Abstract: A tandem mass spectrometer is disclosed having a collisional damping cell that slows down and adapts an ion beam, from a time-of-flight mass spectrometer (TOF MS) to a second mass spectrometer, preferably an orthogonal TOF MS. The cell provides a substantial damping of the energy of the ions in multiple collisions with a gas. An RF-only quadrupole is used to spatially focus the ion beam in the collision cell. As result, the operation of second mass spectrometer can be decoupled from the rest of the instrument, or in some cases with the energy being sufficiently damped the pulsed nature of the primary ion beam can be partially preserved and used to enhance the sensitivity of the second mass spectrometer. An ion selector passes only stable parent ions of interest, thereby introducing ions into the cell at a well controlled low energy. The ion beam can be injected into the collision cell with or without separation as well as with or without fragmentation.

Abstract: A tandem time-of-flight mass spectrometer is described. The spectrometer includes a pulsed source of ions that focuses a packet of ions substantially within a predetermined mass-to-charge ratio range onto a focal plane in a flight path of the ions. An ion selector receives the focused packet of ions and selects ions substantially within the predetermined mass-to-charge ratio range and rejects substantially all other ions. An ion fragmentor that fragments a fraction of the selected ions is positioned in the flight path of the selected ions. A pulsed ion accelerator that accelerates the selected ions and fragments thereof is positioned in a flight path of the selected ions and fragments thereof after the ion fragmentor. An electrode is positioned in the flight path of the accelerated selected ions and fragments thereof after the pulsed ion accelerator. In operation, the electrode is biased with a time varying bias voltage that increases the energy of the fragments relative to the selected ions.

Abstract: A mass spectrometer instrument for determining the molecular weight of labile molecules of biological importance, in particular heavy molecules, such as proteins, peptides or DNA oligomers, is disclosed. The instrument includes a MALDI ion source that is enclosed in a chamber with an inlet for admitting a gas and an ion sampling aperture for limiting gas flow from the chamber. The elevated pressure of the source in the range from 0.1 to 10 torr causes low energy collisions between the gas and the ions that can cause rapid collisional cooling of the excited ions, thereby improving the stability of the produced ions. The formation of clusters of ions (e.g., protein ions) with matrix materials is broken without fragmenting the ions by increasing the downstream gas temperature to between 150 and 250° C.

Abstract: A highly sensitive multiple stage (MSn) mass spectrometer is disclosed, capable of eliminating losses of ions during the isolation stage. Ions of interest are isolated (by m/z value) without rejecting ions of other m/z values, permitting the selected ions to be dissociated, while the rest of the ion population is available for subsequent isolation, dissociation and analysis of fragment ions. One preferred instrument includes a pulsed ion source coupled with a linear array of mass selective ion trap devices, at least one trap being coupled to an external ion detector. Each ion trap is configured with a storing cell for ion trapping interspersed between a pair of guarding cells, all aligned along their z axis. Radio frequency (RF) and direct current (DC) voltages are applied to electrodes of the ion trap device to retain ions within the storing cells.

Abstract: A tandem time-of-flight mass spectrometer is described. The spectrometer includes a pulsed source of ions that focuses a packet of ions substantially within a predetermined mass-to-charge ratio range onto a focal plane in a flight path of the ions. An ion selector receives the focused packet of ions and selects ions substantially within the predetermined mass-to-charge ratio range and rejects substantially all other ions. An ion fragmentor that fragments a fraction of the selected ions is positioned in the flight path of the selected ions. A pulsed ion accelerator that accelerates the selected ions and fragments thereof is positioned in a flight path of the selected ions and fragments thereof after the ion fragmentor. An electrode is positioned in the flight path of the accelerated selected ions and fragments thereof after the pulsed ion accelerator. In operation, the electrode is biased with a time varying bias voltage that increases the energy of the fragments relative to the selected ions.

Abstract: A process and system are provided for forming and transporting precise small volumes of liquid samples by means of controlled gas pressures. As the controlled gas pressures are changed at a multiplicity of control points in the fluid circuit, transitions take place involving the transport of small liquid samples. This transport is arrested by the geometry of the fluid circuit to produce a new state, which state remains stable until another transition is initiated by a change in the multiplicity of controlled gas pressures. Various combinations of control elements are described for effecting formation of fixed liquid volumes, transporting, mixing, and removing entrained bubbles from small liquid samples.

Abstract: A hollow fiber membrane module and its method of manufacture are disclosed wherein the module is fabricated utilizing superior hollow fiber materials, namely high molecular weight (i.e. molecular weight>500,000 Daltons) polymers. In a preferred embodiment, the hollow fibers are fabricated from ultra-high molecular weight polyethylene (UPE). An array of UPE hollow fiber membranes is contacted with an extrusion of molten thermoplastic polymer at a contact temperature which is higher than the UPE membrane polymer. This high temperature application of sealing polymer does not collapse or otherwise deform the lumen of the hollow fiber, while assuring that the polymer can thus be applied with sufficiently low viscosity to provide adequate penetration around the individual fibers of the array to form an integral seal thereabout.

Abstract: A composite porous membrane is provided which comprises a porous membrane substrate having an average pore size between 0.01 and 10 microns formed of a first polymer which is coated over its entire surface with a crosslinked second polymer. The second polymer is dissolved in a solvent with a free radical polymerization initiator in the absence of a crosslinking agent. The second polymer is crosslinked in situ and rendered insoluble by mild heating and/or exposure to ultraviolet light.

Abstract: A vacuum filter device is disclosed which includes a filter body which is adapted to receive in fluid-fight, sealed relationship a pair of closed containers for solutions to be filtered by a membrane filter positioned within the filter body. A vacuum port in the filter body communicates with the downstream side of the membrane and a venting passageway also located in the filter body communicates with the closed sample container to serve as a vent to atmospheric pressure. The venting passageway is made of an air permeable hydrophobic filter or preferably a small enough opening to prevent the sample solutions from leaking out of the device during normal use.

Abstract: A manifold segment is provided for tangential flow filtration apparatus. The manifold segment includes a fluid feed conduit, a retentate conduit, a filtrate inlet and a filtrate outlet. An adaptor manifold is provided which directs filtrate from the manifold segment into a tangential flow filtration module and directs filtrate from the module into the manifold segment. Filtrate introduced into the tangential flow filtrate module reduces pressure drop across a filter layer in the module.

Abstract: A membrane-based tangential flow filtration system is disclosed which includes optimized performance capabilities by taking into account the variety of flux and component passage behavior occurring during filtration processing. The system maximizes the recovery of a desired component in the permeate from a sample solution containing two or more components, in minimum time and with minimum filtration area, by optimizing the mass flux of the desired component by continuously controlling the rate of addition of a diafiltrate solution to the system to maintain the optimum balance of component concentrations.

Abstract: In an electrodeionization apparatus having a cathode compartment and an anode compartment for removing ions from a liquid under the influence of a voltage, the cathode compartment includes electron conductive particles such as metal particles and/or carbon particles.

Abstract: A rapid, highly sensitive determination, in-situ, of the integrity and/or pore size distribution of a porous membrane structure (e.g. a pleated membrane filter cartridge) is disclosed. The identification of the integrity and/or pore size characteristics involves interpreting the residence time distribution (RTD) of the membrane structure under test and includes using a tracer gas in mixture with a carrier gas as part of a diffusion or bubble-point test. The tracer gas mixture exiting the downstream surface of the membrane becomes moisturized and is excited with a pulsed (or otherwise modulated) light source at a wavelength corresponding to the absorption line of the tracer gas. The frequency of modulation is chosen such that the tracer gas preferentially generates a photo-acoustic emission while the emission due to the absorption of water present is suppressed. The detected pressure pulse is processed to produce electrical signals indicative of the concentration of tracer gas that passes through the membrane.

Abstract: A process for potting hollow fibers within a body is disclosed wherein a bundle of hollow fibers is formed within a hollowed portion of the body such that the fibers are substantially aligned and uniformly spaced. A molten thermoplastic composition is dispensed into the body at a contact temperature below the melting point of the hollow fibers. The bundle and the body are both at a temperature which is sufficiently low enough to cause solidification of the molten composition substantially upon contact with the bundle. A pressure differential is applied to the body to assist the flow of the thermoplastic composition around each of the hollow fiber elements such that the bundle and the interior of the hollowed portion of the body are encapsulated by the thermoplastic composition thereby assuring reliable sealing between the hollow fiber elements and the interior of the hollowed portion of the body.

Abstract: A device for conducting biological analysis, such as cell culture, is disclosed having improved contamination prevention features. In a preferred embodiment, a microwell membrane plate for cell analysis is adapted to be inserted into a shallow rectangular tray with elevated side walls which form a single large reservoir for holding an appropriate liquid used in cell growth and analysis. The side surfaces of the tray include a raised ridge extending about the entire periphery of the tray. A series of uniform-height steps formed on the ridge serve as support for the microwell membrane plate when inserted into the tray and also create a narrow capillary gap between the plate and the tray. A ledge extending laterally from the base of the ridge forms a second, wider gap when the microwell membrane plate is inserted into the tray.

Abstract: A composite porous article is formed from a porous polymeric substrate having its entire surface modified with a cross-linked polymer which results in a hydrophobic and oleophobic surface. The composite retains substantially all of the other original properties of the substrate. The cross-linked polymer is formed in situ on the polymeric substrate from a reactant system comprising an ethylenically unsaturated monomer having at least one fluoroalkyl group, a cross-linker, and, if needed, a polymerization initiator, dissolved in a polar solvent system. The porous substrate saturated with the reactant system is exposed to a suitable energy source to effect polymerization and cross-linking of the monomer.

Abstract: A method for covalent immobilization of a carbohydrate molecule with an oppositely charged surface, comprising the steps of adsorbing the carbohydrate molecule to the oppositely charged surface in proximity to reactive moieties bound to the charged surface; and next activating the bound moiety sufficiently for covalent attachment to the adsorbed carbohydrate molecule. Also disclosed is a hydrophobic microporous polymer membrane coated with a cross-linked, cationic polymer having fixed charges thereon, the coating having enhanced epoxide content for covalent immobilization of the oppositely-charged carbohydrate molecule. A novel method for sequencing carbohydrates by covalent attachment of a carbohydrate conjugate to the membrane, and subsequent treatment with glycosidases, is also presented.

Abstract: A composite ultrahigh molecular weight polyethylene microporous membrane is provided having cation exchange capacity. The membrane is useful for removing metal ions from acidic aqueous solutions.

Abstract: A system and process for analyzing a liquid sample is disclosed which includes an ultrasonic nebulizer capable of vibrating at a frequency between about 50 Khz and 760 Khz for converting the liquid sample to a liquid aerosol. The liquid aerosol is heated at a pressure of at least atmospheric pressure to evaporate solvent in the aerosol and to form a solid aerosol. The solid aerosol is separated from the evaporate solvent and the solid aerosol is directed into an electron impact ionizer and a mass spectrometer where it is analyzed.

Abstract: A portion of a hydrophobic membrane, having an unknown concentration of a first molecule in a sample bound to its surface, is incubated with a second molecule that selectively binds to the first molecule so as to allow determination of its concentration. The membrane is first coated with the first molecule and then dried to render the uncoated portion nonwettable with water. The labeled second molecule selectively binds to the first molecule in the absence of a blocking agent on the membrane.