MXPA06010141A - Test element analysis system with contact surfaces coated with hard material - Google Patents

Abstract

The invention relates to a test element analysis system for analytical investigation of a sample, in particular a body fluid, comprising at least one test element with one or more measuring zones, contact surfaces located on the test element, in particular, electrodes or conductors, whereby the sample under investigation is applied to the measuring zone to perform an analysis by determination of a parameter characteristic for the analysis and an analytical device with a testelement retainer for positioning the test element in a measuring position and a measuring device for measuring the characteristic change, whereby the test element retainer comprises contact elements with contact surfaces which permit an electrical contact between the contact surfaces of the test element and the contact surfaces of the test element retainer, characterised in that one of said contact surfaces is provided with an electrically-conducting hard material surface. The invention relates particularly to the coating of a contract surface of the contact connection on a test element analysis device with an electrically-conducting hard material.

Description

TEST ELEMENT ANALYSIS SYSTEM WITH CONTACT SURFACES COATED WITH HARD MATERIAL FIELD OF THE INVENTION The invention relates to an analytical system of test element for the analytical examination of a sample and in particular a body fluid of humans or animals. The system comprises at least two components, that is to say a test element which has a measurement zone in which the sample to be examined is moved to perform an analysis to measure a measurable variable that is characteristic for the analysis and a device for testing. evaluation with a test element holder to place the test element in a measurement position to perform the measurement and a measuring device to measure the characteristic measurable variable. BACKGROUND OF THE INVENTION Test element analytical systems are commonly used especially in medical diagnostics to analyze bodily fluids such as blood or urine. The sample to be examined is first applied to a test element. At this point, the process steps that are required to detect the analyte, which are usually chemical, biochemical, biological or immunological detection reactions or physical interactions, take place which Ref.175005 results in a characteristic and measurable change of the test element especially in the area of the measuring area. To determine this characteristic change the test element is inserted into an evaluation device which determines the characteristic change of the test element and provides it in the form of a measured value for additional display or processing. The test elements are often designed as test strips which essentially consist of an elongated support layer, usually made of a plastic material, and a measuring zone with a detection layer containing detection reagents and, if necessary , other auxiliary layers such as filtration layers. The test elements of the present invention additionally contain contact areas which can be used to make electrical contact between the test element and the evaluation device. In the case of electrochemical test methods, the conductive paths and electrodes are mounted on the test element. Even the test elements which do not use electrochemical analysis methods can have electrically conductive contact areas, for example to transfer calibration data or batch information which are stored in the test element for the evaluation instrument. The accompanying evaluation devices have test element holders with special contact elements which make an electrically conductive contact between the test element and the electronic measurement and evaluation parts of the evaluation instrument. These contact elements are usually in the form of electrical plug connections with metal spring elements which are often provided with a surface of noble metal usually gold or platinum. The test strips are inserted into the test element holder for the measurement during which the contact portions of the contact elements move through the electrodes of the test elements. In a final position, the contact area of the contact elements of the evaluation instrument is then in contact with the contact area of the test element. An electrically conductive connection is made between the test element and the evaluation instrument by a pressing force which is in particular defined by the shape and force of the spring of the contact element. This should ensure in particular that the transition resistance between the contact area of the contact element of the evaluation instrument and the contact area of the test element is so low andt. constant as possible to enable an accurate and reproducible signal transfer. A constant and reproducible transition resistance is especially important to still obtain accurate measurement results even after a test element has previously been obstructed many times and therefore obtain a high and reproducible measurement especially accurate with respect to the fact that such analytical systems Test elements are often used for many years or many tens of thousands of obstruction operations. This is of major importance especially in the clinical field where such test systems frequently have to handle high performance. A major advantage of plug-in contact devices is the ability to easily join and separate the electrical connection so that the test element and evaluation device can be stored and used independently of one another. Since the contact areas, on the one hand, they must ensure that the transfer of electrical current is as optimal as possible which requires a certain contact pressure, on the other hand, the connection of the contact connection and in particular the union and repeated separation of the connection of contact puts a great deformation on the connection, the contact areas are often provided with a layer of noble metal for example plated or galvanized with gold, silver, platinum or palladium. The frequent high mechanical deformation on the contact areas especially due to abrasion, deposition or scratching of the contact areas, therefore is also a problem because a certain contact pressure has to be ensured for a reliable electrical contact and a certain path of insertion of the test element is necessary for mechanical reasons and in particular to ensure guidance when obstructed and mechanical stability in the clogged state. It is very important that the contact areas are as resistant as possible to external influences to make a very safe contact between the contact areas of an electrical contact connection and consider that they have the lowest possible contact resistance. In this connection the external influences can be of a chemical, physical or mechanical type. Consequently, especially during the clogging process, the two contact areas are rubbed against one another resulting in a very high mechanical deformation. The effects of corrosion and especially slit corrosion also have an adverse effect on contact safety and contact resistance. Another problem with such test element analytical instruments is that the support material of the frequently used test elements consists of a relatively soft elastic plastic sheet in which the contact areas and electrodes are mounted so that this structure in a relatively soft base material can have disadvantages for an exact contact. A major disadvantage of noble metal-noble metal pairs for contact areas of such plug connections is that, even without considering their geometry and / or the pressing force, the metal surfaces are very frequently damaged when the contact areas are they unite and therefore electrical contact problems occur. Such contact problems often manifest themselves because the transition resistances between the plug and contact element become very high or in an extreme case can not be longer than any electrical contact between the components of the contact connection . When the damage image that frequently results is observed under the microscope, especially in the case of flat contacts such as conductive paths or electrodes, it is characterized by a major change in the thickness of the metal layer of these contact areas after the insertion. Accordingly, the metal layer of the electrodes is strongly deformed in some areas by the second contact area moving therethrough, in particular in the form of grooves, projections and scratches. This damage configuration occurs especially when the electrodes are mounted on relatively soft base materials. These deformations can become too large that the metal layer completely breaks down in some areas because of the second contact area that moves through it. In this case, the electrical contact between the test element and the evaluation instrument is no longer possible. Such deformations of the metal layers which serve as contact areas manifest themselves as considerably increased and undefined transition resistances or in the complete lack of an electrical contact. Such contact elements are therefore unsuitable for use in analytical systems which are proposed to ensure a reproducible determination of analyte over a period of long use. Therefore to overcome these disadvantages the following solutions have been given in the prior art: To ensure a very secure contact of plug connections especially under high mechanical and / or chemical stress, DE 102 22 271 A1 describes a method for increasing the mechanical and / or chemical resistance of an electrical contact connection between two contact pieces by coating at least one of the contact parts with the aid of a thermal spray process in the area of the contact areas. The purpose of this application is to minimize wear on the contact area by this coating. It mentions plug connection of electronic components such as conductive cards and printed circuit boards, or sliding contacts for example in motors as fields of application for such contact connections. Such contact connections are especially characterized in that after the contact areas involved have been contacted once, the contact connection is subjected to a continuously high mechanical deformation eg by vibrations or continuous grinding together of the contact areas resulting in a lot of wear and tear of the contact areas involved in this area. The object of this application is in particular to minimize the wear on the contact areas by themselves "" before ensuring reliable electrical contact of the contact areas even after the multiple connection and separation of the contact connection. Unalterable metal alloys such as bronze are mentioned as coating materials which are applied to one or both contact areas to reduce wear in these contact areas by themselves. The coating itself is carried out using thermal spraying processes. Such processes which use high temperatures are unsuitable for the test elements whose test supports are very often composed of thin plastic sheets since such plastic sheets do not have the necessary heat resistance. The layer thickness of the coating layer has to be relatively large at 10 μm to 200 μm to enable a durable connection even under high deformation and to enable even unavoidable wear. Such phenomena of increased wear occur in particular when both contact areas are provided with such an unalterable coating. European Patent Application EP 0 082 070 also describes a process for protecting electrical contact connections especially in switches and relays. The purpose of this application is to protect metals and especially metal contacts from coating wear. Similar to DE 102 22 271 The lining should make contact areas more resistant to wear. For this purpose a layer of titanium nitride is applied to the existing metal contacts which is characterized by the following characteristics: an adhesion of more than 180 kg / cm2, high chemical resistance, high resistance to abrasion and a specific resistance of almost 500 μO * cm. In this case, too, the cladding is used to minimize the wear of the contact areas themselves rather than to ensure reliable electrical contact of the contact areas even after multiple connection and separation of the contact connection. US 6,029,344 discloses spring contact elements especially for electrically contactable electronic components which are coated with a hard material. The purpose is to modify the mechanical properties of the contact connection by coating the hard material. This is especially proposed to improve the elastic properties of the contact element. In this case, the coating is not used primarily to reduce the wear of the contact areas or to make a more secure contact, but rather to modify the elastic properties of the spring contacts. For this purpose the spring contacts made of relatively soft base materials such as gold are coated with a material which has a deformation limit greater than the base material at least in the areas that are formed in such a way as to allow a spring action of the contact element. Examples of such materials that are mentioned are in particular metals such as nickel, copper, cobalt, iron, gold, silver, elements of the platinum group and other noble metals, semi-noble metals, tungsten, molybdenum, tin, lead, bismuth. and Indian and alloys thereof. These materials are referred to as hard materials in the sense of US 6,029,344 and are defined as materials which have a deformation limit greater than 80,000 psi. Hard materials are defined completely differently in the sense of the present application. Such hard materials according to US 6,029,344 are not adequate to ensure the requirements with respect to a very high abrasion resistance and high contact reliability even for multiple inserts but more serve to improve the elastic properties of the spring contact. The layer thicknesses of the hard material coating have to be between about 6 and 12 μm and have to be at least one fifth to five times the layer thickness of the base material of the spring contacts according to US 6,029,344 to improve the mechanical properties and in particular elastic properties of the contact element. The documents described above describe processes for coating surfaces of electrical contact elements which either serve to reduce abrasion and wear of the contact areas themselves or improve the elastic properties of the contact element. A fundamental problem which can not be satisfactorily solved by the devices and processes mentioned above is to ensure a reliable and defined electrical connection between the contact areas of a contact element for a long period of time especially under high mechanical deformation and even after numerous contact operations. SUMMARY OF THE INVENTION An object of the present invention is to eliminate or at least reduce the disadvantages of the prior art. In particular, the intention is to provide a test element analytical system that is simple to use and ensures an analyte determination that is as error-free as possible even after a test element has been inserted many times into the test instrument. evaluation. In particular, the purpose is to provide a contact connection for a test element analytical system which ensures a defined and reproducible transition resistance between the test element and the evaluation instrument and therefore an exact and reproducible signal transfer and the analyte determination during the total life time of such system for many thousands of inserts. This is achieved by the subject of the invention as characterized in the claims and patent description. Solution of the invention The invention relates to a test element analytical system for the analytical examination of a sample, in particular a body fluid, at least comprising a test element with one or more measuring zones and contact areas located in the test element in particular conductive paths or electrodes, the sample to be examined is placed in the measurement zone to perform an analysis to determine a measurable variable that is characteristic for the analysis, and an evaluation instrument with a test element holder to place the test element in a position of measurement and a measuring device for measuring the characteristic change where the test element holder contains contact elements with contact areas which make possible an electrical contact between the contact areas of the test element and the contact areas of the support of test element, characterized in that one of these contact areas is provided with a surface of electrically conductive hard material. The solution of the invention in particular comprises coating a contact area of the contact connection of a test element analytical instrument with a hard electrically conductive material.The surface of the hard material of an element involved in the contact connection may be such that the complete element or part of this element consists of a hard material, since the elements of pure hard material often have mechanical and chemical properties such disadvantages as brittleness, poor elastic properties or even a relatively high electrical resistance especially when the The hard material has a large thickness, the surface of hard material is formed in a preferred embodiment by coating a base material with a hard electrically conductive material, Therefore, in the present invention, layers of mainly thin hard material are described as contact areas. The properties and fields of application described In the present invention, for these layers of hard material, however, they can also be applied to surfaces of elements which are completely composed or large parts of a hard material. Surprisingly it was found that a defined and reproducible electrical contact between the test element and the evaluation instrument is especially ensured even after many insertions by covering a contact area with an electrically conductive hard material. Surprisingly, the coating of a contact area with an electrically conductive hard material exhibits considerably improved contact properties compared to the previously widely used contact connections which "often have contact areas made of a noble metal on both sides or on which Both contact areas are often coated with materials which are intended to reduce wear on the contact areas, the former often being used for test items which are proposed to be used only once and the latter are used primarily for connections contact areas which are designed for continuous contact operations and / or are subjected to high mechanical stress.In contrast to metal contact areas, the contact areas which are provided with a surface of hard material have the following special advantages : They have ceramic properties sim ilar to a very high hardness, are very resistant to chemical effects, have very good sliding properties on surfaces and only have extremely low rates of abrasion loss, wear and deposition. Its high degree of wettability by metal castings ensures that the layer of hard material and fundamental metal layer adhere very strongly and therefore are also suitable for applications in composite systems. Furthermore, the hard metal materials have very good electrical properties such as high electrical conductivity so that they are very suitable as a surface material for electrical contact connections especially in analytical test element systems. Hard materials in the sense of the present invention are understood as materials which, due to their specific binding properties, they are very hard and in particular they have a Vickers hardness of >1000 kp / mm2. The melting point of hard materials is usually above 2000 ° C, its chemical and mechanical stability is good and comparable with that of ceramic materials. The term hard materials in the sense of the present invention especially includes metallic hard materials. These are characterized by metallic properties such as electrical conductivity and brightness. Hard metal materials include in particular carbides, borides, nitrides and silisides, high melting metals such as chromium, zirconium, titanium, tantalum, tungsten or molybdenum including mixed crystals and complex compounds thereof. In particular they also include modifications of the hard materials mentioned above which contain additional additions of other metallic or non-metallic substances to further optimize their physical and chemical properties which are often in low concentrations. Such more complex hard material compounds in particular may be aluminum nitrides, carbonitrides or carbide carbons of the metals mentioned above. This definition of hard materials corresponds largely to the definition of "Ropp Lexikon Chemie" (Thieme Publisher Stuttrgart, 10th Edition 1996). The hard material used for coating within the scope of the present invention should have electrically conductive properties to ensure a low transition resistance between the contact areas of the test element holder of the evaluation instrument and the test element which enables a reproducible and exact signal transfer. In particular, the transition resistance between the contact areas of the test element and the contact areas of the test element holder shall be less than 50 Ohm. Surprisingly it was found that such metal hard materials can be used especially as advantageous surface materials according to the invention since they have additional advantageous properties for use in contact elements of test element analyzers such as high mechanical hardness, high chemical stability , very good sliding properties and a good degree of wear. Particularly preferred hard material surface materials of contact areas within the scope of the present invention are metal nitrides and in particular titanium nitride, titanium aluminum nitride, chromium nitride or zirconium nitride. According to the invention, one of the contact areas of the test element or the contact element of the test element holder of the evaluation instrument is provided with a surface of electrically conductive hard material. The contact areas are understood within the scope of the present invention as electrically conductive structures of the test element or the contact element which are directly contacted to make an electrical contact between the test element and the evaluation instrument. In the case of the test carrier preferably are electrodes and conductive paths mounted on this and especially areas of these electrodes or conductive paths which have a specially formed structure, for example flat, to make electrical contact. The contact areas of the contact element can also be formed, for example, as flat elements in order to generate the largest possible contact areas and consequently a very safe contact and low transition resistance. These contact areas can also have curved shapes so that the test element can be inserted as simply and smoothly as possible for example in the case of pin and spring contacts. In a preferred embodiment of a test element analytical system according to the invention, the contact areas of the contact elements of the test element holder are provided with a surface of electrically conductive hard material. The contact elements which are components of the test element support of the evaluation instrument may have a very wide variety of designs. For example, they can be designed as sliding contacts, roller contacts, pin contacts, spring contacts, clamp contacts or zero force contacts. The design of the invention of the contact areas can be particularly advantageous for contact reliability especially for contact element types such as pin contacts, spring contacts and clamp contacts in which the contact areas of the two elements involved in the contact connection they move past one another while in direct contact until their final position is reached. Particularly preferred embodiments of the contact elements are pin contacts, spring contacts and clip contacts. A wide variety of possible embodiments of such contact elements is described in US 6,029,344.

If the surface of hard material is formed as a coating, the base material of the contact elements under the coating of hard material can in principle be any electrically conductive material. Metals and metal alloys which are particularly suitable for this are those which, in addition to a high electrical conductivity, additionally have a high chemical and mechanical stability. The base materials of the plug connections that are typically used are copper alloys such as CuZn or CuSn alloys or low alloy copper materials such as CuAg, CuCrSiTi or CuMg. In the case of spring contact elements, the base materials must also have elastic properties. A coating of hard material can in principle be applied to the base material using a variety of coating processes known to a person skilled in the art. Such processes are, for example, processes in which substances are deposited on the surfaces of liquid solutions, galvanization or electrochemical metallization processes, non-electrochemical metallization processes, chemical deposition processes such as chemical vapor deposition (DQV), processes of physical deposition such as physical vapor deposition (DFV) especially by evaporation processes, electronic deposition processes or laser ablation processes or processes which are based on the decomposition of solid, liquid or gaseous substances. The DFV electronic deposition processes can be particularly preferably used for coating hard material. When a layer of hard material is applied to the base material of the contact element, it may be advantageous to first apply one or more intermediate layers, in particular protective or germ layers, to the base material and then apply the layer of hard material to these layers. The application of such intermediate layers in particular can result in good adhesion and a durable bond between the different materials. Accordingly, for example, the galvanic methods can first be used to apply layers to the base material that generate a particularly suitable surface for the subsequent hard material coating. In addition it is also possible to apply protective layers which can protect the fundamental base material from chemical and / or physical damage such as corrosion when the surface of hard material is damaged. In addition, the electrical properties of the contact element such as the transition resistance can be influenced by a suitable selection of materials for such intermediate layers. Such intermediate layers, for example, can be produced by applying particles made of a suitable material. Alternatively, to obtain a good and durable bond between the base material and hard material layer it is also possible to provide an additional intermediate layer where the surface of the base material of the contact element is treated before the coating in such a way that it has improved coating properties . The thickness and composition of the hard material layer can be influenced by a suitable choice of the coating process and its process parameters such as temperature, evaporation rate, composition of the electronic deposition target or duration of the coating process. Surprisingly it was found that particularly very thin layers of hard metallic materials have very good mechanical properties especially high hardness and good sliding properties but, on the other hand, they also have good electrical properties and in particular a low electrical resistance. previously used for coating surfaces are usually applied to the base material with much larger layer thicknesses Accordingly, DE 102 22 271 A1 describes layer thicknesses of the coating layer from 10 μm to 200 μm, US 6,029,344 describes layer thicknesses of the coating layer between about 6 μm and 125 μm. In contrast, it has been found that very thin layers of hard metal nitride material are particularly preferred within the scope of the present invention. In this connection, layers of titanium nitride, titanium nitride and aluminum, chromium nitride or zirconium nitride are particularly preferred, layers of titanium nitride and aluminum or chromium nitride are very especially preferred. These layers preferably have a layer thickness of less than 2 μm, preferably less than 1 μm, particularly preferably less than 500 nm. Surprisingly it was found that the advantageous effects of a hard electrically conductive material surface as a component of an electrical contact connection can be further improved especially with respect to very reliable and reproducible contact even after many contact processes, when the properties of the second contact area are adapted to the properties of the hard material surface of the first contact area. It was found that there is a large increase in the transition strength between the test element and the evaluation instrument especially after several insertions in the case of contact connections in which both contact areas have noble metal surfaces, which it is, for example, caused by deposits of material in the contact areas, or it may not be possible to make an electrical contact any longer. Such noble metal-noble metal contact connections are widely used in previous test element analytical systems. The use of the contact connections with noble metal-noble metal contact areas in test element analyzers is therefore only of limited adaptability especially with respect to the high reproducibility and accuracy of the analyte determination. The use of a hard material surface as a contact area in an electrical contact connection can avoid the disadvantages of such contact connections with noble metal-noble metal contact areas. With respect to a high and reproducible contact reliability, especially after many contact processes, it has surprisingly been found that the contact reliability can be further improved when only one contact area is provided with a hard material surface and the second Contact area is composed of another material. In particular it was found to be particularly advantageous when the contact area opposite the contact area provided with a hard material surface consists of a material which has a lower hardness than the material of the hard material surface of the other contact area. . The metals are preferably suitable for this and especially noble metals such as gold, palladium or platinum. Such materials are already widely used for contact areas especially for electrodes and conductive paths in test elements. Consequently, in many cases it is sufficient to provide the. evaluation instrument with contact elements having surfaces of hard material according to the invention, in which such conventional test elements can then be inserted. The combination of a contact area with a surface of hard material and a contact area made of a material which has a lower hardness than the material of the surface of hard material makes possible a high reproducibility of the transmission resistance between the element of the test and the evaluation instrument that is achieved. Surprisingly, in tests of strength in which in each case a new test element with contact elements made of gold was inserted several hundred or even thousands of times in a contact element according to the invention with contact areas coated with nitride of chrome or coated with titanium and aluminum nitride, it was observed that the transition resistances remained stable and were below 50 Ohm even after many insertions. The microscopic observation of the surface of the test element showed that, in contrast to the contact connections with noble metal-noble metal contact areas, although the contact area of the test element was deformed, large deposits of material or changes of layer thicknesses were not observed. In particular, a continuous metal layer was preserved in the electrodes and conductive paths. The smallest possible damage of the contact area is of decisive importance for an exact and reproducible analyte determination especially with very thin layer thicknesses of such electrodes, conductive paths or contact areas. Such test elements are, for example, electrochemical test strips which have very thin metal layers, for example noble metal contacts with layer thicknesses in the range of nanometers to micrometers in an electrically insulating plastic sheet. Such metal layers, for example, can be produced in such supports by lithographic methods (layer thicknesses typically 10-100 μm) or laser ablation (layer thicknesses typically 10-10 nm). In the case of such very thin electrically conductive metallic layers on elastic and insulating surfaces, a slight erosion of this layer can considerably increase the transition resistance or in an extreme case completely interrupt the electrical contact. The hard material surfaces of the invention of the opposite contact areas result in much less damage to such metal layers thereby enabling an accurate and reproducible analyte determination in the test element analyzers. There are still technical problems associated with the coating of contact areas of conventional test elements with hard materials since, for example, the application of a relatively fragile hard material layer to an elastic and flexible plastic sheet of a test element it has an adverse effect on the mechanical properties of the test element with respect to simple and error-free handling or the process conditions of the coating process are inadequate for conventional test elements. Therefore in a particularly preferred embodiment the contact areas of the test element are made of a soft material and the contact areas of the contact element of the evaluation instrument are provided with a hard material surface since the mechanical requirements are much more suitable for a coating of hard material in the case of such rigid plug connections. In addition to the preferred embodiment of a combination of a contact area coated with hard material of the evaluation instrument and a contact area of the test element consisting of a material of a lower hardness and especially of a noble metal, all other combinations a surface of hard material and a second contact area comprising a material of lower hardness are possible. In particular, the contact area of the test element may have a surface of hard material and the contact area of the contact element of the evaluation instrument may have a surface made of a material of lower hardness. Such combinations have the same advantages as the invention. Analytical test element systems are preferably used in analytical and medical laboratories. However, the invention is also directed towards fields of application in which the analysis is performed by the patients themselves to continuously monitor their health status (home monitoring). This is of particular medical importance for example to monitor diabetics who have to determine the concentration of glucose in their blood several times a day or patients who take anticoagulant drugs and therefore have to determine their coagulation status at regular intervals. For such purposes the assessment instruments should be as light and small as possible, and be operated with batteries and robust. Such test element analytical systems are described for example in DE 43 05 058. The test elements are often in the form of test strips which essentially consist of an elongated support layer usually consisting of a plastic material and a measurement zone with a detection layer containing the detection reagents and possibly other auxiliary layers such as filtration layers. In addition, the test elements may contain other structural elements, for example dosing and transport devices for the sample such as channels or fleeces, positioning devices such as cut-outs to ensure accurate positioning of the test element and therefore an accurate measurement in the evaluation instrument or coding elements for example in the form of a bar code or an electronic component which are used to transfer specific parameters of the test element such as calibration data or batch information to the evaluation instrument. The test elements usually contain reagents in the measurement zone whose reaction with the sample and in particular with the analytes contained in the sample results in a characteristic and measurable change of the test element which can be determined by the evaluation instrument which It is part of the system. The measuring zone can optionally contain other auxiliary substances. The measuring zone may also contain only parts of the reagents or auxiliary substances. In other cases it is possible that the detection reactions to determine the analyte do not occur directly in the measurement zone but rather the reagent mixture is only transferred to the measurement zone for measurement after the detection reactions are completed. An expert familiar with the technology of analytical test elements or diagnostic test carriers is very familiar with the appropriate reagents and auxiliary agents to perform the specific analyte detection reactions. In the case of analytes that are detected analytically, the measurement zone for example may contain enzymes, enzyme substrates, indicators, buffer salts, inert fillers and the like. In addition to the detection reactions which result in color changes, a person skilled in the art also knows other detection principles which can be performed with the described test element such as electrochemical sensors or chemical, biochemical, biological detection methods molecular, immunological, physical, fluorimetric or spectroscopic. The subject of the present invention can be used in all of these detection methods. This applies particularly to electrochemical analytical methods in which, v as a result of a specific analyte detection reaction, a change in the measurement zone occurs that can be measured electrochemically usually as a current or voltage flow. In addition to such analytical systems that use reagents, the subject matter of the present invention can also be used in reagent-free analytical systems in which, after the test element has been brought into contact with the sample, a property characteristic of the sample (for example its ionic composition by means of ion-selective electrodes) is measured directly without additional reagents. The invention can also be used fundamentally for such analytical systems. The test elements of the present invention additionally contain contact areas which are electrically conductive and by means of which an electrical contact can be made between the test element and the evaluation instrument. In the case of electrochemical analytical methods, the conductive paths and electrodes are mounted on the element These tests can be used to determine the electrochemical changes in the sample and also to apply voltages and / or external currents to the sample to be examined. Electrochemical analyzes in the test element occur in particular in the measuring zone between specially designed electrodes, while the electrical measurement signals that are emitted by them or the actuating signals directed towards them are measured or applied via the conductive paths . These conductive paths contain specially designed flat areas which form contact areas that can be used to make electrical contact between the test element and the evaluation instrument. The conductive paths and contact areas usually consist of noble metals. Test elements which do not use electrochemical analytical methods can also have electrically conductive contact areas. For example it may be advantageous to mount electronic components in a test element which are used to store specific parameters of the test element such as calibration data or batch data and transfer them to the evaluation instrument. For this purpose, these specific data are stored in the test element in circuits or electronic components. When the test element is entered into the evaluation instrument, these data can be read and processed by special electronic reading parts of the evaluation instrument. However, for this it is necessary that the test element makes electrical contact which is because again the aforementioned electrically conductive contact areas of the test element are indispensable. The evaluation instrument contains a test element holder to position a test element in a measurement position to perform the measurement. This test element holder additionally contains the previously described contact elements with special contact areas. To determine the analyte, the test element is placed in an evaluation instrument which determines the characteristic change of the test element that is used by the analyte and provides it in the form of a measured value to be further displayed or processed. The analyte can be determined with a variety of detection methods known to a person skilled in the field of instrument analytics. In particular, electrochemical and optical detection methods can be used. Optical methods, for example, include the determination of characteristic changes in the measurement zone by measuring absorption, transmission, circular dichroism, scattering by optical rotation, refractometry or fluorescence. The electrochemical methods, in particular, can be based on the determination of the characteristic changes in load, potential or current in the measurement zone. The analytes that can be determined by the method according to the invention or by the corresponding devices are, within the meaning of the present application, all the particles that are of interest in analytical in particular in clinical diagnostics. In particular, the term "analyte" includes atoms, ions, molecules and macromolecules, in particular biological macromolecules such as nucleic acids, peptides and proteins, lipids, metabolites, cells and cell fragments. In the sense of the present application, the sample used for the analytical examination is understood as an unchanged medium containing the analyte as well as an already changed medium containing the analyte or substances derived therefrom. The change of the original medium, in particular, can be performed to lyse the sample, process the analyte or perform the detection reactions. The preferred samples are liquids. Liquids can be pure liquids and homogeneous or heterogeneous mixtures such as dispersions, emulsions or suspensions. In particular, the liquids may contain atoms, ions, molecules and macromolecules, in particular biological macromolecules such as nucleic acids, peptides and proteins, lipids, metabolites or also biological cells or cell fragments. Preferred liquids to be examined with body fluids such as blood, plasma, serum, urine, cerebrospinal fluid, tear fluid, cell suspensions, cell supernatants, cell extracts, tissue lysates or the like. The liquids, however, can also be calibration solutions, reference solutions, reagent solutions or solutions containing standardized analyte concentrations, so-called standards. In the present application, an analytical examination or determination of analytes is understood as a qualitative as well as quantitative detection of the analyte. In particular it is understood as a determination of the concentration or amount of the respective analyte where the sole determination of the absence or presence of the analyte is also considered as an analytical examination.

BRIEF DESCRIPTION OF THE FIGURES The invention is further clarified below on the basis of the figures and mode examples. The features and properties described can be used individually or in combination to create preferred embodiments of the invention. Figure 1 shows a partial sectional view of a test element analytical system according to the invention, Figure 2 shows an exemplary view of a test element for electrochemical analytical methods, Figure 3 shows a detailed view of a contact element according to the invention Figure 4 shows a detailed view of a cross section of a contact element coated with a hard material in the region of the contact area Figures 5a-5c show the frequency distributions of resistors of transition experimentally determined between contact elements with contact areas coated with non-hard material of electropolished palladium (figure 5a), between contact elements with contact areas coated with chromium nitride (figure 5b), or contact elements with contact areas coated with titanium and aluminum nitride (figure 5c) and in each case new test elements with contact areas consisting of 50 nm gold.

The numbers in the figures denote: 1 analytical system 2 evaluation instrument 3 test element 4 electrodes 5 test element support 6 spring element 7 measurement zone 8 sample liquid drop 9 sample application area 10 transport zone 11 contact area of the test element 12 contact area of the contact element 13 conductive path 14 contact element 15 electronic measurement and evaluation parts 16 printed circuit board 17 special IC 18 base material 19 intermediate layer 20 hard material layer 21 Reactive layer DETAILED DESCRIPTION OF THE INVENTION The test element analytical system 1 shown in Figure 1 consists of an evaluation instrument 2 and a test element 3. The evaluation instrument 2 has a test element support 5 which places a test element 3 in the measurement position shown in figure 1. Test element 3 is f It is placed in the measuring position by suitable means, for example by a spring element 6. In order to carry out a measurement, the sample liquid is placed in the measurement zone 7 of the test element 3. In the embodiment shown this occurs - applying a drop of liquid 8 to the sample application zone 9 provided at the end of the test element 3 and transporting it, from this position through a transportation zone 10, for example a capillary opening, to the measuring zone 7. A reactive layer 21 is located in the measuring zone 7 which is dissolved by the sample liquid and reacts with its components. The reaction results in a detectable change in the measuring zone 7. In the case of an electrochemical test element the measured electrical quantity is determined by means of the electrodes shown in FIG. 2 which are provided in the measuring zone. In the measuring position an electrical contact is made between the test element 3 and the contact element 14 of the test element holder 5. The contact element 14 is connected to the electronic measuring and evaluation parts 15 which are highly integrated to achieve a very compact construction and high degree of reliability. In the case shown, they are essentially composed of a printed circuit board 16 and a special IC 17. To this extent the analytical system has a conventional construction and does not need further explanation. Figure 2 shows a partial view of an exemplary test element 3 for electrochemical analytical methods. A specific analyte change is detected as part of the analyte determination within the measurement zone 7. In the case shown of an electrochemical test element a measured electrical quantity is measured by means of the electrodes 4 provided in the measurement zone. The electrical signal is passed over the contact areas 11 via the conductor paths 13. These contact areas make direct contact with the contact areas of the contact element 12 when the test element 3 is plugged into the test element holder 5 and therefore make an electrical contact between the test element and the evaluation instrument. The test element shown here is only an exemplary and diminished modality of a test strip. The test elements with other arrangements of electrodes and conductive trajectories and with various electrodes, for example reference electrodes, and additional structures such as transportation zones and sample application or special reaction areas can also be used within the scope of the present invention. Figure 3 shows a detailed view of a contact element according to the invention. The test element 3 is inserted into the test element holder 5 by insertion. The electrical contact is made between the contact areas of the contact element 12 and the contact area of the test element 11. In this case the contact element 14 is specially designed so that it has elastic properties and therefore exerts a defined contact pressure on the test element. 3. This was exhibited by a particularly preferred embodiment in which the contact element 14 secures the electrical contact as well as the positioning and fixing of the test element. In contrast, the functions of the electrical contact and positioning / fixing are divided between two different components in Figure 1, mainly the spring element 6 and the contact element 14. Figure 4 shows a detailed view of a cross section of a contact element coated with a hard material in the region of the contact area. The coating of hard material 20 is, in this case, applied to the base material 18 of the contact element and an intermediate layer 19 is present in this case between the two layers which, in particular, can be designed as a tie layer or protective The coating of hard material 20 functionally corresponds to the contact area of the contact element 12. Examples: For use in test element analytical systems it is important that the contact connections between the test elements and analytical instrument still guarantee casualties and defined transition resistances even after numerous inserts to ensure an accurate and reproducible analyte determination by the test element analyzer. Example 1: Contact elements with contact areas coated with chromium nitride a) Microscopic examination of the surface To demonstrate the advantageous effect of hard material surfaces according to the invention as contact areas in an electrical contact connection of a test element analytical system, the contact areas of such pin connections were coated with chromium nitride. A layer of chromium nitride of 480 nm thickness was applied to the contact areas of the plug connection using a DFV process. In each case new test elements were plugged in 480 times in the plug connections coated in this manner. These test elements had layers of gold having a thickness of 50 nm as contact areas which were applied to a plastic sheet. After 480 insertions the damage image to the contact areas of the plug connection as well as the individual contact areas of the test elements were evaluated microscopically. As a comparison, 480"test elements were inserted into plug connections coated with conventional non-hard material with contact areas made of electropolished palladium under otherwise identical and also microscopically evaluated conditions. the test elements which were inserted into conventional pin connections having contact areas made of electropolished palladium exhibited a large amount of material erosion and deformations of the gold layer of the test elements, these were the result of the relative movement Accordingly, the gold layer in the contact areas and conductive paths of the test element are highly deformed by the second contact area of the plug connection which moves relatively to through this, this deformation can be to such an extent that in some areas the Gold apa is scraped under the plastic sheeting because the second contact area is scratched through it. As a result, the electrical contact is interrupted in these cases and therefore an analyte determination is impossible. In contrast, the damage image to the contact areas of the test elements which were inserted into the plug connections according to the invention whose contact areas were coated with 480 nm chromium nitride exhibited considerably less damage. Microscopic observation of the contact areas of the test element showed that the contact areas of the test element were deformed to a much lesser extent than with pin connections that were not coated with a hard material. In particular, major material erosions or changes in layer thicknesses were not observed and the gold layer of contact areas and conductive paths remained in all cases as a continuous layer. The microscopic image of damage showed a more uniform deformation of the gold layer in the form of a flat channel with small and relatively constant depths without material that was worn heavily or even completely at particular sites. The microscopic damage image of the conventional contact areas of the plug connection contact elements which were not coated with a hard material after 480 inserts was also much worse than the microscopic damage image of the corresponding contact areas with a hard material surface according to the invention consisting of 480 nm chromium nitride. The contact areas coated with non-hard material from the contact elements of the control plug connections exhibited considerable wear of the metal layer when viewed under a microscope which resulted in complete abrasion of the metal layer at some sites.

In some cases ^ the deposits of surface materials of the inserted test elements were also observed in the contact areas of the plug connections. In contrast, the contact areas coated with chromium nitride of the contact elements according to the invention showed no significant signs of wear even after such frequent insertions. In particular, the chromium nitride layer was observed to have an intact and continuous surface and there was a reduced deposition of electrode material from the test strip. b) electrical transition resistance when the electrical transition resistances were measured between the test element and contact element of the plug connection it was observed that, especially after many insertions, the contact elements coated with a hard material enabled connections of most reproducible electrical contacts that are less susceptible to interference than conventional contact elements such as a surface of hard material. For this purpose in each case 480 new test elements of the type described above which had a 50 nm thick gold layer as the electrode material were either inserted into the pin connections whose contact areas were coated with nitride 480 nm chrome or in plug connections with contact areas coated with non-hard material made of electropolished palladium (control) and in each case the transition strengths were determined between 8 electrode areas of a test element and the plug connection so that in each case 3840 transition strength values were obtained for contact areas coated with hard material and control contact areas coated with non-hard material. Figure 5a shows a frequency distribution of the transition resistances determined in this manner for contact elements with contact areas coated with non-hard material made of electropolished palladium. The measured transition resistance R is plotted on the abscissa in 0.1 Ohm intervals and the frequency f of the measured transition resistance normalized to the highest frequency value (= 100) is plotted on the ordinate. This shows that most of the transition resistances in these controls are in the low value range between 0 and 10 Ohm but a non-inconsiderable number of measured transition resistances reaches an "infinite" magnitude. Such transition resistors measured as "infinite" means that there is no electrical contact between the respective contact element of the plug connection and the contact area of the test element and the "resistance can not be measured." These values are marked by the arrow on the right side of figure 5a The evaluation of the average individual transition resistances showed that 32 of the measured transition resistances were larger than 50 Ohm A transition value of 50 Ohm is considered as a threshold value - in test element analytical systems constructed in this way below which a measurement can still be considered reliable 16 of the 480 test items examined, however, had at least one transition resistance value above 50 Ohm This resulted in a high error rate of 3.3% of the test elements measured so that such contact elements are adaptive d only limited for permanent and reproducible use in analytical test element systems. Figure 5b shows a frequency distribution of the measured transition strengths for contact elements according to the invention which were coated with hard material with chromium nitride of 480 nm. It can be clearly seen that values greater than 50 Ohm were not observed in the determination of the 3840 transition resistances. Although most resistance values were between 10 and 50 Ohm, none of the 3840 measured values were above the threshold value of 50 Ohm and none of the transition strength values were "infinite" as with the contact areas coated with non-hard material. Accordingly, such contact connections can be used to transfer electrical signals reproducibly and accurately for many pin operations. The use of such contact connections according to the invention in test element analyzers therefore has the advantage that reproducible and exact analyte determinations can be made in such systems especially even after numerous inserts. Example 2: Contact elements with titanium nitride-coated contact areas Analogous experiments were performed with plug connections with contact elements whose contact areas had a hard material surface according to the invention consisting of titanium-aluminum nitride 120 nm which was also applied by means of a DFV process. a) microscopic examination of the surface Also in this case it was found that a hard material coating of the contact areas of the plug connection with titanium nitride and aluminum according to the invention considerably improves the image of damage to the areas of contact of the test elements. Microscopic observation of the respective contact areas of the test element showed that the contact area of the test element was deformed but to a much lesser extent than with the controls that were not coated with a hard material. In particular, large changes or erosions of material in the layer thicknesses were not observed and the gold layer of the contact areas and conductive paths remained as a continuous layer. The microscopic image of damage showed, similar to a contact area coated with chromium nitride, a more uniform deformation of the gold layer in the shape of a flat channel with a relatively constant and small depth without material that was worn heavily or even completely in particular places. Also the damage to the titanium-aluminum nitride coating itself was much lower after 480 inserts than with the control plug connections coated with non-hard material. The contact areas coated with titanium and aluminum nitride of the plug connections according to the invention exhibited signs of wear or deposits not significant even after frequent insertions. In particular, the surface of the titanium nitride layer was observed to be still intact and continuous, b) electrical transition resistances In the transition resistance measurement, equal to the measurement in example lb), it was found that the contact contacts of titanium-aluminum coated titanium-ionic connections enabled considerably more reproducible electrical contact connections between the plug connection and test element which are considerably less susceptible to interference than conventional plug connections without such a hard material surface . A particular advantage of this mode is that in addition to very high contact reliability (no values above 50 Ohm) compared to the contact areas coated with chromium nitride of Example 1, the values of the measured transition resistances are still considerably smaller. Figure 5c shows a frequency distribution of the measured transition strengths for contact elements according to the invention with contact areas coated with a hard material comprising titanium and aluminum nitride of 120 nm. The determination of transition strengths clearly showed that values that are greater than 50 Ohm were not observed. Also almost all the measured resistance values were between 1 and 3 Ohm and therefore still considerably lower than with the contact areas coated with non-hard material of the example 1 (figure 5a). Accordingly, such contact connections can be used to transfer electrical signals reproducibly and accurately for many pin operations. The use of such contact connections according to the invention in test element analyzers therefore has the advantage that in such reproducible and accurate systems the analyte determinations can be made especially even after numerous inserts. The very low transition strengths in the case of contact elements with contact areas coated with titanium nitride and aluminum have the additional advantage that the current measurement signal is severely affected by the transition resistance and therefore it is possible to make determinations of analyte particularly accurate even with low measurement signals. Example 3: Change in the transition resistances of example 1 and 2 after numerous plug-in processes: For reproducible use in test element analytical systems over a long period of time and for many measurement cycles it is also important that Transition resistances are as constant as possible and do not exhibit wear behavior or extreme performance which is characterized by initially high and then decreased resistance values or initially low resistance values and then increased. The control plug connections with contact areas made of electropolished palladium exhibited dissipated contact faults characterized by "infinite" resistance values during the 480 inserts of a new test element in each case over the entire time period. Such diffuse randomly dissipated contact faults are disadvantageous especially for the reproducibility of the measurement result since a measurement error must always be expected with a certain probability. Pin connections with contact areas which were coated with 480 nm chromium nitride exhibited an increase in transition strengths with an increased number of inserts. In such test systems, therefore it may be advantageous to replace the coated contact elements with the hard material after a certain number of measurements to ensure a high constant measuring accuracy. For this reason, the present invention also includes such contact elements coated with hard material and contact connections as well as evaluation instruments which contain such contact elements and contact connections coated with the hard material. The pin connections with contact areas which were coated with 120 nm titanium and aluminum nitride initially exhibited higher transition strengths which decreased to a very low resistance level with an increased number of inserts. This observation shows that, in contrast to a chromium nitride coating, low and highly reproducible transition strengths can be achieved especially even after many insertions by the use of a titanium-aluminum nitride coating and such coatings of non-metallic areas. Contact are particularly suitable for analytical test element systems which should allow accurate analyte determinations over a very long period of use and many measurements. This shows that it is also possible to adapt the test element analytical system to the requirements of the respective field of application especially with respect to the life time and accuracy of the analyte determination by material selection for the hard material surface. It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims (11)

2. Having described the invention as above, the content of the following claims is claimed as property: 1. Test element analytical system for the analytical examination of a sample, in particular a body fluid comprising - a test element having the less a measurement zone and electrically conductive contact areas, in particular electrodes and conductive paths, the sample to be examined is placed in the measurement zone for the analytical examination, and - an evaluation instrument having a test element support to position the test element containing the sample and a measuring device to measure a change in the measurement area that is characteristic for the analyte, the test element holder contains contact elements with contact areas that enable an electrical contact between the contact areas of the test element and the contact areas of the p-element holder This is characterized in that one of these contact areas has a surface of electrically conductive hard material. Analytical test element system according to claim 1, characterized in that the contact areas of the contact elements of the test element holder are provided with a surface of electrically conductive hard material.
3. 3. Test element analytical system according to one of the previous claims, characterized in that the contact area opposite the hard material surface consists of a material which is different from the material of the hard material surface.
4. 4. Test element analytical system according to one of the previous claims, characterized in that the contact area opposite the hard material surface consists of a material, in particular a noble metal or an alloy containing a material.

   15 noble metal which has a lower hardness than the material of the hard metal surface.
5. 5. Test element analytical system according to one of the previous claims, characterized in that the contact elements of the support

   20 test element are in the form of pin contacts, spring contacts and clamp contacts.
6. 6. Test element analytical system according to one of the previous claims, characterized in that the surface of hard material consists of
7. 25 a metal nitride, in particular titanium nitride, titanium aluminum nitride, chromium nitride or zirconium nitride. Test element analytical system according to one of the previous claims, characterized in that the surface of hard material is produced by coating a base material with a hard electrically conductive material.
8. 8. Test element analytical system according to claim 7, characterized in that the additional intermediate layers, in particular bonding or protection layers, are present between the base material and the hard material surface.
9. Test element analytical system according to one of claims 7 to 8, characterized in that the layer thickness of the hard material coating is less than 2 μm, preferably less than 1 μm, particularly preferably less than 500 nm.
10. Test element analytical system according to one of the previous claims, characterized in that the electrical transition resistance between the contact areas of the test element and the contact areas of the test element holder is less than 50 Ohm.
11. 11. Test element analytical system according to one of the previous claims, characterized in that the analyte is determined using electrical and in particular electrochemical methods.