Fluid sprinkling – spraying – and diffusing – Combining of separately supplied fluids – At or beyond outlet
Reexamination Certificate
2001-12-03
2002-12-31
Morris, Lesley D. (Department: 3752)
Fluid sprinkling, spraying, and diffusing
Combining of separately supplied fluids
At or beyond outlet
C239S421000
Reexamination Certificate
active
06499675
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a nebulizer for spraying a liquid with high efficiency, and particularly to a nebulizer suitable for use in an inductively coupled plasma/mass spectrometry system (ICP-MS), an inductively coupled plasma (ICP) atomic emission spectrometry system and an atomic absorption spectrometry system used for inorganic substance analysis.
2. Description of the Related Art
In analytical apparatuses for inductively coupled plasma-mass spectrometry (ICP-MS), inductively coupled plasma atomic emission spectrometry (ICP-AES), etc., aerosol is produced from a solution sample by a nebulizer and introduced into a plasma. Here, substances to be analyzed are brought into atomization, excitation and ionization. Owing to a mass analysis for the resultant ions or a spectrometric analysis for light emitted from excited atoms or ions, the identification and determination of each substance to be analyzed present in the liquid sample are realized. A concentric glass nebulizer is often used as the nebulizer. A description related to ICP-AES is disclosed in, for example, Analytical Chemistry, 54(1982), p.533-p.537. At an end of each spray tube, atmospheric pressure becomes less than or equal to 1 atom. by a spray gas. A difference in pressure between the two ends of the tubes is used so that the liquid sample is sucked into the nebulizer from a container. The flow rate of the gas is 1.0 L/min. and the flow rate of the liquid is about 1.0 mL/min.
A micro concentric nebulizer (MCN) related to ICP-MS has been described in Journal of Analytical Atomic Spectrometry, 11(1996), p.713-p.720. A liquid sample is delivered to a single capillary and sprayed around its end by gas which passes therethrough. The flow rate of the gas is about 1.0 L/min. Since the velocity of the gas is faster than that for the concentric glass nebulizer, the efficiency of its spraying is relatively high. However, the introduced flow rate of a sample solution for realizing high-efficiency spraying is limited. The efficiency of the spraying is reduced when the flow rate thereof is 50 &mgr;L/min or more.
There is need to prevent deposition of a metal due to heat generated upon cutting work, polishing, etc. Thus, a description related to a spray-like body supply device intended for cooling has been disclosed in Japanese Patent Application Laid-Open No. Hei 8-99051. If a liquid is produced or formed in spray form, then cooling can be carried out more effectively. The device has capillaries through which the liquid flows, and an injection hole (nozzle) from which a spray gas (air) is discharged. The cooling liquid is divided into a plurality of the capillaries, and the ends of the plurality of capillaries are packed into a bundle. The liquid is sprayed at the ends thereof by an air flow discharged through one injection hole. The nozzle is shaped in tapered form.
Japanese Patent Application Laid-Open No. Hei 7-306193 describes a sonic spray ionization technology. A quartz capillary (whose inner and outer diameters are 0.1 mm and 0.2 mm respectively) in which a liquid is introduced, has an end inserted into an orifice (whose inner diameter is 0.4 mm). A high-pressure nitrogen gas introduced inside an ion source is discharged into the air through the orifice, and the liquid is sprayed by a sonic gas flow formed at this time. Gaseous ions are produced in aerosol produced by the spraying. In the present ionizing method, the production of fine droplets by the sonic gas flow essentially plays an important role. The liquid in the sonic gas flow is torn off by a gas flow fast in velocity to thereby produce droplets. The non-uniformity of the concentrations of positive and negative ions in droplets firstly produced by spraying becomes pronounced as the size of each droplet becomes fine. Further, some of the liquid are separated from the surface of the droplet by a gas flow, whereby charged fine droplets are produced. Such fine droplets are evaporated in a short time so that gaseous ions are produced. While the size of each produced droplet decreases with an increase in the velocity of flow of gas, the droplet size increases as the velocity of flow of gas enters a supersonic region. This is because a shock wave is produced in the case of the supersonic flow, and the production of fine droplets is depressed. Therefore, according to the sonic spray ionizing method, when the gas flow is sonic, the finest droplets are produced and the produced amount of ions reaches the maximum. The present method discloses that when the flow rate of the spray gas is 3 L/min., a sonic gas flow is formed.
A sonic spray nebulizer has been described in Analytical Chemistry, 71(1999), p.427-p.432. The nebulizer is similar in structure to the ion source for sonic spray ionization. The inner diameter of a resin orifice is 0.25 mm and a quartz capillary (whose inner and outer diameters are 0.05 mm and 0.15 mm respectively) is used. Since a sonic gas flow is used in a spray gas, the present nebulizer is capable of producing extremely fine droplets. As a result, the spray efficiency of a liquid is greatly improved as compared with the conventional glass nebulizer. In the sonic spray nebulizer, the flow rate of the gas is fixed to the condition for the generation of the sonic gas flow, and the flow rate of a liquid sample is controlled by a pump. The flow rate of the gas ranges from 1.0 L/min. to 1.4 L/min., and the flow rate of the liquid ranges from 1 &mgr;L/min. to 90 &mgr;L/min.
On the other hand, a nebulizer using a supersonic gas flow has been described in Japanese Patent Application Laid-Open No. Hei 6-238211 and U.S. Pat. No. 5,513,798. The present nebulizer is characterized in that a supersonic gas flow is helically produced in the neighborhood of a liquid outlet at an end of a capillary by a helical gas path. Further, a cylindrical path is placed on the downstream side from an orifice unit and a shock wave of a supersonic gas flow is repeatedly reflected by the inner surface of the path. Since the shock wave collides with a liquid flow many times in an in-path central portion, droplets are efficiently produced from the liquid cut to pieces. The length (corresponding to the distance between the end of the capillary and the surface of the cylindrical path, which is brought into contact with the air) is as about twice as the diameter of the cylindrical path. The flow rate of gas ranges from 50 L/min. to 60 L/min., and the flow rate of the liquid ranges from 91 mL/min. to 100 mL/min. Since the spray gas helically circles round, the formation of a gas flow concentrically with the capillary as described in the prior art is not carried out. The velocity of flow of the spray gas is divided or resolved into a horizontal direction and a vertical direction with respect to the axis of the capillary. While the velocity of flow of the gas is supersonic, a flow velocity component horizontal to the capillary axis is considered to be less than or equal to the speed of sound. In a droplet producing process, the application of the shock wave to the liquid is important and no emphasis is placed on the tearing off of the liquid by a high-speed gas flow.
Upon vaporization of the liquid, the flow rate of fully-vaporizable water per gas flow rate 1 L/min. is about 20 &mgr;L/min. at most if calculated from saturated vapor pressure at 20° C. Therefore, if sample solution given at a flow rate of 20 &mgr;L/min. or more is introduced into an ideal nebulizer when the flow rate of the gas is about 1L/min., then the efficiency of its spraying should have been reduced in the ideal nebulizer. However, an actual nebulizer shows a tendency to improve analytical sensitivity even if the sample flow rate is 20 &mgr;L/min. or more. This is because the spray efficiency of the liquid is considered not to have reached an ideal level.
In the concentric glass nebulizer, the flow rate of the liquid is about 500 &mgr;L/min. when the liquid is automatically sucked. Therefore, the full vaporization of liquid cannot be carried out when the
Hirabayashi Atsumu
Huang Min
Mattingly Stanger & Malur, P.C.
Morris Lesley D.
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