Abstract: 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.

Abstract: A new method is presented for measuring the molecular properties of an unfractionated solution of macromolecules. Sharing some similarities with the standard Zimm plot technique, the method begins with the preparation of several sample aliquots spanning a range of concentrations. The aliquots are then injected sequentially into a stream such as provided by a liquid chromatograph. Each aliquot produces, thereby, an effective “peak” whose elements correspond to different concentrations of the diluted aliquot. By analyzing the angular and concentration dependence of the scattering signals throughout the corresponding peaks, the weight averaged molar mass, the mean square radius, and the second virial coefficient may be derived. In contrast to earlier on-line methods, better accuracy is achieved, while using a smaller quantity of sample.

Abstract: An aerosol hazard classification and early warning network is composed of a large number of detector and analysis units, called “detector stations,” which are deployed throughout a region to be warned of a potentially hazardous aerosol intrusion. Such aerosol threats may originate from fires, volcanic eruptions, or overt releases of biological and chemical agents dispersed in aerosol form. Among the former are the characteristic toxic aerosols released during refinery fires or explosions. The latter biological agents include bacterial spores, lyophilized bacterial cells, and virus preparations, whereas chemical agents might include various forms of nerve gasses and other anti-personnel gasses such as mustard, all commonly deployed in aerosol form.

Abstract: Optical flow cells used, for example, for making scattered light measurements on liquid borne samples, are often affected by particulate materials that adhere to the internal optical surfaces. These contaminating particulates can cause distortions of the scattered light signals to be measured from the illuminated samples within the flow cell. Such particulates are difficult to remove, especially while the cell is assembled. A method for dislodging and removing such particulate contaminants is described that consists of attaching externally to the flow cell an ultrasonic generator whose frequency of operation may be tuned to couple most effectively with the internal structures of the flow cell itself. Such ultrasonic coupling must be accompanied by an impressed flow through the cell that can remove from the cell particulates that have been dislodged. In order to assure good mechanical action, the impressed ultrasonic frequency is swept over a range of frequencies.

Abstract: Optical flow cells used, for example, for making scattered light measurements on liquid borne samples, are often affected by particulate materials that adhere to the internal optical surfaces. These contaminating particulates can cause distortions of the scattered light signals to be measured from the illuminated samples within the flow cell. Such particulates are difficult to remove, especially while the cell is assembled. A method for dislodging and removing such particulate contaminants is described that consists of attaching externally to the flow cell an ultrasonic generator whose frequency of operation is swept initially over a range that would couple most effectively with the internal structures of the flow cell itself. The optimal frequency is then selected automatically by monitoring the power dissipated and fixing the ultrasonic frequencies of operation at those values corresponding to regions of maximum power dissipation.

Abstract: A method is described to determine the 2nd virial coefficient of an ensemble of molecules dissolved in a selected solvent. Two distinct classes are described: monodisperse and polydisperse molecules. If the molecules are monodisperse, they must be prepared for a chromatographic separation and suitable columns selected. Following standard chromatographic separation procedures such as exemplified by the method of size exclusion chromatography, the sample passes through the separation columns, a multiangle light scattering detector, and a concentration detector. The effect of the columns is to produce a concentration profile of said sample that appears as a peak as it passes through the light scattering and concentration detectors. For each elution interval, &ngr;i, a corresponding concentration value ci and set of excess Rayleigh ratios Ri(&thgr;j) is measured for each scattering angle &thgr;j.

Abstract: An improved channel for separation of molecular and particulate samples by means of electrical field flow fractionation (FFF) is disclosed. The electrodes therein are made of metal oxide coated flat glass plates and permit the achievement, thereby, all of the seven most desirable features for such an electrical FFF channel, viz. 1) hardness, 2) flatness, 3) smoothness, 4) chemical inertness, 5) durability (does not generate particles), 6) high conductivity, and 7) transparency. In addition, the design of the clamping plates permits high precision in aligning the electrodes for parallelism.

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: 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: 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.

Abstract: A sample cell is described that permits the measurement of the light scattering properties of very small liquid-borne samples with negligible background interference form the illumination source. A technique is described whereby the cell construction permits the measurement of the illumination intensity at the scattering sample itself, permitting, thereby, the normalization of each detected scattered signal. The cell structure and detection method incorporated therein also permit measurement of extremely small angle scattered intensities without interference of the incident light beam itself.