摘要:
A method and apparatus is disclosed for measurement of the Electrophoretic mobility of particles and molecules in solution. A sample of particles is placed in a cell containing two electrodes that apply an alternating electric field. A monochromatic light beam passes through the sample. Light scattered by the particles, along with the unscattered beam, is collected and collimated as it exits the cell. This beam is combined in free space with a phase modulated reference beam. The interference forms a frequency modulated speckle pattern, which is detected by a photodetector array. Each array element collects a narrow range of well-defined scattering angles. The signal from each is demodulated to extract the optical phase information providing a first-principle measurement of the Electrophoretic mobility of the scattering particles. Each detector element provides a simultaneous independent measurement. This inherent parallelism drastically increases the amount of information available in a given time. The resulting increased sensitivity extends the mobility measurement to particles below one nanometer, reduces the required concentration and electric field compared to previous methods. This minimizes damage to fragile samples, increases the electrode useful life, and reduces joule heating. Electrophoretic mobility is a critically important parameter for predicting the stability of nanoparticle suspensions and pharmaceutical formulations such as protein therapeutics. This invention enables reliable free-solution phase measurement of these samples.
摘要:
Methods, systems and devices are described for rapid characterization and screening of liquid samples to determine properties (e.g., particle size, particle size distribution, molar mass and/or molar mass distribution) thereof with static light scattering and/or dynamic light scattering. The liquid samples can be solutions, emulsions, suspensions or dispersions. One method, includes providing a vessel containing a liquid sample having an exposed surface that defines a gas-liquid sample interface, and analyzing the sample by light scattering methods that include transmitting light through the gas-liquid sample interface into the sample, and detecting light scattered from the sample or from a component thereof. Additional methods are directed to characterizing a plurality of liquid samples or components thereof. The methods, systems, and devices have applications in high-throughput screening, and particularly, in combinatorial materials research and in industrial process control.
摘要:
A thermally controlled stage is connected within one arm of a bridge of a capillary bridge viscometer so that the bridge can be balanced in situ to provide accurate measurement signals. The thermally controlled stage includes a tuning capillary tubing portion that is wrapped around a thermally conductive core. A resistance heater or a Peltier thermoelectric device is located in close proximity to the capillary tubing portion. The heater or Peltier device and the capillary tubing portion are located within a thermally insulated housing. The heater or Peltier device varies the temperature of the capillary tubing portion to cause a corresponding change in the flow impedance of the tuning capillary tubing portion of the arm of the bridge in which the thermally controlled stage is connected. The temperature of the tuning capillary tubing portion is monitored and adjusted until any pressure differential across the bridge is eliminated, whereby to trim in the balance of the bridge.
摘要:
A sensitivity-enhanced flow cell to be used in the determination of the differential refractive index increment of a sample fluid relative to a reference fluid is disclosed. The invention permits the use of smaller sample amounts without sacrificing overall sensitivity. Equally important, said improved How cell produces measurements of increased precision without requirement for increased sample amount. This is achieved by means of two chambers within said cell whose volumes are different. The sample fluid chamber is the smaller of the two with the reference fluid chamber constructed so that the incident illumination beam, upon passage through said sample chamber and displacement by the partition element located therebetween said sample and reference chambers, passes through said reference chamber without grazing any of the confining walls or striking corners of said sensitivity-enhanced flow cell. As the amount of deflection of said transmitted beam depends upon the refractive indices of the fluids relative to the transparent matter of which the containing cell is comprised, as well as the RI difference between said fluids themselves, the reference chamber is designed to transmit said incident light beam without grazing degradation thereof for all practical ranges of expected fluid and cell refractive indices.
摘要:
A cell for a walk-off refractometer is disclosed that permits measurement of the differential refractive index, DRI, between a sample fluid and a reference fluid. In addition, the new cell design permits the measurement of the refractive index, RI, of a fluid relative to the refractive index of the material comprising or surrounding the flow cell. Thus a single instrument may be used to measure separately the RI of a sample fluid and the DRI between a sample fluid and a reference fluid. The new flow cell contains two chambers, typical of a DRI instrument, but an asymmetric internal angle in either the sample or the reference chamber. By the provision of this structure, it is an objective of this invention to be able to measure the refractive index of a fluid relative to the refractive index of the material comprising the flow cell or relative to the medium surrounding the flow cell, either of which may be considered a measurement of the RI of the fluid. With the addition of mirror means, it is the further objective of this invention to improve its sensitivity. A further objective of the invention is to measure the asymmetric internal angle of the flow cell using well-characterized reference fluids.
摘要:
A method for determining absolute number densities of particles in a solution is disclosed based on a light scattering method. A light scattering photometer is calibrated to produce the Rayleigh ratio at each angle measured with respect to light scattered per unit incident intensity, per unit volume illuminated within the field of view of each detector per steradian subtended by said detector. In order that the numbers calculated be accurate, the illuminated particles should be effectively monodisperse. From the excess Rayleigh ratios measured at a plurality of angles with respect to the incident light beam illuminating said sample particles, an effective size is calculated which, in turn, is used to calculate the differential scattered intensity at each angle. The number of particles per unit volume element is then determined from the measured excess Rayleigh ratio divided by the corresponding differential scattered intensity.
摘要:
The characterization and/or identification of individual microparticles is achieved by measuring certain optical observables produced as each particle passes through a beam of light, or other electromagnetic radiation. A fine beam of, preferably, monocromatic linearly polarized light passes through a spherical array (30) of detectors (8), or fiber optics means to transmit incident light to a set of detector means, and a stream of particles intersects the beam at the center of the spherical array (30). Selected observables calculated from the detected scattered radiation are then used to recall specific maps, from a computer memory means (11,22) one for each observable. The common overlap region of said maps yields characterizing or identifying particle physical parameters such as size, mean refractive index, and shape. A method for rapidly discriminating non-spherically symmetric particles is also disclosed.