Patent Application
20110192215
This application claims the benefit of Great Britain Patent Application No. 1001901.6 filed on Feb. 5, 2010.
The present invention relates to CO2 capture systems and in particular to a method and system for direct analysis of solvents used to chemically bind with CO2 present in flue gases, and for the monitoring of large-scale CO2 solvent-capture reaction to improve process efficiency, thereby reducing the cost of CO2 capture.
In recent years, interest in the development of efficient processes for the capture of CO2 from coal-flue gas or other carbon fuel sources has increasingly been driven by the concerns about the impact of rising CO2 emissions from fixed sources. Solvent Scrubbing, also known as “sweetening” or acid gas removal, was originally developed to remove H2S and CO2 from gases in natural gas processing plants and other industries. Solvents based on amines are commonly used in CO2 capture (CC) plants. The amine solvent reacts with flue gases to strip out greenhouse gases such as methane and CO2 by chemically binding with them to form carbamates and other reaction products. The chemically-bound CO2 may then be outgassed under conditions of elevated temperature and pressure, and may be collected, transported and stored.
In a solvent-based CC plant, the processes taking place are complex and the chemical reaction mechanisms involved are not well understood. Factors affecting the efficiency of CO2 capture plants include solvent breakdown rates, the mechanisms that chemically bind the CO2, the formation of intermediate reaction products, process transients and the non-measurement of toxic by-products. These factors could be critical to improving the energy balance of a CO2 capture plant and their environmental impact, and therefore pivotal to reducing CC plant operational costs to commercially feasible levels.
Various amines-based solvents have been proposed for CO2 capture processes. While some research has been conducted on amine-based CO2 capture in the past, little has been done to characterise its chemical composition in real-time. Likewise, the chemical processes leading to the degradation of solvents, plant corrosion and the formation of toxic products are not well understood and have not been monitored on capture plants. Amines undergo a variety of degradation processes and form various salts, and the solvent is gradually consumed over time. Capture efficiency falls, and running costs are introduced due to energy imbalances and the requirement for solvent replenishment. Amine degradation is a major concern for long-term full-scale CC plant operation not only because of economics but increasingly because of environmental concerns.
The formation of heat stable salts leads to excessive foaming, reducing gas liquid contact and thus reducing the amount, and increasing the specific energy, of CO2 captured on a single pass through the absorber, as well as leading to increased solvent loss rates and the formation of potentially corrosive species.
So far, solvents have only been analysed off-line using conventional laboratory-based mass spectrometer instruments. While this off-line detection of reaction products such as carbamates demonstrates the feasibility of monitoring reaction composition, the opportunity to intervene and alter reaction conditions (e.g. temperature, pressure, pH, flow rate, solvent composition) in order to maintain capture efficiency during load changes is lost. Clearly, failure to capture CO2 during load changes is unacceptable if limits of 90% capture become set in legislation, especially when permits will have to be purchased for the lost CO2. Moreover, considering that solvent-based CO2 capture plant is expected to add 20% to 35% to energy prices the economic value of further efficiency losses will be considerable.
As mentioned above to date, solvent analysis has been performed off-line in analytical laboratories, often using techniques such as gas chromatography (GC) or gas chromatography mass spectrometry (GC-MS). These analytical laboratories are often located off-site. Samples are collected infrequently from the rich and lean solvent streams, often months apart. The time lag between collecting the sample, analysing it and reporting results can be hours to days depending on the location of the analytical instrumentation. Consequently, the opportunity to intervene and to adjust process parameters to optimise CC plant efficiency is lost. As the quality of the solvent degrades, its capacity to absorb CO2 deteriorates and the energy required by the PCC process rises, increasing operating costs. Therefore monitoring the solvent quality through in-line analysis of its chemical composition will permit the adjustment of conditions to maintain solvent quality, preserving the energy balance and optimising operating costs.
Accordingly there is a need for improved monitoring of CO2 solvent-capture process composition.
To overcome these and other problems, a system and methodology is described for providing a direct analysis of the CO2 capture reaction occurring within a CO2 capture plant. In accordance with a preferred arrangement a mass spectrometer is coupled to a solvent-based CO2 capture reaction chamber. The mass spectrometer (MS) of the invention is used to directly monitor the chemical composition of the solvent during the solvent scrubbing or CO2 capture process. The chemical composition, in particular the formation of chemically bound CO2 as carbamates, may be used to calculate the percentage of CO2 captured and the overall yield of the process. In accordance with the present teaching, data on chemical composition may be used in closed-loop control of the solvent-capture process. Information of this kind could be used to optimise reaction conditions for capture efficiency. Similarly, real-time compositional data could be used as feedback to a closed-loop control system to adjust parameters such as temperature, flow, pH, solvent dilution, solvent replenishment, flow rates and pressure etc. for optimal process performance. This capability would be particularly important because of changes in the composition of flue-gases due to combustion of coal mixes of varying quality. Monitoring the composition of the solvent-based mixtures used in a CO2 capture processes would also permit measurement of the rate of solvent consumption and its degradation mechanisms.
In accordance with the present teaching a MS coupled to a solvent-based capture plant could be used to optimise absorber column conditions and accelerate reactions. A MS system is described that when coupled to a solvent-based post-combustion CO2 capture (PCC) plant, monitors changes in the composition of solvents such as monoethanolamine (MEA), AEPD (2-amino-2-ethyl-1,3-propanediol), AMP (2-amino-2-methyl-1-propanol), AMPD (2-amino-2-methyl-1,3-propanediol), DEA (diethanolamine), MDEA (methyldiethanolamine), PZ (piperazine) and THAM (tris-(hydroxymethyl)aminomethane) in real-time. In accordance with the present teaching it is possible to track degradation of the solvents in a PCC plant. By measuring the reaction conditions that affect solvent consumption ratessolvent consumption, solvent replenishment, energy and operating costs can be minimised.
In a first embodiment, the sytem comprises a MS consisting of an inlet for extracting a sample from a fluid stream, an ion source, a mass analyser and an ion counter. The inlet of the MS of the invention is fluidically coupled to a solvent-based, CO2 scrubbing plant and is used to monitor the chemical composition of the CO2 capture process. The ion source functions by transforming neutral molecules of the species of interest into charged particles called ions. This ion has a mass to charge ratio that corresponds to its molecular mass. To avoid fragmentation or distruction of volatile molecules, and to permit the easy identification of the species of interest based on their molecular ions, the MS system preferably incorporates a ‘soft’ ionisation source and a mass analyser. A soft ionisation source limits fragmentation of the molecules of interest. The soft ionisation source may be based on, but not limited to, electrospray ionisation (ESI), nanospray ionisation, chemical ionisation, secondary eletrospray ionisation (SESI), atmospheric pressure chemical ionisation (APCI), DART, DESI, MALDI, atmospheric pressure photoionisation (APPI) or glow discharge ionisation. The analyser of the MS system may be an ion trap, time of flight, quadrupole, magnetic sector, orbital ion trap, linear ion trap, rectilinear ion trap, cross-field, cycloidal or rotational field mass analyser. The MS system of the invention is used for in-line analysis of CO2 capture reactions and may be based on liquid chromatography mass spectrometry (LC-MS) or GC-MS. The MS system of the invention is coupled to a CO2 capture reactor and used to monitor reactor composition to provide degradation kinetics for solvents such as MEA and related amines. The chemical species of interest are extracted in fluid samples. This MS system generates chemical composition data in real-time that can be linked to process parameters such as temperature, amine concentration, CO2 loading, pH and the influence of reactor vessel materials.
In another embodiment, the MS system of the invention is a compact MS that is configured to be coupled fluidically to a CO2 capture plant. By fluidically coupling the MS to the CO2 capture plant sample may be extracted from a fluid stream in the PCC process. The sample may be taken from rich or lean solvent streams, or from a suitable sample port on the absorption column provided within such CO2 capture plants. The sample will be appreciated as being a fluid mixture containing particulate and may require filtration. Before injection into the MS systems, a solution may be made-up from a reservoir of suitable solvent using a make-up pump. In a first arrangement, the system of the present teaching utilizes a soft ionisation source to couple the sample solution to a MS. The soft ionisation source ionises the chemical species as they elute and the MS identifies the species based on the mass to charge ratios and mass spectra of the ions. The MS analyses the chemical composition of the reactor fluid and detects carbamate species formed by the reaction of solvent and CO2 for online measurement of CO2 loading.
In another a chromatographic separator is used to couple a soft ionisation source to the sample solution. The chromatographic module separates the chemical constituent of the mixture of the sample solution so that they elute individually into a soft ionisation source. The chromatograhic module may be based on GC, LC or supercritical fluid chromatography (SFC). The soft ionisation source ionises the chemical species as they elute and the MS identifies the species based on the mass to charge ratios and mass spectra of the ions. The MS detects the chemical composition of the sample solution and detects carbamate species formed by the reaction of solvent and CO2 for online measurement of CO2 loading.
In another embodiment of an in-line analytical system a sample is extracted from the rich or lean solvent streams of the PCC process, or from a point along the absorption column. A sample solution is made-up and injected onto a chromatographic column by means of a sample injector and a sample loop. The sample loop measures out a known volume of sample solution, and injects it onto the column by means of a valve and injection pump. The chromatographic module be based on GC, LC or SFC. The chemical constituents of the mixture of the sample solution are separated and elute individually into a soft ionisation source where their molecules are transformed into ions. The soft ionisation source preserves chemical bonds and limits molecular fragmentation, minimising chemical interference, easing interpretation of mass spectra and thereby improving system selectivity. The ions are analysed by the MS and mass spectra are used to ‘name’ the chemical species of the sample. The presence of molecular ions in the spectra may be used to identify chemical compounds of interest by means of their molecular mass.
In another embodiment, the analytical system of the invention is a compact MS system that is coupled fluidically with a PCC plant and forms part of its control system. A fluid sample is extracted, using a fluid interface to the PCC plant, from the rich or lean solvent streams of the PCC process, or from a point along the absorption column. A sample solution is made-up as necessary and the fluid sample is ionised by means of a soft ionisation source. The soft ionisation source preserves chemical bonds and limits molecular fragmentation, minimising chemical interference, easing interpretation of mass spectra and thereby improving system selectivity. The use of soft ionisation may avoid the need for chromatography in the case of less complex mixtures composed of known substances. The ions are transported into a vacuum system by means of a vacuum interface and analysed by the mass analyser. Ion current from the mass analyser is collected and measured by an ion counter. The signal from the ion counter is acquired and processed by a computer and used to display mass spectra on an analytical display. The mass analyser may also be operated in selected ion monitoring (SIM) mode where a handful of ions are of interest, each representing a certain species of interest. Mass spectra are used to ‘name’ the chemical species of the sample. The presence of molecular ions in the spectra may be used to identify chemical compounds of interest by means of their molecular mass. The computer may linked to the control system of the PCC and used to transmit data on chemical composition to the control system. The data link may be on-line, forming part of a closed feedback loop, or off-line so that data is monitored by process technicians in a control room. The system of the invention monitors starter materials, intermediate products and reaction products and may provide feedback to a closed-loop control system. The MS system analyzes the chemical composition of the solvent in real-time, thus generating data for the concentration of each chemical present in the mixture. The MS tool continuously measures the relative concentration of starter materials (e.g. MEA, H2O, CO2) and reaction products (e.g. carbamates). Data provided by MS monitoring tool is used to measure the efficiency and yield of the capture reaction at any given moment. The MS system data is used to adjust process conditions in order to accelerate reactions, to minimise solvent degradation and reduce waste products.
In another embodiment, ions generated by the soft ionisation source may be separated by their drift time along the drift tube of an ion mobility spectrometer (IMS). The IMS effects some separation of the ions by means of permitting them to drift in a strong, a potentially varying, electric field. The IMS may be a field-asymmetric ion mobility spectrometer (FAIMS). A vacuum interface couples the IMS to the a mass analyser inside a vacuum chamber. The ions are transported into a vacuum system by means of a vacuum interface and analysed by the mass analyser. Ion current from the mass analyser is collected and measured by an ion counter. The signal from the ion counter is acquired and processed by a computer and used to display mass spectra on an analytical display. The mass analyser may also be operated in selected ion monitoring (SIM) mode where a handful of ions are of interest, each representing a certain species of interest. Mass spectra are used to ‘name’ the chemical species of the sample. The presence of molecular ions in the spectra may be used to identify chemical compounds of interest by means of their molecular mass. The computer may linked to the control system of the PCC and used to transmit data on chemical composition to the control system. The data link may be on-line, forming part of a closed feedback loop, or off-line so that data is monitored by process technicians in a control room. The system of the invention monitors starter materials, intermediate products and reaction products and may provide feedback to a closed-loop control system. The MS system analyzes the chemical composition of the solvent in real-time, thus generating data for the concentration of each chemical present in the mixture. The MS tool continuously measures the relative concentration of starter materials and reaction products and data provided by MS in-line monitoring system is used to measure the efficiency and yield of the capture reaction at any given moment through adjusting process conditions in order to accelerate reactions, to minimise solvent degradation and reduce waste products.
In another embodiment, the analytical system of the invention is a compact MS system that is coupled fluidically with a PCC plant and forms part of its control system. A fluid sample is extracted from the rich or lean solvent streams of the PCC process, or from a point along the absorption column. A sample solution is made-up as necessary and the fluid sample is separated by gas chromatography (GC). The eluent is ionised by means of a atmospheric pressure ionisation source. The atmospheric pressure ionisation source may be a suitable soft ionisation source such as ESI, SESI, APCI or APPI that preserves chemical bonds and limits molecular fragmentation, minimising chemical interference, easing interpretation of mass spectra and thereby improving system selectivity. The vacuum interface is an atmospheric pressure interface (API) that couples the atmospheric pressure ionisation source to the a mass analyser inside a vacuum chamber. The ions are transported into a vacuum system by means of a vacuum interface and analysed by the mass analyser. Ion current from the mass analyser is collected and measured by an ion counter. The signal from the ion counter is acquired and processed by a computer and used to display mass spectra on an analytical display. The mass analyser may also be operated in selected ion monitoring (SIM) mode where a handful of certain ions are of interest, each representing a chemical species of interest. Mass spectra are used to ‘name’ the chemical species of the sample. The presence of molecular ions in the spectra may be used to identify chemical compounds of interest by means of their molecular mass. The computer may linked to the control system of the PCC and used to transmit data on chemical composition to the control system. The data link may be on-line, forming part of a closed feedback loop, or off-line so that data is monitored by process technicians in a control room. The system of the invention monitors starter materials, intermediate products and reaction products and may provide feedback to a closed-loop control system. The MS system analyzes the chemical composition of the solvent in real-time, thus generating data for the concentration of each chemical present in the mixture. The MS tool continuously measures the relative concentration of starter materials and reaction products and data provided by MS in-line monitoring system is used to measure the efficiency and yield of the capture reaction at any given moment through adjusting process conditions in order to accelerate reactions, to minimise solvent degradation and reduce waste products.
In a further embodiment, the analytical system of the invention is a compact MS system that is coupled fluidically with a PCC plant and forms part of its control system. A fluid sample is extracted from the rich or lean solvent streams of the PCC process, or from a point along the absorption column. A sample solution is made-up as necessary and the fluid sample is separated by gas chromatography. The eluent is ionised by means of a ESI source. An atmospheric pressure interface (API) couples the ESI source to the a mass analyser inside a vacuum chamber. The electrospray ions are transported into a vacuum system by means of a vacuum interface and analysed by the mass analyser. Ion current from the mass analyser is collected and measured by an ion counter. The signal from the ion counter is acquired and processed by a computer and used to display mass spectra on an analytical display. The mass analyser may also be operated in selected ion monitoring (SIM) mode where a handful of certain ions are of interest, each representing a chemical species of interest. Mass spectra are used to ‘name’ the chemical species of the sample. The presence of molecular ions in the spectra may be used to identify chemical compounds of interest by means of their molecular mass. The computer may linked to the control system of the PCC and used to transmit data on chemical composition to the control system. The data link may be on-line, forming part of a closed feedback loop, or off-line so that data is monitored by process technicians in a control room. The system of the invention monitors starter materials, intermediate products and reaction products and may provide feedback to a closed-loop control system. The MS system analyzes the chemical composition of the solvent in real-time, thus generating data for the concentration of each chemical present in the mixture. The MS tool continuously measures the relative concentration of starter materials and reaction products and data provided by MS in-line monitoring system is used to measure the efficiency and yield of the capture reaction at any given moment through adjusting process conditions in order to accelerate reactions, to minimise solvent degradation and reduce waste products.
In a further embodiment, the analytical system of the invention is a compact MS system that is coupled fluidically with a PCC plant and forms part of its control system. A fluid sample is extracted from the rich or lean solvent streams of the PCC process, or from a point along the absorption column. A sample solution is made-up as necessary and the fluid sample is separated by liquid chromatography (LC). The eluent is ionised by means of a atmospheric pressure ionisation source. The atmospheric pressure ionisation source may be a suitable soft ionisation source such as ESI, SESI, APCI or APPI that preserves chemical bonds and limits molecular fragmentation, minimising chemical interference, easing interpretation of mass spectra and thereby improving system selectivity. The vacuum interface is an atmospheric pressure interface (API) that couples the atmospheric pressure ionisation source to the a mass analyser inside a vacuum chamber. The ions are transported into a vacuum system by means of a vacuum interface and analysed by the mass analyser. Ion current from the mass analyser is collected and measured by an ion counter. The signal from the ion counter is acquired and processed by a computer and used to display mass spectra on an analytical display. The mass analyser may also be operated in selected ion monitoring (SIM) mode where a handful of certain ions are of interest, each representing a chemical species of interest. Mass spectra are used to ‘name’ the chemical species of the sample. The presence of molecular ions in the spectra may be used to identify chemical compounds of interest by means of their molecular mass. The computer may linked to the control system of the PCC and used to transmit data on chemical composition to the control system. The data link may be on-line, forming part of a closed feedback loop, or off-line so that data is monitored by process technicians in a control room. The system of the invention monitors starter materials, intermediate products and reaction products and may provide feedback to a closed-loop control system. The MS system analyzes the chemical composition of the solvent in real-time, thus generating data for the concentration of each chemical present in the mixture. The MS tool continuously measures the relative concentration of starter materials and reaction products and data provided by MS in-line monitoring system is used to measure the efficiency and yield of the capture reaction at any given moment through adjusting process conditions in order to accelerate reactions, to minimise solvent degradation and reduce waste products.
In a further embodiment, the analytical system of the invention is a compact MS system that is coupled fluidically with a PCC plant and forms part of its control system. A fluid sample is extracted from the rich or lean solvent streams of the PCC process, or from a point along the absorption column. A sample solution is made-up as necessary and the fluid sample is separated by liquid chromatography (LC). The eluent is ionised by means of a ESI source. The vacuum interface is an atmospheric pressure interface (API) that couples the ESI source to the a mass analyser inside a vacuum chamber. The ions are transported into a vacuum system by means of a vacuum interface and analysed by the mass analyser. Ion current from the mass analyser is collected and measured by an ion counter. The signal from the ion counter is acquired and processed by a computer and used to display mass spectra on an analytical display. The mass analyser may also be operated in selected ion monitoring (SIM) mode where a handful of certain ions are of interest, each representing a chemical species of interest. Mass spectra are used to ‘name’ the chemical species of the sample. The presence of molecular ions in the spectra may be used to identify chemical compounds of interest by means of their molecular mass. The computer may linked to the control system of the PCC and used to transmit data on chemical composition to the control system. The data link may be on-line, forming part of a closed feedback loop, or off-line so that data is monitored by process technicians in a control room. The system of the invention monitors starter materials, intermediate products and reaction products and may provide feedback to a closed-loop control system. The MS system analyzes the chemical composition of the solvent in real-time, thus generating data for the concentration of each chemical present in the mixture. The MS tool continuously measures the relative concentration of starter materials and reaction products and data provided by MS in-line monitoring system is used to measure the efficiency and yield of the capture reaction at any given moment through adjusting process conditions in order to accelerate reactions, to minimise solvent degradation and reduce waste products.
In a further embodiment, the analytical system of the invention is a compact MS system that is coupled fluidically with a PCC plant and forms part of its control system. A fluid sample is extracted from the rich or lean solvent streams of the PCC process, or from a point along the absorption column. A sample solution is made-up as necessary and the fluid sample is separated by supercritical fluid chromatography (SFC). The eluent is ionised by means of a atmospheric pressure ionisation source. The atmospheric pressure ionisation source may be a suitable soft ionisation source such as ESI, SESI, APCI or APPI that preserves chemical bonds and limits molecular fragmentation, minimising chemical interference, easing interpretation of mass spectra and thereby improving system selectivity. The vacuum interface is an atmospheric pressure interface (API) that couples the atmospheric pressure ionisation source to the a mass analyser inside a vacuum chamber. The ions are transported into a vacuum system by means of a vacuum interface and analysed by the mass analyser. Ion current from the mass analyser is collected and measured by an ion counter. The signal from the ion counter is acquired and processed by a computer and used to display mass spectra on an analytical display. The mass analyser may also be operated in selected ion monitoring (SIM) mode where a handful of certain ions are of interest, each representing a chemical species of interest. Mass spectra are used to ‘name’ the chemical species of the sample. The presence of molecular ions in the spectra may be used to identify chemical compounds of interest by means of their molecular mass. The computer may linked to the control system of the PCC and used to transmit data on chemical composition to the control system. The data link may be on-line, forming part of a closed feedback loop, or off-line so that data is monitored by process technicians in a control room. The system of the invention monitors starter materials, intermediate products and reaction products and may provide feedback to a closed-loop control system. The MS system analyzes the chemical composition of the solvent in real-time, thus generating data for the concentration of each chemical present in the mixture. The MS tool continuously measures the relative concentration of starter materials and reaction products and data provided by MS in-line monitoring system is used to measure the efficiency and yield of the capture reaction at any given moment through adjusting process conditions in order to accelerate reactions, to minimise solvent degradation and reduce waste products.
These and other features and benefit will be understood with reference to the following exemplary embodiments.
A detailed description of preferred exemplary embodiments in accordance with the present teaching is provided with reference to
Shown in
In
Another exemplary arrangement is described in
A more detailed schematic of a system provided in accordance with the present teaching is shown in
In another embodiment the system forms part of the control system of the PCC and such an exemplary arrangement is shown in
In
In
In
Another embodiment is featured in
In
In
It will be appreciated and understood that what has been described herein are exemplary arrangements of an analysis tool that is directed towards real-time analysis of carbon capture processes which may be generally considered as including any fluid that chemically binds with greenhouse gases in flue streams such as methane and CO2. By employing a soft ionisation source such as the exemplary atmospheric ionisation sources that effect ionisation of the sample in non-vacuum conditions, the chromatographic flow rate is not limited by the pumping speed of the vacuum pumps and the column may have a higher flow rate permitting more rapid separation and a shorter system response time. Soft ionisation, i.e. the formation of ions without breaking chemical bonds, is particularly advantageous in the context of the chemically complex samples as described herein in that soft ionisation advantageously produces one ‘molecular ion’, whose mass to charge ratio or time of flight corresponds to its molecular weight, and has is a faster and easier means of identifying eluted compounds. The separation of the fluid into its chemical constituents has been described with reference to the exemplary use of a chromatography column that could be a gas, liquid or supercritical fluid based chromatography module. However it is possible to separate mixtures using other separation techniques such as ion mobility or capillary electrophoresis and the use of such techniques should be considered within the context of the separation module described herein.
It will be appreciated that samples from PCC processes may be ‘messy’. Due to the complex chemical matrix that is a carbon-capture solvent, lengthy chromatographic separation times are required to ensure adequate separation and purification of all the compounds in the mixture. Gas chromatographic (GC) retention times of several minutes may be required before all the components of have eluted from the GC column. In fact, samples of interest may contain hundreds of components. While users may not need to separate and identify all of the components during operation, nonetheless an analytical solution will need to rapidly separate and analyse complex samples and identify their components. In the context of capture operations, when processing hundreds of tonnes of flue gasses, the cost of delays and missed opportunities would be very high. To address these problems there is provided in accordance with the present teaching, an analytical tool and methodology that would provide rapid response times. To achieve this improved response rate, the tool advantageously employs a chromatographic solution featuring a faster flow rate and shorter separation times than heretofore possible in process solvent analysis. By providing for ionisation of the sample in non-vacuum conditions, i.e. at atmospheric pressure, then the gas chromatographic (GC) flow rate is not limited by the pumping speed of the vacuum pumps and the GC column may have a higher flow rate permitting more rapid separation and a shorter system response time.
It will be appreciated that traditionally where a chromatographic column is used to separate a mixture, a mass spectrometer (MS) detector is used to identify the compounds as they elute. The MS detector is a vacuum instrument and generally features an ion source inside the vacuum chamber to which the GC column is coupled and which ionises molecules of each constituent compound as they elute from the column. Typical ion sources used with GC are electron ionisation (EI) and chemical ionisation (CI). Both EI and CI take place inside the vacuum chamber and involve bombarding eluted molecules with energetic electrons or ions, fragmenting the neutral molecules and producing charged particles (i.e. ions). This fragmentation adds further complexity where some many chemicals are concerned, leading to mass spectral interpretation and further delays. Problems arise when component co-elute from the column and fragments over-lap. Over-lapping fragments can make it impossible to separate mass spectra and identify compounds. Co-eluting compounds will be a problem when separations are accelerated by increasing flow rate or temperature ramp for example. To address these shortcomings of previous systems, a system in accordance with the present teaching employs a ‘soft’ ionisation source that does not fragment chemical species but which instead produces one ‘molecular ion’, whose mass to charge ratio corresponds to it molecular weight, is a faster and easier means of identifying eluted compounds. The use of soft ionisation permits identification of compounds during rapid separation of compounds. Such a ‘soft’ ionisation processes may be conducted outside the GC vacuum chamber at elevated pressures and include those provided by techniques such as atmospheric pressure glow discharge ionisation (APGDI), atmospheric pressure corona discharge ionisation (APCDI), atmospheric pressure chemical ionisation (APCI), electrospray ionisation (ESI), atmospheric pressure photo ionisation (APPI), desorption electrospray ionisation (DESI), secondary electrospray ionisation (SESI) and so on.
While the specifics of the mass spectrometer have not been described herein a miniature instrument such as that described herein may be advantageously manufactured using microengineered instruments such as those described in one or more of the following co-assigned US applications: U.S. patent application Ser. No. 12/380,002, U.S. patent application Ser. No. 12/220,321, U.S. patent application Ser. No. 12/284,778, U.S. patent application Ser. No. 12/001,796, U.S. patent application Ser. No. 11/810,052, U.S. patent application Ser. No. 11/711,142 the contents of which are incorporated herein by way of reference. Within the context of the present invention the term microengineered or microengineering or micro-fabricated or microfabrication is intended to define the fabrication of three dimensional structures and devices with dimensions in the order of millimetres or sub-millimetre scale.
Where done at micron-scale, it combines the technologies of microelectronics and micromachining. Microelectronics allows the fabrication of integrated circuits from silicon wafers whereas micromachining is the production of three-dimensional structures, primarily from silicon wafers. This may be achieved by removal of material from the wafer or addition of material on or in the wafer. The attractions of microengineering may be summarised as batch fabrication of devices leading to reduced production costs, miniaturisation resulting in materials savings, miniaturisation resulting in faster response times and reduced device invasiveness. Wide varieties of techniques exist for the microengineering of wafers, and will be well known to the person skilled in the art. The techniques may be divided into those related to the removal of material and those pertaining to the deposition or addition of material to the wafer. Examples of the former include:
Wet chemical etching (anisotropic and isotropic)
Electrochemical or photo assisted electrochemical etching
Dry plasma or reactive ion etching
Ion beam milling
Laser machining
Whereas examples of the latter include:
Evaporation
Thick film deposition
Sputtering
Electroplating
Electroforming
Moulding
Chemical vapour deposition (CVD)
Epitaxy
While exemplary arrangements have been described herein to assist in an understanding of the present teaching it will be understood that modifications can be made without departing from the spirit and or scope of the present teaching. To that end it will be understood that the present teaching should be construed as limited only insofar as is deemed necessary in the light of the claims that follow.
Furthermore, the words comprises/comprising when used in this specification are to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.
| Number | Date | Country | Kind |
|---|---|---|---|
| GB1001901.6 | Feb 2010 | GB | national |
