Abstract: Achieving high conversion of large multiply charged biological ions into low charge states involves requirements difficult to reconcile when high transmission and good spray quality (resulting in narrow mobility distributions) are sought. These multiple goals are achieved in this invention by partially isolating different regions from each other with electrostatic barriers relatively transparent to ions, such as metallic grids. One such region requires high electric fields for ion generation. The other region, used for ion recombination, is approximately field-free. In an alternative arrangement intended for charge reduction in sub-millisecond times, two sources of ions with opposite polarities are placed contiguously, with a grid in between. In all cases, ion crossing through grids into field free regions is effectively driven by space charge.

Abstract: Achieving high conversion of large multiply charged biological ions into low charge states involves requirements difficult to reconcile when high transmission and good spray quality (resulting in narrow mobility distributions) are sought. These multiple goals are achieved in this invention by partially isolating different regions from each other with electrostatic barriers relatively transparent to ions, such as metallic grids. One such region requires high electric fields for ion generation. The other region, used for ion recombination, is approximately field-free. In an alternative arrangement intended for charge reduction in sub-millisecond times, two sources of ions with opposite polarities are placed contiguously, with a grid in between. In all cases, ion crossing through grids into field free regions is effectively driven by space charge.

Abstract: Improvements are provided in the detection of atmospheric vapors by ionizing them near ambient pressure, and analyzing them as ions. Lowest detection limits of parts per quadrillion (ppq) concentrations are enabled by a combination of improvements, including the use of a filter to remove occasional intense signal from explosive particles. Several sources of chemical background are identified and solutions for their reduction or elimination are presented. Gains in response time may be achieved by operating at elevated temperature. When the ionizer is an electrospray source, the use of high boiling point solvents is indicated. An increased selectivity is achieved by operating a differential mobility analyzer (DMA) in series with a mass spectrometer. However, ppq sensitivities require various improvements in the DMA system including a special coupling to the ionizer, controlling the temperature in the DMA pump circuit, avoidance of induction on the DMA electrodes from heating devices, etc.

Abstract: A rapid method of volatile analysis and interpretation is taught enabling inferences on the surrounding environment as sophisticated as commonly achieved by dogs via olfaction. The method is based on rapid analysis of vapors released by persons or other organisms into a gas, correction of said analysis due to competing ambient volatiles, extraction of abundance patterns of certain preselected metabolites present in said vapor analysis, and classification of said persons or organisms by comparison of said abundance patterns with preestablished standard metabolite patterns. A preferred approach for rapid analysis involves an atmospheric pressure ionization, such as an electrospray cloud, followed by a mass spectrometer with an atmospheric pressure source. A preferred method for background correction is subtraction of the background signal from the sample signal when both are ionized at similar humidity levels. A preferred comparison pattern involves the abundance of fatty acids and other common metabolites.

Abstract: The present invention is based on the observation that radio frequency (RF) electric fields in multi-pole lenses with small rod diameters in the range of 1 mm enables strongly concentrating ions suspended in a gas at pressures much higher than previously used for ion manipulation, including atmospheric pressure. Other lens configurations are described, including one based on the funnels of U.S. Pat. No. 6,107,628, and another on the coiled wire system of Hutchins et al. (1999). The finding provides a method to increase the concentration of ions transmitted to mass spectrometers and other analyzers, both from volatile or involatile species in solution, hence increasing their analytical sensitivity. It also enables improved charging efficiencies of neutral volatile species existing in the gas phase.

Abstract: Improvements are provided in the detection of atmospheric vapors by ionizing them near ambient pressure, and analyzing them as ions. Lowest detection limits of parts per quadrillion (ppq) concentrations are enabled by a combination of improvements, including the use of a filter to remove occasional intense signal from explosive particles. Several sources of chemical background are identified and solutions for their reduction or elimination are presented. Gains in response time may be achieved by operating at elevated temperature. When the ionizer is an electrospray source, the use of high boiling point solvents is indicated. An increased selectivity is achieved by operating a differential mobility analyzer (DMA) in series with a mass spectrometer. However, ppq sensitivities require various improvements in the DMA system including a special coupling to the ionizer, controlling the temperature in the DMA pump circuit, avoidance of induction on the DMA electrodes from heating devices, etc.

Abstract: A method for fast and accurate recognition of species contained in trace amounts in complex mixtures such as ambient air or biological fluids is taught based on the use in tandem of one or several differential mobility analyzers (DMAs) and possibly also a mass spectrometer (MS), all arranged in series. The two DMAs operate in different regions of the ion drag versus drift velocity curve (for instance, linear versus nonlinear regions), hence separating according to more than one independently discriminating parameters of the ion. Very high discrimination can be achieved even with a single stage of mass spectrometric separation by selecting a narrow range of ions with the DMA, and analyzing them in the MS, first without fragmentation, and then with fragmentation. This process does not require necessarily a tandem MS when fragmentation takes place in the inlet region of the MS.

Abstract: A method and an apparatus are described to focus sharply a wide range of particle sizes for particles suspended in a relatively high flow rate of carrier gas. The particles are accelerated through a continuously converging ladder of smooth contractions, each designed such that: (i) the flow remains laminar at substantial Reynolds numbers; (ii) a certain band of particle sizes is focused in each contraction, without substantial defocusing of larger particle focused in one or several preceding contractions; (iii) the form, length, and ratio of entry to exit diameter of each contraction, as well as the number of consecutive contractions are chosen such that all particles within a given relatively wide range of sizes are focused at the end of the ladder of contraction steps into a relatively narrow focal region. The focusing apparatus coupled to a collector device constitutes a new type of virtual impactor, termed a focusing virtual impactor, which can also be used as a powerful particle concentrator.

Abstract: Prior work on differential mobility analysis (DMA) combined with mass spectrometry (MS) has shown how to couple the output of a planar DMA with the atmospheric pressure inlet of an atmospheric pressure ionization mass spectrometer (APCI-MS). However, because the ion inlet to APCI-MS instruments is a round orifice, while conventional DMA geometries make use of elongated slits, the coupling of both has attained less resolving power or tolerated a smaller sample flow rate than a DMA alone. The present invention overcomes these limitations with an axial DMA of cylindrical symmetry using more than two electrodes. The configuration is related to that previously proposed by Labowsky and Fernández de la Mora (2004, 2006), where ions with a critical electrical mobility are brought into the symmetry axis of the DMA. Ions with this critical mobility are now optimally transmitted into the MS, with much higher resolution than possible in planar DMAs.

Abstract: Prior work on differential mobility analysis (DMA) combined with mass spectrometry (MS) has shown how to couple the output of the DMA with the inlet of an atmospheric pressure ionization mass spectrometer (APCI-MS). However, the conventional ion inlet to an APCI-MS is a round orifice, while conventional DMA geometries make use of elongated slits. The coupling of two systems with such different symmetries limits considerably the resolutions attainable by the DMA in a DMA-MS combination below the value of the DMA alone. The purpose of this invention is to overcome this limitation in the case of a parallel plate DMA. One solution involves use of an elongated rather than a circular MS sampling hole, with the long dimension of the MS inlet hole aligned with that of the DMA slit. Another involves use of a more elongated orifice in the DMA exit and a more circular hole on the MS inlet, the two being connected either through a short transfer conduit or through an ion guide.

Abstract: A method for fast and accurate recognition of species contained in trace amounts in complex mixtures such as ambient air or biological fluids is taught based on the use in tandem of one or several differential mobility analyzers (DMAs) and possibly also a mass spectrometer (MS), all arranged in series. The two DMAs operate in different regions of the ion drag versus drift velocity curve (for instance, linear versus nonlinear regions), hence separating according to more than one independently discriminating parameters of the ion. Very high discrimination can be achieved even with a single stage of mass spectrometric separation by selecting a narrow range of ions with the DMA, and analyzing them in the MS, first without fragmentation, and then with fragmentation. This process does not require necessarily a tandem MS when fragmentation takes place in the inlet region of the MS.

Abstract: The present invention is based on the observation that radio frequency (RF) electric fields in multi-pole lenses with small rod diameters in the range of 1 mm enables strongly concentrating ions suspended in a gas at pressures much higher than previously used for ion manipulation, including atmospheric pressure. Other lens configurations are described, including one based on the funnels of U.S. Pat. No. 6,107,628, and another on the coiled wire system of Hutchins et al. (1999). The finding provides a method to increase the concentration of ions transmitted to mass spectrometers and other analyzers, both from volatile or involatile species in solution, hence increasing their analytical sensitivity. It also enables improved charging efficiencies of neutral volatile species existing in the gas phase.

Abstract: A method for fast and accurate recognition of species contained in trace amounts in complex mixtures such as ambient air or biological fluids is taught based on the use in tandem of one or several differential mobility analyzers (DMAs) and possibly also a mass spectrometer (MS), all arranged in series. The two DMAs operate in different regions of the ion drag versus drift velocity curve (for instance, linear versus nonlinear regions), hence separating according to more than one independently discriminating parameters of the ion. Very high discrimination can be achieved even with a single stage of mass spectrometric separation by selecting a narrow range of ions with the DMA, and analyzing them in the MS, first without fragmentation, and then with fragmentation. This process does not require necessarily a tandem MS when fragmentation takes place in the inlet region of the MS.

Abstract: Vapors of relatively heavy species having molecular weights in excess of 290 amu have not been previously detected in the gas phase at ambient temperature. A method to detect them is taught here based on the use of a mass spectrometer with an atmospheric pressure source. Ions produced in detectable quantities from such heavy vapors are claimed as a new state of matter.

Abstract: Prior work on differential mobility analysis (DMA) combined with mass spectrometry (MS) has shown how to couple the output of a planar DMA with the atmospheric pressure inlet of an atmospheric pressure ionization mass spectrometer (APCI-MS). However, because the ion inlet to APCI-MS instruments is a round orifice, while conventional DMA geometries make use of elongated slits, the coupling of both has attained less resolving power or tolerated a smaller sample flow rate than a DMA alone. The present invention overcomes these limitations with an axial DMA of cylindrical symmetry using more than two electrodes. The configuration is related to that previously proposed by Labowsky and Fernández de la. Mora (2004, 2006), where ions with a critical electrical mobility are brought into the symmetry axis of the DMA. Ions with this critical mobility are now optimally transmitted into the MS, with much higher resolution than possible in planar DMAs.

Abstract: A method and an apparatus are described to focus sharply a wide range of particle sizes for particles suspended in a relatively high flow rate of carrier gas. The particles are accelerated through a continuously converging ladder of smooth contractions, each designed such that: (i) the flow remains laminar at substantial Reynolds numbers; (ii) a certain band of particle sizes is focused in each contraction, without substantial defocusing of larger particle focused in one or several preceding contractions; (iii) the form, length, and ratio of entry to exit diameter of each contraction, as well as the number of consecutive contractions are chosen such that all particles within a given relatively wide range of sizes are focused at the end of the ladder of contraction steps into a relatively narrow focal region. The focusing apparatus coupled to a collector device constitutes a new type of virtual impactor, termed a focusing virtual impactor, which can also be used as a powerful particle concentrator.

Abstract: The invention describes a system and method to separate ions (and charged particles) suspended in gas based on their ion electrical mobility. Most common ion mobility analyzers involve two parallel plate (or concentric cylinder) elements (electrodes) between which is imposed an electrical field perpendicular to a sheath gas flow field between the cylinders. Separation occurs because high mobility ions tend to follow the electrical field while low mobility ions tend to follow the flow field. This invention describes various configurations of electrical elements and sheath gas flow fields for ion mobility separation devices with unique performance characteristics. These characteristics include devices in which: the ion inlet and outlet are on the same element; the inlet and outlet are at the same voltage; the outlet is upstream from the inlet; the outlet is on the axis; the inlet is on the axis; and the ions are focused on the outlet.

Abstract: Prior work on differential mobility analysis (DMA) combined with mass spectrometry (MS) has shown how to couple the output of the DMA with the inlet of an atmospheric pressure ionization mass spectrometer (APCI-MS). However, the conventional ion inlet to an APCI-MS is a round orifice, while conventional DMA geometries make use of elongated slits. The coupling of two systems with such different symmetries limits considerably the resolutions attainable by the DMA in a DMA-MS combination below the value of the DMA alone. The purpose of this invention is to overcome this limitation in the case of a parallel plate DMA. One solution involves use of an elongated rather than a circular MS sampling hole, with the long dimension of the MS inlet hole aligned with that of the DMA slit. Another involves use of a more elongated orifice in the DMA exit and a more circular hole on the MS inlet, the two being connected either through a short transfer conduit or through an ion guide.

Abstract: A method for fast and accurate recognition of species contained in trace amounts in complex mixtures such as ambient air or biological fluids is taught based on the use in tandem of one or several differential mobility analyzers (DMAs) and possibly also a mass spectrometer (MS), all arranged in series. The two DMAs operate in different regions of the ion drag versus drift velocity curve (for instance, linear versus nonlinear regions), hence separating according to more than one independently discriminating parameters of the ion. Very high discrimination can be achieved even with a single stage of mass spectrometric separation by selecting a narrow range of ions with the DMA, and analyzing them in the MS, first without fragmentation, and then with fragmentation. This process does not require necessarily a tandem MS when fragmentation takes place in the inlet region of the MS.

Abstract: A fast alternative for detecting dangerous or illegal substances is taught that improves upon the relatively slow conventional batch method of collecting and concentrating particles in filters. The new method concentrates the particles on-line and almost instantaneously, taking advantage of their inertia. Particles are thus concentrated on the fly from a large gas sample flow rate into a small gas flow rate, where they are rapidly volatilized and their vapors sensed in an analytical instrument such as a mass spectrometer or an ion mobility spectrometer.