Patent Publication Number: US-2016233068-A1

Title: Sample collection wand comprising an inductively coupled heater

Description:
The present disclosure relates to methods and apparatus for the detection of substances of interest. More particularly the disclosure relates to methods and apparatus for the thermal desorption of samples for example to enable analysis to detect substances of interest in the samples. Analysis may be performed using spectrometers, such as ion mobility spectrometers and/or mass spectrometers. 
     In facilities such as airports and venues where large numbers of people may gather, there is a need to detect traces of substances of interest such as explosives. 
     One way to detect such substances is to obtain a sample from a surface using a sample collection wand, and then heating the sample to thermally desorb it to be tested for the presence of substances of interest. 
    
    
     
       Embodiments of the disclosure will now be described, by way of example only, with reference to the accompanying drawings in which: 
         FIG. 1  shows a spectrometer with an inductive coupler for providing inductive coupling with a heater of a sample collection wand; 
         FIG. 2  shows another spectrometer with an inductive coupler for providing inductive coupling with a heater of a sample collection wand; 
         FIG. 3  shows another spectrometer with a sample collection wand including an inductive coupler. 
     
    
    
     In the drawings like reference numerals are used to indicate like elements. 
     Embodiments of the disclosure provide spectrometers such as ion mobility spectrometers in which an inductive coupler is arranged to couple, via a time varying magnetic field (H-field), with a heater to provide electrical power for thermally desorbing a sample to enable it to be analysed in the spectrometer. The use of inductive coupling to supply power to the heater may enable the heater to be efficiently thermally insulated from supporting structures, such as a sample collection wand. 
     In addition, it may enable the use of wands which do not comprise heaters because a swab comprising an electrical conductor may function as a heater. 
     The inductive coupler may be carried by the spectrometer for example in a port adapted to couple with a sample collection wand, as illustrated in  FIG. 1  and  FIG. 2 . For example the inductive coupler may be arranged adjacent to an inlet of the spectrometer for coupling with a heater carried by a sample collection wand that presents a sample to the inlet. As illustrated in  FIG. 3 , in some examples the inductive coupler may be carried by a sample collection wand and a conductive coupling may be carried on the wand body to couple the inductive coupler with a power supply of the spectrometer. The conductive coupling can be arranged so that when the sample collection wand is inserted into a port of the spectrometer, power can be provided to the inductive coupler from the spectrometer. 
       FIG. 1  shows a spectrometry apparatus  10  comprising an ion mobility spectrometer  12  for analysing a sample. The apparatus shown in  FIG. 1  comprises a port  14  adapted to couple a sample collection wand  16  to the apparatus. As illustrated, an inlet  18  of the spectrometer  12  is arranged in a wall of the port  14  for enabling a sample that has been thermally desorbed from the wand  16  to be drawn through the inlet  18  into the spectrometer  12 . 
     The port  14  of the apparatus shown in  FIG. 1  is arranged so that, when a sample collection wand  16  is coupled to the port  14 , the wand  16  presents a sample carried by the wand  16  to an inlet  18  of the spectrometer  12 . 
     As illustrated in  FIG. 1 , the spectrometry apparatus  10  comprises an inductive coupler  20  adapted to provide a magnetic field (H-field) in the port for coupling with a heater  22  of the sample collection wand  16  to provide electrical power to the heater  22 . The inductive coupler may comprise a conductor arranged to provide a time varying magnetic field (H-field) such as a radio frequency, RF, field. 
     The inductive coupler  20  carried by the port  14  can be arranged to provide a magnetic field (H-field) in the port  14  for coupling with a heater  22  carried by the sample collection wand  16 . As shown in  FIG. 1 , the inductive coupler  20  can be arranged to at least partially surround the heater  22  when, in use, the wand  16  is inserted into the port  14  to present a sample to the inlet  18  of the spectrometer. In the example illustrated in  FIG. 1 , the inductive coupler  20  comprises a cylindrical inductor arranged so that the wand  16  can carry the heater  22  into a region at least partially surrounded by the inductive coupler  20  to present the sample to the inlet  18 . The dashed lines in  FIG. 2  illustrate one possible configuration of a conductor, e.g. as a helical coil, to provide an inductive coupler  20 . 
     The wand  16  may comprise a temperature sensor  24  for sensing the temperature of the wand  16  near the heater  22 , and a coupling  26  for providing communication to the sensor  24 . The apparatus  10  may comprise a controller  30  configured to obtain temperature signals from the sensor  24  via the couplings  26 ,  32 . The controller  30  may also be configured to control the inductive coupler  20  for providing power to the heater  22 . The temperature sensor  24  may comprise any sensor for providing a signal based on temperature such as a thermocouple or thermistor. 
     The sample collection wand  16  illustrated in  FIG. 1  comprises a wand body of a size selected to enable convenient manipulation of the wand  16 , and a swab support  23  coupled to the wand body for supporting a swab upon which a sample can be collected. The wand  16  shown in  FIG. 1  also comprises a heater  22  for heating a swab carried on the swab support  23 . The heater  22  is arranged to receive power by inductively coupling with a magnetic field (H-field) provided by an inductive coupler  20  of a spectrometry apparatus  10 . This may enable the heater  22  to be electrically isolated from the wand  16  on the swab support  23 . This may in turn provide thermal isolation of the heater  22  from the wand  16 . 
     As illustrated in  FIG. 1 , the wand  16  may comprise a swab support  23  for supporting a swab for collecting a sample. The support may be configured to thermally insulate a swab from the wand  16 . In some embodiments the swab support  23  may comprise the heater  22 . In some embodiments a swab used to collect the sample may itself comprise the heater  22 , for example, if the swab comprises an electrical conductor the magnetic field (H-field) of the inductive coupler can couple with the conductors of the swab to heat a sample carried on the swab. One example of a swab comprising a conductor is a metallised swab. 
       FIG. 2  shows another example of a spectrometry apparatus  210 . In the example shown in  FIG. 2  the spectrometry apparatus also comprises an ion mobility spectrometer  12 , and, similar to the apparatus shown in  FIG. 1 , the apparatus of  FIG. 2  comprises a port  14  adapted to couple a sample collection wand  16  to the apparatus  210 . As illustrated, an inlet  18  of the spectrometer  12  is arranged in a wall of the port  14  for enabling a sample that has been thermally desorbed from the wand  16  to be drawn through the inlet  18  into the spectrometer  12 . Also as illustrated in  FIG. 1 , the port  14  of the apparatus  210  shown in  FIG. 2  is arranged so that, when a sample collection wand  16  is coupled to the port  14 , the wand  16  presents a sample carried by the wand  16  to an inlet  18  of the spectrometer  12 . 
     The inductive coupler  120  shown in  FIG. 2  may be carried by the same wall of the port  14  as the inlet  18  of the spectrometer  12 , and may at least partially surround the inlet  18 . The port  14  is arranged so that, when the wand  16  is inserted into the port  14 , the heater  22  is close enough to the inductive coupler  120  that the magnetic field (H-field) generated by the inductive coupler  120  can cause heating currents in the heater  22 . 
     In operation of the apparatus shown in  FIG. 1  or  FIG. 2 , a swab is used to collect a sample by rubbing the swab against a surface. The wand  16  can then be inserted into the port  14  carrying the swab on the heater  22 . To provide electrical power to the heater  22 , the controller  30  controls the inductive coupler ( 20  in  FIG. 1 ;  120  in  FIGS. 2 ) to provide a time varying magnetic field (H-field) in the port  14 . As the heat capacity of the heater  22  can be very small, and the heater can be thermally and electrically isolated from the wand body, the temperature of the sample can be raised rapidly to thermally desorb the sample from the swab. Rapid desorption of the sample is desirable because where substances are desorbed rapidly the concentration of substances available for analysis by the spectrometer may be increased. By contrast, if the temperature of the sample is raised more slowly the substances may be present at the inlet for a greater period of time, but in lower concentration. The controller  30  may obtain a signal from the sensor  24  indicating the temperature of the heater  22  and control the power provided by the inductive coupler  20 ,  120  based on the signal from the sensor  24 . 
       FIG. 3  shows a further example of a spectrometry apparatus  310 . As shown in  FIG. 3 , the sample collection wand  16  may comprise an inductive coupler  320  arranged to couple inductively with a heater  22  carried on the wand to provide electrical power to the heater  22 . 
     The spectrometry apparatus of  FIG. 3  comprises an ion mobility spectrometer  12 , and, similar to the apparatus shown in  FIG. 1 , the apparatus of  FIG. 3  comprises a port  314  adapted to couple a sample collection wand  316  to the apparatus  310 . As illustrated, an inlet  18  of the spectrometer  12  is arranged in a wall of the port  314  for enabling a sample that has been thermally desorbed from the wand  316  to be drawn through the inlet  18  into the spectrometer  12 . 
     The port  314  of the apparatus  310  shown in  FIG. 3  is arranged so that, when a sample collection wand  316  is coupled to the port  314 , the wand  316  presents a sample carried by the wand  316  to an inlet  18  of the spectrometer  12  to enable the sample to be desorbed and collected by the inlet  18 . In addition, the port  314  comprises a coupling  33  for providing electrical power to the sample collection wand  316 . The coupling  33  can be arranged so that electrical power can only be provided to the wand  316  when the wand is positioned to enable substances thermally desorbed from the wand  316  to be drawn through the inlet  18  into the spectrometer  12 . The coupling  33  may comprise a conductive coupling or a capacitive coupling adapted to couple an alternating current to a corresponding coupling  27  carried by the sample collection wand. The alternating current may comprise a radio frequency, RF, current. 
     The sample collection wand  316  shown in  FIG. 3  comprises a coupling  27  carried on the wand  316  so that, when the wand is inserted into a port  314  of the spectrometry apparatus  310  the coupling  27  cooperates with the coupling  33  of the apparatus  310  to enable the controller  30  to provide electrical power to the inductive coupler  320  carried by the sample collection wand. 
     In operation of the apparatus shown in  FIG. 3 , a swab is used to collect a sample by rubbing the swab against a surface. The wand  316  can then be inserted into the port  314  carrying the swab on the heater  22 . To provide electrical power to the heater  22 , the controller  30  can provide a time varying current to the coupling  33 , so that when the wand  316  is inserted into the port  314 , the coupling  33  of the port  314  and the coupling  27  of the wand  316  are arranged to pass an alternating current to the inductive coupler  320 . The magnetic field (H-field) generated by the inductive coupler  320  can heat the heater  22  to thermally desorb the sample for collection by the inlet. 
     In some embodiments the heater  22  comprises a ferromagnetic material. This may improve the efficiency of energy transfer via the H-field to the heater  22  because of the reduction in skin depth provided by ferromagnetism. In addition it may enable temperature control of the heater  22  to be provided by the Curie point of the ferromagnetic material because, in the event that the heater  22  is heated beyond its Curie point, the heater will lose at least some of its ferromagnetic order, and the skin depth of the heater may be modified. 
     As will be appreciated by the skilled reader in the context of the present disclosure, each of the examples described herein may be implemented in a variety of different ways. Any feature of any aspects of the disclosure may be combined with any of the other aspects of the disclosure. For example method aspects may be combined with apparatus aspects, and features described with reference to the operation of particular elements of apparatus may be provided in methods which do not use those particular types of apparatus. In addition, each of the features of each of the embodiments is intended to be separable from the features which it is described in combination with, unless it is expressly stated that some other feature is essential to its operation. Each of these separable features may of course be combined with any of the other features of the embodiment in which it is described, or with any of the other features or combination of features of any of the other embodiments described herein. 
     The controller  30  may be provided by any control apparatus such as a general purpose processor configured with a computer program product configured to program the processor to operate according to any one of the methods described herein. In addition, the functionality of the controller  30  may be provided by an application specific integrated circuit, ASIC, or by a field programmable gate array, FPGA, or by a configuration of logic gates, or by any other control apparatus.