Method for the qualitative and quantitative detection of vapours from low volatility compounds

Claim 3

A method according to claim 1 in which said conveying of the isolated flow to the detector for detecting the presence of components is along a first path, in which the thereafter continued isolated flow to the detector is along a second path, and in which said separating of the isolated flow into its individual components is carried in said second path and prior to introduction of said individual components into said detector.

Claim 4

A method according to claim 1 including directing said isolated flow along the same path to the detector, both for initially detecting the presence of components of interest and for thereafter identifying the individual components, wherein said separating step includes releasing the separated components individually to the detector for identification therein.

Claim 5

A method according to claim 1 in which said components are low volatility components and said step of isolating includes diFfusion of such low volatility components through a membrane and said step of conveying includes sweeping the rear of the membrane with an inert carrier gas stream to carry such diffused components away from said membrane and on toward said detector.

Claim 6

A method according to claim 1 in which the components of interest are low volatility components and in which said separating step includes passing the continuing isolated flow through a chromatographic column ahead of the detector while initially maintaining such column at ambient temperature to initially trap such low volatility components therein and while allowing volatile components to rapidly pass through such column and detector without separation and identification thereof, thereafter heating the column to increase its temperature gradually from abient temperature to elute said trapped components of interest trapped at corresponding differing temperatures, thereby to separate individual components flowing out of the column to the detector, said step of identifying including operating the detector to provide an output having peaks corresponding to respective individual components and using the elution time or elution temperature of each peak to identify the component.

Claim 7

A method according to claim 5 in which said conveying step includes entraining isolated components in a first carrier gas and in which said flowing step includes introducing a second carrier gas between said column and detector substantially in excess of the flow through the column so as to minimize changes in flow into the detector due to variations in column flow due to temperature change in the column.

Claim 8

A method according to claim 5 in which said conveying and detecting steps include maintaining the path of the flow of isolated components to the detector at a temperature at which even the most involatile components of interest will pass rapidly therethrough without condensation, and in which components of interest with vapors pressures lower than 10 7 Torr are detectible.

Claim 11

An apparatus according to claim 8 in which the isolating means comprises a silastomer membrane.

Claim 12

An apparatus according to claim 8 in which the separating means comprises a chromatographic column and means for selectively raising and lowering the temperature of the column.

Claim 13

An apparatus according to claim 10 wherein a single said gas flow path is provided from said isolating means to said detector and through said chromatographic column interposed therebetween, said means for raising and lowering temperature including heating means for maintaining the column at an elevated temperature at which even the most involatile component of interest will pass rapidly through the column, so as to enable said indication by the detector that at least some component of interest is present in the atmosphere, and means for rapidly cooling said column thereafter to a reduced temperature so as to trap low volatility components of interest in the column, said separating of components one from the other being carried out by thereafter reactuating said heating means to gradually reheat said column and elute said trapped components therefrom as their elution temperatures are reached one by one.

Claim 14

An apParatus according to claim 10 in which said means for raising and lowering temperature comprises a thin wall of electrically conducting material of the column and means for passing an electrical current along said wall for heating the column and further comprises means including a fan for directing cold air at the column for cooling same.

Claim 15

An apparatus according to claim 10 in which said means for raising and lowering temperature include means for normally maintaining said column at least initially substantially at ambient temperature after there is indication of presence of a component of interest and wherein volatile components not of interest and to which the detector may respond pass rapidly through the column and detector at such ambient temperature whereas low volatility components of interest are trapped at the front of the column for later release to the detector for identification.

Claim 16

An apparatus according to claim 8 including first and second gas flow paths between the isolating means and the detector, in which said separating means comprises a chromatographic column in said second path, and further including selectively operable valve means for directing the flow along the first path to provide said indication that some components of interest are present and thereafter for directing the flow along the second path through said chromatographic column to accomplish said separating of components one from another, and means for raising and lowering the temperature of the column.

Claim 17

An apparatus according to claim 14 in which said means for raising and lowering the temperature of the column includes cooling means for normally maintaining said column at a reduced temperature so as to trap low volatility components of interest within said column and heating means for gradually increasing the temperature of the column to a temperature elevated above ambient temperature for eluting, in sequence, the trapped components of interest in separated form for sequential application to said detector, wherein said detector responds sequentially to said released components and the elution time or temperature of each detector signal identifies the particular component.

Claim 18

An apparatus according to claim 8 including a common pump means both for drawing a sample of the atmosphere into the vicinity of the isolating means and for drawing a carrier gas flow through the detector.

Claim 19

An apparatus according to claim 16 in which said common pump means directly connects to the gas output of the detector and connects through a further path to a portion of said isolating means for drawing atmosphere thereinto, the latter connection including a flow restrictor to enable a gas flow to be maintained from said isolating means through said detector.

Claim 20

An apparatus according to claim 8 in which the detector comprises an electron capture detector and said components of interest are electron capturing compounds.

Claim 21

An apparatus according to claim 18 in which the components of interest are nitrated explosives.

Claim 22

An apparatus according to claim 8 including heater means and thermostat means controlling same for heating to a controlled temperature said isolating means, said detector and the path therebetween utilized for carrying out said detecting that components are present.