Abstract:
A test strip incubation device and method for developing a test strip having a reagent test pad disposed thereon, the reagent test pad requiring an incubation time, which allows greater accuracy and reliability of test results as well as a narrower window of PASS and FAIL indication concentrations. The device comprises a test strip holder which allows a wetted reagent test pad to be vertically stored in an enclosed reaction chamber during the incubation period. The reaction chamber is bounded by a substantially clear material to allow the user to easily observe the status of the reagent test pad held in the reaction chamber. The enclosed reaction chamber provides a high humidity environment for minimizing water evaporation from the reagent test pad during the incubation period. The device may be economically formed from low cost materials, is simple to use and facilitates disposal of the sample material after testing. The device is advantageously used in combination with a storage device which includes recesses for easy storage of several devices and allows viewing of the a reagent test pads. The method comprises the steps of wetting the reagent test pad and vertically placing the reagent test pad in an enclosed reaction chamber during the incubation period. The enclosed reaction chamber provides a high humidity environment for minimizing the evaporation of water from the reagent test pad.

Description:
This is a division of application Ser. No. 09/074,532, filed May 7, 1998, now U.S. Pat. No. 5,939,329. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention. 
     The present invention relates to a method and an apparatus for developing a test strip, and more particularly a test strip having a reagent test pad requiring an incubation period for developing the desired test results disposed thereon. 
     2. Description of the Related Art. 
     Test strips having a reagent test pad disposed thereon are conventionally known testing devices which are often used to determine whether a sufficient concentration of a chemical or chemicals is present in a solution. In the conventionally known procedure, the reagent test pad having reagent chemicals disposed thereon is placed in contact with a solution to be tested, typically by dipping the test strip in the solution. When the reagent test pad is sufficiently wetted, the test pad is removed from the solution and the indication on the test pad is examined after a predetermined waiting time. The reagent test pad is usually designed to change to a particular color or range of colors corresponding to the concentration of the chemicals in the solution being examined. In conventionally known procedures, the user places the wetted test pad in an open environment, such as on a lab bench, while waiting for the color change to develop. 
     Although simple to use, one consideration in using such test strips is the accuracy and reliability of the color indications developed on the reagent test pads. In conventional applications, a standardized chart showing various colors and corresponding concentrations is provided. To be effective and reliable, the test performed should always produce a color which corresponds to an accurate concentration of the chemical being tested. In other words, the person performing the test should be able to confidently match the color produced by the test strip with a corresponding color on the standardized chart and the concentration of chemical then taken therefrom. 
     Unfortunately, due to the imprecision inherent in any analytical tests, the desired indication may be observed at concentrations other than the predetermined concentration. For example, in a test producing a mere change in color at a given concentration, such color change could incorrectly occur at a concentration other than the given concentration. The concentration at which the test always reads “PASS” or “FAIL” is determined by the properties and conditions of the test. The difference in the 100% FAIL and the 100% PASS concentration may be called the “window”. It is desirable to have the range of this window be as small as possible to ensure effective management and use of the solutions being tested, for example to ensure that only effective solutions are used and to ensure that effective solutions are not needlessly replaced. 
     The window may be narrowed in many tests by increasing the reaction time between the chemicals in the reagent test pad and the chemicals in the solution. This is most likely due to two factors associated with dry reagents tests, namely 1) the reactants on the test strip need time to completely dissolve, and 2) the diffusion of reactants in a solid matrix is very slow. However, because these reactions occur in aqueous solutions, the reaction time available for the test is limited by the evaporation of water from the reagent test pad. Accurate measurement within a narrow window is difficult if the moisture necessary to maintain the reagents in solution evaporates from the reagent test pad before the reaction is complete. This is particularly true when measuring highly concentrated analytes where the loss of even small amounts of water may cause precipitation of analytes and/or reactants within the test pad. 
     Conventionally known methods and apparatuses are limited in their ability to obtain accurate and reliable results within a narrow window because the water necessary to maintain the reagents in solution typically evaporates from the test pad before allowing a sufficient incubation period. This evaporation leads to improper use of ineffective solutions as well as wasteful replacement of effective solutions. 
     Therefore, what is needed is an accurate and reliable method and apparatus for using test strips described above wherein a sufficient incubation period is provided to allow the reagents to completely react with one another before the requisite moisture evaporates from the test pad. 
     SUMMARY OF THE INVENTION 
     The present invention is a method and an apparatus for providing accurate and reliable results from a test strip having a reagent test pad disposed thereon when the reagent test pad requires an incubation period for the reagents to react. The present invention also provides a more narrow window between PASS and FAIL indications which in turn allows effective use and management of the test solutions. The present invention achieves these results by placing and maintaining the reagent test pad in an enclosed, high humidity environment, in a substantially vertical orientation during the incubation period. 
     The method of the present invention comprises, in one form thereof, the steps of providing a test strip having a reagent test pad disposed on one end and a grip portion disposed on another end. The reagent test pad is wetted with a desired test material and placed in an enclosed chamber and after a predetermined waiting period, the results indicated on the reagent test pad are read. The enclosed chamber is advantageously adapted to provide a high humidity environment and the reagent test pad is advantageously maintained in a vertical manner in the enclosed chamber during the incubation period. 
     In another form, the present invention comprises a test strip holder of reagent test strips having a reagent test pad requiring an incubation period comprising a base and a cover, the base and cover adapted to fittingly engage each other to form an enclosed reaction chamber. The enclosed reaction chamber is adapted to store the reagent test pad. One of the base and cover includes a holding portion adapted to engage the test strip to thereby securely maintain the reagent test pad in the reaction chamber. One of the first and second holders includes a substantially clear portion allowing viewing of the test strip. 
     The present invention also comprises, in another form thereof, a combination comprising a test strip having a reagent test pad disposed thereon, the reagent test pad requiring an incubation period, and a test strip holder, the test strip holder comprising a base and a cover. The base and cover are adapted to fittingly engage each other to form an enclosed reaction chamber. The enclosed reaction chamber is adapted to receive and hold the reagent test pad and one of the base and cover includes a substantially clear portion allowing viewing of the reagent test pad. 
     Additionally, a test strip storage device may advantageously be provided for use with the test strip holder of the present invention wherein the test strip storage device includes a storage element disposed on a pedestal, the storage element having a plurality of recesses formed on a top surface thereof for placement of the test strip holders therein in a manner which allows the user to easily store the test strip holder and view the indication on the reagent test pad. 
     Therefore, it is an objective of the present invention to provide a method and an apparatus for accurately checking the concentration of a chemical in a solution using a test strip reagent pad. 
     It is also an objective of the present invention to provide a method and an apparatus for accurately checking the concentration of a chemical in a solution using a test strip pad having a reagent test pad which requires an incubation period. 
     It is also an objective of the present invention to provide a method and an apparatus which permits a reagent test pad to be vertically stored in a high humidity environment for a sufficient period of time to allow the reactants to fully react. 
     It is also an objective of the present invention to provide a method and an apparatus which allows a very narrow window between the 100% FAIL and the 100% PASS indications on the reagent test pad. 
     It is also an objective of the present invention to provide a method and an apparatus which accomplishes the above cited objectives in a simple, easy to use, economical manner. 
     It is also an objective of the present invention to provide a disposable or reusable apparatus which accomplishes the above cited objectives. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above mentioned and other features and objects of this invention, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of the embodiment of the invention taken in conjunction with the accompanying drawings, wherein: 
     FIG. 1 is a perspective view of an embodiment of a test strip holder of the present invention in the open position and a test strip having a reagent test pad disposed thereon; 
     FIG. 2 is a perspective view of a test strip placed in the test strip holder of FIG. 1 of the present invention which has been moved toward the closed position; 
     FIG. 3 is a perspective view of a test strip placed in the test strip holder of FIG. 1 of the present invention which is in the closed position; 
     FIG. 4 is a front elevational view of the test strip held in the test strip holder of FIG. 1 of the present invention; 
     FIG. 5 is a sectional view taken along line  5 — 5  of FIG. 4; 
     FIG. 6 is a perspective view of a storage device for storing test strip holders of the present invention; 
     FIG. 7 is a cross-sectional view of an alternative embodiment of the test strip holder of the present invention; 
     FIG. 8 is a perspective view of an alternative embodiment of a test strip holder of the present invention in the open position and a test strip having a reagent test pad disposed thereon; 
     FIG. 9 is a perspective view of a test strip placed in the test strip holder of FIG. 8 of the present invention which has been moved toward the closed position; 
     FIG. 10 is a perspective view of a test strip placed in the test strip holder of FIG. 8 of the present invention which is in the closed position; and 
     FIG. 11 is a cross sectional view along line  11 — 11  of FIG.  10 . 
    
    
     Corresponding reference characters indicate corresponding parts throughout the several views. Although the drawings represent embodiments of the present invention, the drawings are not necessarily to scale and certain features may be exaggerated in order to better illustrate and explain the present invention. The exemplifications set out herein illustrate embodiments of the invention, in several forms, and such exemplifications are not to be construed as limiting the scope of the invention in any manner. 
     DETAILED DESCRIPTION OF THE INVENTION 
     The embodiments disclosed below are not intended to be exhaustive or limit the invention to the precise forms disclosed in the following detailed description. Rather, the embodiments are chosen and described so that others skilled in the art may utilize their teachings. 
     Referring now to FIGS. 1-5, test strip holder  10  of the present invention comprises base  12  and cover  14  which are integrally connected by flexible connection  32 . Base  12  and cover  14  are configured and adapted to engage each other to form an enclosed reaction chamber for holding test strip  15 . As particularly shown in FIGS. 1-2 and further described below, base  12  and cover  14  can pivot with respect to each other about the axis of flexible connection  32  in order to form sealed reaction chamber  50  which provides a high humidity environment for minimizing the evaporation of water from test strip  15  during the incubation period of the test. A typical test strip  15  suitable for use with test strip holder  10  includes reagent test pad  15   a , grip portion  15   b  and middle portion  15   c.    
     Base  12  comprises substantially rectangular back panel  25  having raised edge  16  disposed around the periphery thereof. Raised edge  16  is in a spaced apart relationship from the edge of back panel  25  along shoulder  18 . Raised edge  16  comprises outer sidewalls  20 , top wall  22 , and inner sidewalls  24 . Rounded corner portions  23  are disposed along the four comers of raised edge  16  and interconnect the linear portions of raised edge  16 . Back panel  25  in combination with raised edge  16  define recessed space  26 . As described further below, recessed space  26  is used in combination with recessed space  46  of cover  14  to form reaction chamber  50 . Also, indentation  28  is disposed on a lower portion of raised edge  16 . Indentation  28  is adapted to fittingly receive test strip  15  and maintain test strip  15  in a vertically held position after base  12  and cover  14  have been joined. Thus, in the present embodiment, indentation  28  comprises a holding portion for test strip  15 . Although the present embodiment uses a notched arrangement as a holding portion for test strip  15 , it is to be understood that any conventionally known method for securely holding test strip  15  in holder  10  may be used, for example raised portions on base  12  or cover  14  as described hereinbelow, or adhesive elements disposed on base  12  or cover  14 . 
     Back panel  25  further includes handle  30  disposed at a lower end thereof to provide an easy handling mechanism for the user. It is to be understood that although handle  30  is only on one corner of back panel  25 , other handling mechanisms may be placed in many locations around back panel  25  to facilitate the handling of back panel  25 . 
     Cover  14  is integrally connected with base  12  via flexible connection  32  and is adapted to fittingly engage base  12 . As shown in FIGS. 1-3, cover  14  comprises front panel  36  which is integrally joined with flat edge portion  34  via sidewalls  38 , flat portion  40  and rounded shoulder portion  39 . The combination of front panel  36 , rounded shoulders  39 , sidewall  38 , and flat portion  40  defines recessed space  46 . Straight line portions of sidewall  38  are joined by rounded comers  33  and straight line portions of rounded shoulder  39  are joined by rounded comers  43 . Front panel  36  included handle  31  to provide an easy handling mechanism for the user. Front panel  36  is made of a relatively clear, see-through plastic, such that a user can easily look through front panel  36  to check the indication on reaction portion  15   a  of test strip  15 . 
     The dimensions of raised edges  16 , particularly rounded portions  23 , and sidewalls  38 , particularly comer portions  43 , are sized and adapted to fittingly engage each other such that base  12  and cover  14  snap tight. It is to be understood that any conventionally known method for achieving a snap tight engagement of base  12  and cover  14  may be used, for example, the area encompassed by outer sidewall  20  may be slightly larger than the are encompassed by sidewall  38 , or rounded comers  23  may bulge out slightly wider than the inside areas of rounded comers  33 , or sidewall  38  and sidewall  20  may fittingly contact each other and outer movable snaps may be placed on the edges of flat portions  18  or  34  to achieve the snap tight engagement. 
     The snap tight engagement of base  12  and cover  14  combines recessed spaces  26  and  46  to form enclosed chamber  50 . Enclosed chamber  50  is sealed sufficiently to provide a high humidity environment for minimizing water evaporation from reagent test pad  15   a  while holding test strip  15  for a required incubation period. 
     With reference to FIG. 6, test strip holder  10  is advantageously used in combination with holder device  60  which can be used for storing and maintaining a plurality of test strip holders  10  in a vertical position while waiting for an indication to develop on test strip  15 . Holder device  60  is a receptacle comprising top wall  61  and sidewalls  62  disposed on pedestal  70 . Recesses  64  having inner walls  66  are disposed in top wall  61  to receive and hold test strip holder  10 . Recesses  64  are oriented along the length of top wall  61  and have a depth wherein clear front panel  36  of a test strip holder  10  placed therein can be easily viewed by a user. Also, notches  68  are disposed along the ends of inner walls  66  to facilitate the insertion of test strip holder  10  into recess  64 . It is to be understood that although holding device  60  shown in FIG. 6 comprises three recesses  64 , it is possible to have holding device  60  which includes any suitable number of recesses  64 , aligned as desired to provide easy viewing of front panel  36  by the user. 
     The method for using test strip  15  with test strip holder  10  to test for the concentration of in a test solution is now described. The user initially holds grip portion  15   b  and dips reagent test pad  15   a  into the test solution and then withdraws reagent test pad  15   a  from the test solution after reagent test pad  15   a  has been sufficiently wetted. Test strip  15  is then transferred to test strip holder  10  and held against test strip holder  10  by placing intermediate portion  15   c  against indentation  28  of base  12 . While continuing to hold intermediate portion  15   c  against indentation  28 , the user rotates cover  14  about the axis of pivot connection  32  until the associated surfaces of base  12  and cover  14  come in contact with each other. The user then snaps together base  12  and cover  14  to form enclosed reaction chamber  50  and to thereby secure test strip  15 , particularly reagent test pad  15   a , therein. At this point, reaction portion  15   a  is vertically disposed inside enclosed chamber  50  which maintains a high humidity environment for minimizing the evaporation of water from reagent test pad  15   a.    
     The vertical alignment of test strip  15  allows excess solution on reagent test strip pad  15  to fall off test pad  15  by gravity to provide more consistent test results. Previously, excess solution on a reagent test pad formed a bead which was removed by either shaking off the excess or blotting the test pad with an absorbent material. In either method, the amount of solution which was removed from the test pad varied greatly such that the test results also varied greatly. Storing test strip holder  10  in a vertical position obviates this problem as the excess solution falls off test pad  15  by gravity flow and a consistent amount of solution remains on test pad  15 , thereby resulting in more consistent results. 
     Once test strip  15  has been secured onto test strip holder  10  as described above, the user may continue to hold test strip holder  10  in a vertical position until the incubation period has elapsed or may place and store test strip holder  10  in holder device  60 . To place test strip holder  10  in holder device  10 , the sides of test strip holder  10  are aligned with notches  68  of recess  64  and test strip holder  10  is slidingly placed into recess  64 . Holder device  60  or equivalent may be aligned to face the user to facilitate the reading of the indication on reagent test pad  15   a . In this manner, test strip holder  10  is maintained in a vertical position and front panel  36  faces outward such that the user can readily observe any color changes on reagent test pad  15   a.    
     Once the test is completed, the entire assembly may be discarded without the user coming in contact with the test solution or the reagent test pad. In this manner, the present method and apparatus facilitates the disposal of the test products. 
     An alternative embodiment of the present invention is shown in FIG. 7 wherein clear tube  80 , for example a test tube, serves as a cover and stopper  82  provides a base. In combination, tube  80  and stopper  82  provide a sealed, high humidity chamber for developing a reagent test pad. In the embodiment shown in FIG. 7, slot  84  is disposed on stopper  82  for holding test strip  15  in a vertical manner during the incubation period. Here, end portion  15   b  of test strip  15  is inserted into slot  84  and then stopper  82  is partially inserted into open end  86  of test tube  80  to form enclosed reaction chamber  90  for holding reagent test pad  15   a  therein. Once test strip  15  has been placed in tube  80 , tube  80  may be left in the vertical position until the incubation period has elapsed. The user can then easily view any indication changes on reagent test pad  15   a  through tube  80 . 
     An alternative embodiment of the present invention is shown in FIGS. 8-11 wherein test strip holder  200  comprises base  212  and cover  214  which are integrally connected by flexible connection  232 . Base  212  and cover  214  are configured to engage each other to form an enclosed reaction chamber for holding test strip  15 . As particularly shown in FIGS. 8-9 and further described below, base  212  and cover  214  can pivot with respect to each other about the axis of flexible connection  232  in order to form sealed reaction chamber  250  which provides a high humidity environment for minimizing the evaporation of water from test strip  15  during the incubation period of the test. Base  212  comprises bottle-shaped back panel  225  having raised edge  216  disposed around the periphery thereof. Raised edge  216  is spaced apart from the edge of back panel  225  along shoulder  218 . Raised edge  216  comprises outer side walls  220 , top wall  222  and inner side walls  224 . Rounded comer portions  223  are disposed along the four outside comers of raised edge  216 . Back panel  225  in combination with raised edge  216  define recessed space  226 . Recessed space  226  combined with recess space  246  in cover  214  form reaction chamber  250 . 
     Indentation  228  is disposed on the lower portion of raised edge  216  as shown in FIG.  8 . As shown in FIGS. 9-11, indentation  228  is adapted to fittingly receive test strip  15  in a vertically held position. With reference to FIGS. 8 and 11, tab portion  229  extends from flat portion  240  of cover  214  so that when the test strip holder is closed, as shown in FIGS. 10 and 11, tab  229  serves as a holding portion to hold test strip  15  securely in place in apparatus  200 . That is, tab  229  abuts against test strip  15  when cover  214  and base  212  are sealingly engaged as shown in FIG.  11 . 
     Back panel  225  further includes handle  230  disposed at a lower end thereof to provide an easy handling mechanism for the user. Similarly, cover  214  includes handle portion  231  at a lower end thereof to provide an easier handling mechanism for the user. 
     Cover  214  is integrally connected with base  212  via flexible connection  232  and is adapted to fittingly engage base  212 . As shown in FIGS. 8-10, cover  214  comprises front panel  236  which is integrally joined with flat edge portion  234  via sidewalls  238  and flat portion  240 . A combination of front panel  236 , sidewall  238  and flat portion  240  defines recess space  246 . Front panel  236  is made of a relatively clear, see-through plastic, such that a user can easily look through front panel  236  to check the indication on reaction portion  15   a  of test strip  15 . The dimensions of raised edges  216 , particularly rounded portions  223 , and sidewalls  238  and corner portions  233  on cover  214  are sized and adapted to fittingly engage each other such that base  212  and cover  214  snap tightly together. The snap-tight engagement of base  212  and cover  214  combines recessed spaces  226  and  246  to form enclosed chamber  250  as shown in FIG.  10 . 
     It can be seen in the above-described embodiments that a reaction chamber for holding a reagent test pad may be provided in a simple, easy to use, disposable and economical package. It is also obvious that the apparatus may be easily manufactured using a number of inexpensive materials, including, but not limited to plastic, and a number of conventionally known processes. 
     The use of an enclosed reaction chamber in tests using test strips having an incubation period is effective in producing accurate test results. One test where such a method and apparatus was shown to be particularly effective is the test for determining the active concentration in chemical germicides. A typical use for chemical germicides is to disinfect or sterilize endoscopes which contain heat-sensitive optical systems. Many of the chemical germicides are reusable and used for sequential loads of instruments until the active ingredient becomes too dilute to be effective against microorganisms. Depletion of the germicide can result from dilution or chemical inactivation. The lowest concentration at which the active ingredient in the germicide will kill all test microorganisms is termed the Minimum Effective Concentration (“MEC”). The germicide is routinely tested to avoid using solutions containing less than the MEC because such solutions are ineffective. 
     To ensure that an ineffective solution is never used, the test should always show FAIL at the MEC. However, due to the imprecision inherent in any analytical test, FAIL results may be observed at concentrations greater than the MEC. The concentration at which the test always reads PASS is determined by the properties of the test. The difference in the 100% FAIL and the 100% PASS concentrations is the “window”. It is desirable to have the window size be as small as possible to ensure that the germicide is effective and that effective germicide is not needlessly replaced. If the test frequently indicates FAIL when the disinfectant level is above the MEC, the germicide will be replaced more often than necessary. 
     A dry reagent test strip may be used to measure the level of the active ingredient, hydrogen peroxide, in a reusable germicide solution, for example, SPOROX®, manufactured by Reckitt &amp; Coleman, Inc. of Montvale, N.J. The test strip comprises a reagent-containing test pad (the “indicator pad” or “pad”) attached at one end of a polystyrene handle. 
     The chemistry of the test strip is based on the reduction of the hydrogen peroxide with a fixed amount of sulfite ion in the presence of iodide and starch. When the hydrogen peroxide concentration is 6.0% or less, it is entirely consumed by the sulfite. When its concentration is sufficient to overwhelm the reducing agent, the excess oxidizes the iodide to iodine producing a dark brown/black color in the presence of starch. The chemical reactions include the following: 
     H 2 O 2 +Iodide-→Iodine+H 2 O 
     Iodine+Sulfite-→Iodide 
     Excess H 2 O 2 +Iodide-→Iodine+H 2 O 
     Iodine+Starch-→Starch-Iodine Complex (Brown/Black) 
     It has been determined that the smaller the window, the longer the reaction period needs to be. This is most likely due to two factors associated with dry reagent tests: 1) the reactants supplied by the strip need time to completely dissolve; and 2) the diffusion of reactants in a solid matrix is very slow. 
     Thus, the window can be narrowed by increasing the reaction time. However, unless evaporation of water from the pad is prevented, there is an upper limit to the reaction time. A typical filter paper matrix absorbs about 0.25 ml per square inch. This means that the sample exists as a layer of about 0.5 mm thickness. The high surface area to volume ratio results in a very high relative evaporation rate. Accurate measurement is impossible if significant amounts of water evaporate from the pad prior to completion of the analytical reaction. This is particularly true when measuring highly concentrated analytes when the loss of even small amounts of water may cause the precipitation of analyte and/or reactants within the pad. 
     Two separate sets of tests were performed to demonstrate the effectiveness of the present invention. In the first set of tests, the test strip was developed with the reagent test pad placed in a reaction chamber. In the second set of tests, the test strips were developed with the reagent test pad left in the open. 
     To run the first set of tests, the test pad was dipped into the sample for a period of five seconds, removed and then placed in a vertical position with the test pad up. A reaction chamber was placed over the strip to prevent evaporation of water from the test pad. After a reaction period of 12 to 15 minutes, the color of the test pad was observed. If the solution contains 7.0% or more hydrogen peroxide, the test pad will be completely brown/black indicating a PASS result. If the solution contains 6.0% or less hydrogen peroxide, a white area will appear in the center of the test pad indicating a FAIL result. At intermediate concentrations, the strip may indicate either PASS or FAIL. 
     The relationship between hydrogen peroxide concentration and time to develop the FAIL result when using an enclosed reaction chamber are summarized as follows: 
     
       
         
               
             
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Effect of Hydrogen Peroxide Concentration on Time Required to 
               
               
                 Develop FAIL Result 
               
               
                 Strips protected from evaporation 
               
             
          
           
               
                 Hydrogen Peroxide Concentration 
                 Time to Develop FAIL result 
               
               
                 (%) 
                 (mean +/− s.d., n = 10) 
               
               
                   
               
               
                 5.6 
                  8.3 +/− 0.7 
               
               
                 6.0 
                 12.0 +/− 0.8 
               
               
                 6.6 
                 18.9 +/− 2.6 
               
               
                 7.0 
                 all &gt; 25 
               
               
                   
               
             
          
         
       
     
     Based on the above, distinguishing 5.6% from 7.0% hydrogen peroxide would require a 10 minute wait, 6.0% from 7.0% a 14 minute wait and 6.6% from 7.0% a 25 minute wait. These wait times were calculated by adding 2 s.d. to the mean. 
     The relationship between hydrogen peroxide concentration and time to develop the FAIL result without using the enclosed reaction chamber was determined to be as follows: 
     
       
         
               
             
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 Effect of Evaporation on Strip Reaction 
               
               
                 Strips not Protected from Evaporation 
               
             
          
           
               
                 Hydrogen Peroxide Concentration 
                 Time to Develop FAIL result 
               
               
                 (%) 
                 (mean +/− s.d., n = 10) 
               
               
                   
               
               
                 5.6 
                 18.1 +/− 4.0 
               
               
                 6.0 
                 all &gt; 25 
               
               
                 6.6 
                 all &gt; 25 
               
               
                 7.0 
                 all &gt; 25 
               
               
                   
               
             
          
         
       
     
     The results of Table 2 indicate that it would not be possible to distinguish 5.6% from 7.0% hydrogen peroxide all of the time and that it would never be possible to distinguish either 6.0% or 6.6% from 7.0%. Thus, a comparison of the two sets of test results indicates that the use of a reaction chamber to prevent water evaporation from the reagent test pad improves the strip precision considerably. 
     Other tests that have extended reaction times will benefit from the use of a container to prevent sample evaporation. Therefore, other test strips which may be advantageously used with the method and apparatus of the present invention include, but are not limited to, Serim DisIntek Strips for 1.0-2.5% glutaraldehyde in endoscope disinfection baths, Serim Formaldehyde Reagent Strips for 4% formaldehyde in hemodialyzer disinfectant, Serim Formaldehyde Reagent Strips for 1-2% formaldehyde in hemodialyzer disinfectant, Serim Glutaraldehyde Reagent Strips for 0.8% glutaraldehyde in hemodialyzer disinfectant, Johnson &amp; Johnson Cidex, Solution Test Strips for 1.5-2.5% glutaraldehyde in Cidex® Activated Dialdehyde Solution, Johnson &amp; Johnson Cidex® Plus Solution Test Strips for 1.5-3.4% glutaraldehyde in Cidex® Plus Activated Dialdehyde Solution, and Wavicide-01® Solution Test Strips for glutaraldehyde in Wavicide-01® disinfecting and Sterilizing Solution. 
     While this invention has been described as having an exemplary design, the present invention may be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. For example, a clear straw or other similar tubular devices which may be held in vertical position and which reduce the evaporation of water from reagent test pad  15   a  may be used to provide a reaction chamber. Also, although the test strip holder of the present invention uses generally rectangular bases, it is to be understood that any shapes may be used, as long as the segments allow a snap tight engagement to form an enclosed reaction chamber for vertically holding a test strip therein. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains.