a Heraeus photoreactor.     

Regeneration of expanded graphite electrodes by joined electrochemical and ozone treatment in liquid phase

The researches presented in this work were devoted to electrochemico-chemical regeneration of exhausted electrode made of expanded graphite (EG). The aimed process was conducted by electrochemical treatment and ozone flow performed together in wet environment. EG was covered with insoluble products of incomplete oxidation of phenol formed during cyclic voltammetry measurement. The same electrochemical technique was applied for evaluation of regeneration efficiency. To understand the process of EG regeneration, the electrode was characterized by calculating of BET surface, FTIR and XPS analysis. Moreover, SEM images of the investigated samples were also done. Obtained results have showed the success of regeneration treatment, which led to significant enhancement of electrode activity compared to original EG. The present work also revealed that the mechanism of phenol electrooxidation is changed after the regeneration treatment of electrode material. This effect is probably caused by the modification of chemical composition of EG surface due to its interactions with OH radicals intensively generated during the process of regeneration.

     

Photodegradation of Hydrophobic Pyridineketoximes in Toluene and Heptane

The goal of the research was to study the reactivity of the hydrophobic 2‐ and 3‐pyridineketoximes under exposure to UV‐VIS light. The photodegradation was conducted in both toluene and heptane for 10 h under atmosphere of argon. Ten‐hour irradiation experiments demonstrated that the pyridineketoximes underwent the facile E‐Z photoisomerization, photo‐Beckmann rearrangement, and to a lesser extent, the photosubstitution to the pyridine ring. From LC‐MS and NMR analysis of the irradiated solutions, it was found that the photosubstitution proceeded to give the corresponding 6‐substituted 2‐ or 3‐pyridylketoxime via the replacement of the ring hydrogen by the benzyl or heptyl group. The photo‐Beckmann rearrangement led to the formation of the corresponding amides, but also other products formed in the photo‐decomposition reaction.     

Quantitative analysis of amphiphilic <Emphasis Type="Italic">N</Emphasis>-alkyloxypyridinecarboximidamide by liquid chromatography–tandem mass spectrometry

LC–MS/MS method to determine hydrophobic N-alkyloxy substituted amidines: N-(2-ethylhexyloxy)pyridine-2-carboximidamide, N-(2-ethylhexyloxy)pyridine-3-carboximidamide, N-(2-ethylhexyloxy)pyridine-4-carboximidamide, N-decyloxy pyridine-2-carboximidamide, N-decyloxypyridine-3-carboximidamide and N-decyloxypyridine-4-carboximidamide was developed and validated in terms of linearity, precision and accuracy. The developed method was successfully applied to monitor and control the synthesis process. The experimental data points indicated that the straight chain alkyl bromide reacted most rapidly than branched alkyl bromide and the enhancement of the reaction efficiency strongly depended on reaction temperature.     

Determination of dodecanol and ethoxylated fatty alcohols from environmental samples using diatomaceous earth as a green sorbent for solid‐phase extraction

This study describes the use of diatomaceous earth during solid‐phase extraction as an efficient sorbent for separation and concentration of dodecanol and ethoxylated dodecanol containing 1–9 ethoxyl groups. The efficiency of different eluents was evaluated for model samples which allowed to select methanol and chloroform for tests with river water samples. During model experiments, it was observed that the recovery rates of specific compounds in the studied mixture were influenced by the character of the solvent used for desorption. Hydrophobic compounds, such as dodecanol and ethoxylated dodecanol with 1–3 ethoxyl groups, were eluted by chloroform with 100% efficiency. In case of the remaining compounds, which were more hydrophilic, a 97% recovery rate was achieved during elution with methanol. Such dependencies were not observed in case of river water samples, as the results obtained for both studied sorbent‐eluent systems were comparable. In both variants the recovery of dodecanol and ethoxylated dodecanol containing 1–9 ethoxyl groups ranged from 33 to 99%.