U.S. patent number 3,715,192 [Application Number 05/062,017] was granted by the patent office on 1973-02-06 for indicator strip.
This patent grant is currently assigned to Merck Patent Gesellschaft mit beschrankter Haftung. Invention is credited to Dieter Schmitt, Alfred Stein, Adolf Wenz.
United States Patent |
3,715,192 |
Wenz , et al. |
February 6, 1973 |
INDICATOR STRIP
Abstract
An indicator strip, useful in analytical chemical procedures,
which comprises an impregnated capillary material having at least a
partially transparent film on one side and on the other side, a
film forming a hollow space which is in communication with said
capillary material.
Inventors: |
Wenz; Adolf (Darmstadt,
DT), Stein; Alfred (Darmstadt, DT),
Schmitt; Dieter (Darmstadt, DT) |
Assignee: |
Merck Patent Gesellschaft mit
beschrankter Haftung (Darmstadt, DT)
|
Family
ID: |
5742577 |
Appl.
No.: |
05/062,017 |
Filed: |
August 7, 1970 |
Foreign Application Priority Data
|
|
|
|
|
Aug 12, 1969 [DT] |
|
|
P 19 40 964.4 |
|
Current U.S.
Class: |
422/421;
422/69 |
Current CPC
Class: |
C12Q
1/46 (20130101); G01N 33/525 (20130101) |
Current International
Class: |
C12Q
1/46 (20060101); C12Q 1/44 (20060101); G01N
33/52 (20060101); G01n 031/22 (); G01n
033/16 () |
Field of
Search: |
;23/230,232,253,253TP,254 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Wolk; Morris O.
Assistant Examiner: Reese; R. M.
Claims
What is claimed is:
1. An indicator strip characterized by quick absorption of a liquid
medium to be analyzed, comprising at least one absorbent,
reagent-impregnated capillary material disposed between
liquid-impermeable films, wherein at least one of said films is at
least partially transparent, said strip having open ends and said
capillary material having its edges exposed at least at said ends,
and at least one slot extending longitudinally through said strip
to said open ends and disposed adjacent said capillary
material.
2. An indicator strip in accordance with claim 1 wherein the said
slot extends over at least 40 percent of a surface of the
impregnated absorbent capillary material.
3. An indicator strip in accordance with claim 1 wherein said
capillary material contacts one of said films on one side, and
wherein said slot is between said other film and said capillary
material.
4. An indicator strip in accordance with claim 1 wherein said slot
is subdivided into several smaller slots.
5. An indicator strip in accordance with claim 1 wherein said
capillary material is also exposed on at least one of its lateral
edges.
6. An indicator strip in accordance with claim 1 wherein said
capillary material is exposed on all of its edges.
7. An indicator strip in accordance with claim 1 wherein the ratio
of the thickness of said capillary material to the maximum height
of said slot, in cross section, is about 1 : 0.5 to about 1 :
10.
8. An indicator strip in accordance with claim 1 wherein the ratio
of the thickness of said capillary material to the maximum height
of said slot, in cross section, is about 1 : 1 to about 1 : 2.
9. An indicator strip in accordance with claim 1 wherein said
capillary material has a thickness of about 0.05 to 3 mm.
10. An indicator strip in accordance with claim 1 wherein the
capillary material is filter paper.
11. An indicator strip in accordance with claim 1 wherein said
strip has a length of about 30 - 100 mm., and a width of about 3 -
10 mm.
12. An indicator strip in accordance with claim 1 wherein said
strip has a length of about 50 - 70 mm., and a width of about 5 - 7
mm.
13. An indicator strip in accordance with claim 1 wherein said
capillary material has a surface of about 10 - 50 mm.sup.2 and an
approximately square configuration.
14. An indicator strip in accordance with claim 1 wherein said
capillary material has been impregnated in situ.
15. An indicator strip in accordance with claim 1 wherein one of
said films is transparent.
16. An indicator strip in accordance with claim 1 wherein one of
said films forming said slot has a geometrical configuration.
17. An indicator strip in accordance with claim 1 wherein said film
forming said slot has a patterned inner surface.
18. An indicator strip in accordance with claim 1, comprising at
least two adjacent indicator strips wherein each of said strips is
independent from the other and comprises a said capillary material
and a said slot, and each of said strips have common films.
19. An indicator strip in accordance with claim 1 wherein said slot
is partially filled by projections extending from the inner side of
one of said films.
20. An indicator strip in accordance with claim 19 wherein up to
about 60 percent of the volume of said slot is filled by said
projections.
21. An indicator strip in accordance with claim 1 wherein said
capillary material is disposed on one of said films and between
hydrophobic separating layers.
22. An indicator strip in accordance with claim 21 wherein the
ratio of the thickness of the said capillary material to the
thickness of said hydrophobic separating layers is about 1 : 0.5 to
about 1 : 10.
23. An indicator strip in accordance with claim 21 wherein the
ratio of the thickness of the said capillary material to the
thickness of said hydrophobic separating layers is about 1 : 1 to
about 1 : 2.
24. An indicator strip in accordance with claim 21 wherein one of
said films is secured to the separating layers.
Description
BACKGROUND OF THE INVENTION
In analytical chemistry procedures, indicating devices permitting a
rapid determination of the identity of substances dissolved in a
liquid have become of increasing importance. Mainly, the detection
procedures are conducted with colorimetric indicating devices,
wherein qualitative as well as quantitative determinations are
possible. However, especially in connection with the quantitative
or semiquantitative detection procedures, the indicating devices
known heretofore are less than satisfactory.
Indicating devices are known, for example, which contain
capillary-type test papers, enveloped by casings of a synthetic
resin material, which change color in the presence of a specific
substance in the medium to be examined. Normally, the length of the
portion of the capillary material which has been color-changed is a
measure of the concentration of the substance to be determined in
the examined medium. The intensity of color produced is not
considered in most cases in the analytical procedure. It is not
possible to use, in this respect, reagents for the indicator
portion which are soluble in the medium to be examined, since the
reagents will be irregularly distributed in the impregnated layer
by the penetration of the medium, and thereby cause a non-uniform
coloring of the indicator portion. Test rods have been used which
contain one or more test paper indicator strips sealed between
plastic films. These rods exhibit a serious disadvantage, because
relatively viscous liquid media, such as serum, for example, are
very slowly absorbed by the indicator paper. Furthermore, during
the absorption of the liquid media, an undesired partial
chromatographical separation usually takes place. The reagents
contained in the indicator papers, insofar as they are soluble in
the liquid to be tested, are also subjected to this chromatographic
effect, as well as the components dissolved in the liquid to be
tested. This results in a non-uniform color change of the
impregnated zone, and it is difficult to be coordinated with a
corresponding color scale. The determination is additionally
impaired by an air bubble, which normally forms between the
indicator paper and the top film when the test rod is immersed into
the medium to be examined.
SUMMARY OF THE INVENTION
A principle object of this invention is to provide an improved
indicator strip useful for qualitative and quantitative analytical
chemical procedures, which avoids the disadvantages heretofore
mentioned.
Another object of this invention is to provide a novel construction
of an indicator strip having at least one side of a
reagent-pregnated capillary material in communication with a hollow
space.
Another object of this invention is to provide a novel construction
of an indicator strip having a partially transparent film on one
side of a reagent pregnated capillary material.
Upon further study of the specification and appended claims, other
objects and advantages of this invention will become apparent.
To attain these objects, there is provided a novel indicator strip
comprising a reagent impregnated capillary material having on one
side a partially transparent film and on the other side, a film
construction which provides at least one slot or hollow space in
communication with the capillary material. The indicator strip is
constructed in a variety of forms to provide versatility to various
analytical conditions. The main advantages of the construction is
to enable the capillary material to absorb the liquid medium to be
examined quickly, to prevent chromatographic separation and other
problems associated with analytical procedures using heretofore
conventional indicator strips.
DETAILED DISCUSSION OF THE INVENTION
This invention relates to a novel, improved indicator strip
consisting of an absorbent, impregnated capillary material
enveloped by at least partially transparent films, wherein the
films expose the absorbent capillary material in at least one area,
and wherein at least one side of the impregnated capillary material
is in communication with at least one hollow space. Thus, an
absorbent capillary material, impregnated with reagents, can be
incorporated between two plastic films in such a manner that one
film contacts the capillary material and that a hollow space, which
can also be subdivided into several small spaces is formed between
the capillary material and the other film. It is also possible to
provide the plastic films in such a manner that hollow spaces are
formed above as well as below the impregnated capillary material.
Furthermore, two impregnated strips of the capillary material can
also be disposed between two plastic films in such a manner that
the hollow space is produced between the capillary material
strips.
Decided advantages are obtained by providing the hollow spaces
above the capillary material impregnated with reagents. The
impregnated capillary material absorbs the liquid medium to be
examined essentially more quickly than is the case in the
conventional indicator paper strips. A defined and predetermined
volume of the liquid medium is absorbed. Because of the rapid,
complete absorption by the impregnated indicator portion, there is
neither a chromatographic separation impairing the coloring mode,
nor a migration of reagents soluble in the liquid in the capillary
material. The impregnated capillary material assumes a
characteristic color or color change corresponding to the content
of the components in the liquid medium to be tested, and
accordingly makes it possible to conduct a quantitative, or at
least a semiquantitative, determination. The formation of undesired
air bubbles between the capillary material and the plastic film
when the indicator is immersed in the liquid to be examined is
avoided. Accordingly, the read-off accuracy is increased, and the
coordination of the resultant characteristic color or color change
with a color scale is essentially facilitated.
Suitable films of a synthetic material are conventional films
employed heretofore for such purposes. The films must not be
porous, and they must be liquid-impermeable. At least one of the
films is to be transparent. Suitable materials for the films are,
for example, polyethylene, polypropylene, polyvinyl-type polymers,
or copolymers, such as polyvinyl chloride, polyvinyl acetate,
polyvinylidene chloride, or polyethylene glycol terephthalates and
the like. Also laminated films can be employed if an increased
rigidity and a sufficient heat sealing strength of the films is
desired. Plastic films coated with fusion adhesives or heat-sealing
varnishes are likewise suitable. The thickness of these films can
vary between 20 and 1000.mu., preferably between 50 and 200 .mu..
It is not necessary for both films to exhibit the same thickness.
Rather, the film covering the capillary material can, for example,
be very thin (e.g., 30 .mu.), whereas the film forming the hollow
space on the other side of the capillary material can suitably be
substantially thicker (up to 1000 .mu.) so that it exhibits
sufficient strength and rigidity. If desired, either or both of the
films can also be self-sealing, so that a sealing step can be
omitted. In this case, the adhesive must, of course, be selected so
that is does not interfere with the detection reactions to be
conducted. Alternatively, the films enveloping the capillary
material can be welded together according to all customary methods,
for example by pressure, heat, or high frequency, or also by the
effect of solvents and/or swelling agents. At least one of the
films must be transparent. It is often advantageous to make the
other film opaque or even colored, since, in this manner, the
resultant color effects can sometimes be enhanced, whereby the
read-off accuracy is increased.
Any absorbent material can be employed for the capillary material
which is to be saturated with reagents. Thus, all porous materials
can be utilized which can absorb or take up a liquid or a solid
substance. The material should exhibit capillary properties due to
a porous structure. Preferred materials are fibrous substances,
e.g., paper, especially filter paper and the like, however any
other material having a capillary or wick-type effect can also be
employed. Some further examples are other cellulose materials,
synthetic fibers, glass fibers, finely divided granulated
substances, natural and synthetic fibrous meshwork, and the
like.
Advantageously, this capillary material is employed in thicknesses
of about 0.05 - 3 mm., preferably about 0.2 - 0.4 mm. The surface
of the capillary material, not covered by plastic films, intended
for reaction, preferably has an approximately square configuration
and has an area of about between 10 and 50 mm.sup.2. The capillary
material should be uniform with respect to porosity, density, and
chemical properties.
The indicator strips of this invention are suitably designed so
that the hollow space preferably extends over the entire surface of
the impregnated capillary material at least on one side. In any
event, at least 40 percent of one surface of the capillary material
should be in communication with a hollow space in order to obtain
the desired results. The hollow space can also be subdivided into
several smaller spaces, and this can also be done either on one or
on both sides of the capillary material. In order to permit the
liquid medium to be tested to penetrate and enter into a reaction
with the applied reagents on the capillary material, it must be
exposed at least on one and preferably on both lateral edges, i.e.,
the film must not cover the capillary material at those places.
However, it is also possible to expose the capillary material on
all edges, whereby ventilating is afforded.
If it is desired, in individual cases, to provide additional
ventilating, the films can also contain perforations at any desired
places. However, in general, such modifications are unnecessary in
connection with the embodiments of this invention.
It is important to design the hollow space over the capillary
material in such a manner that it exhibits a certain height as
compared to the thickness of the capillary material. It was found
that especially advantageous indicator strips are obtained if the
proportion of the thickness of the capillary material with respect
to the maximum height of the hollow space, or spaces, disposed
thereabove, as seen in cross section, is from about 1 : 0.5 to
about 1 : 10, preferably from about 1 : 1 to about 1 : 2.
Surprisingly, it is not the volume of the hollow space which is of
particular importance, but rather the ratio of thickness to
height.
It is also possible to accommodate several different capillary
materials, or several capillary materials saturated with different
reagents, on one indicator strip, when it is desirable for several
investigations to be conducted simultaneously, or in the case,
during an examination step, the detection is to be carried out
simultaneously by means of different reactions. In this regard, the
individual hollow spaces above the capillary materials can
optionally be in communication with one another, or they can also
be segregated from one another. Thus, in the latter case, a
multiple-chamber indicator strip is obtained, and it is preferred
if there is the danger that reagents contained in the capillary
material, or the colorations which occur, influence one another and
thus can impair the determinations. Even in the case where several
individually independent reactions are to be conducted by means of
a single test strip, this concept is of special advantage. The
separation can be obtained either by the shape of the film or by
special separating layers. Thus, it is possible, for example, to
encompass the capillary material on one or both sides with
materials, preferably hydrophobic, e.g., resins, waxes, or
synthetic materials. In a multiple-chamber indicator strip, the
capillary material and the separating layers, optionally can be
arranged in an alternating series. Such indicator strips can be
very advantageously manufactured if the thickness of the separating
layers exceeds the thickness of the capillary material by the
desired height of the hollow space above the capillary material. In
this way, the separating layers, preferably a synthetic material,
function as spacers, since the cover films can then be sealed or
glued directly onto the separating layers extending beyond the
capillary material. The width of the separating layers can be
selected as desired and can thus be adapted to the respective
purpose of the indicator strip.
It is also possible to impregnate two strips of the capillary
material with various reagent substances, especially for example,
with mutually incompatible substances, and then to provide these
strips of capillary material in one indicator strip in such a
manner that a common hollow space is produced in the center. One
surface of the capillary materials, in each instance, closely
contacts the films, whereas, respectively, the other surface faces
the common hollow space present in the center. In such an
arrangement, both films are preferably transparent.
Reference is now made to the drawings wherein various embodiments
of the indicator strips according to the invention are illustrated.
The drawings, in order to attain greater clarity, are not drawn to
scale.
FIGS. 1-6 show longitudinal sectional views of various embodiments
of the indicator strips of the invention;
FIGS. 7a and 7b show cross-sectional views through two embodiments
of the invention;
FIGS. 8-13 show longitudinal sectional views of additional
embodiments of the indicator strips of the invention;
FIG. 14 is a perspective view of the embodiment shown in FIG.
5;
FIG. 15 shows eight variations (a through h) of film designs for
providing a series of smaller spaces next to the capillary material
of the indicator strips; and
FIG. 16 is a top view of another embodiment of the indicator strip
of the invention showing two variations of the inner surface of the
film of the indicator strip.
In all the embodiments shown in the drawings, the numeral 1 denotes
the capillary material, 2 denotes one of the films, 3 denotes the
cover film, 4 denotes the slot or hollow space above the capillary
material, and 5 denotes projections, bulges, curved sections,
peaks, and the like in the film 3.
In FIG. 1, the capillary material 1 of the indicator strip is
sealed or glued to the film 2 on one side, whereas the cover film 3
forms the slot or hollow space 4 above the capillary material 1.
Near the upper and lower edges of the capillary material 1, the
films 2 and 3 are welded or sealed together.
The indicator strip shown in FIG. 2 corresponds essentially to that
in FIG. 1. The film 3 is designed to contain a small shoulder, in
such a manner that the capillary material 1 is sealed to the film 3
and it is not attached to the film 2 in this instance.
In FIG. 3, the film 3 is provided with projections or protuberant
portions 5, which can subdivide the hollow space 4 into various
smaller cavities if the projections 5 contact the capillary
material 1.
In FIG. 4, another embodiment is disclosed for subdividing the
hollow space 4 into various smaller spaces. In this case, the cover
film 3 is of serpentine form and can contact or firmly touch the
capillary material 1, or an interstice between 1 and 3 can be left
so that a coherent hollow space is produced as shown.
FIG. 5 shows an embodiment wherein the capillary material 1 is not
sealed within the film, but rather it is covered for protection on
one side by the film 2, whereas the film 3 forms the required
hollow space 4. Thus, according to this embodiment, the capillary
material is not only exposed from the side of the edges along the
lateral sides, but also from above and from the bottom at the
narrow sides.
FIG. 6 corresponds essentially to the modification of FIG. 5, with
the difference that here the film 3 is designed so that the hollow
space 4 is subdivided, by the projections 5 and into individual
smaller spaces when the projections 5 touch the capillary material
1.
FIGS. 7a and 7b represent cross sections through the indicator
strips of this invention and in particular show a serpentine film 3
parallel to the longitudinal edges of the indicator strips.
Suitably, the lower edges of the capillary material on the narrow
sides of the indicator strips are left free in these embodiments,
whereby the capillary effect by the individual hollow cylinders
produced above the capillary material is increased.
In FIG. 7a, the capillary material 1 is sealed onto the film 2 and
onto the projections 5 of the film 3, whereas, according to FIG.
7b, the capillary material 1 merely rests on the film 2 and is
sealed within the films 2 and 3.
FIG. 8 shows an embodiment of the indicator strips according to the
invention wherein a hollow space 4 is provided on both sides of the
capillary material 1. The films 2 and 3 are in each case welded
together below and above the capillary material 1. Basically, the
hollow spaces 4 can exhibit different volumes, but, for the sake of
simplicity, symmetrical arrangements will normally be selected.
FIG. 9 represents another embodiment of the indicator strip wherein
two, optionally different, strips of the capillary material 1
contact the films 2 and 3, respectively, whereas a common hollow
space 4 is formed between the two capillary materials 1. Above and
below the capillary material 1, the films 2 and 3 are joined to
each other, for example by cementing or welding. In this
embodiment, it is advantageous to employ transparent film for films
2 and 3.
In FIGS. 10 and 11, embodiments of indicator strips are illustrated
which contain several strips of the capillary material 1. The
remaining design corresponds approximately to FIGS. 1 and 2.
FIGS. 12 and 13 show embodiments of indicator strips wherein the
capillary material 1 is disposed between hydrophobic separating
layers 6. The capillary material 1 and the hydrophobic material 6
are sealed to the film 2. The height of the separating layers 6
determines the height of the hollow space 4. The film 3 is sealed
to the separating layers 6. A sealing between the films 2 and 3 can
be omitted in this embodiment, wherein the impregnation of the
capillary material 1 is especially well protected.
FIG. 14 is a perspective view from the side and the embodiment
essentially corresponds to FIG. 5. FIG. 14 is to demonstrate the
exposed edges 7 and 8 of the capillary material 1.
FIG. 15 shows, in embodiments (a) through (h), various shaped
designs for the film 3. Basically, any shape can be chosen which
makes it possible to subdivide the hollow space 4 into various
smaller spaces. In this regard, it is unnecessary to provide that
the film 3 exhibits the same shape over the entire surface above
the capillary material 1. Rather, a multitude of possibilities of
variation, as well as all types of transitions conceivable are
possible. Accordingly, projections, grooves, curves, peaks, mosaic
configurations, etc. can be provided regularly or irregularly, and
can either rest on the capillary material 1, or can terminate above
the material 1 in the hollow space 4.
FIG. 16 shows, in a top view, an indicator strip according to the
invention wherein the inner surface 5 of film 3 can be formed of
various patterns. Two types are shown as examples.
Normally, the film 2 is to be transparent, whereas the film 3 is
opaque or colored. The read-off then takes place, if a hollow space
is provided only on one side, i.e., on the side which faces away
from this hollow space.
The required shaping of the film 3 can be done in accordance with
conventional methods, for example by embossing or deep-drawing.
However, it is also possible to apply plastics, powders or
granulated substances by sintering. Also other small particles
suitable for this purpose, e.g., glass fibers or minerals and the
like, can alter the inner surface of the film 3 in the desired
manner by being melted or sprayed thereon.
The novel indicator strips can be successfully used in all cases
where a qualitative, or also quantitative determination of
substances dissolved or suspended in a liquid test medium is to be
conducted. The mode of application does not differ from that of the
conventional indicators. Normally, the indicator strips are
immersed into the liquid to be tested, the color changes caused
after a period of time are noted, and/or compared with a color
scale. The speed and the accurate reproducibility attainable by the
indicator strip according to the invention represents a
considerable advance in this art.
During the manufacture, the impregnated capillary material,
preferably paper, is cut to the desired width and incorporated in
between the films depending on the design selected. In many cases,
it proved to be especially advantageous to seal or cement the
strip-shaped capillary material to a film prior to the impregnation
step. If a capillary material thus joined to a film is then
impregnated, it is generally possible to avoid the bending or
curling of the saturated papers after drying, which interferes with
the further processing operations. The thus-obtained welded plastic
bands are then cut transversely, so that indicator strips are
produced which are open from the edges at the narrow sides. The
indicator strips normally exhibit a width of about 3 - 10 mm.,
preferably about 5 - 7 mm., and a length of about 30 - 100,
preferably about 50 - 70 mm. However, other dimensions are, of
course, likewise possible.
Without further elaboration, it is believed that one skilled in the
art, can, using the preceding description, utilize the present
invention to its fullest extent. The following preferred specific
embodiments are, therefore, to be construed as merely illustrative,
and not limitative of the remainder of the disclosure in any way
whatsoever.
EXAMPLE 1
Copper Test Strips
A filter paper strip having a width of about 6 mm. and a thickness
of about 320 or 370 .mu. ("Schleicher and Schull No. 2316 or 1450
CV") is sealed, approximately 6 mm. from the lower edge, to a
transparent film band having a width of about 60 mm. (and a
thickness of about 100 .mu.), and is continuously saturated with a
solution having the following composition:
0.2 g. of "Cupron"
1 g. of hydroxylamine hydrochloride
50 ml. of methanol
50 ml. of benzene
Thereafter, the band is dried by means of hot air or infra red
light. Then, an opaque film having also a width of about 60 mm. and
a thickness of about 100 .mu., exhibiting a bulge of a height of
700 .mu. according to FIG. 1, is sealed on with the aid of a pair
of rolls (heatable roll and chill roll). The bulge extends in a
width of about 6 mm. at a spacing of 5 - 12 mm. from the lower
edge. The center of the bulge is located approximately over the
center of the impregnated capillary material. The thus-sealed film
band is reeled up, and the rolls are cut, at right angles to the
conveying direction of the film band, into test strips having a
length of 60 mm. and a width of about 6 mm. Thereafter, the
capillary material is exposed on the cut edges.
EXAMPLE 2
Nitrite Test Strip
A roll of raw paper having a with of about 50 cm., with a thickness
of the capillary material of about 320 .mu. ("Schleicher and Schull
No. 2316") is impregnated with a solution having the following
composition:
0.15 g. of 1-naphthylamine
0.85 g. of sulfanilic acid
5 g. of tartaric acid
100 ml. of water
After drying, the band is cut into paper rolls having a width of
about 6 mm. The thus-obtained rolls are continuously placed on a
transparent film having a thickness of 100 .mu., and simultaneously
an opaque cover film having a thickness of 100 .mu. is applied as
well and sealed together with the transparent film. The latter
contains a bulge corresponding to FIG. 2, the height of which bulge
is about 600 .mu. and the breadth of which is about 4 mm. The cover
film is attached in such a manner that the center of the bulge is
disposed approximately above the center of the capillary material.
The capillary material is placed onto the transparent film
approximately so that its lower edge is 4 - 6 mm. removed from the
lower edge of the film.
The projections provided at the bulges of the cover film in
accordance with FIG. 2 retain the capillary material in the desired
position. After cutting the thus-obtained rolls at right angles to
the traveling direction, test strips are obtained having a length
of about 60 mm. and a width of 6 mm. The lateral edges of the
capillary material are exposed.
EXAMPLE 3
Nickel Test Strip
A roll of raw paper having a width of about 50 cm., laminated with
a thin polyvinyl chloride film (thickness 40 - 100 .mu.), which
paper is a product bearing "Schleicher und Schull No. 1451" and has
a thickness of 330 - 350 .mu., is impregnated with the following
solution, and then dried:
0.5 g. of dimethylglyoxime
2 g. of sodium acetate
100 ml. of methanol
The thus-obtained roll is cut into paper rolls having a width of 6
mm. and then cemented to an embossed film web, containing a bulge
according to FIG. 5. The bulge has a height of about 300 .mu. and a
width of about 4 mm., so that respectively 1 mm. is available for
the attachment of the deep-drawn film on the capillary material at
the top and at the bottom. The thus-obtained film band is cut
transversely, so that test strips are obtained having a length of
about 60 mm. and a width of 6 mm.
In this embodiment, the capillary material is exposed on all four
edges.
EXAMPLE 4
Chloride Test Strip
A paper strip having a width of about 6 mm. ("Schleicher und Schull
No. 604" -- thickness about 220 .mu.) is sealed onto the
transparent film band described in Example 1. Thereafter, the band
is impregnated with a 0.3 percent aqueous potassium chromate
solution and dried. Then, the thus-impregnated paper is saturated
with a 0.5 percent aqueous silver nitrate solution, and during this
process, uniformly distributed silver chromate is formed in and on
the raw paper.
Thereafter, the cover film described in Example 1 is employed for
sealing the band, in accordance with the procedure set forth in
this example. After cutting the band at right angles to the
traveling direction, an indicator strip is obtained along the lines
of FIG. 1.
EXAMPLE 5
Cholinesterase Test Strip
Similarly as in Example 1, an indicator strip is produced wherein
the impregnating liquid is obtained as follows:
100 mg. of phenol red, 100 mg. of naphthol phthalein, and 15 g. of
acetylcholine hydrochloride are dissolved in 100 ml. of methanol
and thereafter adjusted to a pH of 6.0 by the addition of sodium
hydroxide solution.
The impregnation can be conducted prior to or after the application
of the filter paper to the transparent film. The thus-obtained
strips have a length of 60 mm. and a width of 6 mm. The strip
serves for the determination of cholinesterase.
The preceding examples can be repeated with similar success by
substituting the generically or specifically described reactants
and/or operating conditions of this invention for those used in the
preceding examples.
From the foregoing description, one skilled in the art can easily
ascertain the essential characteristics of this invention, and
without departing from the spirit and scope thereof, can make
various changes and modifications of the invention to adapt it to
various usages and conditions.
* * * * *