Abstract: One or more homogenizing elements are employed in a flow through, multi-detector optical measurement system. The homogenizing elements correct for problems common to multi-detector flow-through systems such as peak tailing and non-uniform sample profile within the measurement cell. The homogenizing elements include coiled inlet tubing, a flow distributor near the inlet of the cell, and a flow distributor at the outlet of the cell. This homogenization of the sample mimics plug flow within the measurement cell and enables each detector to view the same sample composition in each individual corresponding viewed sample volume. This system is particularly beneficial when performing multiangle light scattering (MALS) measurements of narrow chromatographic peaks such as those produced by ultra-high pressure liquid chromatography (UHPLC).

Abstract: An improved version of the capillary bridge viscometer that compensates for the effect of solvent compressibility is disclosed. A novel, yet simple and inexpensive modification to a conventional capillary bridge viscometer design can improve its ability to reject pump pulses by more than order of magnitude. This improves the data quality and allows for the use of less expensive pumps. A pulse compensation volume is added such that it transmits pressure to the differential pressure transducer without sample flowing there through. The pressure compensation volume enables the cancelation of the confounding effects of pump pulses in a capillary bridge viscometer.

Abstract: A method to filter out pump pulses from data collected with a chromatography system is disclosed. Baseline data is collected as a pump delivers solvent to an analytical instrument, which may be the IP signal of a capillary bridge viscometer. A Fourier transform is applied to the data to generate the power spectrum of the baseline signal. Fundamental and harmonic frequencies are determined and a comb filter is constructed therefrom and applied to sample collected from all of the affected instruments. The comb filter may be correlated to the pump and flow rate and stored in data analysis software or database. Other systems using other pumps may also generate associated comb filters, and the resulting filters and the flow rates at which they were generated may be stored in a database accessible to the data analysis software.

Abstract: Methods and apparatus for controlling interdetector band broadening during the analysis of a sample injected into a chromatography system. A column flow is diluted with a dilution flow after the sample exits the chromatography system, and the diluted sample is analyzed by one or a combination of analysis instruments such as a light scattering detector, refractive index detector, an ultraviolet absorption detector.

Abstract: A pressure transducer is disclosed wherein no wetted areas have been welded. A cavity is milled into the back of each of the blocks of a material which will make up the body of the transducer. Pickup coils are placed into these cavities and are held in place generally with epoxy cement. With the coils mounted within the sensor body, the surface which will be exposed to the sample or reference fluids is comprised of a single, solid material with no welding joints. Further, as the sensor block half is made of a single, solid material, fluid fitting connections may be machined directly into the body. The pickup coil placed within the improved sensor body may be wound on an open frame of nickel superalloy (NiSA). Another embodiment involves coating or encapsulating the sensing membrane within a soft, non-magnetic material protecting it from corrosion.

Abstract: An electrode for use in instruments capable of measuring the electrophoretic mobility of particles in solution is disclosed. The electrode is comprised of an inexpensive support member, generally made of titanium, onto a flat surface of which has been connected, generally by microwelding, a flat electrically conductive but chemically inert foil member, preferably platinum. A uniform texture can be generated on the exposed surfaces of the electrode by various means including tumbling the electrode with an abrasive. An oxide layer can be generated on the support member by soaking the composite electrode in an appropriate medium, protecting the exposed surface of the support member from fluid contact with the sample solution, while the foil member, unaffected by the oxidation process, is able to contact the sample solution.

Abstract: A method and apparatus are disclosed which enable the reduction of sample carryover in the measurement cell of an analytical instrument. A sample cell is defined as a region sealed within a first o-ring. Located outside of said sample region is another o-ring which seals and defines a seal wash region as the region between the first and second o-ring. After the fluid sample is injected into the measurement cell a pressure is applied to the seal wash region, forcing the first o-ring to the innermost extent of the groove in which it sits, expelling any trapped solvent and removing from the measurement cell a significant dead volume while the cell is flushed and prepared for a new sample and corresponding measurement.

Abstract: A method and apparatus is disclosed for suppression of bubbles in an optical measurement cell. A measurement cell is filled with a fluid sample. Valves connected through plumbing connections to the cell are operated such that any flow in and out of the cell is stopped. A pressure source is then applied through a valve and flow impedance mechanism to the liquid contained within the cell, causing any bubbles contained or generated within the cell to be dissolved back into solution or reduced in size such that optical measurements taken of the sample are more accurate and free of interference with the measurement beam and of measured stray light. Possible pressure sources include compressed gas, a piston, and a constant flow-rate pump.

Abstract: A cuvette for use with light scattering detectors is disclosed. A trough or moat within the cuvette can be filled with solvent which is not in fluid contact with the sample to be measured. This solvent moat creates saturated vapor pressure in the chamber preventing evaporation from the sample when the cuvette is capped. The cuvette itself may be made of an inexpensive polymer which can be polished to high optical quality while still being moldable in complex forms capable of enabling further utility, such as extra griping surfaces, identification tabs allowing the detection instrument to determine the cuvette model, and various sample chamber forms. The novel cuvette may have extremely small sample volumes, while allowing significant overfill of the measurement chamber, improving ease of sample loading. The polymers used may be relatively inexpensive, and therefore the cuvette can generally be discarded after a single use.

Abstract: A pressure transducer is disclosed wherein no wetted areas have been welded. A cavity is milled into the back of each of the blocks of a material which will make up the body of the transducer. Pickup coils are placed into these cavities and are held in place generally with epoxy cement. With the coils mounted within the sensor body, the surface which will be exposed to the sample or reference fluids is comprised of a single, solid material with no welding joints. Further, as the sensor block half is made of a single, solid material, fluid fitting connections may be machined directly into the body. The pickup coil placed within the improved sensor body may be wound on an open frame of nickel superalloy (NiSA). Another embodiment involves coating or encapsulating the sensing membrane within a soft, non-magnetic material protecting it from corrosion.

Abstract: Methods and apparatus for controlling interdetector band broadening during the analysis of a sample injected into a chromatography system. A column flow is diluted with a dilution flow after the sample exits the chromatography system, and the diluted sample is analyzed by one or a combination of analysis instruments such as a light scattering detector, refractive index detector, an ultraviolet absorption detector.

Abstract: An electrode for use in instruments capable of measuring the electrophoretic mobility of particles in solution is disclosed. The electrode is comprised of an inexpensive support member, generally made of titanium, onto a flat surface of which has been connected, generally by microwelding, a flat electrically conductive but chemically inert foil member, preferably platinum. A uniform texture can be generated on the exposed surfaces of the electrode by various means including tumbling the electrode with an abrasive. An oxide layer can be generated on the support member by soaking the composite electrode in an appropriate medium, protecting the exposed surface of the support member from fluid contact with the sample solution, while the foil member, unaffected by the oxidation process, is able to contact the sample solution.

Abstract: A method and apparatus is disclosed for suppression of bubbles in an optical measurement cell. A measurement cell is filled with a fluid sample. Valves connected through plumbing connections to the cell are operated such that any flow in and out of the cell is stopped. A pressure source is then applied through a valve and flow impedance mechanism to the liquid contained within the cell, causing any bubbles contained or generated within the cell to be dissolved back into solution or reduced in size such that optical measurements taken of the sample are more accurate and free of interference with the measurement beam and of measured stray light. Possible pressure sources include compressed gas, a piston, and a constant flow-rate pump.

Abstract: A cuvette for use with light scattering detectors is disclosed. A trough or moat within the cuvette can be filled with solvent which is not in fluid contact with the sample to be measured. This solvent moat creates saturated vapor pressure in the chamber preventing evaporation from the sample when the cuvette is capped. The cuvette itself may be made of an inexpensive polymer which can be polished to high optical quality while still being moldable in complex forms capable of enabling further utility, such as extra griping surfaces, identification tabs allowing the detection instrument to determine the cuvette model, and various sample chamber forms. The novel cuvette may have extremely small sample volumes, while allowing significant overfill of the measurement chamber, improving ease of sample loading. The polymers used may be relatively inexpensive, and therefore the cuvette can generally be discarded after a single use.

Abstract: A method is disclosed for measurement of the electrophoretic mobility of particles in solution. A sample 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 provide a first-principle measurement of the electrophoretic mobility of the scattering particles.

Abstract: A method and apparatus are disclosed for measurement of the electrophoretic mobility of particles in solution. A sample 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 provide a measurement of the electrophoretic mobility of the scattering particles.

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 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.