Title of Invention

"AN IMPROVED PORTABLE GAS CHROMATOGRAPH"

Abstract

This invention relates to an improved portable gas chromatograph for detection identification and quantification of organic toxic chemical agents in a sample gaseous mixture or sample atmospheric air utilising atmospheric air as carrier gas and comprising: (a) a sample processing module (1) is having a pre-concentration device such as sorbent tube (6) with a inlet port (5) at one end for introduction of atmospheric air an outlet at the opposite end; (b) an analysical module comprising a capillary column (10) disposed within a housing (11) and having an inlet end adapted to be connected to the outlet of said tube and an outlet at the opposite end adapted to be connected to a detector base (G); (c)pump assembly module (4) comprising a sample draw pump (17) adapted to be connected to the said capillary column (10) and a needle valve (18) adapted to be connected to the said capillary column (10) at the said detector base (16); (d) microprocessor module (4) for controlling heating of sorbent tube (6) end for analysis and processing of the data.

Full Text

FIELD OF INVENTION The present invention relates to a portable gas chromatograph lor on site detection, identification and quantification of organic toxic chemical agents present in a sample gaseous mixture or a sample of atmospheric air. PRIOR ART A gas chromatograph is an analytical instrument that separates a gaseous sample into individual components thus allowing detection, identification and quantifiecation of these components. Basically, conventional portable gas chromatographs. known in the art, comprise sample processing module, analytical module and data processing module. These gas chromatographs employ a carrier gas for transporting sample into the analytical module. A small lecture bottle of carrier gas acts as a reservoir of carrier gas. (ienerally. these carrier gases are inert gases which do not react with the sample gases. The earrier gas sweeps the sample gases inside the analytical module. Analytical module separates the sample gaseous sample into individual components and a detector detects and measures the individual components. In these known portable gas ehromatogiaphs analysis of sample gas mixture is done at room temperature. However these gas chromatographs, known in the art, suffer from following disadvantages. Primary disadvantage of known portable gas chromatographs is that when the carrier gas of the lecture bottle is consumed, it needs refilling for the next opeiaiion oi the instrument Another disadvantage of known portable gas chromatographs is that with the gradual consumption of carrier gas, the gas pressure gradually drops down thus adversely affecting the separation and identification efficiency of the instrument. Yet another disadvantage of known portable gas chromatographs is that provision of separate gas cylinder along with its pneumatics makes the s\steni bulky and inconvenient for transportation. Still another disadvantage of known portable gas chromatographs is that semi-volatile and chemical agents with high boiling points condense at the detector resulting in gradual decrease in sensitivity of the detector over a period of time. Yet another disadvantage of known portable gas chromatographs is that there is no provision for pre-concentration during the sampling of gaseous samples so that it is unable to detect sample components which are present in very low coneentiations Still another disadvantage of known portable gas chromatographs is that (hcse chromatographs can analyse the sample mixture on one time basis and can not perform analysis on continuous basis. Yet another disadvantage of known portable gas chromatograplis is that these can not be operated by both AC and DC supply for use in laboratory as well as field. OBJECTS OF THE INVENTION Primary object of the invention is to propose a portable gas chromatograph which utilises atmospheric air itself as a carrier gas thereby obviating the need for a separate carrier gas cylinderTor analysing the sample mixture gas. Another object of the invention is to propose a portable gas chromatograph which does not need complex interfacing pneumatics for carrier gas thereby making the system compact and lightweight. Still another object of the invention is to propose a portable gas chromatograph which can detect the presenceofany organic toxicants present in the air. Yet another object of the invention is to propose a portable gas chromatograph which utilises a pre-concentration device for the sampling gas mixture in the lorni of a sorbent tube thereby making the system more sensitive in detecting any cheniical agent. Yet further object of the invention is to propose a portable gas chromatograph which utilises a highly thermally stable sorbent tube with better desorption efficiency for semi-volatile toxic chemicals thereby resulting in enlianced sensitivity of the instrument. Still another object of the invention is to propose a portable gas chromatograph which utilises a polymeric sorbent having higher adsorption capacity for organic toxicants present in the sample mixture or air thus enabling the instrument to anal>se even in presence of higher concentration of any particular component in sampled gas. Still further object of the invention is to propose a portable gas chromatograph which utilises a heater at the detector thereby preventing condensation ol any semi-volatile components in gas sample with high boiling points on the detector. Yet another object of the invention is to propose a portable gas chromatograph which can detect and analyse even small traces of organic toxic chemical agents present in the sample gas in the order of parts per billion . Still further object of the invention is to propose a portable gas chromatograph which can be operated by AC or DC thereby making it possible to transport it in the field for analysis of sample gaseous mixture or air. Yet another object of the invention is to propose a gas chromatograph which is microprocessor controlled thereby making it automatic and highly versatile. Still another object of the invention is to propose a portable gas chromatograph which utilises a analytical column having minimum deterioration in the presence of oxygen in the same mixture or in the art. STATEMENT OF THE INVENTION According to this invention there is provided an improved portable gas chromatograph for detection, identification and quantification of organic toxic chemical agents in a sample gaseous mixture or sample atmospheric air utilising atmospheric air as carrier gas and comprising: a. a sample processing module is having a pre-concentration device such as sorbent tube with a inlet port at one end for introduction of atmospheric air an outlet at the opposite end; b. an analytical module comprising a capillary column disposed within a housing and having an inlet end adapted to be connected to the outlet of said tube and an outlet at the opposite end adapted to be connected to a detector base (G); c. pump assembly module comprising a sample draw pump adapted to be connected to the said capillary column and a needle valve adapted to be connected to the said capillary column at the said detector base; d. microprocessor module for controlling heating of sorbent tube and for analysis and processing of the data. SUMMARY OF THE INVENTION In accordance with the present invention there is provided a microprocessor controlled portable gas chromatograph with a capability to detect, identily and uantify organic toxic chemical agents present in sample mixture or sample atmospheric air. The instrument has capability to detect even small traces of organic toxic chemical agents present in the sample mixture or air in as small concentration as one part in one billion. The proposed gas chromatograph utilises atmospheric air itself as carrier gas and docs not need any separate carrier gas cylinder to transport the sample mixture gas into the analytical module of the instrument for analysis. The proposed portable gas chromatograph is compact, lightweight and can be operated on continuous and unattended basis. It can be operated by AC as well as DC power supply and can be mounted on a vehicle and transported to the field for detection and analysis purpose. The proposed gas chromatograpgh comprises sample processing module. analytical module, pump assembly module and a microprocessor module. It employs a highly thermal stable sorbent tube which acts as pre-concentration unit by trapping individual chemical components of the sample mixture thereby enhancing the sensitivity of the instrument. Sorbent tube also acts as injector and injects the sample mixture into the analytical module when it is heated to a preset time period. It also utilises a heater in detector so as to prevent condensation of semi-volatile and gases with high boiling point on the detector. The sample is sucked along with the atmospheric air through the inlet port, on to the photoionisation detector through sorbent tube and a wide bore capillary column . A sample draw pump is connected to the capillary column which pulls the air from the inlet port to the sample outlet port . The functioning of proposed portable gas chromatograph is controlled by microprocessor module. The microprocessor controls the heating of the sorbent tube. detector power supply and complete data processing. It presents the results of the sample analysis in strip-chart as well as in tabulated form through a built-in printer. The microprocessor also actuates the built-in audio-buzzer, when the amount ot any component of the sample mixture exceeds the preset value. DESCRIPTION OF FIGURES Additional advantages and features of the present invention will become apparent from the detailed description of the preferred embodiment which has been described with the help of the following drawings wherein : Fig. (1) shows schematic diagram of the proposed portable gas chromatograph Fig. (2) shows schematic diagram of the sample processing module Fig. (3) shows schematic diagram of the analytical module Fig. (4) shows schematic diagram of the pump assembly DETAILED DESCRIPTION OF THE PREFRRRRI) EMBODIMENT Referring to Fig.l, the portable gas chromatograph comprises ol sample processing module(l), analytical module (2), pump assembly module (3) and microprocessor module (4). Referring to Fig. 2, the sample processing module comprises a soibeni tube (6) filled with a trapping polymer (7) of high thermal stability and with an inlet-poii (5) made up of stainless-steel and a suitable heater arrangement (8). The outlet of the sorbent tube (6) is connected to one end of the capillary column (10) in the analytical module (2) through a teflon adopter (9). The atmospheric air comprising the sample mixture is sucked through the inlet-port (5) on to the sorbent tube (6) during the sampling proeess; After the sampling cycle, the sorbent tube (6) is electrically heated for the preset time duration. It facilitates the thermal desorption of the sample mixture into the analytical module (2) as a single plug. Thus, the sorbent tube (6) acts as a pre-conceniiator as well as an injector. Referring to Fig. 3, the analytical module (2) comprises a wide bore capillary column (10) of suitable non-polar bonded phase of requisite length housed in the column housing (11), photoionisation detector (12), heater (13) and a thermocouple arrangment (14). Sample processing module (1) is connected to the analytical module(2) through teflon ferrule connection (15). One end of the capillary column (10) is fitted straight into the sorbent tube (6) through teflon ferrule connection (15) and the other end is connected to the detector base (16) in order to minimise the dead volume. Referring to Fig. 4, the pump assembly module (3) comprises a small sample draw pump (17), a fine needle valve (18) and outlet port (19). The pump assembly (3) helps in sampling of the sample mixture and facilitates atmospheric air to work as carrier gas. The sample draw pump (17) is connected to the capillary column (10) in the analytical module (2) through a T joint at the detector base (16) . The fine needle alve (18) is also connected to the capillary column (10) through the same I Joint at the detector base (16). The needle valve (18) acts as a metering valve and controls the sample mixture flow from the capillary column (10) to the photoionisation detector (12). Sample contamination via the sample draw pump (17) is avoided as it is placed down the stream of the capillary column (10). The sample mixture is sucked along with the atmospheric air throuuh the inlet port (5), located in front panel of the instrument, on to the photoionisation detector (12) through sorbent tube (6) and wide bore capillary column(lO). The sample draw pump(17) is connected to the capillary column (10) through a T joint at the detector base (12). It pulls the air from the inlet port (5) to the sample outlet port (19) locaiecl in lionl panel of the instrument. The sample is pre-cohcentratcd by adsorptive trapping on a bed of polymeric sorbent and subsequently thermally desorbed into the capillary columnn (10). The polymeric sorbent (6) of the proposed instrument has particularly large adsorption capacity and higher desorption efficiency for the toxic chemical agents. Moreo\er. ii has desirable high thermal stability upto 500°C and low affinity for water vapor. Rapid cooling of the sorbent tube (6) is also facilitated by keeping a small fan placed benealh the sorbent tube (6) and by allowing cool ambient air to circulate. The functioning of proposed portable gas chromatograph is conrrolled by microprocessor module (4). The microprocessor controls the heating of the sorbent lube. detector power supply and complete data processing. It presents the results of the sample analysis in strip-chart as well as in tabulated form through a built-in printer. The microprocessor (4) also actuates the built-in audio-buzzer, when the amount ot any component of the sample mixture exceeds the preset value. The microprocessor has nonvolatile memory for process options and alarm levels that are user selected, 1 hese values are retained even when power is turned off It provides the result of the analysis on a LCD display. Alarm levels for selected components of the sample mixture can be user input and if the amount of the selected component in the sample air exceeds this limit an alarm is triggered and visual LED and the audio buzzer is actuated. The embodiment of the invention which has been set forth above is for the purpose of illustration only and it is not intended to limit the scope of the invention. It is to be understood that various changes and modifications may be made in the unemion described above by those skilled in the art without departing from the seope ol the invention which has been defined by the following claims. WE CLAIMS ;- 1. An improved portable gas chromatograph for detection, identification and quantification of organic toxic chemical agents in a sample gaseous mixture or sample atmospheric air utilising atmospheric air as carrier gas and comprising: a. a sample processing module (1) is having a pre-concentration device such as sorbent tube (6) with a inlet port (5) at one end for introduction of atmospheric air an outlet at the opposite end; b. an analytical module comprising a capillary column (10) disposed within a housing (11) and having an inlet end adapted to be connected to the outlet of said tube and an outlet at the opposite end adapted to be connected to a detector base (G); c. pump assembly module (4) comprising a sample draw pump (17) adapted to be connected to the said capillary column (10) and a needle valve (18) adapted to be connected to the said capillary column (10) at the said detector base (16); d. microprocessor module (4) for controlling heating of sorbent tube (6) and for analysis and processing of the data. 2. A portable gas chromatograph as claimed in claim 1 wherein the said sorbent tube (6) is filled with a trapping polymer (7) as herein described and is provided with a heater arrangement (8). 3. A portable gas chromatograph as claimed in claim 1 wherein the said pump assembly module (3) has an outlet port (19) for the gaseous sample mixture. 4. A portable gas chromatograph as claimed in claim 1 wherein said sample draw pump is connected to the capillary column (10) at a detector base. 5. A portable chromatograph as claimed in claim 1 wherein the housing of said analytical module is provided with a photoionisation detector. 6. A portable gas chromatograph as claimed in claim 1 comprising a heater disposed within said housing of the analytical module. 7. A portable gas chromatograph substantially as herein described and illustrated.

Documents:

1368-del-1999-abstract.pdf

1368-del-1999-claims.pdf

1368-del-1999-complete specification (granted).pdf

1368-del-1999-correspondence-others.pdf

1368-del-1999-correspondence-po.pdf

1368-del-1999-description (complete).pdf

1368-del-1999-drawings.pdf

1368-del-1999-form-1.pdf

1368-del-1999-form-19.pdf

1368-del-1999-form-2.pdf

1368-del-1999-form-26.pdf

1368-del-1999-form-3.pdf