DE2818826A1 - METHOD OF MANUFACTURING DIAGNOSTIC TEST STRIPS - Google Patents

Description

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1-50

Patent application

Applicant:

MILES LABORATORIES, INC.
Elkhart, Indiana 46514
United States

Title:

Process for the production of diagnostic test strips

809846/0714

DR. ING. F. WUESTirOKF DR-E. ν. Ι'ΚΟΙΙΜΛΝΝ

DR. IKG. IJ. UKirUKNS KIPI .. IWG. H. GOETZ I = ATSKTAHWJiLTU

M <where. _IK 2J318826

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TELKfJRAMMB ϊ I ¹ KOTECXIMTENt ΜϋΝΟΠΕϊΓ

1Δ-50 899 Applicant: Miles

description

The invention relates generally to diagnostic means for rapidly examining biological fluids Proof of certain components, e.g. B. for the detection of glucose, ketones, etc., in blood and other fluids.

Known diagnostic test strips generally comprise an absorbent carrier which is impregnated with reagents is to produce a certain color reaction when it comes into contact with the liquid to be examined.

The usual carrier material in most test strips is usually filter paper, which has clear advantages, but also certain disadvantages and limitations, such as unsatisfactory physical and chemical stability of the paper support, when impregnated with certain test reagents at high concentrations, to a satisfactory level To obtain color reaction.

It has already been indicated to make filter papers more stable by laminating them with a film made of a synthetic resin or by using fibers made of a synthetic resin to either reinforce or completely replace the cellulose fibers. However, it has been shown that cellulose fibers swell ₉ during the impregnating and thus partially absorb the reagents in the fibers ^ while the impregnation allows TTUR ρ that a relatively small amount of reagents to be deposited on the surface of the synthetic fibers "

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In addition to these limitations with regard to the absorbent carrier material The usual production of test strips generally requires many impregnation steps which are quite difficult can be carried out on a large scale and in a reproducible manner and also significantly increase production costs,

The object of the present invention, the above-mentioned disadvantages can be avoided as far as possible zn by developing a simple method for the production of diagnostic test strips on a large scale in a reproducible and economical manner.

The invention therefore essentially relates to a method for the production of diagnostic test strips for the detection of specified components that are present in biological fluids, such as urine, the test strips comprising a solid support containing at least two reagents therewith when wetting with a liquid to be examined a certain Color reaction occurs. The inventive method is characterized in that one

a) provides at least two reagents, each consist of a mixture of mutually compatible components / including at least one of the reagents for Performing the desired test reaction, a liquid solvent and a binder comprising a polymer;

b) the carrier in the form of a film with an Oberflacne suitable for printing with the reagents / ί wherein the film is im is substantially insoluble in water and inert to the reagents on at least one side;

c) one after the other the reagents a large number

of dots, stripes or other patterns on each reagent
ink "on this surface / ζ creating at least two separate patterns of printed dots or lines from the reagent inks, the dots of each pattern being dried after printing and arranged so that they match both dots from the same reagent ink and the Pattern the other inks in close proximity

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^ are such that the printed dots are arranged separately from each Reagenstinte between dea points of each other Reagenstinte, to eat close lachbarsehaft are thus However ,, but without contact between different points _P Sinten occurs so that the dry reagents in the respective. Points remain separated from one another, while "'in the presence of the liquid sample to be examined, the reagents can diffuse over the surface and thereby mutually interact with one another

d) Cut this film with the printed, separate print patterns on the surface into a large number of test strips of the washed 5 ¹ Oi ¹ egg and size _{or similar}

The application of printing processes for the production of diagnostic. Strip according to the invention presents various practical advantages and in particular the overlapping

The possibility ρ is simply different components of the Reaction system ρ that would usually react with each other, to separate them from each other by dividing them into different ones Incorporate reaction inks which are then used to print separate patterns on the print side of the test strip?

The possibility of having a lighter, more reproducible _9, faster and relatively simple printing process available for applying precisely predetermined amounts of reagents to the printing substrate, whereby the production of diagnostic strips on a large scale can be made much easier and more economical}

The ability to dispense with separate Earbvergleichskarten by printing the respective test colors for comparison to predetermined areas of the same test strip.

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Various considerations of practical interest in reaching these advantages according to the principles of the method according to the invention are discussed below.

Compositions of reagent inks (reagent printing compound)

It is easy to see that the particular compositions of the units depend primarily on the particular color reaction that takes place to be performed with the aid of the test strips, i.e. the particular reagent system that is required, to enable the desired test reaction in each case.

The ingredients of each reagent ink should also be selected so that they are chemically and physically interrelated are compatible and with the substrate to which they are applied.

To ensure satisfactory printing, you should the physical properties of the reagent inks, moreover, to the ^. the printing medium as well as the printing technology and the printing devices, used to make the strips.

As used herein, the term "reagent ink" embraces an intimate mixture of at least one major reagent such as this for the color test reaction is necessary with auxiliaries and a suitable liquid carrier to obtain an ink having suitable geological (flow) properties suitable for Printing techniques are suitable and have good ink transfer

Enable printing on the print carrier in any case.

The main reagents used in each. sum printing according to the The inks used in the invention obviously depend in each case on the particular type of test reaction, for which the test strips are to be manufactured.

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The reagent system is applied to the _s to obtain a specific color reaction on the test strip produced according to the invention ^ may comprise generally customary reagents, such as are known in the prior art for diagnostic test reactions. Known reagents are contained in the inks described in the examples described below to illustrate the invention

On the other hand, as mentioned above, all of the components of the reagent ink must be compatible with one another and should be suitable Have oesological properties, to enable good printing. The selection of a solvent and auxiliaries for the preparation of the ink besides the main reagent depend on this from various considerations discussed in more detail below

Solvent for the ink

The puncture of the solvent in the reagent ink is to obtain a liquid medium, which is necessary to keep the main reagent and auxiliaries of the ink in solution or suspension until the ink is applied to print on the substrate _e after printing has that Solvent fulfills its role and should be able to be removed by drying in order to achieve printing points that are fixed on the surface of the print carrier «

When enzymes or other biologically active substances contained in the Reagenstinten _s, the solvent is preferably water or an aqueous mixture of water-ethanol type, and more exotic solvents ^ the biologically active in the presence of substances should not be applied, can not contain "A number of other Solvents, such as anhydrous benzene, dimethyl sulfoxide or higher alcohols, can also be of interest as solvents ₉ s _o B ₀ glycols So any suitable solvent can be used ₉ that is compatible with the other components of the ink in any case. Certain

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Inorganic salts that are used in the reagent inks as a buffer or Enzyme activators can be included, but have ice limited solubility in organic solvents, among other things must be invoiced when selecting the components for the ink «

Binders for the

In order to provide the unity (or printing inks) with the necessary frhsologisoheii Properties to lend ^ to get a satisfying aaea 3ruck ensure contain these l'inks or printing inks iia general binder "

Modern binder for dieting or printing inks are generally made of polymers that dissolve in the solvent for the ink in sufficient quantity or in suspea & ISRT, satisfactory to the ink ideology properties which are adapted to the respective printing method in which they are applied to lend _p.

The binders used in the reagent inks for the production of printing strips for biological liquids according to the Invention would have to go with the solvent and the other constituents. parts of the ink should be compatible and should preferably be hydrophilic so that they can also use the biological test fluids can freely accept, creating the desired test reactions Natural hydrophilic binders which are suitable for the reagent inks used according to the invention are gelatine and gum arabic, which each have a high swelling power and thus allow considerable To absorb amounts of water.

It is also used during the subsequent wetting or soaking of the printed test strip, when used for the diagnostic color test, the binding agent to prevent that the main reagents in the surrounding

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Go looking for a solution (solution of the analyte).

The binder should be able to easily at room temperature To take up water to enable the reagents diffuse along the printed surface «,, whereby the desired color reaction occurs «

Various natural or synthetic binders come for the reagents according to the invention into consideration, such as. B.

Cellulose derivatives

G-slate
Collages

j? oly (H ~ vinylpyrrolidoüe)

Erfiriduugsgemäß preferred binders for Reageestinten are the Callulosebiademittelj that will be used in the examples given later ti ₀

buffer

The reagent inks can generally contain a buffer to keep the pH of the printed reagents within a predetermined range to maintain a narrow range and to allow the desired color reaction to take place in a suitable pH environment on the test strip.

In the examples given later, various suitable ones will be found Buffer applied.

A major requirement in the selection of the buffer in the reagent inks to carry out a specific test reaction in that the buffer is chemically associated with the entire reaction system Should be compatible and especially with the polymeric binder contained in the reagent inks.

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In principle, the following four types of buffers are mainly used to regulate the pH value of biochemical test reactions between 5 and 7 are appropriate to consider.

(i) citric acid / sodium citrate (ii) trishydroxymethylaminoethane (iii) phosphate
(iv) phthalate

Preliminary tests carried out to determine the compatibility of different buffers with a number of polymers have shown that the following buffer systems because of their buffering properties at the pH (4-7), the is required for experiments to detect occult blood

.low as well as due to their relative / costs.

1) Na-H-Maleate - NaOH (pH 5-6)

2) succinic acid - NaOH (pH 5-6)

3) K-H phthalate - NaOH (pH 5-6)

4) β, β'-dimethylglutaric acid - NaOH (pH 5-6)

5) Na citrate - citric acid buffer (pH 5-6)

In addition, a sodium citrate / citric acid / buffer (pH 5-6) can also be used in a reagent ink for a glucose test can be applied.

A phosphate buffer (pH 8-10) can be used in a reagent ink for a ketone test.

The following Table I shows the results of a series of compatibility or Compatibilitätstests in which the above-mentioned buffer systems were each mixed with a number of polymers and the solubility of the Pol7 / was observed mers both at normal room temperature and at 80 ⁰ C .

609846/0714

IABELIE I

Compatibility of Pufferaysterneα with polymers

POLYMER

Citrate 0.8 M.

Buffer system

Dimethylglutaric acid 0 _; l M

Succinic acid 0.2 M.

Phthalate
0.1 M.

Maleate 0.2 M.

HYDROXY THYL CELLULOSE
m "Natrosol 250 HXR"

"Natrosol 250 HHR"

"Natrosol 250 MH"

"Natrosol 250 M"

"Natrosol 250 HR"

"Natrosol 250 MX"

UAIRIÜKÄRBOXYMETHYL CELLULOSE "CMC 7 HF"

"CMC 4 LF"

POLYVINYLPYRROLIDONE "PVP K-90"

"PVP K-30"

25 ⁰ C

80 ⁰ C

+ partially + + partially +

2S ° C

80 ⁰ C

partly + partly +.

25 ⁰ C

8O ⁰ C

+ partially

+ partially

25 ° C

+ partially ^ +

• Hydroxyethyl cellulose

"Cellosize QP-4400H" "Cellosize QP 100MH"

METHYLiTHYL CELLULOSE "Edifas BX 100" (ICI) "Edifas B 300" (ICI) "Edifas B 1500" (ICI) "Edifas B 10" (ICI) "Edifas A" CICI)

POLYCMETHYLVINYL ETHER

^ o ANHYDRIDE

s ^ "Gantrez AN 169" - -

+: dissolves. -. does not dissolve or swell g: .grainy appearance ·.

«Β + - + - - - + + + - + + + + + + + + + + + + + + + + + + + + + + + + _ + A.

ro CX3

OO OO K) cn

U-50 Ö99

As can be seen from Table I, the maleate, succinic acid, pathalate and glutaric acid buffers are compatible with most of the polymers tested ₉ while the citrate buffers are

is not.

Surface active agents.

The reagent inks may preferably contain surfactants

contained as a wetting agent «,

For example, z _o B ₀ ITatrium dodecyl sulfate (SDS) ₉ gum arabic and gelatin are surface-active agents that can be used as emulsifiers or as sulphation stabilizers in a first reagent ink, containing cuinol hydroperoxide as the main reagent for the detection of occult blood in urine in test strips as described below given examples are produced

Similarly äthyloxiliertes Alky! Phenol (z. B. "Renex 698" Atlas Chemical Industries ^ Inc _o) advantageously be added as a surfactant in a second Reagenstinte containing o-tolidine as the second main agent for Kachweis of occultem blood in urine "■"

Darüberlainaus _s can be obviously applied to any surfactant in the Reagenstinten as Polyosyäthylensorbitan monolaurate ( "iDween 20" Atlas Chemical Industries, Inc.) or polyethylene glycol ( "Carbowax" ICI America, Inc.).

It goes without saying that the use of the terms: "binder, surface-active agent _s emulsifier, stabilizer" depends largely on the main function that these substances perform in the respective inks or ink constituents and that these functions / obviously can overlap or a relative one Have meaning or varying meanings in a particular ink or in different reagent situations.

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So are ζ. B. Gum arabic and gelatin natural polymers that absorb a large amount of solvation water can and thus act as emulsion stabilizers while at the same time increasing the viscosity of the reagent ink and act as a binder for the ink at the same time.

The various components of the reagent inks must of course are selected so that they are compatible with each other in each case and relatively simple compatibility tests, such as those which gave the results in Table I can be carried out for this purpose.

For example, it was found that a

Reagent ink for the detection of occult blood cumene, water, cumene hydroperoxide (CHP), sodium dodecyl sulfate (SOS), gum arabic and gelatin, all of which are compatible with one another, together with 0.5 M Tris buffer as well as with the following water-soluble binders.

Na-carboxymethy! -Cellulose (NaCMC) Hydroxyethyl cellulose (HEC) and methylethyl cellulose ("EDIPAS A», ICI)

Print carrier

The dots or patterns from the reagent inks can be used according to the invention can be applied to any suitable surface (sheet) that is not chemically compatible with the different applied for printing Reagent inks reacts.

The printing medium used to produce the printed test strips depends in particular on the reagent inks to be used in each case. This carrier or sheet should be the following Meet requirements as far as possible.

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1. It should be essentially insoluble in water and the Print area chemically opposite the respective reagent stintea to be inert »

2. It should pick up and fix the print samples with good adhesion of the reagent inks to the printed surface,

3. It should be wettable by the liquid to be analyzed be.

4. It should be able to diffusely reflect all wavelengths of the visible light spectrum or be completely transparent, if it is applied to a white surface.

5. It should not curl up and be stable against heat.

A wide variety of synthetic resins can be used in order to produce suitable print media. Various thermoplastic resins that can be applied to a suitable print carrier for the test strips according to the invention are given by way of example in Table II.

-H-

809846/0714

Table II

Polyethylene (low, ^ medium and high density) Polypropylene

Polyvinyl chloride (rigid) Polyvinylidene chloride (rigid)

Polystyrene (e.g. with high impact resistance or A.B.S «

Resins)

Styrene-acrylnilsil copolymer

Acrylic resins (eg with high impact strength ar) chlorinated polyethers polychlorotrifluoroethylene fluorinated ethylene ~ propylene copolymer polytetrafluoroethylene nylon (66 or 6) acetal resins
Polycarbonate resins Polymethane resins Cellulose resins Cellulose acetate butyrate Cellulose propionate Ethy-cellulose

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The printed labels should have an essentially white background in order to reflect as much visible light of all wavelengths as possible and thereby ensure good visual (or photometris) observation or detection of the color change that occurs when the test strip is subsequently applied to give the desired n _o

Her pressure support preferably has eiae matte surface, the light scattered in all directional lengths diffusely reflected and su a much better detection results than if the surface is highly glossy _s whereby the light as reflected at a mirror would _β

to give a strong contrast, the material of the substrate surface itself can be made white, either by incorporating a white pigment or by applying a white coating. On the other hand, the printing substrate can also be transparent and colorless and lie on a white base, for example paper, _e

White foils or printing substrates made entirely of plastics (or "synthetic papers") are commercially available and are used for graphic purposes, especially for photographic prints. Xylonite Ltd. UK) consists of modified polyethylene that has been cast into a thin film. «It has the feel and handling properties of good (art print) paper, but otherwise the properties of a tough (firm) ₉ continuous plastic film. Another synthetic paper ("Q ¹ per" from Nippon Art Paper Mfg. Co., Ltd., Japan) consists of a continuous polystyrene film.

Another material that can be applied to make a light reflective To obtain pressure medium or a pressure medium for the test equipment according to the invention, a combined

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Set material of plastic and paper, comprising a paper base covered with a thin transparent layer is covered from a plastic material. The optical properties of the paper are so in the composite Maintain material while the surface is polymeric. Such material is in different types with different Surfaces (semi-gloss, glossy and matte) available in stores, TJm the adhesion of the printed dots or To increase the pattern, the print carrier can have a more or less rough and / or porous surface.

The use of a more or less porous print carrier has two advantages over non-adsorbent plastic materials cannot be reached. A first benefit is the improved adhesion between the reagent inks and the porous substrate, which has a much larger surface area than a non-porous material and thus a larger surface area for adhesion and also for the subsequent performance of the color test reaction.

A second advantage of a porous substrate is related to the subsequent mixing of the reagent inks in Presence of the sample to be examined. A thin porous membrane allows the reagents to. itself in the substrate mix yourself. In addition, as in the case of a non-absorbent substrate, mixing also takes place in the liquid phase between the dots or patterns of the reagent ink printed on the surface of the substrate in liquid phase instead.

From the above it can thus be seen that the use of microporous plastics provides an absorbent substrate surface which has the advantages that, firstly, there are no adhesion problems for the reagent inks, and secondly the printed reagents in a chemically inert matrix be absorbed.

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With respect to the resins listed in Table II above, it should be noted that polyethylene and polypropylene substrates are used Improvement of the adhesion can be pretreated.

For surface treatment of Iu / ststoffolien various conventional methods are known to increase the adhesion to be increased ^1, is by reactive chemical groups on the surface of te polymer: oxidation of the polymer can be achieved by treatment with a sulfuric acid-dichromate or with similar solutions " The polymer is then washed before printing. The effect of UV light, especially in the presence of ozone, can also be used to make certain polymer substrates more receptive to inks. Electrical pretreatment either by high voltage corona discharge or by glow discharge under reduced pressure can also be used to modify the polymer surface. An electron beam can also be used for this purpose.

In addition to the "Polyart" films, other films made of synetetic Resin such as a film or sheet made of a fibrous polyester ("SIlBOND" fiber products GmbH), a Foil made of fibrous polyamide ("SYNTOSIl" SIHl, Papeteries Zürichoises sur Sihl, Zurich) and a film made of spun polyethylene ("TYVEK" E.I. DuPont de Nemours and Go.) successfully applied as a print carrier for the printed test strips according to the invention.

Another material that can be used to obtain a light-reflecting print carrier contains glass fibers and is available in the form of thin foils with a density of 70g / m (Schleicher and Schall). Another material which can be used _s a light reflecting print carrier obtained su, is absorbent paper that can be successfully used as a carrier obtained su discrete points or patterns of two Reagenstinten.

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satisfactory In order to ensure a sufficient color intensity to enable visual or photometric detection with the help of the larbreactions occurring on the surface of the test strip, should the Dicice üeü ü'iluis from aer Keagenstini; e, aer ia lorm voa printedβα dots or patterns deposited, is like that be as big as possible.

It should also be mentioned that every reagent stine is sufficiently viscous should be printed to the formation of a thick dot-shaped Layer on a specific print substrate, whereby the thickness »in which the ink is applied, depends on the printing process depends. This means that a high viscosity ink alone does not allow the deposition of a thick 3 film guaranteed when printing.

An offset printing process with a viscous ink allows ■ or printing ink only the printing of layers that are only a few / um thick. A similar limitation occurs on application of letterpress printing works in which a paste-like ink or printing ink is used, but only a thin application of paint arises. Consequently, offset and letterpress printing result in the Printing work in addition to flexography and lettering or printing under impact, each with certain limitations the thickness of the applied printing paste (approximately 2 to 5 µm).

In rotogravure printing, an ink is generally used which has a low viscosity and a high proportion of

contains, organic. Solvent (about $ 50) that after printing Evaporates and thereby leaves a relatively thicker layer of, for example, approximately 12 μm.

In contrast to this, the method of screen printing can be regarded as particularly suitable for the purposes according to the invention, since it the use of highly viscous inks allowed in one thickness

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ORIGINAL INSPECTED

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upset xverden. can that many times larger is than that achieved by the above methods, namely with the thickness of the dried layer in the range from 15 and 16 / Uia with various known screen printing processes «

It was determined ,, the usual commercially available reagent strip in a thickness of approximately 300 / To impregnated are C, to give a 2est for occult blood Parbänderungen ₅ easily vismLl / um thick layer of soaked by light reflection from the to the top 70 Test strips appear a _e

From the above it can be seen that the points of Reagenstinte preferably be applied by screen printing or a similar process applied to the viscous SnTeN werdeη _β The dimensions of the printing screen and the lieologischen properties of Reagenstinten used are adapted to one another in each Pail that print points of a minimum size and maximum thickness are achieved. The printed dots can be as small as 50 µm in diameter, but larger reagent dots ranging in size from about 30 to 430 µm could be obtained by screen printing processes in the manner further described below.

The different reagent inks are printed on the inert print carrier in individual successive printing stages deposited, i.e. first a first pattern of dots is deposited from a reagent ink and dried, before applying a second pattern of printing dots from a second reagent ink, etc.

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The dots of each pattern are preferably arranged between the dots of the other pattern and the dots of the different ones Patterns are arranged so that they are a short distance from one another so that the main reagents in the respective Inks are fixed separately on the print carrier of the test strip, while only a short Diflussionsweg for the reagents is required during the subsequent wetting of the test strip with the solution to be examined.

The printed items are packed as tightly as possible to create a to achieve maximum concentration of the different reagents by printing per unit area of the surface of the test strips are fixed for a quick test reaction with the occurring! color change of sufficient intensity to enable a satisfactory, visual Evidence made possible

The relative arrangement of the printed at a distance from one another Points of different reagent inks to give a close-packed distribution can be specified for the arrangement of two types of points, namely A and B with the radius R + E, which exactly touch each other, where R is the Diameter of the printed point and E the

Is the distance between adjacent points.

A very close packed arrangement of points A and B that can consist of two different reagent states particularly simple way v / ground using a greatly simplified screen printing process, in which a Metal foil is used which has tiny holes spaced apart in parallel rows The holes in each row are staggered from the holes in the next rows.

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Punch
This creates through / the holes provided in the

Metal foil has a basically triangular print pattern, which means

(MasTcen)
the mapping stage that is usually used to form a

desired hole pattern are required in a printing screen can be completely omitted.

Thus, a screen printing process can use two different reagent inks, denoted by the letters A and B. will * simply be carried out as follows with the help of the specified perforated metal foil.

The perforated metal foil is clamped as a printing screen in a metal frame, which is in a screen printing device is appropriate.

The print carrier, e.g. a synthetic paper film

(Polyart), is brought into the appropriate position on the printing table under the perforated metal foil that forms the printing screen.

area
A small / von RasterpuhWen is first converted into a

The corner of the print substrate is printed on by placing a small Amount of a colored (e.g. red) marking ink or printing ink on a small corner area of the perforated print - applies sieves and runs a rubber roller (squeegee) over it to apply this ink over a limited area to a To distribute corner of the sieve.

A second small pattern of marking or raster points can also be applied to the opposite corner of the print carrier to determine the exact position of the screen on the Ensure print substrate.

Then the first reagent ink is poured from the edge of the screen furthest from the printer

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applied in such an amount that for the whole slide and thus the print substrate is enough.

A rubber squeegee with a hardness on the Shore scale between 80 and 90 »of a sheet with a rectangular profile, is now slowly sucked over the surface of the pressure sieve, which is down in contact with the print substrate is popped while the Ink or printing ink is pressed through the holes of the screen. The ink is brought into contact with the printing medium and remains sufficiently adhered to it so that when the printing screen returns to its original position after-after the pressing device has passed over-the Ink remains on the print substrate in the arrangement of PuoJrcen, with a diameter? which is equal to or slightly larger than the diameter of the holes in the applied one Sieve. The overall pattern of ink dots printed in this way is identical to the arrangement of the holes in the printing screen.

A first pattern of printed dots A is thus made with the first reagent ink by screen printing on the oil or the Print carrier applied. The frame holding the screen is then removed from the printing device The sieve was washed under running water, rinsed with acetone and dried and the frame was placed back in the printing device brought as close to the original position as possible »and the pattern (s) of colored Marking points - will then be made with the appropriate holes of the printing screen brought into agreement by adjusting the printing table on which the printing medium rests accordingly moves what may be necessary to bring the marking points exactly under the corresponding openings, whereby all the printed dots A of the first pattern are brought into alignment with the openings of the printing screen.

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The printing screen is then parallel to the edges of the frame moved, by moving the printing table over previously Almost set distances J and I shifts so that the openings of the printing screen over the unprinted areas substantially in the middle between neighboring points A, which already

,,though
are printed and / each either in the mite one

Triangle made up of three adjacent printed dots A- or within a rhombus of four adjacent points A of the first

Pattern «

The physical displacement of the printing table by X and Y v / is precisely determined by micrometer screws on this table

The second reagent ink is finally applied to the white described above on the printing screen and used to print the second arrangement of printed dots B on the zones of the printing surface ₅ which lie in the middle between the schot / printed dots A of the first arrangement «

In this way, a good pressure from two Reagetistinten could be _s who had the composition as mentioned in the examples below achieved "

For this purpose, perforated MitiäLfolien (Zeefplatenfabrick N ₀ V. in Eerbeek / Holland) were used as printing screens in order to generate the pressure in the planes above.

Six types of commercially available eolias (Yeco 25R, 3OR, 6OP, 8OP or 125P) were used as printing screens, each having the dimensions given in Table III.

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Veco sheet metal thickness Hole size. Hole spacing (mm) (mm) (mm) 25R 0.51 0.50 1 3OR 0.25 0.25 0.85 4OR 0.31 0.19 0.63 6OP 0.09 0.17 0.42 8OP 0.07 0.15 0.31 125P 0.05 0.08 0.20

Various series of pressure tests with these perforated sheets led to good results with those given in Table V. Printing inks or inks, where the size of the printed dots was slightly larger ($ 5 to $ 20) than the hole size of the perforated sheets, while the point size decreased significantly with decreasing hole size. '

Table IV shows the mean size of the four different Veco perforated sheets, with those given in Table III
Dimensions printed points, in this case the
Printing inks used the same compositions
such as the reagent inks identified in Table V as RI, A $, and RI.B4.

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TABLE IV Mean diameter of the points

Veco sheet hole diameter mm

1. Reagent 2 _a reagent ink RI. Afc ink RI. B4 0.30 0.314 0.317 0.17 0.187 0.180 0.13 0.147 0.30 0.08 0.083 0.078

25R

The printed dots A and B from the two reagent inks do not touch each other and the portion of the printed area which is covered by the points to the total printing area of the Print substrate varies between $ 1.1 and $ 50 and then yields a clearly visible color reaction to show the presence of blood in urine.

It should also be noted that the dimensions of the printing screens are preferably specially adapted to the reagent inks should to give maximum coverage of the printing area. For example, a Veco perforated sheet has from Type 125P has a hole size of 0.08 mm with an interaxial distance of 0.20 mm and thus results in much more densely packed printed arrangements as a Veco perforated sheet of type 25R with a hole size of 0.30 mm and an interaxial Distance of 1 mn.

The increased density of the printing dots when using screens of the type 6OP, 8OP and 125P (Tables III and I ¥) thus results a more homogeneous and more intense color change in the test reaction «

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This is how the results of printed pulses from Reapi inks lead as »described here, regularly leads to a visually detectable parbe test reaction, although the packing density and The film density of the printed dots of the reagent ink is safe Can be increased significantly when going through holes with lesser

Distance prints and using reagent inks with a significantly reduced solvent content in order to obtain a correspondingly increased viscosity *

The invention is illustrated in more detail by the following examples.

The composition of the different reagent inks as used in Examples 1 to 7 below is summarized in Table V, the abbreviations and trade names having the following meanings;

Reagent:

Cumene hydroperoxide = CHP

o ~: & luidine = (C ₆ H ₃ (CH ₅ ) ΪΓΗ ₂ ) ₂ = o-Iolidine

Binder:

Hydroxyethyl cellulose: "3IATROSOL" (250 LR, Hercules) Polyvinylpyrrolidone: "PVP" (K90, BASS ¹ ) Sodium carboxymethyl cellulose: UaCMC (7HE, Hercules) Methyläthy! -Cellulose: MEC: "EDIPAS A" (ICI) Hydroxypropyl cellulose: "KLTJCEL" (LP, Hercules) Dextran (Pharmacia, Uppsala, Sweden)

Fillers:
Silica powder

Surface active agents:

Sodium dodecyl sulfate: SDS
ethyloxylated alkylphenol: "RENEX 698"

Buffer:

Sodium hydrogen maleate buffer, pH 5.8: MALEATE **** ^ * M ί> / 07 1

399

TABLE V

Rea ^ institutions for the detection of occult blood

ink

Solvent reagent binder surface buffer

Example 1 ;\

RI. Al water 2: V / a s s he 3: 79 / 74.5 / RI. B1 Ethanol Ethanol $ 82 83 / example RI. A2 RI. B2 example

RI. A3

RI-B3

Water 76 /

Ethanol 83%

filler (20g) active participation Maleates tel (30 ml) GHP ITaGMG SDS (3.14g) (0.5g) (0.5g) PVP - (14g) o-toluidine pyp Renex 698 (0.4g) (0.5g)

CHP NaCMC (3.14g) (0.6g) PVP (18g)

o-toluidine PVP (0.6g) (27g)

GHP NaCMG (3.14g) (0.6g)

PVP (16g)

o-Tolidine PVP (0.6g) (27g)

SDS Maleate (0.5g) (30ml)

Renex (0.6g)

SDS Maleate (0.5g) (30ml)

Renex (0.6g)

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Examples 4 to 7:

Ink! Solvent RI-. A4

water

RI. B4

Ethanol

Reagent binder, surface buffer
Filler active agent

Maleate (35 ml)

CHP "NATROSOL" SDS (6.3g) (8g) (1g) "AEROSIL" o-toluidine (5g) GELATIN (0.5g) o-toluidine "KLUCEL" Renex 698 (0.8g) (10g) (1g)

example 1

Diagnostic test strips for the detection of urine or so-called test strips for occult blood were produced as follows:

a) Manufacture of the reagent inks

Two reagent inks RI.A1 and Ri.B1 (see Table 5) were used as a liquid carrier medium for the reagents cumene hydroperoxide (CHP) and o-toluidine, which in the presence of blood produce a Resulting color reaction, produced.

The inks were obtained by mixing the aqueous buffer with an aqueous solution containing the dissolved binder and the emulsifier (surfactant) together with the respective reagent. The resulting mixture was vigorously stirred to produce an ink in the form of a viscous, homogeneous, stable emulsion or colloidal suspension with the appropriate Composition as for RI.A1 and RI.B1 in Table 5 is given.

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The resulting reagent inks had a relatively high viscosity, which is particularly suitable for screen printing processes, with the help of which these inks should be applied to the test strips.

The inks listed in Table V above had viscosity for AI = 1,000 to 20,000 cP and BI = 1,000 to 20,000 c "P.

b) print media

A sheet of white, synthetic "paper" ("Polyart" 90 g / m) with a matte finish and a thickness of approximately 80 / in was used as a print carrier for the production of the test strips.

This type of paper consists of a modified polyethylene, which is cast into a thin film. It is commercially available for the graphic industry.

c) Printing with the reagent inks

The two reagent inks RI.A1 and RI.B1 were sequentially with the help of a special screen printing process on the surface of the above-mentioned white polyart paper as a print carrier imprinted.

Each reagent stinoe was in the form of tiny, discrete dots imprinted, which had a small distance from each other and formed a triangular printing pattern.

A perforated sheet of the Veco 25R type (see Table IV) was first used to create a first, triangular pattern of reagent ink in the form of points A with a diameter between 300 and 370 μm. and to print an interaxial distance of 1 mm using reagent ink RI «A1 (see Table V) in the manner described above under the heading" Printing Process ".

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The same perforated plate Veco 25R was used for screen printing, ■ as described above to create a second triangular arrangement of Reagent ink dots B, each in the center of one of four adjacent printed dots A formed rhombus. These points B had a diameter between 300 and 350 pi and the same interaxial Distance of 1 mm, like points A, and the holes of the perforated plate that was used for printing.

The proportion of the printed surface that was printed with points A and B was 17.7 % of the total surface of the print carrier in this case.

d) Cut into test strips

The printed polyart film was cut into test strips with a width of 4 mm.

When these test strips were immersed in urine containing hemoglobin in an amount of 0.0014 mg / 100 ml or more, a blue coloration could be clearly observed.

Example 2

Occult blood test strips were prepared essentially as described in Example 1 with the exception that the reagent inks RI.A2 and RI.B2 (see Table Y) were used to print through a Veco perforated sheet 3OR (see Table III).

The interaxial spacing of the holes in the perforated plate and thus the printed dots was 0.83 mm in this case, while the printed reagent dots had a diameter of 315 to 335 μm or up to 360 mm and the proportion of the printed area marked with points A and B was covered, was approximately 16.5% of the total printing surface.

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The change in color observed when the printed test strips were used to detect blood in urine was essentially the same as the test strips of Example 1.

Example 3

Test strips for the detection of occult blood were essentially prepared in the manner described in Example 1 with the exception that the reagent inks RI.A3 and RI.B3 (see Table Y) were used to pass through a Veco perforated screen 4OR (see Table III) to print.

The interaxial distance between the holes and thus the printed dots was 0.63 mm in this case, while the printed reagent dots A and B had a diameter of 235 to 255 / Ω or with points A and B was covered, made up about 15 ° of the total surface.

The color change to blue observed when these printed Test strips used for the "detection of blood in urine" were essentially the same as with the test strips according to examples 1 and 2,

Example 4

Test strips for the detection of blood were mainly used on the prepared in the manner described in Example 1 with the exception that the reagent inks RI.A4 and RI.B4 (see Table V) were used and a Yeco 6OP perforated sheet (see Table III) was used to approach a sheet of absorbent white paper to press.

The interaxial distance between the holes in the screen and therefore the printed one In this case, points of each pattern were Q.42 mm, while the reagent points A and B have diameters of about 0.18?

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and 0.80 mm, respectively, and the portion of the printed area covered by points A and B was approximately 34 "of the total printing area.

The printed dots from the RI.A4 and RI.B4 inks spread do not appear on the absorbent paper, but remain as small discrete dots on the surface of the paper. These The property of the bottom not to flow is due to its high viscosity and paste-like rheology, which nevertheless allows print them accurately using the above procedure.

A blue color change was observed when the printed test strips were used to detect hemoglobin in solution in the manner described in relation to the test strips according to Examples 1, 2 and 3, but with there was the additional advantage that a more homogeneous, deeper color was obtained with the test strips of this example.

Example 5

Test strips for the detection of occult blood were essentially in the manner described in Example 1 with the same reagent inks and a Veco perforated plate (6OP) as described in Example 4, with the exception that the second reagent ink RI.B4 printed twice in succession in enormous form of two patterns of discrete dots.

The RI.A4 ink was first applied to absorbent paper in the above-mentioned triangular dot arrangement is printed. When these printed dots dried, the RI.B4 printed with the same Veco perforated plate 6OP within the triangles of the dots formed by the ink RI.A4, while adjacent Triangles of points of RI.A4-Tin.te existed in which no point of RI-B4 ink was included. Hence, in one second print run the RI-B4 ~ Iiate imprinted in these empty triangles.

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The proportion of the total printed area which was printed with points A and B was then 50 % of the total surface.

A blue color change was observed when the printed Test strips were used to detect hemoglobin in solution in the manner described for the strips of Example 4, however, there was the additional advantage that a more homogeneous and deeper color was obtained than in the case of Examples 1 to 4.

Example 6

Test strips for the detection of occult blood were essentially produced in the manner described in Example 4 with the exception that the print carrier in this case is a thin special filter paper made of a glass fiber film with a weight of 10.70 g /

2
m was Schleicher und Schüll GmbH.

The printing surface was receptive to the inks and the Ink dots adhered well to it. The printed test strips obtained with the aid of this paper had a hydrophilic surface for the hemoglobin solutions and spoke with a color change to blue to hemoglobin concentrations of 0.0154 mg / ml or above.

Example 7

Test strips for the detection of blood were prepared essentially in the manner described in Example 5, with the exception that the print carrier used in this case was a microporous plastic film based on polyvinyl chloride (Amerace Corporation, Microporous Division).

The test strips made from this print substrate were used for test reactions with hemoglobin in solution and gave a very satisfactory color change as in the case of Example 5.

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The following Examples 8 and 9 also show the preparation of diagnostic test strips for the detection of glucose in urine.

The agents for reagent inks for the glucose test used in Examples 8 and 9 are given in Table VI, where the abbreviations and trade names that are not already explained in the previous examples have the following meaning to have.

Reagents

Glucose oxidase Peroxidase Potassium iodide Brilliant blue FCF

= GOD = POD = KI = ED and O blue no.

binder

Carboxymethyl cellulose polyvinylpyrrolidone = "PLASDONE" (K29-32), GAP Corp.

surfactants

Polyoxyethylene sorbitan monolaurate

CMC (7LP, Hercules) PVP

"Tween 20" (ICI Americas, Inc.)

buffer

0.8 m citrate

550 ml H ₂ O + 257.3 g sodium citrate dihydrate + 25 g anhydrous citric acid

809846/071 A

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TABLE VI Reagent Inks for G-luose Tests

ink Solution
middle
(Wt. -4) water
85% water
73% Reagent Bandage
middle surfaces
active
middle buffer Example 8: ^N jithanol
72% 77% RI. A8 Example 9: GOD (0.06 g)
POD (0.01 g) CMC
(6 g) "Tween 20"
(0.3 g) Citrate
(50 ml) RI.B8 RI. A9 o- toluidine
(0.8 g) "Klucel"
(10 g) "Renex 698"
(1 g) - RI. B9 GOD (0.3 g)
POD _(0; 04 g) CMC
C2 g) "Tween 20"
(0.06 g) Citrate
(10 ml) KI (0.08 g)
blue colour
(0.06 g) PVP (0.2g)
CMC (2.0g) "Tween 20"
(0.08 g) Citrate
(15 ml)

Example 8

Diagnostic test strips for the detection of glucose in urine were made as follows:

a) Manufacture of the reagent inks

Two reagent inks, RI.Δ8 and RI.B8 (see Table VI) were used as a liquid carrier medium for the reagents plucose oxidase (GOD) and peroxidase (POD) on the one hand and o-toluidine on the other produced which, in the presence of glucose, undergoes an oxidation color reaction result.

The first reagent ink from RI.A8 was obtained by mixing the aqueous citrate buffer (0.8 m) with the two reagents (GOD and POD in powder form) and with the surface-active agent "Tween 20 ^l!" And dissolving the binder

809846/0714

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in this. The resulting mixture was vigorously stirred, around the first reagent ink RI.A8 in the form of a viscous, homogeneous, stable solution with the one specified in Table VI Composition.

The second reagent ink, RI.A8, was the same as that second reagent ink RI.B4 in Table V, based on the above Examples 4 to 7

These reagent inks RI.A8 and RI. £ 8 both had one relatively high viscosity, which is particularly suitable for screen printing processes, to apply these inks to the test strips to raise.

b) print media

A white absorbent paper was used as the printing medium to make the glucose test strips.

c) Printing with the reagent inks

Glucose test strips were printed, essentially as indicated in Example 1, except that the reagent inks RI.A8 and RI.B8 in this example were used to pass through a perforated sheet Veco 1.253? (see Table III) to print.

The proportion of the printed surface, which was covered by the points A and B, was in this EaIIe more than 30 fo the total surface ·

d) Cut into test strips

The resulting printed paper sheets were finally cut into glucose test strips with a width of 4 mm.

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A strong color change to blue could be observed, when the test strips thus obtained are immersed in urine containing glucose in an amount of 0.1 g / ml or more became.

Example 9

Diagnostic test strips for the detection of glucose in urine were made prepared in essentially the same manner as described in Example 8 except that the reagent inks RI.A9 and RI.B9 were used which are those given in Table YI Composition possessed.

These reagent inks RI.A9 and RI.B9 were applied to by a perforated plate Veco 6OP (Table III) to be printed on absorbent paper, as in Example 8, and the resulting printed Finally, paper was cut into test strips with a width of 4 mm.

The printed glucose test strips thus obtained, which had not yet come into contact with the sample liquid, were blue due to the presence of a small amount of oxidizable blue dye (FD and C blue Ur. 1) besides the water soluble one Iodide (KJ) in the second reagent ink RI.B9

A change in color could be clearly observed when the test strips obtained in this way were in urine containing glucose in a Amount of 0.1 g / 100 ml or more.

The swelled color changes were related to the as follows Glucose concentration together;

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809846 / 07U

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Glucose in 1 minute

(g / 100 ml) developed color

0 blue

0.1 light green

0.5 brown-green

1 brown

The following examples show how to make diagnostic test strips for the detection of ketone bodies (acetone, acetoacetic acid, ß-hydroxybutyric acid) in body fluids, especially acetoacetic acid in urine.

The composition of the ketone test strips in example The inks used are given in Table VII, the abbreviations and trade names for the binders being the same, as indicated above in the previous examples.

"GAFAC RE-610" (Table YII) is a surfactant of GAP Corp.

"PVP / YA" is a polyvinylpyrrolidone / vinyl acetate copolymer (50 % in ethanol)

809846/0714

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TABLE 711 Reagent ink for Ketotmachweis

ink Solution
middle water
(36 ml) reagent Bandage
middle surfaces
active agent buffer "GAFAC RE-
610 "
(0.3 g) Example 10: "Dioctyl
sodium-
sulfoccinate RI.AlO Amino acetic acid
acid (9 g) CMC-76F
(3 g) . Na ^ PO.'12H ₇ O
(1Ö g) EtOH
(54 ml) Na ₂ HPO ₄ (4/3 g) RI.BIO Na- KLtroferri-
cyanide [I ^ 9g) PVP / VA
Copolymer
(23 ml) "KLUCEL JF
(10 g)

Example 10

Diagnostic test strips for the detection of ketone bodies in body fluids were prepared essentially in the manner described in Examples 8 and 9, with the exception that the reagent inks RI.A10 and RI.B10 used here, the aqueous phosphate compounds, the sodium nitroferricyanide and the ethanol-soluble ones Binder (PVP / VA, "KLUCEL JF") contained in the alcoholic phase, as indicated in Table YII.

These reagent inks RI.A10 and RI.B10 were used to to print a perforated plate Veco 6OP (see Table III) on absorbent paper, as in Examples 8 and 9, and the resulting Printed papers were eventually turned into test strips of the desired Width cut.

809846 / 07U

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A purple color change could clearly be observed, when containing the printed ketone test strips in liquids Acetoacetic acid.

The colors varied from very light purple in the presence of 10 to 20 mg / 100 ml to a very dark purple that is more as 100 mg acetoacetic acid per 100 ml.

As can be seen from the previous examples, it could be shown that the area printed by all points in the print patterns with different reagent inks for the production of printed test strips according to the invention should be 30 and preferably 45 ° of the total area including the different patterns in order to achieve the best color changes and thereby obtain the best color reactions with the help of the printed test strips.

Such a coverage of at least $ 30 of the surface of the Print carrier can easily be reached by selecting the perforated plates used for printing accordingly, namely Perforated sheets or screens with holes, the size and spacing of which is as narrow as possible, while providing a satisfactory, successive printing of different, more discreet tiny dots that lie between each other and one very have a small distance without touching each other, allow.

For example, the Veco perforated plates or screens of types 60P, 8OP and 125P with the dimensions given in Table III, as used in Examples 4 to 10, are particularly suitable for printing patterns of different dots, which are approximately 30 to 50 % cover the corresponding surface of the print substrate.

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It could also be shown by way of example that the total number of areas printed per unit area on the Substrate should be equal to or greater than 1300 dots per square centimeter for the best color changes and thereby to achieve the most favorable color reactions with the help of the printed test strips in all cases.

A total density of the discrete printed dots of more than 1300 points per square centimeter can also easily be achieved by appropriate selection of the perforated sheets or Screens used for printing, e.g. B. from Veco 7 of the types 6OP, 8OP and 125P, as in Examples 4 to 7 can be applied.

Further, in order to obtain satisfactory color tests in all cases, it has been found experimentally that by printing Test strips made according to the invention should have dots with a thickness of 5 to 60 µm. It has also been shown that for similar reasons the viscosity of the reagent inks used for printing the test strips according to the invention should preferably be in the range of 5,000 to 300,000 cp in order to enable satisfactory printing.

The reagent inks described above (Table Y) used in the previous examples have been used, have sufficient viscosity and give a sufficient point thickness and a Satisfactory surface coverage and total dot density in order to achieve the most favorable color reactions with the help of the printed To achieve streaks.

From the above it appears that the manufacture of printed diagnostic strips according to the invention is also applied can be used to obtain similar benefits in a variety of color reaction tests where more or less conventional Reagents and other ink ingredients are used, with

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the chemical compatibility with each other and with more or less common print carriers experimentally without beforehand Difficulty can be determined.

It is understandable that the composition of the reagent inks, the printing media and the printing devices, as they are used in each case, are adapted to one another must based on experience in the field of the corresponding diagnostic means and printing processes,

The invention is applicable to the currently known reagents, how they are used to manufacture diagnostic test equipment. "

Typical agents of this type are given, inter alia, in U.S. Patents 3,438,737, 3,095,277, 3,212,855, 3,164,534, 3,050,373,

2 981 606, 3 123 443, 3 252 762, 3 290 117, 3 092 463, 3 012 976,

3 122 420, 3 453 180, 3 585 001, 3 585 004 and 3 447 905. The test means according to the invention are particularly favorable of course, for diagnostic means where it is important or cheap, different reactants from one another keep separate.

6292

809846/0714

Claims (18)

Process for the production of diagnostic test strips for the detection of certain components in biological fluids, such as urine, the strips comprising a solid support carrying at least two reagents which after wetting with the liquid sample to be examined result in a certain color reaction, characterized in that one a) produces at least two "reagent inks", each containing a mixture of mutually compatible components at least one of the reagents for carrying out the desired detection reaction, a liquid solvent and a polymer based binder; b) provides a carrier in the form of a sheet or a film with a surface that is suitable for printing with the reagents, the film being substantially insoluble in water and insoluble to the reagent inks at least on the surface to which they are applied, is inert; c) successively applying the reagents to the surface of the support by successively dotting each reagent ink printed on to form at least two separate patterns of printing dots from the reagent inks, the dots of each pattern can be dried after printing and the dots are arranged so that they are close to dots of the same pattern as well as at points of the other pattern without touching each other and 809846/0714 - - & · "- 1A-50 · 899 d) the printed film is cut into test strips of the desired shape and size. 2. The method according to claim 1, characterized in that the dots are printed by that you can each reagent ink through a sieve or Itochblec'a with a regular arrangement of holes presses. 3 · Method according to claim 2, characterized in that the holes of the sieve or Perforated plate in parallel rows at a distance from each other, with the holes of alternating rows against each other are offset. 4. Process according to Claims 1 to 3, characterized in that the two reagent inks one after the other by first applying the first reagent ink through a perforated sheet onto the underlying surface the film presses, the pressure points of the first pattern thus created dries, the relative position of the perforated plate opposite the surface on which the first pattern is printed, changed so that the holes of the perforated plate over unprinted Areas of the surface come up and a second reagent ink presses through the perforated sheet in the same way as the first and again drying the dots of the resulting second pattern. 5. The method according to claim 4, characterized in that the relative position of the perforated plate is changed so that the holes are located over unprinted areas which are symmetrical between adjacent points of the first pattern. 6. The method according to claim 4 or 5, characterized in that the position of the perforated plate changes so that the holes come over unprinted areas that are essentially the same distance from opposite one another adjacent pressure points of the first pattern, whereby the pressure points of the second pattern in the center of a rhombus come to lie from neighboring points of the first pattern. 809846/0714 _ ₃ _ - 3 '- 1A-50 899 7 «A method according to claim 4 or 5, characterized _s that so changes the location of the iDchblecbs that the holes come to lie on imbedruckte areas which have the same distance of three neighboring points of the first pattern substantially, so that the Points of the second pattern are located in the middle of a triangle that is formed from three neighboring points of the first pattern. 8. The method according to claim 1 to 7, characterized in that such a perforated plate used that the area of the printed surface covered by the various points is at least 30 ^ of the total surface amounts to· 9 · Method according to Claims 1 to 8, characterized in that the total number of different Points per unit area is at least 1300 points per square centimeter, 10. The method according to claim 1 to S _3, characterized in that the thickness of the different printed dots is in the range of 5 to 60 µm. 11. The method according to claim 1 to 10, characterized in that the inks are so composed are that they have a viscosity of 5,000 to 300,000 cP. 12. The method according to claim 1 to 11, characterized in that the reagent inks contain a wetting agent contain. 13. The method according to claim 1 to 12, characterized in that the reagent inks have a buffer 'contain the one suitable for the desired color reaction adjusts the pH value. 80984S / 0714 - 4 - 11-50 899 14 «Method according to claim 1 to 15, characterized in that - indicates; that for strips for the detection of Blood in urine the first seagenstiate cumene hydroperoxide as a reagent, water as a solvent, hydroxyethyl cellulose as a binder and a buffer, while the second one contains o-toluidine as a reagent, ethanol as a solvent and Contains hydroxypropyl cellulose as a binding agent » 15. The method according to claim 14 »characterized g e Ic e η η draws ^ that the first Tint © is a maleate buffer slit a pH of about 5 16, '/ experienced according to claim 14 or 15 »thereby g e kennssictaaetj, that the first ink is latriumcarboxymethylcellulose contain 17 · Method according to claims 1 to 16, characterized in that that at least one of the reagent inks contains a surfactant " 18. The method according to claim 1 to 17, characterized; that the first Seagenstiate sodium dodecyl sulfate contains as a surface-active agent » 19. Process according to Claims 1 to 18, characterized in that the second reagent ink is ethoxylated Alky! Phenol contains as a surface-active agent. 809840/0714