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Capillary Electrophoresis
Published in Grinberg Nelu, Rodriguez Sonia, Ewing’s Analytical Instrumentation Handbook, Fourth Edition, 2019
Zwitterionic buffers such as Bicine, Tricine, CAPS, MES, and Tris are used particularly for protein and peptide separations. Some buffers, such as MES, Tricine, and glycylglycine, bind calcium, manganese, copper, and magnesium ions. Metal binding may be useful, or it may interfere with the subsequent separations. The advantage of the zwitterionic buffer is low conductivity when the buffer is adjusted to its pI. This provides for low current draw and reduced Joule heating, allowing higher buffer concentrations to be used. High buffer concentrations are sometimes useful to minimize interaction between the solute and the capillary wall. Alternatively, high field strengths can be used to speed up the separation. Mobility matc hing between the BGE and sample has been proposed to improve the peak symmetry when the sample concentration is high [11].
Biotransformation of chromium (VI) by Bacillus sp. isolated from chromate contaminated landfill site
Published in Chemistry and Ecology, 2020
Md. Ekramul Karim, Shamima Akhtar Sharmin, Md. Moniruzzaman, Zeenath Fardous, Keshob Chandra Das, Subrata Banik, Md. Salimullah
Heavy metal can be present in the aqueous phase of the medium in many different forms, depending on chemical composition and the pH of the medium [36]. However, much less importance has been paid to the nature of metal species present in the microbiological medium during metal-micorbe toxicity studies. Throughout this study, we have used a previously formulated MES [2-(n-morpholino) ethane sulfonic acid] buffered minimal medium, commonly known as Low Phosphate (LP) medium, instead of, nutrient-rich media and high-phosphate containing media. The complex organic substrates such as beef extract, yeast extract etc. used in nutrient-rich media such as nutrient Broth (NB) or Luria–Bertani Broth (LB) and high-phosphate used in high-phosphate containing media is the cause of metal-complexation, metal-chelation or precipitation which is responsible for the overestimation of bacterial metal-resistance than the expected or genuine toxicity [21, 37]. Whereas in LP medium the conventional phosphate buffers were substituted with Zwitterionic biological buffer, such as MES [2-(n-morpholino) ethane sulfonic acid, pKa = 6.15] which have a low interferences with biological processes due to the presence of anionic and cationic sites as non-interacting sulfonate and cationic ammonium groups, and is more water-soluble [38]. In addition, the LP medium contained a very low phosphate (0.01 g.L−1) and glucose (0.2%) content to meet the nutritional requirement of the bacteria and thus making this medium a better choice than other available media to study metal-microbe interactions.
Arsenic, lead and cadmium removal potential of Pteris multifida from contaminated water and soil
Published in International Journal of Phytoremediation, 2018
Farzana Rahman, Kazuki Sugawara, Yi Huang, Mei-Fang Chien, Chihiro Inoue
To determine the As(III), Pb and Cd accumulation potential of P. multifida and to establish its efficiency compared with P. vittata, 5-day hydroponic trials were conducted with both P. multifida and P. vittata. In this study, the more toxic form of As, As(III), was used during the hydroponic experiments to obtain the responses of Pteris multifida and Pteris vittata to As(III). Plants were precultivated in 5 times diluted Hoagland's nutrient solution. The nutrient solution was composed of: 8 mM of KNO3; 4 mM Ca(NO3)2; 2 mM MgSO4; 1 mM NH4H2PO4; 50 lM H3BO3; 9 lM MnSO4; 1 lM ZnSO4; 0.2 lM CuSO4; 0.1 lM Na2MoO4; and 60 lM Fe(III)-EDTA. The acclimatized plants were incubated in 0.1 M 2-morpholinoethanesulfonic acid monohydrate (MES) buffer solution for three days to allow them to adjust to the buffer solution. Then P. multifida and P. vittata plants were transplanted to mixed metal solution where they have been growing for 5 days. Before plantation, initial concentrations were about 21 µg/L for As(III) (NaAsO2) and 24 µg/L for both Cd (Cd(NO3)2. 4H2O) and Pb (Pb(NO3)2) in mixed metal solution during short term hydroponic experiment of P. multifida. Metal solutions were prepared by using 0.1 M MES buffer. In case of P. vittata, initial concentrations of As(III) and Cd were about 30 µg/L and Pb was 20 µg/L before transplantation. Every day, 1 mL of sample solution was collected at a fixed time for analysis and initial solution level (400 mL) was supplemented very carefully by adding MilliQ water. pH was kept at around 6.0 by adding 0.1 M HNO3 or 0.1 M NaOH initially and was not adjusted again during the experiment. The buffer solution maintained the pH within the range of 5.98 to 6.04 during the 5 day experiment.
A review of design, operational conditions and applications of microbial fuel cells
Published in Biofuels, 2018
Rachna Goswami, Vijay Kumar Mishra
To rectify the problem created by the pH gradient between anode and cathode (one of the main causes for the sink of voltage efficiency in microbial systems), active pH control such as acid/base dosing or addition of chemical buffer (such as phosphate or bicarbonate buffer) is necessary to sustain steady current generation and some work has been performed regarding this matter [36,131-136]. The buffer assists to reduce alterations in pH in the bulk solution and in the biofilm, and therefore it retains the pH in the range fit for the growth of microorganisms. An ideal buffer should be capable of maintaining constant pH without disturbing it with chemical reactions or microbial physiology, make easy proton transfer to the electrode for high power densities in MFC and augment the solution conductivity [133,135]. Phosphate buffers are frequently used in MFCs [36,131,133,137] and it has been observed that increasing phosphate concentration within certain ranges will enhance power output [133]. However, addition of high concentrations of phosphate buffer is costly, particularly for wastewater treatment, and phosphates can cause the eutrophication conditions of water bodies if the effluents are released without the removal of these compounds, thus making it impractical for wastewater treatment. Bicarbonate buffer can be another option, a low cost and effectual pH buffer particularly for wastewater treatment, although higher carbonate concentrations can augment the growth of methanogens [131]. The effect of a borax buffer was studied by Qiang et al. [135] and they found that adding a suitable concentration of borax buffer improves the electron recovery efficiency. Several synthetic zwitterionic buffers, like MES [2(N-morpholino) ethane sulfonate], HEPES [4(2-hydroxyethyl)1-piperazine ethane sulfonic acid] and PIPES [piperazine-N,N_-bis (2-ethane sulfonate)] can be utilized as buffers in MFCs. These zwitterionic buffers have benefits in comparison to traditional buffers, like phosphate and carbonate buffers in biological research, because their pKa values are in the array of pH 6.0 and 8.0, they are chemically steady, nondeleterious and do not encumber biochemical reactions.