A radioanalytical technique to study the behavior of organic toxicants applied to a study of the photodegradation of 2,3,7,8-tetrachlorodibenzo-p-dioxin

A general method for tritium labeling of organic compounds by the use of thermal activation of tritium is described. It allows obtaining uniformly tritium-labeled organic compounds with high specific activity (up to 50 Ci/mmol) which permits tracing the majority of the biodegradation products of compounds studied. More than 40 compounds were labeled using this simple, rapid and inexpensive method. Separation of the biodegradation products is performed by thin layer chromatography. Quantification is performed by direct measurement of the radioactivity by liquid scintillation counting after transfer of the layer from TLC plates into scintillation vials, or by densitometry of autoradiographs. The technique is useful for a wide range of organic compounds, including ones with unknown structure, and can be applied to various in vivo and in vitro studies.     

A new technique for tritium labeling of complex technical mixture of PCB congeners

The method of labeling by thermally activated tritium of technical mixture of PCB congeners (Sovol) has been developed. Influence of labeling procedure on mixture of PCB congeners was investigated and optimum conditions of producing of tritium labeled complex mixture of PCB congeners were determined. The system purification of tritium labeled Sovol by thin layer chromatography was developed. Purified tritium labeled Sovol was analyzed by gas chromatography. The developed technique can be used for producing of tritium labeled similar complex mixtures of congeners of other organic compounds.     

Synthesis of tritium-labeled compounds using a fibroid carbon carrier

The results of tritium labeling of organic compounds by solid phase catalysis, using fibrous carbon, were compared with those, obtained by using activated carbon purchased from Norit. It was found that utilization of multi-wall carbon nanotubes lead to a considerable growth of the yield (10–20 times) and molar radioactivity (1.5–2 times) of the labeled compounds. Using such a carrier it became possible to obtain a tritium-labeled biologically active compound like diazepam, Etomidate, and phenylalanine with molar reactivity 10–25 Ci/mmol.     

Automatic isotope gas analysis of tritium labelled organic materials

An analytical procedure and an automatic apparatus are described for the determination of tritium in organic compounds by gas counting. The sample is pyrolysed in hydrogen atmosphere at 1000°C, then, with hydrogen, the decomposition products are rinsed through a column of molecular sieve-5A heated to 550°C. Tritium in water, hydrogen sulphide, ammonia and hydrogen cyanide is transferred into the hydrogen stream by isotope exchange completed on the column. The inactive water vapor, hydrogen sulphide, ammonia and hydrogen cyanide as well as carbon dioxide are removed from the gas stream by appropriate absorbents, and the radioactive hydrogen together with tritiated methane, carbon monoxide and nitrogen included in the pyrolytic products is led into an internal proportional counter tube for radioactivity measurement. The method provides quantitative recovery, it is free of memory effect and suitable for the rapid assay of a wide variety of organic compounds containing C, H, N, O, S in addition to tritium.     

Automatic isotope gas analysis of tritium labelled organic materials

An isotope analytical procedure and an automatic instrument developed for the determination of tritium in organic compounds and biological materials by internal gas counting are described. The sample is burnt in a stream of oxygen and the combustion products including water vapour carrying the tritium are led onto a column of molecular sieve-5A heated to 550 °C. Tritium is retained temporarily on the column, then transferred into a stream of hydrogen by isotope exchange. After addition of butane, the tritiated hydrogen is led into an internal detector and enclosed there for radioactivity measurement. The procedure, providing quantitative recovery, is completed in five minutes. It is free of memory effect and suitable for the determination of tritium in a wide range of organic compounds and samples of biological origin.     

Catalytic tritiation studies using tritium NMR spectroscopy

The development of tritium nuclear magnetic resonance spectroscopy now makes it possible to determine the tritium distribution in virtually any organic compound at the millicurie level of radioactivity. Results of catalytic experiments show that in some cases a remarkable degree of specificity can be achieved when using procedures that are expected to produce generally labelled compounds. Conversely there are instances where specific labelling procedures are less than 100% successful.     

Self-radiolytical processes in ethyl-phenyl siloxanes labeled with tritium

Radioluminescent sources, containing as excitant agent ethyl-siloxan polymers labeled with tritium, represent the most studied constructive variants. The required high specific activities induce significant self-radiolytical processes in labeled polymers, their study being necessary for technological, radiobiological, and radioecological reasons. In the present study, the protective effect of phenyl fragments in tritium labeled ethylsiloxane structures has been analyzed. In this sense, the ethyl and phenyl siloxane structures with phenyl group positioned at the same Si atom or at different Si atoms have been synthesized and analyzed.     

α-Melanotropin Labelled at its Tyrosine2 Residue: Synthesis and Biological Activities of 3′-Iodotyrosine2-,3′-125Iodotyrosine2-,3′,5′-Diiodotyrosine2-, and (3′,5′-3H2)tyrosine2-α-Melanotropin,and of Related Peptides

α-MSH was labelled at its tyrosine² residue with tritium and iodine. Several synthetic routes were investigated by preparing 13 precursor or mode compounds and 4 different labelled products (via about 40 intermediates). Their melanotropic activity was determined with an in vitro frog skin assay and, for some of the compounds, with a tyrosinase assay. The tritiation was performed on [Tyr(I₂)²]α-MSH by catalytic halogen/tritium exchange, yielding α-MSH of high specific radioactivity (34 Ci/mmol) and full biological activity. Iodination was studied in detail using five different techniques. An equimolar chloramine T procedure proved to be the most convenient and reproducible method, resulting in monoiodinated α-MSH containing 99% of the label in position 2. The biological activity was 50% that of α-MSH; the specific radioactivity, determined in a competitive binding assay with a highly specific α-MSH antiserum and [Tyr(I)²]α-MSH as competitor, was 1530 Ci/mmol. The labelling techniques and the bioligical results are discussed.     

Measurement of tritium with plastic scintillators in large vials of a low background liquid scintillation counter: an organic waste-less method

The tritium compounds, tritiated water as a volatile compound and ³H-methionine as a non-volatile compound, were measured with two types of plastic scintillators (PSs) using a low background liquid scintillation counter (LSC). It is advantage that minimal organic waste is generated when a plastic scintillator is used for LSC measurement. The effect of large vials on counting efficiency, plasma effects with three types of plasma devices for PS-sheets, the effect of UV-light on PS-pellets, the relationship between the activity and the count rate, and the detection limits of tritium were studied with respect to the development of large-scale measurement systems.

     

Tritium labeling: A unique tool for studying the behavior of humic substances in living systems

A range of labeled humic substances was obtained by the tritium thermal activation method. The high specific radioactivity and radiochemical purity allowed direct determination of the hydrophobicity and surface activity of humic substances, and investigation of the behavior of humic substances in bacteria and plants.     

Scintillation phase method: A new approach for studying surfactant behavior at liquid/liquid interface

Radiochemical approach for the investigation of partitioning and adsorption of surfactants at water-oil interfaces has been developed. The so-called “scintillation phase method” is based on the introduction of tritium labeled surfactant in an aqueous phase of the water-oil system followed by measuring radioactivity of the whole system. Partition coefficients and the value of adsorption at water-non-polar liquid interfaces of homologous series of alkyltrimethylammonium bromides (DTAB, TTAB and CTAB) have been experimentally determined by means of scintillation phase method. The influence of non-ionic surfactants on TTAB adsorption has also been studied.     

Study of kinetics,equilibrium and isotope exchange in ion exchanger systems

An automatic, rapid combustion method has been developed for the determination of tritium and¹⁴C in singly or doubly labelled organic materials by liquid scintillation counting. The sample is burned in a stream of oxygen. The water formed and its tritium content are retained from the gas stream in an absorber containing a small amount of diethyleneglycol monoethyl ether. Radioactive carbon dioxide, if included in the combustion products, is transferred into 3-methoxypropylamine. The final solutions ready for counting are obtained in less than three minutes. Quantitative collection recoveries for both tritium and¹⁴C are achieved and no cross-contamination occurs.     

In vitro study of proteins surface activity by tritium probe

A new technique for in vitro studies of biomacromolecules interactions, their adsorption at aqueous/organic liquid interfaces and distribution in the bulk of liquid/liquid systems was developed. The method includes (1) tritium labeling of biomolecules by tritium thermal activation method and (2) scintillation phase step with organic phase, which can be concerned as a model of cellular membrane. Two globular proteins lysozyme and human serum albumin tested. We have determined the conditions of tritium labeling when labeled by-products can be easy separated by means of dialysis and size-exclusion chromatography. Scintillation phase experiments were conducted for three types of organic liquids. Thus, the influences of the nature of organic phase on proteins adsorption and its distribution in the bulk of aqueous/organic liquid system were determined. It was found that proteins possess high surface activity at aqueous/organic liquid interface. Furthermore, values of hydrophobicity of globular proteins were found by the experiment.     

中国部分煤种二氯甲烷萃取液中极性和烃类有机物分布特性研究

利用高分辨气相色谱－低分辨质谱联用仪（HRGC／LRMS）检测原煤二氯甲烷萃取液中极性有机物和烃类有机物（脂肪烃和芳香烃）的浓度分布，研究了萃取液中这两类有机物和煤种、煤种成分（固定碳、挥发分、灰分、水分）之间的联系。研究发现萃取液中的有机物浓度和固定碳、挥发分关系密切；极性有机物分布较集中，主要为酯类和醇类；芳香烃以菲、二苯并蒽和苯并Bai为主，烟煤和贫煤多环芳烃含量和毒性当量（TEQ）相对较高，并发现煤的碳化程度越高，芳香化程度越大。本文的结果为将来进一步研究燃煤过程中有机污染物形成机理提供依据。     

Assessment of radioecological situation of a site contaminated by technologically enhanced natural radioactivity in Croatia

The paper deals with radioactivity contamination originating from the coal fired power plant and its waste dumps located in a bay of the Adriatic which is due to geographical characteristics sensitive to any kind of pollution including radioactivity. Investigations of coal used in regular plant operation and of solid incombustible ash and slag showed increased concentrations of natural radioactivity which may cause general environmental contamination of the bay as well as contamination of the marine environment of this part of Croatian Adriatic. There are two coal slag and ash piles, one of them was closed and covered by soil and the other is a still operating pile. The location of both piles presents a considerable environmental problem: situated close to the seaside, slag and ash are accumulating in the littoral zone and, in the case of operating pile, are being filled-up directly into the sea. The aim of this study was to determine the radioactivity level at the ash and slag deposits and to assess the risk of increased radioactivity for the inhabitants of the nearby urban area, for the plant workers and general environment of the bay including the marine environment of this part of the Croatian Adriatic.     

Tritium-labeled abscisic acid

A simple method for the preparation of biologically active abscisic acid (growth inhibiting plant hormone) labeled with tritium is described. The product obtained has a specific radioactivity of 1.12 GBq mmol^–1: the yield is about 60% as compared to the initial amount of the substance used.     

Electrochemical oxidation of tetracycline on a boron doped diamond electrode within the stability potentials of water

Electrochemical oxidation of tetracycline on a boron doped diamond electrode within the stability potentials of water was studied in order to develop an approach for the purification of waste water containing medicinal agents. Cyclic voltammetry, HPLC, and high resolution mass spectrometry were used to establish that in the electrochemical oxidation process, tetracycline adds one oxygen atom to further form organic compounds with molecular weights higher than that of tetracycline. It was found that tetracycline in this region of potentials can be almost completely deactivated without its mineralization.     

Radiation-induced nitration of organic compounds in aqueous solutions

Radiation-induced nitration of organic compounds in aqueous solutions was studied. It was found that γ-irradiation of solutions containing acetic and nitric acid and/or their salts gives nitromethane. Dependences of the product yield on the absorbed dose and the contents of components were established. The mechanism of radiation nitration involving radicals is discussed.     

Modeling of the adsorption of organic compounds on polymeric nanofiltration membranes in solutions containing two compounds.

The adsorption of organic compounds in aqueous solution on polymeric nanofiltration membranes is studied; this process is one of the most important fouling mechanisms influencing the flux and retention behavior of nanofiltration membranes. It is shown that the adsorption of dissolved organic compounds on polymeric nanofiltration membranes is comparable to that on activated carbon. Freundlich and Langmuir isotherms are used to describe the relation between the adsorbed mass on the membrane and the equilibrium concentration of the organic compound in a single-compound solution. Based on these results, three models for the adsorption of solutions containing several compounds [i.e., the simple competitive adsorption model (SCAM), the model of Jain-Snoeyinck, and the model of Butler-Ockrent] were used to predict the adsorption behavior of an organic compound in an aqueous solution containing two compounds. The results of the three models were compared to experimental observations. It is shown that the SCAM allows a good prediction of the adsorption behavior.     

Thermogravimetric investigations of carbonaceous materials—Syndiotactic polystyrene systems

A system of a syndiotactic polystyrene (s-PS)-carbonaceous material, obtained as a result of syndiotactic polymerisation of styrene in the presence of carbonaceous materials of organic origin of different degree of coalification before and after their ammoxidation, was studied. The initial materials were plum stone waste, brown coal and hard coal. The interactions between the system components were studied by the method of differential scanning calorimetry (DSC). It has been found that the type of the carbonaceous material used determines the thermal effects of the phase transitions in s-PS (detected on thermograms) and the melting point of s-PS. It has been shown that on melting of the syndiotactic polystyrene in the presence of the carbonaceous materials containing a relatively large number of oxide groups, the polymer oxidation reactions occur. This effect does not occur when carbonaceous materials with preliminary ammoxidation are applied.