Abstract:
A device and method is described for the collection of breath or air samples into a chemically clean bag or balloon, to facilitate analysis of volatile organic compounds (VOCs) in low concentrations in the collected samples. A reservoir of activated charcoal is introduced into the bag or balloon for initial removal of VOCs and it is then replaced with a similar reservoir of activated charcoal until the bag or balloon is employed to collect a sample. The device fulfills a long-felt need for collection of breath and air samples with a high VOC signal-to-noise ratio.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The modern era of breath testing dawned in 1971, when Linus Pauling first reported that normal human breath contains large numbers of volatile organic compounds (VOCs) in low concentrations. The majority of these VOCs are exhaled in low parts per million (ppm) or parts per billion (ppb). Different analytical technologies have been employed to assay VOCs in breath, including 1-dimensional gas chromatography with mass spectrometry (GC MS) and electronic noses. Analysis of breath VOCs with comprehensive 2-dimensional gas chromatography and time-of-flight mass spectrometry (GC×GC TOF MS) has revealed a complex matrix of more than 2,000 different VOCs in individual samples of breath. 
         [0002]    Breath collection is intrinsically safe, painless, and non-invasive, and breath VOC analysis has applications in diagnostic medicine because it provides clinically useful information. The composition of breath VOCs is altered in several diseases including lung cancer, breast cancer, and infections such as active pulmonary tuberculosis and influenza. Breath acetone is increased in diabetic ketoacidosis and breath nitric oxide is increased in bronchial asthma. Breath VOCs changes also occur in normal physiological processes such as exercise, oxidative stress, and pregnancy. 
         [0003]    Breath VOC analysis holds great promise as a new tool for detection of diseases, but progress has been impeded by a major technical obstacle: the difficulty of collecting a sample that is suitable for analysis. Breath samples collected by inflation of a bag or balloon can be employed to assay VOCs that are exhaled in high concentrations e.g. ethanol. However, analysis of bag or balloon samples with sensitive detectors such as GC MS cannot detect most VOCs in breath because of their low signal-to-noise ratio. The high background noise of VOCs in bags or balloons usually overwhelms the detector, and drowns out the signals generated by the breath VOCs. 
         [0004]    The background noise in bags and balloons arises from volatile chemical contaminants (e.g. adhesives and plasticizers) that are introduced during manufacture. Even gas collection bags that are constructed from low-emission materials (e.g. Tedlar, Nylon) are generally contaminated by background VOC noise that may exceed the breath VOC signal by two or more orders of magnitude. This background noise persists even after a bag has been flushed several times with clean gases because the walls of the bag continue to outgas residual contaminants for long periods of time. 
         [0005]    As a consequence, researchers have developed instruments for breath VOC collection that do not employ bags and balloons. These instruments are generally complicated and expensive, and require a trained operator to collect a sample. Other devices have been developed for the collection of breath into bags and balloon, but none have employed methods for making them chemically clean prior to use. 
         [0006]    It is desirable to provide an improved apparatus and method to collect breath sample having a high signal-to noise ratio and at low cost. 
       SUMMARY OF THE INVENTION 
       [0007]    The present invention relates to an improved apparatus and method to collect breath samples. The present invention has the advantages of: 
         [0008]    1. A high signal-to-noise ratio that enables the assay of breath and air VOCs in low concentrations (ppm or ppb). 
         [0009]    2. Low cost 
         [0010]    3. Convenience and simplicity of operation, so that technically satisfactory samples can be collected by operators without special training. 
         [0011]    An apparatus and method for collecting breath samples includes a housing. The housing can be an inflatable bag or balloon constructed from a low-emission material, such as biaxially-oriented polyethylene terephthalate. For example, the housing can be formed of a metallized Mylar. Activated charcoal is associated with the housing for removing background VOC contamination. A breath sample is collected in the housing after the removal of background VOC contamination. 
         [0012]    In one embodiment, the present invention provides a method of sustaining the low level of background VOC contamination using indwelling activated charcoal prior to collection of a breath sample. In one embodiment, the present invention provides a method of collecting a breath sample that can be employed for assay of VOCs in low concentrations. In one embodiment, the present invention provides a method for collecting an air sample that can be employed for assay of VOCs in low concentrations. 
         [0013]    In one embodiment, an initial cleaning uses a first strip of activated charcoal inserted into a neck of the housing. The first strip is removed and a second strip is inserted into the neck of the housing. The second cleaning procedure ensures that the housing is chemically cleaned of VOCs down to parts per billion prior to use. In this embodiment, two separate cleaning processes are used, both with a strip of activated carbon impregnated paper. The first cleaning can occur in a lab or production facility before the housing is sent to a user. The first strip of activated charcoal is then removed and replaced with a second strip of activated charcoal. The housing is folded such that the second strip is not exposed to most of housing. The folded housing can be placed in a container such as an envelope and forwarded to a user. A second cleaning is performed by the user who unfolds the housing. This exposes the second strip to the entire interior surface of the housing for a second cleaning. For example, the second cleaning can be performed overnight, prior to use. 
         [0014]    The invention will be more fully described by reference to the following drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  is a schematic diagram of breath collection device before use. 
           [0016]      FIG. 2  is a schematic diagram of breath collection device before use. 
           [0017]      FIG. 3  is a schematic diagram of a conduit used with the breath collection device. 
           [0018]      FIG. 4  is a schematic diagram of breath collection device during use. 
           [0019]      FIG. 5  is a schematic diagram of the breath collection device after use. 
           [0020]      FIG. 6  is a schematic diagram of an ambient air collection device. 
           [0021]      FIG. 7  is a schematic diagram of breath collection device before use. 
           [0022]      FIG. 8A  is a schematic diagram of breath collection device before use. 
           [0023]      FIG. 8B  is a schematic diagram of the breath collection device including a reservoir of activated carbon. 
           [0024]      FIGS. 9A-9D  are schematic diagrams of packaging which can be used with the breath collection device. 
           [0025]      FIG. 10  is a schematic diagram of breath collection device before use. 
           [0026]      FIG. 11  is a schematic diagram of breath collection device before use. 
           [0027]      FIG. 12  is a schematic diagram of breath collection device prepared for use. 
           [0028]      FIG. 13  A- 13 C are schematic diagrams of a box which can be used with the breath collection device. 
           [0029]      FIGS. 14A-14C  are diagrams of a chromatograph after use of the breath collection device. 
       
    
    
     DETAILED DESCRIPTION 
       [0030]    Reference will now be made in greater detail to a preferred embodiment of the invention, an example of which is illustrated in the accompanying drawings. Wherever possible, the same reference numerals will be used throughout the drawings and the description to refer to the same or like parts. 
         [0031]      FIG. 1  is a schematic diagram for an apparatus for collection of breath  10  in accordance with the teachings of the present invention. Housing  12  is inflatable with breath. In one embodiment, housing  12  is an inflatable bag or balloon. Preferably, housing  12  is a low-emission metallized Mylar inflatable balloon with a volume of about 1.0 to about 1.5 l when inflated. It will be appreciated that other sizes or configurations of housing  12  can be used in accordance with the teachings of the present invention. 
         [0032]    Contaminant removal material  14  is associated with in housing  12 . In one embodiment contaminant removal material  14  is a reservoir of activated carbon. This reservoir may take different forms, including a strip of activated-carbon paper, or a perforated tube filled with granules of activated charcoal. Containment removal material  14  is inserted through opening  19  of neck  18  into interior  21  of housing  12 . Contaminant VOCs in the bag diffuse into the ultra-clean helium and are then captured on the activated charcoal by sorbent trapping. Serial analysis of the VOCs in the helium with GC MS have shown that overnight cleaning of the bag with this method removes approximately 99.9% of all VOCs that were initially detectable. 
         [0033]    In a method of sustaining low background VOC contamination prior to collection of breath sample, following the initial removal of contaminant VOCs described above, a new reservoir of activated charcoal is inserted into the bag in the same fashion, and kept in place until the bag is used for a breath sample collection. The neck of the bag is temporarily sealed in order to prevent entry of ambient air VOCs into housing  12 . 
         [0034]    In a method of removing background VOC contamination as shown in  FIGS. 2-5 . A reservoir of activated charcoal is introduced into housing  12  through its neck as shown in  FIG. 2 . This reservoir may take different forms, including a strip of activated-carbon paper, or a perforated tube filled with granules of activated charcoal. Closure  20  can be used for closing housing  12  before use. Closure  20  can be a spring-loaded clip. Label  22  can be affixed to housing  12 . Housing  12  is gently inflated with ultra-clean helium in a quantity sufficient to separate the walls of housing  12 . Conduit  16  can be inserted into neck  18  of housing  12  through opening  19 . 
         [0035]    In the method for collecting a breath sample: 
         [0036]    1. Closure  20  as shown in  FIG. 2  is removed, and the reservoir of activated charcoal is withdrawn from housing  12 . 
         [0037]    2. Residual helium is removed by manually stroking housing  12 . 
         [0038]    3. Conduit  16 , such as a drinking straw, is inserted into the bag through its neck  18  as shown in  FIG. 3 . 
         [0039]    4. The subject inflates the housing  12  with breath as shown in  FIG. 4 . 
         [0040]    5. The conduit  16  is removed, and a tight knot is tied in the neck  18  of the housing  12  to prevent loss of the breath sample as shown in  FIG. 5 . 
         [0041]    6. When required, a sample of breath is withdrawn from the bag for assay with a standard analytic method e.g. GC MS. 
         [0042]    In a method for collecting an air sample: Ambient air may collected for assay in an analogous fashion with ambient air collection device  100  as shown in  FIG. 6 . In this ambient Handles  30  are affixed to housing  12 , such as with adhesive to the opposite walls of the bag. In the method for collecting ambient air: 
         [0043]    1. Closure  20  is removed, and the reservoir of activated charcoal is withdrawn from housing  12 . 
         [0044]    2. Residual helium is removed by manually stroking housing  12 . 
         [0045]    3. Housing  12  is inflated with ambient air by drawing the two handles apart from one another. 
         [0046]    4. A tight knot is tied in the neck of  18  housing  20  to prevent loss of the air sample. 
         [0047]    5. When required, a sample of air is withdrawn from the bag for assay with a standard analytic method e.g. GC MS. 
         [0048]      FIGS. 7-13  illustrate a method of initial cleaning, removing background VOC contamination and collecting a sample. 
         [0049]    In the method: 
         [0050]    1. Housing  12  is labeled with label  22  which can be affixed to housing  12  as shown in  FIG. 7 . 
         [0051]    2. A first reservoir of activated charcoal  30   a  is introduced into housing  12  through opening  19  in neck  18  as shown in  FIG. 8A . This reservoir may take different forms, including a strip of activated-carbon paper. For example, the strip of activated carbon paper can be a 1 inch by 12 inch strip of Onyx Cellulose paper. The strip of activated carbon paper can be heated in an oven that is debris free and does not contain VOC emitting materials. For example, the activated carbon paper can be heated for 15 minutes at 150 degrees C. The activated carbon paper can be removed from the oven and cooled. The activated carbon paper can be folded and insert into neck  18  leaving end portion  25  extending from neck  18 . For example, end portion  25  can be about 1.0 to about 1.5 cm. 
         [0052]    3. During initial cleaning of housing  12 , a small amount of purified Helium is filled through opening  19  in neck  18  to allow inner surfaces of housing  12  to be separated from one another. End  23  of housing  12  can be folded and secured with closure  20  as shown in  FIG. 10  to ensure Helium does not escape housing  12 . Housing  12  can sit at room temperature for at least one day. In one embodiment, before folding housing  12 , conduit  16 , such as a drinking straw, can be inserted into housing  12  through opening  19  in neck  18  for example as shown in  FIG. 3 . 
         [0053]    4. After initial cleaning, referring to  FIG. 8A , reservoir of activated charcoal  30   a  is removed from housing  12 . Housing  12  can be pressed together to release Helium from housing  12 . A second reservoir of activated charcoal  30   b,  inserted through opening  19  in neck  18  as shown in  FIG. 8B . Neck  18  can include a pocket for receiving reservoir of activated charcoal  30   b.  End  23  of housing  12  can be folded and secured with closure  20  to prevent reservoir of activated charcoal  30   b  from being exposed to the inner portion of housing  12 . Housing  12  can be sealed and placed in inner envelope  40  as shown in  FIGS. 9A-D . 
         [0054]    5. On the day before use, housing  12  can be removed from inner envelope  40  as shown in  FIG. 10 . Housing  12  can be unfolded with closure  20  remaining in place and left for a period of time, for example overnight. 
         [0055]    6. On the day of use, closure  20  is removed from housing  12  as shown in  FIG. 11 . Neck  18  is unfolded. Second reservoir of activated charcoal  30   b  is removed from housing  12  and discarded. 
         [0056]    7. If conduit  16  is not present in housing  12 , conduit  16  is inserted into opening  19  in neck  18  of housing  12  as shown in  FIG. 12 . 
         [0057]    8. Housing  12  is inflated with breath from a subject through conduit  16 . 
         [0058]    9. Conduit  16  is removed and a tight knot is tied in neck of  18  housing  12  to prevent loss of the air sample. 
         [0059]    10. Housing  12  is placed in box  50 . For example, box  50  can be prepared as shown in  FIGS. 13A-13C . 
         [0060]      FIG. 14  A-C relate to is a chromatograma of a breath VOC sample collected with an apparatus for collecting breath  10  and then analyzed with GC SAW (gas chromatography surface acoustic wave detection) in which the x-axis=time, y-axis=instrument response.  FIG. 14A  is an image of an entire chromatogram. The first peaks, acetone and isoprene, are present in great abundance relative to the other peaks which causes the presence of the other peaks to be difficult to discern.  FIG. 14  B is an image of a chromatogram which expands the x axis scale to demonstrate that there are many small peaks with one large peak eluting at 26.92 min.  FIG. 14  C is an image of a chromatogram which expands the x axis and truncates the peaks in the y axis in order to demonstrate that there are many small peaks present. It is to be understood that the above-described embodiments are illustrative of only a few of the many possible specific embodiments, which can represent applications of the principles of the invention. Numerous and varied other arrangements can be readily devised in accordance with these principles by those skilled in the art without departing from the spirit and scope of the invention.