Abstract: 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.

Abstract: A sample cell for making light scattering measurements, incorporating an exterior surface acting as both a lateral and vertical lens, is described. This unique structure permits greatly improved measurement of the light scattered by molecules and particles suspended in a fluid contained therein or flowing therethrough while illuminated by a fine light beam incident thereon. The resultant lensed structure of the cell, when integrated into a scattered light photometer and combined with suitable apertures before each scattered light collecting detector, reduces significantly stray light from entering each such detector.

Abstract: Chromatographic separations are often characterized by multiple detectors through which the sample flows serially. As the sample flows between detectors, it becomes progressively diluted due to mixing and diffusion. This phenomenon is traditionally called interdetector “band broadening” and often results in significant distortion of the sample's derived physical properties such as molar mass. This method to characterize the broadening present in a chromatographic system, and an algorithm whereby the narrow peaks of the upstream detector are numerically broadened so they can be compared to the broadened peaks of the downstream detector, is described. Although the technique results in some loss of resolution, its stability and generality allow it a broad range of application. Examples are presented for data collected by dRI, MALS, UV, and viscometric detectors.

Abstract: A new method is presented for characterizing the associative properties of a solution of macromolecules at high concentration. Sample aliquots spanning a range of concentrations are injected sequentially into a light scattering photometer. Equilibrium association constants and association stoichiometry are derived from an analysis of the angular and concentration dependence of the scattering signals. Thermodynamic nonideality, which becomes important at high concentrations, is dealt with in the analysis in a simplified manner which is applicable to multiple associated species.

Abstract: A sample cell for making light scattering measurements, incorporating an exterior surface acting as both a lateral and vertical lens, is described. This unique structure permits greatly improved measurement of the light scattered by molecules and particles suspended in a fluid contained therein or flowing therethrough while illuminated by a fine light beam incident thereon. The resultant lensed structure of the cell, when integrated into a scattered light photometer and combined with suitable apertures before each scattered light collecting detector, reduces significantly stray light from entering each such detector.

Abstract: A new method is presented for measuring the molecular properties of an unfractionated solution of macromolecules. Sample aliquots spanning a range of concentrations are injected sequentially into a stream of solution and flow towards the detectors. Each aliquot produces, thereby, an effective “peak” whose elements correspond to different concentrations of the diluted aliquot. The weight averaged molar mass, the mean square radius, and the second virial coefficient of the macromolecules in solution are derived from an analysis of the angular and concentration dependence of the scattering signals throughout the corresponding peaks. In contrast to earlier on-line methods, better accuracy is achieved, while using a smaller quantity of sample. A similar method for determining cross virial coefficients between two distinct species of macromolecules is also presented.

Abstract: The invention relates to a spectroscopy system and improved membrane formation techniques. The system has at least one light source operable to generate a source beam and a prism having a rear surface. A support block is disposed on the rear surface of the prism. The support block is formed with at least one sample well having a center and defines a substantially vertical rear cell surface having a center. The source beam is aimed at the sample well. A syringe filled with a membrane solution and having a needle with a distal end disposed in front of the sample well. The distal end is aimed at a point above the center of the rear cell surface. The syringe is operable to eject a steady stream of membrane solution from the needle onto the circular rear cell surface thereby forming a membrane defining at least a portion of a layer under test. The membrane has a substantially uniform thickness that covers substantially the entire rear cell surface.

Abstract: A new type of asymmetric flow field flow fractionator, A4F, is described permitting improved sample fractionation means by providing a range of available channel lengths within the same A4F unit. With such an apparatus, samples may be optimally separated by performing such fractionations as a function of channel length. The ability to vary channel length within the same A4F unit has heretofore been unavailable.

Abstract: A spectroscopy system has at least one light source operable to generate a source beam and a prism having a rear surface. A support block is disposed on the rear surface of the prism. The support block is formed with at least one sample well having a center and defines a substantially vertical rear cell surface having a center. The source beam is aimed at the sample well. A syringe filled with a membrane solution and having a needle with a distal end disposed in front of the sample well. The distal end is aimed at a point above the center of the rear cell surface. The syringe is operable to eject a stead stream of membrane solution from the needle onto the circular rear cell surface thereby forming a membrane defining at least a portion of a layer under test. The membrane has a substantially uniform thickness that covers substantially the entire rear cell surface. The system also includes a detector operable to detect light that is at least one of reflected and scattered by the layer under test.

Abstract: Chromatographic separations are often characterized by multiple detectors through which the sample flows serially. As the sample flows between detectors, it becomes progressively diluted due to mixing and diffusion. This phenomenon is traditionally called interdetector “band broadening” and often results in significant distortion of the sample's derived physical properties such as molar mass. This method to characterize the broadening present in a chromatographic system, and an algorithm whereby the narrow peaks of the upstream detector are numerically broadened so they can be compared to the broadened peaks of the downstream detector, is described. Although the technique results in some loss of resolution, its stability and generality allow it a broad range of application. Examples are presented for data collected by dRI, MALS, UV, and viscometric detectors.

Abstract: Chromatographic separations are often characterized by multiple detectors through which the sample flows serially. As the sample flows between detectors, it becomes progressively diluted due to mixing and diffusion. This phenomenon is traditionally called interdetector “band broadening” and often results in significant distortion of the sample's derived physical properties such as molar mass. A method to characterize the broadening present in a chromatographic system, and an algorithm whereby the narrow peaks of the upstream detector are numerically broadened so they can be compared to the broadened peaks of the downstream detector, is described. Although the technique results in some loss of resolution, its stability and generality allow it a broad range of application. Examples are presented for data collected by dRI, MALS, UV, and viscometric detectors.

Abstract: A bridge viscometer for measuring specific viscosity, ?sp(t), includes four capillaries, a delay volume, and a pressure transducer. The pressure transducer generates a signal indicative of a pressure differential, ?p(t), as a sample is introduced into the bridge viscometer. The specific viscosity, ?sp(t), of the sample is calculated based on the pressure differential, ?p(t), and a predetermined internal pressure, IP0.

Abstract: A method and apparatus is described by which means molecules in suspension may be characterized in terms of the size and mass distributions present. As a sample solution is separated by centrifugal means, it is illuminated at a particular radial distance from the axis of rotation by a fine, preferably monochromatic, light beam. Despite the high resolution of such devices, a key problem associated with most separators based upon use of centrifugal forces is the difficulty in deriving the absolute size and/or molar mass of the separating molecules. By integrating means to detect light scattered, over a range of scattering angles, from samples undergoing centrifugal separation, molecular sizes in the sub-micrometer range may be derived, even in the presence of diffusion. Adding a second light beam at a displaced rotational angle, preferably of an ultraviolet wavelength, that intersects the sample at the same radial region as the first beam permits determination of the molecular concentration at that region.

Abstract: An improved 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 unique 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.

Abstract: The invention relates to a surface plasmon resonance system method. The system has at least one light source operable to generate a source beam, a prism having a rear surface at least partially coated with a metallic coating and optionally a dielectric layer. At least one layer under test is positioned on the rear surface of the prism. The source beam is directed at the layer under test thereby defining an angle between the source beam and the rear surface of the prism. A detector is operable to detect light that is reflected or scattered by the layer under test. The source beam is directed towards the layer under test at a selected angle. The source beam is also shifted in at least one plane to illuminate a specific portion of the layer under test based on the selected relative angle and the position of the layer under test on the rear surface of the prism. The rear surface of the prism can be illuminated in one-dimensional or two-dimensional array like fashion.

Abstract: 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.

Abstract: A bridge viscometer for measuring specific viscosity, ?sp(t), includes four capillaries, a delay volume, and a pressure transducer. The pressure transducer generates a signal indicative of a pressure differential, ?p(t), as a sample is introduced into the bridge viscometer. The specific viscosity, ?sp(t), of the sample is calculated based on the pressure differential, ?p(t), and a predetermined internal pressure, IP0.

Abstract: An improved differential refractometer incorporating a photodetector array is disclosed. Using a multi-element photo array provides the basis for measurement of differential refractive index values with a heretofore unattainable combination of sensitivity of measurement and concurrent range of measurement. Within the large dynamic range attainable, the detector structure provides equal sensitivity irrespective of deflection within the range. The transmitted light beam is tailored to provide a spatial variation of the light intensity at the array improving thereby the precision of measurement of its displacement. This in turn results in improved precision in the reported differential refractive index and in the calculation of the differential refractive index increment dn/dc. Integrating the detector array into the flow cell structure of the parent case results in a detector of exceptional sensitivity and range for sample quantities far smaller than required by conventional differential refractometers.

Abstract: 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 flow 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.

Abstract: A method and apparatus are described by which previously identified aerosol particles that may have precipitated onto surfaces and/or into specific physical regions are detected, removed from said regions, and stored for later examination or destruction. The method includes means such as an ultrasonic probe to loosen said aerosol particles from the surfaces to which they have precipitated and then withdraw them into an optical read head for measurement. The optical read head illuminates each particle, previously diluted and entrained in a sheath flow, as it passes therethrough with a fine beam of light such as produced by a laser. The scattered light produced by each such particle is collected over a range of scattering angles, converted into a digital representation for each value collected, and stored in a computer means.