CA2097269A1 - Sampling device for determining wood species using rapid desorption of organic compounds - Google Patents
Sampling device for determining wood species using rapid desorption of organic compoundsInfo
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- CA2097269A1 CA2097269A1 CA 2097269 CA2097269A CA2097269A1 CA 2097269 A1 CA2097269 A1 CA 2097269A1 CA 2097269 CA2097269 CA 2097269 CA 2097269 A CA2097269 A CA 2097269A CA 2097269 A1 CA2097269 A1 CA 2097269A1
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- Prior art keywords
- wood
- vapor
- sampling
- sample
- emissions
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/46—Wood
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- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Health & Medical Sciences (AREA)
- Medicinal Chemistry (AREA)
- Food Science & Technology (AREA)
- Wood Science & Technology (AREA)
- Physics & Mathematics (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Sampling And Sample Adjustment (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A sampling device rapidly desorbs organic compounds from a wood surface using a laser desorption cell. The device may be used with an ion mobility spectrometer to produce an ion drift time signature which can be used to determine wood species. Wood pieces are conveyed on a conveyor and a laser desorption cell is placed adjacent to a surface of the wood. A laser beam is projected onto the wood surface through the laser desorption cell in a series of pulsed emissions, and permits the identification to be made as wood pieces are moving on a conveyor. A high energy beam such as a laser is projected onto a sample in a series of pulsed emissions, the time of each emission is controlled, the pause between emissions is controlled, the number of emissions per series is controlled and the energy per emission is controlled to ensure temperature increase of the sample is sufficient to desorb a vapor and the vapor is heated sufficiently for analysis in the ion mobility spectrometer.
A sampling device rapidly desorbs organic compounds from a wood surface using a laser desorption cell. The device may be used with an ion mobility spectrometer to produce an ion drift time signature which can be used to determine wood species. Wood pieces are conveyed on a conveyor and a laser desorption cell is placed adjacent to a surface of the wood. A laser beam is projected onto the wood surface through the laser desorption cell in a series of pulsed emissions, and permits the identification to be made as wood pieces are moving on a conveyor. A high energy beam such as a laser is projected onto a sample in a series of pulsed emissions, the time of each emission is controlled, the pause between emissions is controlled, the number of emissions per series is controlled and the energy per emission is controlled to ensure temperature increase of the sample is sufficient to desorb a vapor and the vapor is heated sufficiently for analysis in the ion mobility spectrometer.
Description
2~972~9 SAMPLING DEVICE FOR DET~RMI~IN~
WOOD SPECIES USING RAPID DESORPTION
OF ORGANIC C~MPOU~DS
The present invention relates to a sampling device suitable for identification of wood species. More specifically the present invention provides a rapid desorption method and apparatus for desorption of organic compounds from solid and liquid samples. By utilizing an ion mobility spectrometer, wood may be sampled to determine its species.
The method of identifying wood species using an ion mobility spectrometer (referred to as an IMS detector) is disclosed in U.S. Patent 5,071,771. In this patent is disclosed taking a sample of wood, heating it and then collecting a trace vapor from the wood sample and analyzing the trace vapor in the IMS detector to produce an ion mobility signature. This signature i8 then compared with known signatures of different species of wood, and the species of wood is determined.
The patent discloses heating a wood surface at a temperature in the range of about 220 to 350C, and then sampling a trace vapor of desorbed wood. The vapor is transferred to the ionizing zone of an IMS detector. The vapors are ionized at a temperature in the range of about 220 to 350C, the ions are pulsed from the ionizing zone through a gate into a drift region and then the time of -arrival of the ions and the ion flux is determined for each pulse with a collector electrode located at the end of the drift region to produce an ionic signal. The signal is amplified and averaged to provide an ion drift time signature for the wood sample. Rapid sampling allows identification of wood species in short times.
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.
It is an aim of the present invention to provide a sampling device and a method of sampling for determining wood species in lumber yards, sawmills and the like, particularly when timber and lumber pieces are advancing on a conveyor. It is another aim of the present invention to provide a device that identifies the species when the wood is stationary or moving on the conveyor without stopping the conveyor. It is a further aim to sample and identify at least thirty pieces of wood a minute.
A still further aim of the present invention is to provide a method and apparatus to rapidly desorb organic compounds from solids or liquids. The desorption is controlled by utilizing a high energy beam, such as a laser. The intensity of the beam and duration of the beam are controlled to provide the required desorbed v~por sample that can be used for further analysis.
The present invention provides a method of rapidly desorbing an organic compound vapor from a solid or liquid sample, and further analyzing the sample, comprising the steps of projecting a high energy beam, such as a laser beam, onto a surface of the sample in a series of pulsed emissions, controlling time of each emission, controlling pause between each emission, controlling energy per emission to ensure temperature increase of the sample is sufficient to desorb the vapor, and the vapor is heated to a predetermined temperature, and further analyzing the vapor.
In a further embodiment a method of sampling a wood piece is disclosed comprising the steps of projecting a series of pulsed beam emissions from a laser source onto a surface of the wood piece, controlling the series of pulsed emissions to desorb a wood sample, and extracting vapor from the wood sample for further analysis.
, . . . . . .
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' ' . ' '~ ' . ' ~ ~' ' ' 2~97269 In a still further embodiment the present invention provides a method of sampling a wood piece comprising the steps of projecting a series of pulsed beam emissions from a laser source onto a surface of the wood piece, controlling the series of pulsed beam emissions to desorb organic vapor from a wood sample, extracting the vapor from the heated wood sample, transferring the vapor to an ionizing zone in an IMS detector, analyzing the vapor to produce an ion drift time signature for the wood sample, and comparing the ion drift time signature of the wood sample with known ion drift time signatures of different wood species, to determine species of the wood sample.
~ et a further embodiment provides a method of sampling wood pieces advancing on a conveyor, comprising the steps of moving a laser desorption cell on a carriage at the same speed and aligned with a wood piece advancing on the conveyor belt, moving the laser desorption cell to contact the wood piece, projecting a series of pulsed beam emissions from a laser source onto the wood piece through the laser desorption cell, controlling the series of pulsed beam emissions to desorb organic vapor from a wood sample, extracting the vapor from the heated wood ~:
sample in the laser desorption cell, transferring the vapor to an ionizing zone in an IMS detector, analyzing the vapor to produce an ion drift time signature for the wood sample and comparing the ion drift time signature with known ion drift time signatures of different wood species to determine the species of the wood sample.
Another embodiment provides an apparatus for sampling wood pieces comprising a laser desorption cell adapted to be placed on a wood surface, a laser source for projecting a laser beam through the laser desorption ~:
cell onto the wood surface, control means for the laser source to produce a series of pulsed beam emissions to desorb organic vapor from a wood sample, extraction and .. j . ,~ , :. -~ :
2~97269 , transfer means to extract the vapor from the heated wood sample and transfer the vapor to an ionizing zone in an IMS detector, and means to produce an ion drift time signature from the IMS detector and identify species of the wood sample.
In a still further embodiment, there is provided an apparatus for sampling wood piece~ advancing on a conveyor, comprising a carriage containing a laser desorption cell mounted on slide means positioned adjacent the conveyor, the slide means providing a path for movement of the carriage, engaging means on the carriage to engage a wood piece advancing on the conveyor, so the carriage advances a predetermined distance on the path in conjunction with the wood piece, return means for returning the carriage to a start position on the path after the pickup pin has disengaged the wood piece, cross movement means for the laser desorption cell to move and contact an end of the wood piece when the carriage is advancing on the path, laser source for projecting a laser beam through the laser desorption cell onto the wood piece, control means for the laser source to produce a series of pulsed beam emissions to desorb organic vapor from a wood sample, extraction and transfer means to extract the vapor from the heated wood sample and transfer to an ionizing zone in an IMS detector, and means to produce an ion drift time signature from the IMS detector and identify species of the wood sample.
In drawings which illustrate embodiments of the present invention, Figure 1 is a diasrammatic view showing a laser desorption cell positioned against a wood piece and showing a sampling tube to an IMS detector, ~-- .,. :. :.. ~ : . . .
.... . ~ . .
2~972~9 .
Figure 2 is a schematic diagram showing sampling of a wood piece including the controlsO
Figure 3 is an isometric view showing wood pieces moving on a conveyor with a laser desorption cell supported by a carriage moving backwards and forwards on a sliding track, Figure 4 is a sampling cycle diagram according to one embodiment of the present invention for the steps involved in sampling and detecting wood species.
An IMS detector 10 is shown in Figure 1 which is similar to the detectors shown in U.S. Patent 5,071,771.
A heater coil 12 is provided to heat an ionizing and drift zone 14 where trace vapor is analyzed. The method of analysis and comparison is similar to that described in the above mentioned U.S. patent.
A quartz tube 16 leads from the ionization and drift zone 14 through an insulator 18 and has a heated inlet 20 where it i8 connected to an insulated sampling tube 22 in one embodiment made of tetrafluoroethylene material such as ~old under the trade mark Teflon. Other suitable material~ may be used. The sampling tube 22 has a resi~tance heated element 24 surrounding it to ensure that the temperature of the trace vapor within the sampling tube 22 does not drop.
A laser desorption cell 26 is shown positioned adjacent a wood piece 28, the cell 26 has an internal cylindrical portion 30 and the sampling tube 22 joins to the side of the cylindrical portion 30. An aperture 32 is provided at the center of the cell 26 and in one embodiment has a window 34 made of diamond or other suitable material not effected by the heat from a laser.
The laser beam is projected through the laser desorption ~;
:
:
.
- ~097269 cell 26. The cell 26 has a heater 36, linked to the sampling tube heater 24, to maintain the cylindrical portion 30 at the desired temperature.
A high energy beam, which in one embodiment is a laser, although the beam may be a magnified and intensified energy beam that can desorb organic vapors from the liquid or solid sample being analyzed. The desorption of the material is important, if the energy is too high, burning can occur which does not provide a sample that can be analyzed, if the energy is too low, then the time taken to desorb is too long or the compounds of interest will not desorb. It is important to provide a rapid desorption of organic compounds and to control this desorption, the high energy beam is sent in a train or series of energy packets or emissions. The length of each emission is controlled, the pause between each emission is controlled, the number of emissions fsr each series is controlled and the intensity of energy per emission is controlled. The series of emissions need not necessarily be from a pulsed laser, although a pulse laser may be used. Other high energy beams are also applicable from for example a continuous source. By controlling the energy from the beam, the sample is heated sufficiently to desorb the vapor in the minimum amount of time. Furthermore the vapor is heated to the desired temperature for further analysis.
The series of emissions can be controlled for the organic compound being analyzed. In the case of wood, the vapor is produced, separated from the surface of the wood and heated to the desired temperature. By varying the control factors, the analy~is technique can be varied for different woods, however, optimum control factors are determined suitable for all woods.
- . . - ............... - " ... - . .. ; . -. . ~ ., . : , - . . :
In the embodiment for differentiating wood species a laser with a variable power from 8 to 40 watts was used. A typical power was 16 watts. Each emission was for 8 milli-seconds with an energy per emission of 0.1 to 0.2 joules. The pause between emissions was 7 milli-seconds providing a repetition rate of 66 emissions per second and a typical series was 20 emissions. The heated spot size was 2.5 mm diameter and the wood surface temperature reached 300C within 300 milli-seconds. The typical energy per sample was in the range of 2 to 4 joules with a typical rate of heating of 10 to 20C per milli-second.
Energy sources with different wave lengths may be used to excite specific organic compounds.
Figure 2 shows another embodiment with the laser beam being deflected by a mirror 40 and passing through a beam splitter 42 wherein one beam is directed through the window 34 and the cylindrical portion 30 of the cell 26 onto the surface of the wood piece 28. The second beam passes through the beam splitter 42 to a second mirror 44 and through an aperture 46 to the wood surface at a point below the first beam. A temperature sensor 36 determines the heat of the lower heated spot which is substantially the same as the upper spot.
The embodiment shown in Figure 2 shows an arrangement wherein two spots on a surface are heated.
This system can cause some variations because there may be differences in the temperature of the two spots. In other embodiments, no beam splitter 42 is used and only one spot is heated as shown in Figures 1. The temperature of this spGt may be measured but it is not always necessary.
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~97269 Desorption of the organic vapor from the wood surface occurs and a pump 48 extracts a trace vapor through the sampling tube 22 and into the ionizing and drift zone 14 of the IMS detector (as shown in Figure 1).
The trace vapor is analyzed in the IMS controller 50, with the PC controller 52 providing control from the temperature detector 36, and having a laser power supply 54 and laser modulator 56 to control the series of emissions from the laser 52. The PC controller 52 has a keyboard, a monitor 58 and printer 59. A signal from the PC controller 52 provides a signal to an automatic sorter for sorting wood by species.
The trace vapor is analyzed and an ionic drift time signature is determined and compared with known drift time signatures for different species of wood and, in this manner, the species of the wood sample is identified.
Wood pieces 28 are shown advancing on a conveyor 60 in Figure 3. The laser desorption cell 26 is mounted in a cross traverse guide 62 located on a carriage 64 which in turn moves backwards and forwards on a sliding track 66 within a longitudinal slide assembly 68. The cross traverse slide 62 for the laser desorption cell 26 is operated by a solenoid 70 which moves the cell 26 out to make contact with an end of a wood piece 28. A laser beam source 52 is mounted on the end of the longitudinal slide assembly 68 and is fixed so that it does not move, a laser beam is projected from the laser source 52 onto a mirror 40 mounted on the carriage 64 and arranged at 45 so that the laser beam is projected through the aperture 32 of the cell 26 as shown in Figure 1. Thus, at any -location of the carriage 64 on the track 66 the laser beam is always projected via the mirror 40 into the cell 26 and consequently onto the surface of the wood piece 28.
- .i .. - ;~: -- - : ........ ~ .. -:
20~7269 g A retractable lumber pickup pin 72 is mounted in a slide 74 adjacent to the cross traverse slide 62 for the laser desorption cell 26, and a solenoid 76 activates the retractable pickup pin 72 so that it projects beyond the carriage 64 and is contacted by a wood piece 28 on the conveyor 60. Thus the carriage 64 is moved along the sliding track 66. A wood piece sensor 78, diagrammatically illustrated, senses when a wood piece 28 is approaching the longitudinal slide assembly 68 and automatically triggers the retractable lumber pickup pin 72 to move out so that it is contacted by the end of the wood piece 28, the carriage 64 is moved along the sliding track 66, and the end of the wood piece is aligned with the laser desorption cell 26.
At the end of travel, the retractable lumber pickup pin 72 is withdrawn, either by the solenoid 76 or by a ramp 80 shown mounted at the end of the longitudinal ~:
slide assembly 68, which disengages the pin 72 from the ~
wood piece 28, and the carriage 64 stops on the sliding :
track 66. A carriage retract drive in the form of a pneumatic or compressed air cylinder 82 returns the carriage 64 to the start position on the sliding track 66.
In operation a wood piece 28 advances on conveyor 60, trips the sensor 78 which causes the retractable lumber pickup pin 72 to move out and the wood piece 28 contacts the pin 72 and moves the carriage 64 with the wood piece 28. The laser desorption cell 26 is moved in the cross traverse guide 62 so that the cell touches the wood surface and the laser source 52 projects a laser beam which is deflected by the mirror 40 to pass through the aperture 32 in the laser desorption cell 26 to heat the surface of the wood piece 28. Desorption takes place from the wood surface and a trace vapor is collected ;~
within the cell and extracted through the sampling tube :. . .. . . .
. - - : ~ .
. ' ~ ` ' ~
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-' 2~9726~
22 into the ionizing and drift zone 14 of the IMS
detector 10. The vapor is analyzed and a drift time signature prepared and compared with known drift time signatures, thus the wood species is identified.
When the carriage 64 has moved a predetermined distance, the solenoid 76 for the retractable lumber pickup pin 72 is deactivated and the pin 72 springs back so that the carriage 64 is disconnected from the wood piece 28. At substantially the same time that this occurs, the laser desorption cell 28 also moves back in the cross traverse guide 62 by means of deactivating the solenoid 70. At this stage a purging step occurs wherein air is extracted through the sampling tube and in some cases a reverse purge occurs wherein air is also blown through the sampling tube 22 to purge all the trace vapor that was present in the sampling tube, and in the cylindrical portion 30 as well as in the ionizing and drift zone 14 of the IMS detector 10. The hydraulic or pneumatic cylinder 82 pulls the carriage 64 back to the start position awaiting the next wood piece to trip the sensor 78 and start the next sampling cycle.
One embodiment of a sampling cycle is illustrated in Figure 4 for a particular embodiment and as can be seen a sampling cycle occurs in 1.2 seconds which permits a lumber processing rate of 50 wood pieces per minute.
Laser desorption occurs over 0.2 seconds, the trace vapor transfer takes a further 0.2 seconds and the analysis within the IMS detector occurs over a half second from commencement of the cycle. Purging then occurs for 0.7 seconds during which time the carriage is returned to the start position for commencing the next cycle.
The contact between the laser desorption cell 26 and the end of the wood piece 28 is 0.4 seconds in one embodiment. The temperature of desorption is within the ...
: - .. -. , - , , . ., :
: . -:
0~7269 range of 220 to 350C and in one embodiment is kept at about 270C. The temperature of the trace vapor is maintained from desorption within the cell 26 through the transfer line 22 and within the IMS detector 10. As can be seen the transfer line 22 is flexible and thus moves with the carriage 64 whereas the IMS detector 10 has a fixed location.
Tests were conducted with jack pine, balsam fir, douglas fir, lodgepole pine, white spruce and amabilis fir and drift time signatures were obtained that allowed identification of wood species tested.
Increasing the flow during purging to 1,000 cc per minute allowed 0.7 seconds purging time. Furthermore, leaving out the window 34, as shown in Figure 1, increased suction was obtained for the purging, creating air flow from both sides of the cell 26, thus allowing shorter purging times to be obtained.
Signals processed representing ion drift time signatures were displayed on the monitor 58 and printed on the printer 59. The signals were compared in the PC
controller 52 with programmed signatures representing different specie~ of wood, and the selected signal fed to either a mill operator to make him aware of the wood species or to an automatic sorter to sort the wood based 25 on species. ~ -In one embodiment where the wood pieces were moving comparatively fast on a conveyor, every second wood piece was analyzed, for faster speeds the sampling may occur at every 3 or 4 wood pieces. Two or more sampling units are required for sampling ht mill speeds.
The embodiment of the specific equipment described herein is not limiting, for example other solutions than , . . , ,, ~ - , : -, -, , .: .: :: : -:
.
- 2097~69 a retractable pickup pin may be used to synchronize the movement o~ the wood piece with the laser desorption cell. The carriage need not reciprocate but may rotate or move on a belt. In yet another embodiment, each wood piece may stop at a station where the analyzing occurs without having to move to the laser desorption cell on a carriage. This avoids the necessity of having a flexible sampling tube.
Various changes may be made to the embodiments described herein without departing from the scope of the present invention which is limited only by the following claims.
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-: . . . , ~, .. - :
. .
WOOD SPECIES USING RAPID DESORPTION
OF ORGANIC C~MPOU~DS
The present invention relates to a sampling device suitable for identification of wood species. More specifically the present invention provides a rapid desorption method and apparatus for desorption of organic compounds from solid and liquid samples. By utilizing an ion mobility spectrometer, wood may be sampled to determine its species.
The method of identifying wood species using an ion mobility spectrometer (referred to as an IMS detector) is disclosed in U.S. Patent 5,071,771. In this patent is disclosed taking a sample of wood, heating it and then collecting a trace vapor from the wood sample and analyzing the trace vapor in the IMS detector to produce an ion mobility signature. This signature i8 then compared with known signatures of different species of wood, and the species of wood is determined.
The patent discloses heating a wood surface at a temperature in the range of about 220 to 350C, and then sampling a trace vapor of desorbed wood. The vapor is transferred to the ionizing zone of an IMS detector. The vapors are ionized at a temperature in the range of about 220 to 350C, the ions are pulsed from the ionizing zone through a gate into a drift region and then the time of -arrival of the ions and the ion flux is determined for each pulse with a collector electrode located at the end of the drift region to produce an ionic signal. The signal is amplified and averaged to provide an ion drift time signature for the wood sample. Rapid sampling allows identification of wood species in short times.
' ~
., , ~,.
.
It is an aim of the present invention to provide a sampling device and a method of sampling for determining wood species in lumber yards, sawmills and the like, particularly when timber and lumber pieces are advancing on a conveyor. It is another aim of the present invention to provide a device that identifies the species when the wood is stationary or moving on the conveyor without stopping the conveyor. It is a further aim to sample and identify at least thirty pieces of wood a minute.
A still further aim of the present invention is to provide a method and apparatus to rapidly desorb organic compounds from solids or liquids. The desorption is controlled by utilizing a high energy beam, such as a laser. The intensity of the beam and duration of the beam are controlled to provide the required desorbed v~por sample that can be used for further analysis.
The present invention provides a method of rapidly desorbing an organic compound vapor from a solid or liquid sample, and further analyzing the sample, comprising the steps of projecting a high energy beam, such as a laser beam, onto a surface of the sample in a series of pulsed emissions, controlling time of each emission, controlling pause between each emission, controlling energy per emission to ensure temperature increase of the sample is sufficient to desorb the vapor, and the vapor is heated to a predetermined temperature, and further analyzing the vapor.
In a further embodiment a method of sampling a wood piece is disclosed comprising the steps of projecting a series of pulsed beam emissions from a laser source onto a surface of the wood piece, controlling the series of pulsed emissions to desorb a wood sample, and extracting vapor from the wood sample for further analysis.
, . . . . . .
~` : ' ' ,' .:
' ' . ' '~ ' . ' ~ ~' ' ' 2~97269 In a still further embodiment the present invention provides a method of sampling a wood piece comprising the steps of projecting a series of pulsed beam emissions from a laser source onto a surface of the wood piece, controlling the series of pulsed beam emissions to desorb organic vapor from a wood sample, extracting the vapor from the heated wood sample, transferring the vapor to an ionizing zone in an IMS detector, analyzing the vapor to produce an ion drift time signature for the wood sample, and comparing the ion drift time signature of the wood sample with known ion drift time signatures of different wood species, to determine species of the wood sample.
~ et a further embodiment provides a method of sampling wood pieces advancing on a conveyor, comprising the steps of moving a laser desorption cell on a carriage at the same speed and aligned with a wood piece advancing on the conveyor belt, moving the laser desorption cell to contact the wood piece, projecting a series of pulsed beam emissions from a laser source onto the wood piece through the laser desorption cell, controlling the series of pulsed beam emissions to desorb organic vapor from a wood sample, extracting the vapor from the heated wood ~:
sample in the laser desorption cell, transferring the vapor to an ionizing zone in an IMS detector, analyzing the vapor to produce an ion drift time signature for the wood sample and comparing the ion drift time signature with known ion drift time signatures of different wood species to determine the species of the wood sample.
Another embodiment provides an apparatus for sampling wood pieces comprising a laser desorption cell adapted to be placed on a wood surface, a laser source for projecting a laser beam through the laser desorption ~:
cell onto the wood surface, control means for the laser source to produce a series of pulsed beam emissions to desorb organic vapor from a wood sample, extraction and .. j . ,~ , :. -~ :
2~97269 , transfer means to extract the vapor from the heated wood sample and transfer the vapor to an ionizing zone in an IMS detector, and means to produce an ion drift time signature from the IMS detector and identify species of the wood sample.
In a still further embodiment, there is provided an apparatus for sampling wood piece~ advancing on a conveyor, comprising a carriage containing a laser desorption cell mounted on slide means positioned adjacent the conveyor, the slide means providing a path for movement of the carriage, engaging means on the carriage to engage a wood piece advancing on the conveyor, so the carriage advances a predetermined distance on the path in conjunction with the wood piece, return means for returning the carriage to a start position on the path after the pickup pin has disengaged the wood piece, cross movement means for the laser desorption cell to move and contact an end of the wood piece when the carriage is advancing on the path, laser source for projecting a laser beam through the laser desorption cell onto the wood piece, control means for the laser source to produce a series of pulsed beam emissions to desorb organic vapor from a wood sample, extraction and transfer means to extract the vapor from the heated wood sample and transfer to an ionizing zone in an IMS detector, and means to produce an ion drift time signature from the IMS detector and identify species of the wood sample.
In drawings which illustrate embodiments of the present invention, Figure 1 is a diasrammatic view showing a laser desorption cell positioned against a wood piece and showing a sampling tube to an IMS detector, ~-- .,. :. :.. ~ : . . .
.... . ~ . .
2~972~9 .
Figure 2 is a schematic diagram showing sampling of a wood piece including the controlsO
Figure 3 is an isometric view showing wood pieces moving on a conveyor with a laser desorption cell supported by a carriage moving backwards and forwards on a sliding track, Figure 4 is a sampling cycle diagram according to one embodiment of the present invention for the steps involved in sampling and detecting wood species.
An IMS detector 10 is shown in Figure 1 which is similar to the detectors shown in U.S. Patent 5,071,771.
A heater coil 12 is provided to heat an ionizing and drift zone 14 where trace vapor is analyzed. The method of analysis and comparison is similar to that described in the above mentioned U.S. patent.
A quartz tube 16 leads from the ionization and drift zone 14 through an insulator 18 and has a heated inlet 20 where it i8 connected to an insulated sampling tube 22 in one embodiment made of tetrafluoroethylene material such as ~old under the trade mark Teflon. Other suitable material~ may be used. The sampling tube 22 has a resi~tance heated element 24 surrounding it to ensure that the temperature of the trace vapor within the sampling tube 22 does not drop.
A laser desorption cell 26 is shown positioned adjacent a wood piece 28, the cell 26 has an internal cylindrical portion 30 and the sampling tube 22 joins to the side of the cylindrical portion 30. An aperture 32 is provided at the center of the cell 26 and in one embodiment has a window 34 made of diamond or other suitable material not effected by the heat from a laser.
The laser beam is projected through the laser desorption ~;
:
:
.
- ~097269 cell 26. The cell 26 has a heater 36, linked to the sampling tube heater 24, to maintain the cylindrical portion 30 at the desired temperature.
A high energy beam, which in one embodiment is a laser, although the beam may be a magnified and intensified energy beam that can desorb organic vapors from the liquid or solid sample being analyzed. The desorption of the material is important, if the energy is too high, burning can occur which does not provide a sample that can be analyzed, if the energy is too low, then the time taken to desorb is too long or the compounds of interest will not desorb. It is important to provide a rapid desorption of organic compounds and to control this desorption, the high energy beam is sent in a train or series of energy packets or emissions. The length of each emission is controlled, the pause between each emission is controlled, the number of emissions fsr each series is controlled and the intensity of energy per emission is controlled. The series of emissions need not necessarily be from a pulsed laser, although a pulse laser may be used. Other high energy beams are also applicable from for example a continuous source. By controlling the energy from the beam, the sample is heated sufficiently to desorb the vapor in the minimum amount of time. Furthermore the vapor is heated to the desired temperature for further analysis.
The series of emissions can be controlled for the organic compound being analyzed. In the case of wood, the vapor is produced, separated from the surface of the wood and heated to the desired temperature. By varying the control factors, the analy~is technique can be varied for different woods, however, optimum control factors are determined suitable for all woods.
- . . - ............... - " ... - . .. ; . -. . ~ ., . : , - . . :
In the embodiment for differentiating wood species a laser with a variable power from 8 to 40 watts was used. A typical power was 16 watts. Each emission was for 8 milli-seconds with an energy per emission of 0.1 to 0.2 joules. The pause between emissions was 7 milli-seconds providing a repetition rate of 66 emissions per second and a typical series was 20 emissions. The heated spot size was 2.5 mm diameter and the wood surface temperature reached 300C within 300 milli-seconds. The typical energy per sample was in the range of 2 to 4 joules with a typical rate of heating of 10 to 20C per milli-second.
Energy sources with different wave lengths may be used to excite specific organic compounds.
Figure 2 shows another embodiment with the laser beam being deflected by a mirror 40 and passing through a beam splitter 42 wherein one beam is directed through the window 34 and the cylindrical portion 30 of the cell 26 onto the surface of the wood piece 28. The second beam passes through the beam splitter 42 to a second mirror 44 and through an aperture 46 to the wood surface at a point below the first beam. A temperature sensor 36 determines the heat of the lower heated spot which is substantially the same as the upper spot.
The embodiment shown in Figure 2 shows an arrangement wherein two spots on a surface are heated.
This system can cause some variations because there may be differences in the temperature of the two spots. In other embodiments, no beam splitter 42 is used and only one spot is heated as shown in Figures 1. The temperature of this spGt may be measured but it is not always necessary.
- ' . : . , : : , .:
~97269 Desorption of the organic vapor from the wood surface occurs and a pump 48 extracts a trace vapor through the sampling tube 22 and into the ionizing and drift zone 14 of the IMS detector (as shown in Figure 1).
The trace vapor is analyzed in the IMS controller 50, with the PC controller 52 providing control from the temperature detector 36, and having a laser power supply 54 and laser modulator 56 to control the series of emissions from the laser 52. The PC controller 52 has a keyboard, a monitor 58 and printer 59. A signal from the PC controller 52 provides a signal to an automatic sorter for sorting wood by species.
The trace vapor is analyzed and an ionic drift time signature is determined and compared with known drift time signatures for different species of wood and, in this manner, the species of the wood sample is identified.
Wood pieces 28 are shown advancing on a conveyor 60 in Figure 3. The laser desorption cell 26 is mounted in a cross traverse guide 62 located on a carriage 64 which in turn moves backwards and forwards on a sliding track 66 within a longitudinal slide assembly 68. The cross traverse slide 62 for the laser desorption cell 26 is operated by a solenoid 70 which moves the cell 26 out to make contact with an end of a wood piece 28. A laser beam source 52 is mounted on the end of the longitudinal slide assembly 68 and is fixed so that it does not move, a laser beam is projected from the laser source 52 onto a mirror 40 mounted on the carriage 64 and arranged at 45 so that the laser beam is projected through the aperture 32 of the cell 26 as shown in Figure 1. Thus, at any -location of the carriage 64 on the track 66 the laser beam is always projected via the mirror 40 into the cell 26 and consequently onto the surface of the wood piece 28.
- .i .. - ;~: -- - : ........ ~ .. -:
20~7269 g A retractable lumber pickup pin 72 is mounted in a slide 74 adjacent to the cross traverse slide 62 for the laser desorption cell 26, and a solenoid 76 activates the retractable pickup pin 72 so that it projects beyond the carriage 64 and is contacted by a wood piece 28 on the conveyor 60. Thus the carriage 64 is moved along the sliding track 66. A wood piece sensor 78, diagrammatically illustrated, senses when a wood piece 28 is approaching the longitudinal slide assembly 68 and automatically triggers the retractable lumber pickup pin 72 to move out so that it is contacted by the end of the wood piece 28, the carriage 64 is moved along the sliding track 66, and the end of the wood piece is aligned with the laser desorption cell 26.
At the end of travel, the retractable lumber pickup pin 72 is withdrawn, either by the solenoid 76 or by a ramp 80 shown mounted at the end of the longitudinal ~:
slide assembly 68, which disengages the pin 72 from the ~
wood piece 28, and the carriage 64 stops on the sliding :
track 66. A carriage retract drive in the form of a pneumatic or compressed air cylinder 82 returns the carriage 64 to the start position on the sliding track 66.
In operation a wood piece 28 advances on conveyor 60, trips the sensor 78 which causes the retractable lumber pickup pin 72 to move out and the wood piece 28 contacts the pin 72 and moves the carriage 64 with the wood piece 28. The laser desorption cell 26 is moved in the cross traverse guide 62 so that the cell touches the wood surface and the laser source 52 projects a laser beam which is deflected by the mirror 40 to pass through the aperture 32 in the laser desorption cell 26 to heat the surface of the wood piece 28. Desorption takes place from the wood surface and a trace vapor is collected ;~
within the cell and extracted through the sampling tube :. . .. . . .
. - - : ~ .
. ' ~ ` ' ~
-: , . . . :-.
-' 2~9726~
22 into the ionizing and drift zone 14 of the IMS
detector 10. The vapor is analyzed and a drift time signature prepared and compared with known drift time signatures, thus the wood species is identified.
When the carriage 64 has moved a predetermined distance, the solenoid 76 for the retractable lumber pickup pin 72 is deactivated and the pin 72 springs back so that the carriage 64 is disconnected from the wood piece 28. At substantially the same time that this occurs, the laser desorption cell 28 also moves back in the cross traverse guide 62 by means of deactivating the solenoid 70. At this stage a purging step occurs wherein air is extracted through the sampling tube and in some cases a reverse purge occurs wherein air is also blown through the sampling tube 22 to purge all the trace vapor that was present in the sampling tube, and in the cylindrical portion 30 as well as in the ionizing and drift zone 14 of the IMS detector 10. The hydraulic or pneumatic cylinder 82 pulls the carriage 64 back to the start position awaiting the next wood piece to trip the sensor 78 and start the next sampling cycle.
One embodiment of a sampling cycle is illustrated in Figure 4 for a particular embodiment and as can be seen a sampling cycle occurs in 1.2 seconds which permits a lumber processing rate of 50 wood pieces per minute.
Laser desorption occurs over 0.2 seconds, the trace vapor transfer takes a further 0.2 seconds and the analysis within the IMS detector occurs over a half second from commencement of the cycle. Purging then occurs for 0.7 seconds during which time the carriage is returned to the start position for commencing the next cycle.
The contact between the laser desorption cell 26 and the end of the wood piece 28 is 0.4 seconds in one embodiment. The temperature of desorption is within the ...
: - .. -. , - , , . ., :
: . -:
0~7269 range of 220 to 350C and in one embodiment is kept at about 270C. The temperature of the trace vapor is maintained from desorption within the cell 26 through the transfer line 22 and within the IMS detector 10. As can be seen the transfer line 22 is flexible and thus moves with the carriage 64 whereas the IMS detector 10 has a fixed location.
Tests were conducted with jack pine, balsam fir, douglas fir, lodgepole pine, white spruce and amabilis fir and drift time signatures were obtained that allowed identification of wood species tested.
Increasing the flow during purging to 1,000 cc per minute allowed 0.7 seconds purging time. Furthermore, leaving out the window 34, as shown in Figure 1, increased suction was obtained for the purging, creating air flow from both sides of the cell 26, thus allowing shorter purging times to be obtained.
Signals processed representing ion drift time signatures were displayed on the monitor 58 and printed on the printer 59. The signals were compared in the PC
controller 52 with programmed signatures representing different specie~ of wood, and the selected signal fed to either a mill operator to make him aware of the wood species or to an automatic sorter to sort the wood based 25 on species. ~ -In one embodiment where the wood pieces were moving comparatively fast on a conveyor, every second wood piece was analyzed, for faster speeds the sampling may occur at every 3 or 4 wood pieces. Two or more sampling units are required for sampling ht mill speeds.
The embodiment of the specific equipment described herein is not limiting, for example other solutions than , . . , ,, ~ - , : -, -, , .: .: :: : -:
.
- 2097~69 a retractable pickup pin may be used to synchronize the movement o~ the wood piece with the laser desorption cell. The carriage need not reciprocate but may rotate or move on a belt. In yet another embodiment, each wood piece may stop at a station where the analyzing occurs without having to move to the laser desorption cell on a carriage. This avoids the necessity of having a flexible sampling tube.
Various changes may be made to the embodiments described herein without departing from the scope of the present invention which is limited only by the following claims.
-: : .-......... .:
:: .
-: . . . , ~, .. - :
. .
Claims (27)
1. A method of rapidly desorbing an organic compound vapor from a solid or liquid sample, and further analyzing the vapor, comprising the steps of:
projecting a high energy beam onto a surface of the sample in a series of pulsed emissions;
controlling time of each emission;
controlling pause between each emission;
controlling number of emissions per series, controlling energy per emission to ensure temperature increase of the sample is sufficient to desorb the vapor, and the vapor is heated to a predetermined temperature, and further analyzing the vapor.
projecting a high energy beam onto a surface of the sample in a series of pulsed emissions;
controlling time of each emission;
controlling pause between each emission;
controlling number of emissions per series, controlling energy per emission to ensure temperature increase of the sample is sufficient to desorb the vapor, and the vapor is heated to a predetermined temperature, and further analyzing the vapor.
2. The method of rapidly desorbing an organic compound vapor according to claim 1 wherein the high energy beam is a laser beam.
3. The method of rapidly desorbing an organic compound vapor according to claim 1 wherein the sample is wood and wherein the series of pulsed emissions occurs in less than 0.5 seconds.
4. A method of sampling a wood piece comprising the steps of:
projecting a series of pulsed beam emissions from a laser source onto a surface of the wood piece;
controlling the series of pulsed emissions to desorb organic vapor from a wood sample, and extracting vapor from the heated wood sample for further analysis.
projecting a series of pulsed beam emissions from a laser source onto a surface of the wood piece;
controlling the series of pulsed emissions to desorb organic vapor from a wood sample, and extracting vapor from the heated wood sample for further analysis.
5. A method of sampling a wood piece comprising the steps of:
projecting a series of pulsed beam emissions from a laser source onto a surface of the wood piece;
controlling the series of pulsed beam emissions to desorb organic vapor from a wood sample;
extracting the vapor from the heated wood sample;
transferring the vapor to an ionizing zone in an IMS
detector;
analyzing the vapor to produce an ion drift time signature for the wood sample, and comparing the ion drift time signature of the wood sample with known ion drift time signatures of different wood species, to determine species of the wood sample.
projecting a series of pulsed beam emissions from a laser source onto a surface of the wood piece;
controlling the series of pulsed beam emissions to desorb organic vapor from a wood sample;
extracting the vapor from the heated wood sample;
transferring the vapor to an ionizing zone in an IMS
detector;
analyzing the vapor to produce an ion drift time signature for the wood sample, and comparing the ion drift time signature of the wood sample with known ion drift time signatures of different wood species, to determine species of the wood sample.
6. The method of sampling a wood piece according to claim 5 wherein time of each emission is controlled, pause between each emission is controlled, number of emissions per series is controlled, and the energy per emission is controlled to ensure temperature increase of the sample is sufficient to desorb the organic vapor from the wood sample, and the vapor is heated to a predetermined temperature.
7. The method of sampling a wood piece according to claim 6 wherein the vapor is heated to a temperature in the range of about 220 to 350°C.
8. A method of sampling wood pieces advancing on a conveyor, comprising the steps of:
moving a laser desorption cell on a carriage at the same speed and aligned with a wood piece advancing on the conveyor belt;
moving the laser desorption cell to contact the wood piece;
projecting a series of pulsed beam emissions from a laser source onto the wood piece through the laser desorption cell, controlling the series of pulsed beam emissions to desorb organic vapor from a wood sample;
extracting the vapor from the heated wood sample in the laser desorption cell;
transferring the vapor to an ionizing zone in an IMS
detector;
analyzing the vapor to produce an ion drift time signature for the wood sample, and comparing the ion drift time signature of the wood sample with known ion drift time signatures of different wood species to determine species of the wood sample.
moving a laser desorption cell on a carriage at the same speed and aligned with a wood piece advancing on the conveyor belt;
moving the laser desorption cell to contact the wood piece;
projecting a series of pulsed beam emissions from a laser source onto the wood piece through the laser desorption cell, controlling the series of pulsed beam emissions to desorb organic vapor from a wood sample;
extracting the vapor from the heated wood sample in the laser desorption cell;
transferring the vapor to an ionizing zone in an IMS
detector;
analyzing the vapor to produce an ion drift time signature for the wood sample, and comparing the ion drift time signature of the wood sample with known ion drift time signatures of different wood species to determine species of the wood sample.
9. The method of sampling wood pieces according to claim 8 wherein wood pieces are sampled at the rate of at least thirty per minute.
10. The method of sampling wood pieces according to claim 8 wherein the vapor is transferred through a flexible heated sampling tube to a fixed IMS detector containing the ionizing zone.
11. The method of sampling wood pieces according to claim 8 wherein the laser source is stationary and projects a laser beam onto a mirror mounted on the carriage, the mirror deflecting the beam so that it is projected onto the wood piece regardless of position of the carriage.
12. The method of sampling wood pieces according to claim 10 including the steps of purging the laser desorption cell, the flexible heated sampling tube, and the ionizing zone of the IMS detector between each sampling step.
13. The method of sampling wood pieces according to claim 8 wherein the carriage moves on slide rail means, the carriage being moved by a wood piece advancing on the conveyor during the sampling step, and returns to an initial starting position to commence another sampling step.
14. The method of sampling wood pieces according to claim 13 wherein a sampling cycle occurs within 1.2 seconds and includes desorption, transfer, data acquisition, and purging.
15. The method of sampling wood pieces according to claim 5 wherein the ion drift time signature is interpreted to provide an immediate identification of wood species.
16. The method of sampling wood pieces according to claim 8 wherein time of each emission is controlled, pause between each emission is controlled, number of emissions per series is controlled, and the energy per emission is controlled to ensure temperature increase of the sample is sufficient to desorb organic vapor from the wood sample, and the vapor is heated to a predetermined temperature.
17. The method of sampling wood pieces according to claim 16 wherein the vapor is heated to a temperature in the range of about 220 to 350°C.
18. The method of sampling wood pieces according to claim 17 wherein each emission occurs for about 8 milli-seconds, each pause is for about 7 milli-seconds, about 20 emissions occur per series and the energy per emission is in the range of about 0.1 to 0.2 joules.
19. An apparatus for sampling wood pieces comprising:
a laser desorption cell adapted to be placed on a wood surface;
a laser source for projecting a laser beam through the laser desorption cell onto the wood surface;
control means for the laser source to produce a series of pulsed emissions to desorb organic vapor from a wood sample;
extraction and transfer means to extract the vapor from the heated wood sample and transfer the vapor to an ionizing zone in an IMS detector, and means to produce an ion drift time signature from the IMS detector and identify species of the wood sample.
a laser desorption cell adapted to be placed on a wood surface;
a laser source for projecting a laser beam through the laser desorption cell onto the wood surface;
control means for the laser source to produce a series of pulsed emissions to desorb organic vapor from a wood sample;
extraction and transfer means to extract the vapor from the heated wood sample and transfer the vapor to an ionizing zone in an IMS detector, and means to produce an ion drift time signature from the IMS detector and identify species of the wood sample.
20. An apparatus for sampling wood pieces advancing on a conveyor, comprising:
a carriage containing a laser desorption cell mounted on slide means positioned adjacent the conveyor, the slide means providing a path for movement of the carriage;
engaging means on the carriage to engage a wood piece advancing on the conveyor, so the carriage advances a predetermined distance on the path in conjunction with the wood piece;
return means for returning the carriage to a start position on the path after the engaging means has disengaged from the wood piece;
cross movement means for the laser desorption cell to move and contact the wood piece when the carriage is advancing on the path;
laser source for projecting a laser beam through the laser desorption cell onto the wood piece;
control means for the laser source to produce a series of pulsed beam emissions to desorb organic vapor from a wood sample;
extraction and transfer means to extract the vapor from the heated wood sample and transfer to an ionizing zone in an IMS detector, and means to produce an ion drift time signature from the IMS detector and identify species of the wood sample.
a carriage containing a laser desorption cell mounted on slide means positioned adjacent the conveyor, the slide means providing a path for movement of the carriage;
engaging means on the carriage to engage a wood piece advancing on the conveyor, so the carriage advances a predetermined distance on the path in conjunction with the wood piece;
return means for returning the carriage to a start position on the path after the engaging means has disengaged from the wood piece;
cross movement means for the laser desorption cell to move and contact the wood piece when the carriage is advancing on the path;
laser source for projecting a laser beam through the laser desorption cell onto the wood piece;
control means for the laser source to produce a series of pulsed beam emissions to desorb organic vapor from a wood sample;
extraction and transfer means to extract the vapor from the heated wood sample and transfer to an ionizing zone in an IMS detector, and means to produce an ion drift time signature from the IMS detector and identify species of the wood sample.
21. The apparatus for sampling wood pieces according to claim 20 wherein a solenoid provides cross movement for the laser desorption cell to move and contact the wood piece when the carriage is advancing on the path.
22. The apparatus for sampling wood pieces according to claim 20 wherein the laser source is positioned at one end of the slide means to project a laser beam onto a mirror mounted on the carriage, the mirror projecting the laser beam through the laser desorption cell at any position of the carriage on the slide means.
23. The apparatus for sampling wood pieces according to claim 20 wherein the laser desorption cell has a cylindrical chamber with an axial connection to a flexible sampling tube leading to the ionizing zone in the IMS detector.
24. The apparatus for sampling wood pieces according to claim 23 wherein the laser desorption cell, the sampling tube, and the ionizing zone are heated and maintained at a temperature in the range of about 220 to 350°C.
25. The apparatus for sampling wood pieces according to claim 20 including:
means to control time of each emission;
means to control pause between each emission;
means to control number of emissions per series, and means to control the energy per emission to ensure temperature increase of the sample is sufficient to desorb the vapor and the vapor is heated to a predetermined temperature.
means to control time of each emission;
means to control pause between each emission;
means to control number of emissions per series, and means to control the energy per emission to ensure temperature increase of the sample is sufficient to desorb the vapor and the vapor is heated to a predetermined temperature.
26. The apparatus for sampling wood pieces according to claim 23 including means for purging the laser desorption cell, the sampling tube, and the ionizing zone in the IMS
detector in between each sample.
detector in between each sample.
27. The apparatus for sampling wood pieces according to claim 20 including indication means to identify species of wood pieces.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2097269 CA2097269A1 (en) | 1993-05-28 | 1993-05-28 | Sampling device for determining wood species using rapid desorption of organic compounds |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2097269 CA2097269A1 (en) | 1993-05-28 | 1993-05-28 | Sampling device for determining wood species using rapid desorption of organic compounds |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2097269A1 true CA2097269A1 (en) | 1994-11-29 |
Family
ID=4151710
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2097269 Abandoned CA2097269A1 (en) | 1993-05-28 | 1993-05-28 | Sampling device for determining wood species using rapid desorption of organic compounds |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2097269A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2015014294A1 (en) | 2013-08-01 | 2015-02-05 | 同方威视技术股份有限公司 | Method used for rapid testing of highly volatile substances of very high concern in textiles |
-
1993
- 1993-05-28 CA CA 2097269 patent/CA2097269A1/en not_active Abandoned
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2015014294A1 (en) | 2013-08-01 | 2015-02-05 | 同方威视技术股份有限公司 | Method used for rapid testing of highly volatile substances of very high concern in textiles |
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