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Electrophysiology
Published in Jay L. Nadeau, Introduction to Experimental Biophysics, 2017
Jay L. Nadeau, Christian A. Lindensmith, Thomas Knöpfel
Usually external solution is made 1 L at a time, and internal solution 100 mL at a time. After preparation, the solutions’ pH should be adjusted while checking with a pH meter, usually to 7.1 to 7.3. Solutions are usually too acidic as prepared, so the adjustment is done using the hydroxide of the predominant ion (e.g., KOH or CsOH for internal, NaOH for external). Pellets or concentrated stock solutions can be used for this purpose. After adjusting pH, the osmolarity of the solutions should be matched to prevent cell shrinking or swelling. An osmometer measures the freezing point of a solution to determine osmolarity and is much more reliable than osmolarity calculations. Measure the osmolarity of both solutions, and adjust the one that is lower with sucrose. This may take what seems like a lot of sucrose, but be careful not to overshoot the mark or you will have to throw the solution out and start over again. Make sure to calibrate the osmometer with standard solutions as its absolute values are often wrong by a fixed amount.
Molecular Weight
Published in Béla G. Lipták, Analytical Instrumentation, 2018
The membrane osmometer (Figure 34a) consists of two compartments separated by a semipermeable membrane. A pure solvent and a dilute polymer solution are introduced into the two compartments, respectively. The membrane acts as a filter to permit passage of solvent molecules, but not polymer. Migration of solvent molecules into the solution results in a change in pressure between the two compartments until osmotic pressure is reached. Osmotic pressure, defined as that pressure which must be applied to the solution to stop osmosis from the pure solvent, is used to obtain the number average molecular weight. Static osmometers are provided with a capillary connection to the solution compartment so that osmotic pressure can be read as hydrostatic head. The principal disadvantage of the static osmometer is the long time required to reach equilibrium—1 to 2 hours and longer. Automatic osmometers (Figure 34b) are available which determine osmotic pressure dynamically; that is, the rate of solvent flow through the membrane is measured as a function of externally applied pressure. One type of automatic osmometer has a solvent reservoir mounted on a screw elevator and connected to the solvent side of the membrane by a capillary in which there is a small air bubble. A light source and photocell sense the position of the air bubble as it tends to move with any flow of solvent in the capillary. The photocell output activates a servomotor, which in turn positions the solvent reservoir to reduce pressure on the solvent compartment, thus stopping osmotic flow. As a result, the static head of the solvent is exactly opposed to the osmotic pressure of the solution. The hydrostatic head on the solvent side can be continuously displayed in digital form or the pressure can be recorded providing a permanent record of the measurement (Figure 34c).
Acids, Bases, and Salts
Published in Armen S. Casparian, Gergely Sirokman, Ann O. Omollo, Rapid Review of Chemistry for the Life Sciences and Engineering, 2021
Armen S. Casparian, Gergely Sirokman, Ann O. Omollo
Osmosis is a commonly occurring biological process, regulating and maintaining the proper concentrations of electrolytes in the cells of the human body. Osmometry is often used to find the molar mass (MM) of an unknown substance dissolved in solution through its molarity, M, when the other quantities—mass of unknown substance, volume of solution, temperature, and osmotic pressure—can be measured experimentally.
Application of molasses as draw solution in forward osmosis desalination for fertigation purposes
Published in Environmental Technology, 2021
Bizhan Bagheri, Ayoub Karimi-Jashni, Mohammad Mahdi Zerafat
A freezing point depression osmometer (Gonotec-OSMOMAT 3000, Scientific Group, Germany) is used to measure the osmolality of the solutions. The instrument compares the freezing points of each solution with pure water [43] and determines their osmolality using a 50 µL of sample in a 60 s for each test [44]. At the standard atmospheric pressure that water has a freezing point of 0°C, the freezing point of an aqueous solution with saline concentration of 1 Osmol/kg is −1.858°C. Osmolality (n/V) measurements from the osmometer are reported in mOsmol/kg that can be converted to osmotic pressure (π) in bar using Van’t Hoff equation (Equation (1)) [42]. Sugar content materials unlike sodium chloride and other salts do not dissociate [45]. Therefore, when one mole of such materials like molasses is dissolved in water, one mole of dissolved particles is yielded (i = 1).
Hyperhydration using different hydration agents does not affect the haematological markers of the athlete biological passport in euhydrated volunteers
Published in Journal of Sports Sciences, 2020
Ioanna Athanasiadou, Sven Christian Voss, Wesal El Saftawy, Mohammed Al-Maadheed, Georgia Valsami, Costas Georgakopoulos
Osmolality (Osmol/kg) was measured to all the serum samples via freezing point depression with an osmometer (OSMOMAT 030, Gonotec, Berlin, Germany). Standard sodium chloride (NaCl) solutions with an osmolality of 0.300 and 0.850 Osmol/kg were used for the calibration of the instrument before analysis. A zero calibration was also performed using distilled water.
Ultrasonic freezing of polymers of various compositions before freeze drying: Effect of ultrasound on freezing kinetics and ice crystal size
Published in Drying Technology, 2023
Elizaveta Mokhova, Mariia Gordienko, Natalia Menshutina, Igor Gurskiy, Antonina Tvorogova
For the polymer solutions listed above (Section 2.1), cryoscopic temperatures were determined using an OSKR-1 cryoscope-osmometer (Russia). The principle of operation of an cryoscope-osmometer is based on the accurate measurement of the phase transition temperature of a solution during freezing compared to the freezing point of a pure solvent (in this case, water).