Title of Invention

"A CHEMICAL VAPOUR MONITOR BASED ON ION MOBILITY SPECTROMETRY"

Abstract

This invention relates to an ion mobility spectrometric chemical vapour monitor comprising a housing having an ion mobility spectrometric tube (1), power supply and control grid operating circuit (5), and data acquisition system (6), all interconnected and connected with the said ion mobility spectrometric tube (1), input port alarm (8), output port alarm (9), LED display (10) and audio alarm (12), all interconnected and connected with the said ion mobility spectrometric tube (1).

Full Text

FIELD OF INVENTION: This invention relates to a based on ion mobility spectrometry, particularly to an ion mobility spectrometric chemical vapour monitor utilising time of flight ion mobility spectrometry. PRIOR ART Chemical vapour/gas monitors are utilised to sense various types of chemical vapours/gases including industrial pollutants like chlorine, nitrogen oxide (NO2), ammonia (NH3) etc or toxic vapours. Some of these chemical vapour/gas sensors are based upon the ion mobility spectrometry. These types of sensors are more versatile as they can be programmed/tuned to detect any particular gas/vapour. In ion mobility spectrometry, a spectrum of the mobility values or time of flight of ions is derived and a particular mobility value/time of flight is monitored for identification of the chemical vapour. In ion mobility spectrometry, the incoming chemical vapours are ionised using an ionisation source and the ions are introduced into a drift space in the form of thin ion bunch. This ion bunch is made to traverse within the drift space under a constant electric field gradient. During this traverse, ions of different mobility values are separated out as theses ions take different times to reach at the collector electrode, which is placed at the rear side of the drift space. These ions, arrived at collector electrode, form ion mobility spectrum. The arrival time of ions (time of flight) is observed from this spectrum, which is a characteristic of the individual chemical vapour. The sensor provides the indication of the presence of the chemical vapours based on its identification of the time of flight of the ions. A number of chemical vapour sensors, based on time of flight ion mobility spectrometry, are known in the art. However, these sensors, known in the art, suffer from the following disadvantages Primary disadvantage of the chemical vapour sensors, known in the prior art, is that these sensors require a carrier gas to carry the samples of chemical vapour inside the'ion mobility spectrometry tube. Another disadvantage of the chemical vapour sensors, known in the prior art, is that these sensors require humidity free and clean environment inside the ion mobility spectrometry tube. Yet another disadvantage of the chemical vapour sensors, known in the prior art, is that these sensors require consumables like molecular sieve, dehumidifiers, active chemicals etc in order to remove the humidity and to provide clean environment inside the ion mobility spectrometry tube, thereby needing a periodic replenishment of consumables. Still another disadvantage of the chemical vapour sensors, known in the prior art, is that these sensors can not be utilised continuously over a period of time without replenishment of the consumables. Yet further disadvantage of the chemical vapour sensors, known in the prior art, is that these sensors require periodic maintenance, depending upon the life span of the consumables used. OBJECTS OF THE INVENTION Primary object of the invention is to provide an ion mobility spectrometric chemical vapour monitor, which is based on time of flight ion mobility spectrometry. Another object of the present invention is to provide an ion mobility spectrometric chemical vapour monitor, which is capable of monitoring industrial pollutants chlorine (C12), Ammonia (NH3), Nitrogen oxides (NO, N02), toxic chemical pollutants and even nerve agents agents like sarine, soman, tabun etc. Yet another object of the invention is to provide an ion mobility spectrometric chemical vapour monitor, which utilises differential spectrum (real time spectrum - background spectrum) for chemical vapour sensing purposes. Still further object of the invention is to provide an ion mobility spectrometric chemical vapour monitor, which can be programmed to sense any of the chemical vapour depending upon its differential mobility spectrum, and can be used for monitoring its presence in external environment. Yet further object of the invention is to provide an ion mobility spectrometric chemical vapour monitor, which does not require any carrier gas for sampling of the input chemical vapour/gas. Still further object of the invention is to provide an ion mobility spectrometric chemical vapour monitor , which does not require any chemical gas for dehumidising or cleaning the environment inside the instrument. Yet further object of the invention is to provide an ion mobility spectrometric chemical vapour monitor , which utilises ambient air, present in the environment, as the carrier gas for carrying the input chemical vapour inside the chemical vapour/gas monitor. Still further object of the invention is to provide an ion mobility spectrometric chemical vapour monitor, which can monitor incoming chemical vapor/gas within 30 seconds and provide an appropriate audio alarm if necessary. Yet further object of this invention is to provide an ion mobility spectrometric chemical vapour monitor, which can detect the presence of any chemical vapour in sub PPM (Part Per Million) levels. Still further object of the invention is to provide an ion mobility spectrometric chemical vapour monitor, which can provide an alarm indicating the presence of any toxic chemical vapour/nerve agent, if necessary. Yet further object of the invention is to provide an ion mobility spectrometric chemical vapour monitor, which is portable, easy to deploy and easy to transport for use in actual field conditions. Still further object of the invention is to provide an ion mobility spectrometric chemical vapour monitor, which can continuously operate for 24 hours with the help of a 12 Volt DC/230 V AC supply. SUMMARY OF THE INVENTION According to the present invention, there is provided an ion mobility spectrometric chemical vapour monitor comprising a housing having:- an ion mobility spectrometric tube (1); power supply and control grid operating circuit (5), and data acquisition system (6), all interconnected and connected with the said ion mobility spectrometric tube (1); input port alarm (8), output port alarm (9), LED display (10) and audio alarm (12), all interconnected and connected with the said ion mobility spectrometric tube (1). In accordance with the present invention the ion mobility spectrometric chemical vapour monitor is based on time of flight ion mobility spectrometry. The sensor of the present invention is capable of sensing industrial pollutant gases like chlorine (C12), Ammonia (NH3), Nitrogen oxides (NO, NO2) etc. as well nerve agents like sarine, soman, tabun etc. within half a minute. The monitor of the present invention does not require carrier gas for sampling of input gas vapours and it utilises ambient air, present in the environment, as the carrier gas for sampling the input chemical vapours. The monitor does not need any other means to remove humidity or chemical contamination within the instrument as it utilizes differential spectrum (real time spectrum-background spectrum) for chemical vapour sensing purposes. The monitor of the present invention can operate over an extended period of time as it does not require replenishment of carrier gas or any other consumables. The monitor is capable of providing differential spectrum with the help of electric circuits which serve as characteristic for monitoring particular chemical vapours. The sensor is portable, easy to transport and deploy in actual field conditions. The monitor comprises of ion mobility spectrometry tube (IMS), High Voltage Source and pulse generation electronics, suction pump, a micro control based data acquisition system, and LED Display and Alarm board, input output ports and power supply connectors. The sensor is capable of sensing the presence of input vapour in sub PPM (Part Per Million) levels within half a minute. The monitor can be programmed to sense any of the chemical vapour depending upon its differential mobility spectrum, and can be used for monitoring its presence in external environment. Any further characteristics, advantages and applications of the invention will become evident from the detailed description of the preferred embodiment which has been described and illustrated with the help of following drawings wherein, DESCRIPTION OF THE DRAWINGS Fig 1 - describes the isometric view of the ion mobility spectrometric chemical vapour monitor of the present invention. Fig 2 - shows the schematic layout of the ion mobility spectrometric (IMS) tube DESCRIPTION OF INVENTION WITH RESPECT TO DRAWINGS: Referring to Fig (1), the ion mobility spectrometric chemical vapour monitor of the present invention comprises of a suitably designed ion mobility spectrometry (IMS) tube (1), which works as basic sensor component. It further comprises two main cylindrical regions namely reaction region (2) and drift region (3) both formed by a state of circular metal rings, which are biased to linearly dropping voltage generating a uniform axial electric field for causing drift of ions from a radioactive ionisation source (Ni63) (13) in reaction region (2) to the collector (4) in drift region (3). Ambient air, water vapour and other gas molecule, on inhaling by input port (21), pass through ionisation source, get ionised and drift towards collector (4), At the entry point to drift region (3), there is an electronic control grid (14), which on momentary opening, allows a bunch of ions to enter the drift region (3). The time of flight (TOF) of ions from control grid (14) to collector (4), measured between instants of applied control pulse and ion peak, due to different mobility of different product ions form the basis of identifying them. The IMS tube is made of stainless steel rings (15), separated by Teflon spacers (16), closely fitted so as to make a partially sealed structure. Front end opening of the tube acts as input for the air sample to be sensed and is fitted with ionization source Ni 63 (13) of suitable activity. At the approximate rear end of the drift end tube there is an exhaust port (19) fitted with a suction pump (7). An electronic control grid is fitted just on entry to the drift region. At the rear end of the drift tube, a suitably designed Faraday cup (17) is present to receive the ions. Before the Ni 63 ionisation source a front end heater and diffuser needle (20) is mounted. All the rings are connected with a resistive network (11) to a source which is excited with a specially designed low noise high voltage (3.5 Kv) power supply and control grid operating pulse generating circuit (5). The Faraday cup present at the rear end is connected to a suitably designed low noise electrometer amplifier (18) and data acquisition system (6). The system contains various control switches; display LEDs (10), relay port for remote alarm and diagnostic indications like low battery ready etc. The above assembly has been housed in a rectangular sheet metal enclosure, having input (8) and output port (9) alarm, ON/OFF switches and various other controls. To enable the satisfactory function of instrument, the equipment has been guarded by EMI shielding on its amplifier, micro controller block and high voltages PCB. Also the capacitor filters have been put at various nodes of the, resistive network, so as to prevent the conducted noise to the signal. The output signal of the IMS tube is amplified and received by data acquisition system (6), which performs the task of signal averaging and storing the spectral output of the basic sensor. When the chemical vapour sensor is switched on and when its warm up time is over, the data acquisition system (6) stores the spectral output of the background (air) which is taken as reference background spectra. When the chemical vapour sensor, to be sensed, reaches at the input port of the instrument, it modifies the IMS spectral output. The IMS spectral output, in this situation, is the spectral output of the chemically contaminated air. The differential spectra is obtained by subtracting the background spectra from the chemically contaminated air spectra (in the presence of chemical vapour). The differential spectra, thus obtained, indicates the increase in charge at definite position depending upon the ion mobility of the input chemical vapour. The ion mobility spectrometric chemical vapour monitor can also provide an alarm indicating the presence of any particular chemical vapour. For this purpose, the peak position data pertaining to different chemical vapours are pre stored in the micro controller from data library/ earlier experiments. In case of presence of chemical vapours in the input sample, the peak positions ( indicating the presence of chemical vapours ) are compared with the pre-stored data and an alarm is given by the instrument in case of a match between the two. The sample containing the air and chemical vapours is taken through direction suction into the ion mobility spectrometric chemical vapour monitor. The sample is pre-heated moderately and is ionised by a NI-63 radio source (13) resulting. in a molecular cluster. These clusters move forward under the potential gradient within the IMS tube depending upon the polarity with respect to the reflector electrode, which is kept at a positive potential. The positive ion clusters move towards the Faraday cup. The ions reach in the drift region (3) through shutter grid (14), which opens for a small duration (0.2-0.5 ms) at every 40 ms interval. The bunches of ions of different chemical vapours reach at Faraday cup (17) at different interval depending upon their respective mobility ranges. The peaks, pertaining to ions of different mobility ranges, are isolated using differential signal isolation and signal averaging techniques. The amplifier circuit (18) in the Faraday cup (18) amplifies these peaks. The data acquisition system (6) of this device receives the amplified signals. It does the signal averaging to reduce the noise and isolates the ion spectra out of background spectra, processes it and finally compares it with the pre-loaded database to provide identification and intensity for setting off the audio alarm (12). The instrument is initially exposed to clean atmosphere and after a short warm up time of about 5 minutes becomes ready to be exposed to the contaminated air brought at its input port (21). The data acquisition window of the device is programmed/tuned for particular type of chemical or for particular peak position, which is occupied by the spectra of the input signal. The instrument provides an intensity of the contamination and even an audio alarm (12) when the contamination exceeds pre-set limits. The contamination is passed out from the exhaust port to outside atmosphere. The present embodiment of the invention, which has been set forth above, was for the purpose of illustration and is not intended to limit the scope of the invention. It is to be understood that various changes, adaptations and modifications can be made in the invention described above by those skilled in the art without departing from the scope of the invention, which has been defined by following claims. WE CLAIM: 1. An ion mobility spectrometric chemical vapour monitor comprising a housing having: an ion mobility spectrometric tube (1); power supply and control grid operating circuit (5), and data acquisition system (6), all interconnected and connected with the said ion mobility spectrometric tube (1); input port alarm (8), output port alarm (9), LED display (10) and audio alarm (12), all interconnected and connected with the said ion mobility spectrometric tube (1). 2. An ion mobility spectrometric chemical vapour monitor as claimed in claim (1), wherein the said ion mobility spectrometric tube (1) is made of metallic rings (15) closely fitted and separated by Teflon spacers (16) so as to make partially sealed structure having two main cylindrical reaction region (2) and drift region (3) and comprising: an input port (21) and exhaust port (19) fitted with a suction port (7), the said input port (21) and exhaust port (19) fitted at opposite ends of the said ion mobility spectrometric tube (1); a radioactive ionisation source (13) for preheating and ionising the input sample gas in the said reaction region (2), an electronic shutter grid (14) and collector (4) in the said drift region (3), a Faraday cup (17) connected with a low noise electrometer amplifier (18), a front end heater and diffuser needle (11), and a resistive network (11) all fitted inside the said ion mobility spectrometric tube (1) . (3). An ion mobility spectrometric chemical vapour monitor as claimed in claim (1), wherein the said electronic shutter grid (14) opens for a duration of about 0.2-0.5 ms at every 40 ms interval. (4). An ion mobility spectrometric chemical vapour monitor as claimed in claim (1), wherein the said input port (21) passes the ambient air and sample gas to the said collector (4) in the said drift region (3) after passing through the said ionisation source (13) in the said reaction region (2) in the said ion mobility spectrometric tube (1) (5). An ion mobility spectrometric chemical vapour monitor as claimed in claim (1), wherein the said ion mobility tube sensor performs the task of basic sensor (6). An ion. mobility spectrometric chemical vapour monitor as claimed in claim (1), wherein the said data acquisition system (6) performs the task of signal averaging and storing the spectral output of the basic sensor. (7). An ion mobility spectrometric chemical vapour monitor as claimed in claim (1), wherein the said audio alarm (12) send an audio alarm when a particular contamination exceed pre-set limits. (8) utilizes ambient air, present in the environment, as the carrier gas for sampling the input chemical vapours (9) An ion mobility spectrometric chemical vapour monitor substantially as cla-imed and illustrated herein.

Documents:

1434-Del-2003-Abstract-16-04-2008.pdf

1434-del-2003-abstract.pdf

1434-Del-2003-Claims-16-04-2008.pdf

1434-del-2003-claims.pdf

1434-Del-2003-Correspondence-Others-16-04-2008.pdf

1434-del-2003-correspondence-others.pdf

1434-del-2003-correspondence-po.pdf

1434-Del-2003-Description (Complete)-16-04-2008.pdf

1434-del-2003-description (complete).pdf

1434-del-2003-drawings.pdf

1434-del-2003-form-1.pdf

1434-del-2003-form-18.pdf

1434-Del-2003-Form-2-16-04-2008.pdf

1434-del-2003-form-2.pdf

1434-Del-2003-Form-3-16-04-2008.pdf