Abstract: A method and apparatus is disclosed for measuring the refractive index difference between a reference and sample liquid based on an interferometric design. The resultant device has an almost unlimited range of operation in contrast to a conventional interferometric refractometer of the so-called polarization type whose dynamic range is restricted to a relatively narrow range of refractive indices. The measurement of the refractive index difference between a sample and reference cell is achieved by measuring the angle through which the plane of polarization of a combined beam has rotated. For the conventional device, this angle is restricted to about .pi. radians which corresponds to a half wavelength shift between the reference and sample components of said combined beam. The extended range device disclosed permits this angle to be tracked and measured accurately over many rotations.

Abstract: A capillary tube used to transfer a liquid sample into a detection cell following separation by a chromatographic system is modified by plugging or otherwise severely restricting its flow. Near its plugged end, said tube is drilled to provide a plurality of holes or ports perpendicular thereto and penetrating to the central flowing core of said tube so as to direct outflow from the tube perpendicularly therefrom. The outer diameter of this somodified capillary tube is selected to be of a size comparable to, though smaller than, the detection cell diameter into which it transfers the flowing sample. In this manner, fluid transferred into a detection cell by said modified capillary tube will be split into a plurality of smaller streams flowing outwardly therefrom and striking the adjacent detector cell walls almost immediately.

Abstract: A capillary tube used to transfer a liquid sample into a detection cell following separation by a chromatographic system is modified by plugging or otherwise severely restricting its flow. Near its plugged end, said tube is drilled to provide a plurality of holes or ports perpendicular thereto and penetrating into the central flowing core of said tube so as to direct outflow from the tube perpendicularly therefrom. The outer diameter of this so-modified capillary tube is selected to be of a size comparable to, though smaller than, the detection cell diameter into which it transfers the flowing sample. In this manner, fluid transferred into a detection cell by said modified capillary tube will be split into a plurality of smaller streams flowing outwardly therefrom and striking the adjacent detector cell walls almost immediately.

Abstract: A modified light scattering cell, and associated method, whereby an eluant of very small dimension transverse to its direction of flow is entrained successively by two sheath flows and presented to a fine light beam that illuminates the entrained eluant as it flows through the light beam. The light scattered by the entrained eluant is collected by detectors outside of a transparent flow cell enveloping the sheath flow entrained eluant. The windows of the transparent flow cell through which the light beam enters and leaves are far removed from the scattering eluant and kept clear of eluant-contained particles by means of flow components that will form subsequently one of the eluant sheath flows employed. The eluant source is typically from a fine capillary such as found in capillary electrophoresis, capillary hydrodynamic fractionation, and flow cytometry applications.

Abstract: This invention describes a method by which the precision of the reported molecular weights and radii of chromatographically separated molecules may be estimated. By suitably analyzing both the baseline and peak regions of a chromatogram, one may determine standard deviations of the signals from the various chromatographic detectors used in the analysis. This procedure yields standard deviations of the calculated values of molecular weight and root mean square radius of the separated molecules, as well as standard deviations of the calculated moments of the distribution of molecules. These standard deviations provide an estimate of the precision of the measurements.

Abstract: The incorporation of certain classes of solid state lasers into light scattering instrumentation is desirable because of their compact structure. However, mode hopping often causes the output power produced by such lasers to be unstable. The frequency of such output power fluctuations is often so broad that output power monitoring means, characteristic of the light scattering instrumentation into which such lasers are incorporated, cannot track accurately the temporal output power fluctuations. A method, and associated apparatus, is described whereby the laser drive current is modulated at low frequency and amplitude sufficient to induce and thereby control mode hopping so as to permit accurate measurement of the ratio of light scattering signals to the laser output power.

Abstract: This invention measures the change of a fluid's refractive index with changes in the concentration of a solute dissolved therein. A determination of this quantity is required for many types of chemical analyses especially for the determination of molecular weights. The fluid is restricted to a thin capillary channel (11) within a transparent material (10) such as glass. A fine light beam (18) is incident upon the capillary at an angle close to the critical angle. The axes of the light beam and capillary intersect at a point within the capillary defining thereby a plane within which the refraction occurs. A position sensing (27) device is placed to measure the displacement of the beam twice refracted during its passage through the capillary channel, said measure being used to generate a numerical value of the ratio dn/dc, where dc is the change of solute concentration resulting in a change dn of the solution's refractive index.

Abstract: A method is disclosed based on a single injection into a modified HPLC line by which means the light scattering data required to characterize the injected molecular suspension in terms of its weight-average molecular weight, z-average square radius, and second virial coefficient may be measured and collected. The method requires that a molecular suspension at a fixed concentration be prepared and injected into a flowing stream of pure solvent following standard liquid chromatographic procedures. The sample is then passed directly to a mixing chamber whose volume is preferably several times that of the injected volume. After this mixing, the sample enters a light scattering detector where its absolute scattering intensity as a function of angle is measured for each eluting fraction. From the data so-recorded, the concentration of each fraction may be calculated and a Zimm plot may be made to yield the required molecular parameters.

Abstract: A differential refractometer is described capable of measuring the refractive index charge, dn, of a transparent fluid corresponding to a change dc of the concentration of a solute in said fluid. The fluid is restricted to a fine capillary within a transparent material such as glass. Incident upon the capillary at an angle close to the critical angle is a fine light beam incident from said transparent material. The axes of the light beam and capillary intersect at a point within the capillary defining thereby a plane within which the refraction occurs. A position sensing device is placed to measure the displacement of the beam twice refracted during its passage through the capillary, said measure being used to generate a numerical value of the ratio dn/dc.

Abstract: The light intensity incident on a scattering sample contained in a scattering cell is monitored by simultaneous measurements of the light incident on the cell before entering it and the light transmitted through the cell after leaving it. Means to monitor the product of these signals is disclosed and how this product is related to the actual incident intensity at the sample is explained. The invention is presented in the context of the scattering cell of the parent application.

Abstract: A highly collimated light beam, such as produced by a laser, is coupled by optical means directly onto a semi-opaque object such as a human breast. The light transmitted and scattered therein is collected at a fixed surface element and direction relative to the incident light, and coupled optically into an image intensifier, preserving the spatial intensity variations passing through said fixed surface element. The intensified image is then collected on an array of detector elements which digitizes and then transfers said preserved image into memory means where it is processed to characterize the interior of said object. This invention has particular application to the early detection of breast cancer.

Abstract: An apparatus and process are described for the characterization and/or identification of suspensions of microparticles based upon the measurement of certain optical observables produced as the suspension is illuminated by a beam of light, or other electromagnetic radiation. Selected observables calculated from the scattered radiation detected by a plurality of detectors surrounding the thus-illuminated suspension are then used to recall specific maps, from a computer memory means, one for each observable. The common overlap region of said map yields characterizing or identifying particle suspension physical parameters.

Abstract: The measurement of the scattering properties of very small particles by electro-optical means generally requires the use of an intense, though highly spatially inhomogeneous, light source such as a laser. Many instruments require, therefore, that the intersection of the particle stream with the illumination source be precisely regulated so that the flux incident on the particle be known accurately. A method and apparatus are described by which means the absolute intensity of the light incident on the particle need not be known. A special structure and measurement process are described by which means small particles are differentiated from larger particles grazing the illumination beam.