Chemical apparatus and process disinfecting – deodorizing – preser – Control element responsive to a sensed operating condition
Reexamination Certificate
2000-06-14
2003-05-06
Warden, Jill (Department: 1743)
Chemical apparatus and process disinfecting, deodorizing, preser
Control element responsive to a sensed operating condition
C422S091000, C436S180000, C436S174000, C435S287300, C384S152000, C384S156000, C118S261000
Reexamination Certificate
active
06558630
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a dosing unit for continuous introduction of liquid solution samples into a system. Moreover it relates to a method of continuous introduction of liquid solution samples into a system from a chamber containing the solution.
BACKGROUND OF THE INVENTION
A number of arrangements are known for dosing small samples of liquid into a system in the form of a treatment apparatus. These will be explained later. First an explanation of the prior art arrangements in association with mass spectrometry will be given.
U.S. Pat. No. 4,705,616 describes a process and an interface probe for discharging chemicals from one end of a capillary tube into a mass spectrometer. Chemicals are fed into the other end of the capillary tube by a valve comprising a housing and a rotable member inside the housing. The rotable member, which is rotable between two positions, is constructed with a transversal fluid passage by which chemicals can be transported from a reservoir into the capillary tube. In one of the two positions, where the fluid passage is parallel to the capillary tube, the fluid passage allows a continuous flow of chemical from a reservoir into the capillary. In the other position, where the passage fluid is perpendicular to the capillary, chemicals from a second reservoir are fed into the passage, but these chemicals are only released when the rotable member is back in the first position. Thereby, an intermittent operation is obtained.
Continuous mass spectrometric monitoring of a reaction mixture or the effluent from a separation device requires continuous introduction of a minute. stream of sample into the vacuum of the mass spectrometer. Established techniques use either pervaporation through a solid polymer membrane or mass flow through a capillary or porous membrane for this purpose. In addition a mechanical device, the moving belt, has been designed to introduce continuously the remnant of evaporated sample. Each technique has its own advantages and disadvantages and no single technique has universal applicability.
In the pervaporation technique, membrane inlet mass spectrometry, the sample is separated from the vacuum of the mass spectrometer by a thin, solid polymer membrane. Compounds such as gases and organic volatiles diffuse through the membrane into the mass spectrometer where they are ionized and give rise to mass spectrometric signals, which are proportional to the activities of the compounds in the liquid or gaseous sample. Ionisation usually takes place by collision with electrons emitted from a hot filament. Electron impact ionisation (EI) causes extensive disintegration of analyte molecules to form fragment ions which can be used to identify the analyte. Chemical ionisation, where analyte molecules are ionized by capturing charges from
The path through which analyte travels from the sample to the vacuum has three stages, namely the unstirred layer (Nernst layer) of liquid sample adjacent to the membrane, the membrane itself and the space in vacuum from the inside of the membrane to the ion source. The detection limit of the measurement is mainly determined by the stage that has the highest resistance to the transport process and the response time is mainly determined by the stage where the transport process has the longest relaxation time. Both limitations are often located in the membrane stage. The permeability of a polymer membrane is a product of the solubility of the compound in the membrane material and the mobility of the dissolved compound. Whereas high solubility in the membrane material is favorable for the sensitivity of the measurement, it is unfavorable for the response time because an increased accumulation of analyte in the membrane leads to an increased relaxation time of the transport process. Thus FAX high sensitivity and rapid response are mutually exclusive as far as these properties are determined by the membrane. The transport of analyte from the inside of the membrane to the ion source takes place by molecular flow. Molecules that collide with the walls surrounding the flow path may be absorbed to the walls and later desorbed. This gives a contribution to the response time which depends strongly on the volatility of the analyte.
Since only small amounts of gases and volatiles enter the mass spectrometer, the pervaporation technique is very clean and can be carried on for long periods of time without the need for internal cleaning of the mass spectrometer. Another advantage is that measurements with the pervaporation technique of favoured compounds, i.e. compounds that partition in favour of the membrane material, do not require any pretreatment of the sample. Measurements can be done in cell suspensions and in strongly acidic or alkaline solutions. The sensitivity of the pervaporation technique for a compound which partitions strongly in favour of the membrane may be very high. However, the response time may be too long for practical use in monitoring of reaction systems. In addition the accumulation of analyte in the membrane may change the properties of the membrane material leading to a non-linear response.
Whereas the solid membrane excludes a large class of compounds which do not readily pervaporate through the membrane material, a mass flow technique utilizing a porous membrane allows sample to enter the mass spectrometer with little change in composition. The flow through a porous membrane is a combination of laminar and turbulent flow depending on the pore size of the membrane material. This type of flow is much faster than diffusion through a solid membrane and, consequently, the response time may be much shorter with a porous membrane than with a solid membrane. Another difference is that because the flow through the porous membrane is not selective, no depletion of solute takes place in the sample adjacent to the surface of a porous membrane as it occurs at a solid membrane. A major drawback of mass flow techniques in general is that comparatively large amounts of material including salts and other non-volatiles enter and accumulate in the mass spectrometer making frequent cleaning necessary. In addition filtration of the sample is often necessary since clogging may otherwise occur. The most common use of porous membrane inlets is in the field of electrochemistry. Electron impact as well as chemical ionisation is used.
Continuous fluid introduction through a capillary includes thermospray, electrospray, particle beam and continuous-flow fast atom bombardment (CF-FAB). Thermospray operates by the generation of a fine mist of droplets from the sample solution and the evaporation of the solvent from the droplets to yield ions of the analyte. Enrichment is achieved because much of the solvent is evaporated and pumped away, whereas the analyte molecules, being charged, can be electrically focused to enter the analyzer. In the particle beam technique the remnant after vaporization of the droplets forms particles which are guided into the analyzer by translational momentum. In CF-FAB the sample liquid is not nebulized but mixed with glycerol and made to flow onto the target area of a xenon atom source in the mass spectrometer.
The moving belt technique for continuous sample introduction is neither a pervaporation technique nor a mass flow technique. It belongs to a third category where sample is brought into the mass spectrometer by mechanical transport. Sample is applied to a moving belt from where the solvent evaporates and the remnant, sticking to the surface of the belt, is dragged into the mass spectrometer through a vacuum lock.
As it occurs from the above a number of drawbacks are associated with the prior art systems.
It is the purpose of the present invention to provide a unit and a method in which these drawbacks are obviated and which provides for a new and simple arrangement for continuous sample introduction in which it is possible in a simple and reliable manner to adjust the rate of the sampling of different types of solution.
According to the present invention this is obtaine
Degn Hans
Graf Thomas
Ørsnes Henrik
Gordon Brian R
Ladas & Parry
Warden Jill
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