File Name: determination of partition coefficient of iodine between water and tetrachloromethane .zip
This page describes the phenomena of a solute dissolving in two immiscible liquids in contact with one another — known as a partition equilibrium. Simple calculations are described using an equilibrium expression and the partition coefficient.
Optimization and validation of FTIR method with tetrachloroethylene for determination of oils and grease in water matrices. Cristina M. Revez II. General Humberto Delgado, lote 7, Sines, Portugal.
Optimization and validation of FTIR method with tetrachloroethylene for determination of oils and grease in water matrices.
Cristina M. Revez II. General Humberto Delgado, lote 7, Sines, Portugal. The development of methods for oils and grease OG determination presents several difficulties and challenges for analytical laboratories, mainly for drinking water analysis regarding its low parametric value.
FTIR method with tetrachloroethylene was developed for OG monitoring and control in several water matrices, such as natural waters surface water, groundwater and bathing water , wastewaters and drinking water.
The method was validated through the application of statistical tests and calculus of the uncertainty of the analytical assay, and proved to be a good alternative to Freon Results regarding the calibration, linearity, OG recovery, precision, limits of detection and quantification, and uncertainty estimation are presented and discussed.
The validated method was applied for the analysis of water samples from all studied matrices and was found to be appropriate for monitoring oil and grease in these matrices at levels higher than 0. Keywords: oils and grease, FTIR, water analysis, tetrachloroethylene. It is clear that nowadays and in the near future, our society will have to face serious problems, such as over-exploitation of resources, environmental degradation, deterioration of ecological goods and services, for sustainable development.
Among them, the availability of water of good quality is a critical issue since it represents an essential component for sustainable socio-economic development.
Urban wastewaters, which include domestic and some industrial waters, among others, have a strong contaminating effect on the natural aquatic systems, even when they are submitted to treatment because multiple organic compounds, escape conventional wastewater treatments and some of them may become ubiquitous in the environment and sometimes more toxic.
This impact varies according to the treatment applied and chemicals present in wastewater. The concentration of dispersed oils and grease OG is an important parameter for water quality and safety.
OG in water can cause surface films and shoreline deposits leading to environmental degradation, and can induce human health risks when discharged in surface or ground waters. OG is a measure of a variety of substances including fuels, motor oil, lubricating oil, hydraulic oil, cooking oil and animal-derived fats. Although not particularly toxic in and of itself, OG is a key indicator of water pollution and has many deleterious effects in the environment.
In sewage, it hinders the proper operation of the water treatment facility. In storm drains, it makes an efficient cover, preventing aeration and providing a food source for bacteria leading to anaerobic conditions. Total petroleum hydrocarbon TPH is a term used to describe a broad family of several hundred chemical compounds that originally come from crude oil.
In this sense, TPH is really a mixture of chemicals. They are called hydrocarbons because almost all of them are made entirely from hydrogen and carbon.
The term TPH was traditionally used to classify aliphatic hydrocarbon materials. Because modern society uses so many petroleum-based products for example, gasoline, kerosene, fuel oil, mineral oil and asphalt , the contamination of the environment by them is potentially widespread.
Contamination caused by petroleum products will contain a variety of these hydrocarbons. Because there are so many, it is not usually practical to measure each one individually. However, it is useful to measure the total amount of all hydrocarbons found together in a particular sample of soil, water or air. Although OG is the conventional term used to define pollutants of this nature, including TPH, there are other terms that include the used extractant, like n- hexane extractable materials HEM and silica gel treated n -hexane extractable material SGT-HEM.
The term HEM indicates the extractant solvent hexane and that method may be applied to other materials than oil and greases. SGT-HEM indicates that the method may be applied to other materials than aliphatic petroleum hydrocarbons that are not adsorbed by silica gel.
Sources of oil and grease are mainly anthropogenic. Domestic cooking oil should be poured into a disposable container and thrown out in the trash. Used motor oil and hydraulic fluids should be disposed of at a local automotive part store or a certified hazardous waste facility.
Spill prevention kits should be used to help to clean up spills that occur at the work place. Since the oil and grease constituents and petroleum hydrocarbons are defined based on results from the test procedure, interferences are precluded by definition. However, the interpretation of test results on the basis of chemical structure, pollution potential or treatability should be approached with caution because of the diversity of substances measured by this procedure.
Organic solvents and certain other organic compounds not considered as OG on the basis of chemical structure may be extracted and measured as OG. From those measured, certain ones may be adsorbed by silica gel while others may not.
Those which are not adsorbed are measured as petroleum hydrocarbons. Whereas to enable water-supply undertakings to meet the quality standards for drinking water, appropriate waterprotection measurements should be applied to ensure that surface and groundwater are kept clean. Whereas the same goal can be achieved by appropriate water-treatment measurements to be applied before supplying.
The production of safe drinking water is an important issue and the legislation establishes the levels of chemical substances allowed in drinking water, whether occurring naturally, as deliberate additions or as contaminants.
As a consequence of European Union legislation, 7 and their recent implementation for national law, 8 the number of organic compounds in drinking water to be monitored is higher but there is no parametric value related to OG, or even TPH. Oil and grease analyses, like many analytical methods for determination of water quality, do not measure a specific substance or compound.
Oil and grease analyses attempt to quantify compounds which have a greater solubility in an organic solvent than in water, therefore OG and TPH include any material that may be recovered as a substance that is soluble in the solvent extractant.
These include substances such as relatively non-volatile hydrocarbons, vegetable oils, animal fats, fatty acids, waxes, soaps, greases and related materials. The contribution of each of these substances will depend upon the origin of the wastewater being analyzed and the type of extracting solvent used. While imposing relatively simple analytical requirements, OG tests result in measurement of a broad range of compounds with widely varying chemistry and toxicity.
Several methods are available for identification of specific organic fractions but tend to be too demanding of expertise, time and equipment to be used as a regulatory tool.
OG in water is commonly determined by extraction into a non-polar, hydrocarbon free solvent followed by a gravimetric method or measurement of the infrared absorption spectrum of the extract. For liquid samples, the 21 st edition of Standard Methods for the Examination of Water and Wastewater 13 specifies four alternative methods for OG determination: the liquid-liquid partition-gravimetric method B , the partition-infrared method C , the Soxhlet method D , and the solid-phase, partition-gravimetric method G.
Method C is designed for samples that might contain volatile hydrocarbons that otherwise would be lost in the solvent-removal operations of the gravimetric procedure. Method D is the method of choice when relatively polar, heavy petroleum fractions are present, or when the levels of nonvolatile greases may challenge the solubility limit of the solvent.
Method F can be used in conjunction with other methods B, C, D or G to obtain a hydrocarbon measurement in addition to, or instead of, the OG measurement. This method makes use of silica gel to separate petroleum hydrocarbons from the total OG on the basis of polarity. Throughout the various editions of the Standard methods, different extraction solvents were used such as hexane and petroleum ether 12 th edition and Freon 13 th to 17 th edition.
In the 20 th and 21 st edition, Freon was dropped from all gravimetric procedures retained for C , and replaced with n- hexane. In detailed studies involving wastewaters and solid matrices, it was shown that n- hexane produced results statistically different from results produced by Freon EPA Method A requires use of n -hexane as the extraction solvent.
However, there may be samples for which Method may not be suitable, e. In those situations, analysts in the past may have used EPA Method However, this method uses Freon The silica gel treatment allows for the separate determination of total petroleum hydrocarbons TPH.
Although gravimetric methods 5,13 are simple, quick and inexpensive, they present the disadvantages of low sensitivity usually limits of detection are mg L -1 , loss of constituents that volatilize at temperatures above those used for the evaporation of the solvent and inclusion of compounds which are not oil and grease but are extracted by the solvent and therefore contribute to the final mass.
Infrared-based methods are generally more sensitive. IR methods measure the absorbance of the C-H bond, i. It is self-evident that IR methods can only use solvents without C-H bonds, but since no evaporation of the solvent is needed, there are no losses of volatile components. The Montreal Protocol on Substances that Deplete the Ozone Layer is a landmark agreement that has successfully reduced the global production, consumption and emissions of ozone-depleting substances ODSs.
Since this protocol and its amendments and settled a timetable for the phase-out of the production and consumption of some solvents, manufacture and their use have dropped and some of them became illegal. As example, the use of Freon was phased out by and the use of tetrachloromethane became illegal in These facts have resulted in the development of new official methods for OG analyses that use hexane and more recently the use of tetrachloroethylene.
This study began as a result of lack of information on the use of tetrachlorethylene solvent extraction in the analysis of OG by FTIR method in different water matrices, according to the requirements of national and international legislation, especially studies that allow accreditation of the method.
In natural waters and wastewaters, the quantification of any target compound with a guidevalue in the order of ng L -1 and the accreditation of the method for their quantification, requires compliance with all validation requirements for each matrix under study.
Tetrachloroethylene C 2 Cl 4 is a rather non-volatile b. Farmaki et al. The study of Farmaki et al. LOQ is higher than the guideline value of 0. Moreover, in the accreditation of an analytical method is necessary to calculate uncertainties, but it was not performed in this study. The liquid-liquid extraction LLE is a useful technique, but it is laborious, time consuming and requires large amounts of frequently toxic organic solvents and for these reasons, it has been developed other extraction methods, such as microwave extraction methods 17 and solid phase extraction methods SPE.
The SPE method without elution step with organic solvent 22 also has some time limitations because the water must be removed as far as possible from the disk and several spectra must be recorded in several position of the filter. However, its selectivity can become a major drawback in the analysis of wastewater where the objective is to analyze the total OG from an aqueous matrix.
Moreover, in case of wastewaters, because they have a lot of material in suspension, disk or filter may be clogged or blocked. This problem is overcome in LLE with a good selection of solvent extraction. For the analysis of TPH, other methods have been used such as gas chromatography with a flame ionization detector GC-FID 23 and gas chromatography-mass spectrometry GC-MS , 19,24 which have the advantage of providing identification or even fingerprinting capabilities, but it is often difficult to extrapolate their results in order to obtain the total OG values.
To meet the requirements of national and community legislation on OG, laboratories must use IR methods, which are more sensitive than gravimetric methods, but less specific than chromatographic methods. Therefore, it is necessary to implement methods of extraction with other solvents, as a substitute to Freon and validate the modified methods. The accredited laboratories must demonstrate in accreditation audit that validated method meets the requirements of International Standard Organization, Eurachem guides for calculating uncertainties and recoveries studies in all target matrices under accreditation.
The freon replacement for tetrachlorethylene created serious problems for laboratories because the replacement of solvents with different characteristics cannot show similar results. This problem is greater in water for human consumption, which guidevalue is lower. The aim of this study is to present the development and validation data of an FTIR method for determination of OG in waters using tetrachloroethylene, an alternative solvent that has already been proposed in ASTMD , 6 as the extraction solvent.
Tetrachloroethylene does not have the adverse environmental effects of Freon and it is well-suited to OG determination because it is an excellent solvent for organic compounds and has no C-H groups. The LALA laboratory is located in a heavily industrialized area, which has an environmental monitoring program controlled and supervised by the competent authorities, ensuring that the limits imposed by legislation are met. Changing the solvent extraction required the laboratory to validate the method with the new solvent and undergo re-evaluation by the competent authorities for accreditation.
The FTIR method with tetrachloroethylene was validated through the application of several statistical methods which allow defining the linearity, working ranges, instrumental analytical limits limits of detection and quantification , and the limit of determination of the global method. Method accuracy was also assessed by inter-laboratory assay. The method accreditation is renewed annually and it was renewed with the tetrachloroethylene as extraction solvent.
The following materials were used: filter paper, ashless, quantitative, general-purpose, 11 cm or equivalent Whatman, Kent, England , glass bottle, approximately 1. Reagents and standard solutions.
Volatilization: a soil degassing coefficient for iodine. Iodine , an element essential to some animals, is ubiquitous in the biosphere. Unlike other metallic elements, molecular I is volatile, and other inorganic species present in aerated soils, such as I - and IO 3 - , may also volatilize as hydrides, hydrogen iodide HI , or hydrogen iodates HIO 3 , HIO 4. Methyl iodide has been measured in soils, and it is likely evolved from soils and plants. The long-lived radioisotope I is abundant in nuclear wastes, and its high solubility in groundwater makes it an important element in the performance assessment of underground disposal facilities. Overestimates of soil I residence half-times by traditional foodchain models may be due to underestimation of volatilization.
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Carbon tetrachloride , also known by many other names such as tetrachloromethane , also recognised by the IUPAC , carbon tet in the cleaning industry , Halon in firefighting, and Refrigerant in HVACR is an organic compound with the chemical formula CCl 4. It is a colourless liquid with a "sweet" smell that can be detected at low levels.
Под его ногами была потайная дверь, почти неразличимая на полу. В руке он сжимал ключ, взятый из лаборатории систем безопасности. Чатрукьян опустился на колени, вставил ключ в едва заметную скважину и повернул. Внизу что-то щелкнуло. Затем он снял наружную защелку в форме бабочки, снова огляделся вокруг и потянул дверцу на. Она была небольшой, приблизительно, наверное, метр на метр, но очень тяжелой.
Стратмор мгновенно взвесил все варианты. Если он позволит Хейлу вывести Сьюзан из шифровалки и уехать, у него не будет никаких гарантий.
В чем дело? - Беккер не рассчитывал, что все это займет так много времени, и теперь опаздывал на свой обычный субботний теннисный матч. Часовой пожал плечами. - С вами хочет поговорить начальник шифровалки.
- В трубке воцарилась тишина, и Джабба подумал, что зашел слишком. - Прости меня, Мидж. Я понимаю, что ты приняла всю эту историю близко к сердцу. Стратмор потерпел неудачу. Я знаю, что ты о нем думаешь.
Так ты со мной, Сьюзан? - спросил. Сьюзан улыбнулась: - Да, сэр. На сто процентов.
Халохот пробирался между деревьями с пистолетом в руке.
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