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- Metformin (3)
- Dynamic scanning calorimetry (2)
- Advanced oxidation (1)
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Eingeladener Vortrag
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A first pilot study on the sorption of environmental pollutants on various microplastic materials
(2017)
With the drastic increase in plastic production, the input of plastic particles into the environment has become a recognised problem.
Xenobiotics are able to sorb to polymer materials, and this process is further enhanced where they Encounter microplastics (plastic fragments <5 mm). In this work we studied the sorption of metformin, a type-2 diabetes drug, and difenoconazole, a fungicide, onto the virgin polymer materials polyamide (PA), polypropylene (PP), and polystyrene (PS). Additionally, PP was cryo-milled and PA was treated with acid to investigate the influence of an increase in surface area and chemical modification. The material properties were also studied by dynamic scanning calorimetry (DSC), gel permeation chromatography (GPC) and Fourier transform infrared spectroscopy (FTIR). Sorption experiments were performed on the basis of a full factorial design examining the effect of agitation, pH value, and salinity. Experimental results showed that difenoconazole sorbs readily to all microplastics, whereas the more polar analyte metformin did not show any affinity to the materials used. For difenoconazole the governing factor in all cases is agitation, while both pH and salinity exhibited only a slight influence. The modification of polymers leads to enhanced sorption, indicating that an increase in surface area (cryo-milled PP) or inner volume (acid-treated PA) strongly favours adsorption. Moreover, long-term experiments demonstrated that the time until equilibrium is reached depends strongly on the particle size.
For years there have been more and more reports on the presence of drugs in the aquatic environment. Due to the demographic change, the consumption of pharmaceuticals has risen sharply. After taking the drugs, they are partly metabolized in the human body. However, the metabolism is not complete so that both the metabolites and non-metabolized amounts of the parent compounds are excreted. These compounds reach the waste water and afterwards the sewage treatment plants. In sewage treatment plants transformation products can be formed by the oxidative conditions during wastewater treatment processes. The transformation products may have a higher toxicity than the actual environmental pollutants and are often only partly removed during the waste water treatment. Since a lot of these compounds are still unknown, the transformation products are not detected by target analysis used in sewage treatment plants and are often released undetected in the aquatic ecosystems. The released substances may be subject to additional transformation processes in the environment. Pharmaceuticals produced in high amounts can be already detected in the μg/L range in water bodies worldwide.
Metformin and its major transformation product guanylurea are one of the main representatives. Metformin is the drug of choice for treating type 2 diabetes. The drug therapy for diabetes mellitus has increased significantly in recent years. In the year 2015 1500 tons of metformin were prescribed in Germany (for statutory insured persons). Metformin is not metabolized in the human body and is excreted unchanged therefore concentrations between 57 μg/L and 129 μg/L are found in German waste water treatment plants influents.
In this work the transformation of the antidiabetic drug metformin is investigated. The degradation of metformin is initialize by commercial water treatment techniques like UV-radiation or noncommercial techniques like heterogenous photocatalysis based on titanium dioxide. The degradation of metformin and resulting transformation products are analyzed by LC-MS/MS and LC-HRMS.
Drug therapy for diabetes mellitus has increased significantly in recent years. 1,1-Dimethylbiguanide hydrochloride (metformin) is the most common drug used for the treatment of diabetes. Metformin is not metabolized in the human body and enters thewater cycle via sewage.
A new gas chromatography-mass spectrometry (GC-MS) method has been developed which enables the quantification of metformin in surface water samples even at low concentrations in the ng L-1 range.
A solid phase extraction (SPE) method for the preconcentration of metformin and the internal standard 1-butylbiguanide (buformin) was established, and the method parameters such as the composition and volume of the eluent were optimized. Derivatization of metformin and
buformin was obtained by using n-methyl-bis (trifluoroacetamide)(MBTFA). The reaction conditions of the derivatization, such as the reaction temperature and volume of the derivatization agent, were evaluated. The limit of detection (LOD) and limit of quantification (LOQ) were determined to be 3.9 ng L-1 and 12 ng L-1 in surface water samples. Linearity was shown over a concentration range of 10–50 ng L-1. The good performance of the method was demonstrated by comparison with a liquid chromatography tandemmass spectrometry (LC-MS/MS) method. The results indicate that the GC-MS method is a reliable and sensitive alternative for the quantification of metformin in surface water.
1.
Nano-TiO2 powder is known to show high photocatalytic reactivity in the degradation of several organic pollutants.
In thiswork, the powderwas fixed on the surface of SiO2 granuleswith the size of several micrometers using a high shear granulation process. Nanozirconia sol was applied as an inorganic binder. When the samples were tempered at 300 °C, they showed high stability in an aqueous solution for several hours. An energy dispersive x-ray spectroscopy (EDX) analysis confirmed that the cores and shells of the granules consisted solely of SiO2 and TiO2 respectively, and that ZrO2 was found throughout the whole granules. Methylene blue (MB) was employed as amodel systemto evaluate the photocatalytic activity of the TiO2 nanopowder and coated granules.
Itwas shown that the TiO2-coated granules lead to the degradation ofMB under UV irradiation,whereas no effect was observed in the dark. After the Degradation experiments the granules could be recovered and they remained active for further applications.
Plastics are used in many applications, such as packaging, building and construction, mobility and transport and more. Due to their favourable properties like light weight, flexible processing and low costs their production and consequently their input into natural systems has increased significantly over the last decades. In the environment (photo )oxidation processes and mechanical abrasion lead to the decomposition of the plastics. During this process microplastics (<5 mm) can be formed. It has been shown that environmental pollutants can sorb to these microplastics.[1,2] Nevertheless, knowledge on this topic is still limited.
Our work aims at the investigation of the sorption behaviour of the triazole fungicide difenoconazole to simulated microplastics made of virgin polyamide (PA), polypropylene (PP), and polystyrene (PS). Sorption experiments were planned based on a full factorial design with agitation, salinity, and pH value as parameters. The results of our study revealed that difenoconazole indeed, has sorbed to all microplastics tested here. Data analysis showed that agitation is the main influencing factor, whereas salinity and the pH value held little to no significance on the amount of sorbed difenoconazole.
To simulate the behaviour of naturally aged microplastics, sorption to cryo-milled PP and acid-treated PA was also studied. The thus treated samples were characterised by Fourier transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC), and dynamic scanning calorimetry (DSC). FTIR spectroscopy did not show any changes in the chemical structure but GPC and DSC measurements indicated a systematic chain scission of the treated PA. Scanning electron microscope (SEM) images illustrate that milling of the microplastics leads to non-spherical, star-shaped particles. This fact has a huge influence on the surface properties and consequently on the absorption.
The results of our study are important in terms of i) creating realistic sorption scenarios with relevant parameters for the sorption process, as well as for ii) the choice of proper materials to simulate naturally occurring microplastics. We could show that not only the characteristics of the material like particle size distribution or surface properties are important, but also the applied analytical technique which is used for the characterization of the material . Since there is no standard methodology for microplastic identification and quantification, we suggest to combine several methods to obtain a reliable overall characterization.
Das Ziel des OEMP-Projektes ist die Entwicklung neuer Materialien, um den Rückhalt von Mikroplastik-Partikeln (MP) aus verschiedenen urbanen Eintragspfaden (Kläranlagenablauf, Mischwasserüberlauf und Straßenabfluss) zu optimieren. Grundlage für die Bewertung ist die Entwicklung von geeigneten Untersuchungsverfahren (Probennahme, Probenaufbereitung, Detektion) zur Qualifizierung und Quantifizierung von MP in den relevanten Umweltmatrices. Diese Verfahren müssen zeiteffizient und zuverlässig sein.