KR101170853B1 - A handheld device with a disposable element for chemical analysis of multiple analytes - Google Patents

Abstract

The present invention relates to a handheld system and method for determining the concentration of multiple chemical or biological materials requiring in situ analysis of multiple chemical or biological materials. The new and unique handheld sensor system utilizes a spectroscopic detector and one-time optical test elements that measure test element responses to specific analytes through changes in absorbance, changes in luminescence, and other forms of light-based response. In this manner, the reflected light intensity representing the test element response can be used to measure the concentration of the target analyte. The sensor system may be interfaced to an information processing unit or computer to manipulate or electronically store analysis data.

Description

System and method for measuring analyte concentration of chemical or biological substance {A HANDHELD DEVICE WITH A DISPOSABLE ELEMENT FOR CHEMICAL ANALYSIS OF MULTIPLE ANALYTES}

The present invention relates generally to methods and apparatus for the analysis and measurement of chemicals by spectrophotometry, and more particularly, to a portable handheld sensor system for quantitative determination of multiple materials using one-time optical test elements and spectroscopic detectors. .

Various chemicals are known to absorb light in proportion to the concentration of the substance present in the sample. In addition, the light passing through such a material has an absorption spectrum characterized by the light absorption properties of the material and the properties of any other medium through which the light passes. This absorbance spectrum can be shown in prismatic form for analysis. By ignoring part of the absorption spectrum due to intensity loss and other absorbers, the spectrum of the chemical can be separated and the nature and concentration of the material can be determined. Ignoring or referencing is done by determining the absorbance spectrum and any spectrophotometric component of the light source in the absence of chemicals. References are generally made in close proximity to absorbance measurements of chemicals over time and space to minimize errors.

Portable battery power supplies are widely known for commercial use in measuring chemical concentrations. Examples include Hach handheld photometers and Merck handheld reflectometers. Detailed descriptions of photometric and reflective systems are provided in Comprehensive Analytical Chemistry, Chemical Test Methods of Analysis, (YA Zolotov et al., Elsevier, New York (2002)), and Review of Scientific Instruments, (Kostov, Y. and Rao, G., Vol. 71, 4361, (2000)). Using these systems allows chemical analysis outside the laboratory. However, the following parts need to be improved.

1. Some tests with portable instruments use toxic or corrosive reagents. Some use large amounts of solid reagents for a single test. For example, many Hach test methods use more than 200 mg of solid reagent for a single analyte.

2. The operator must deliver reagents and samples into the measurement unit. Sample handling and reagent handling are inconvenient for chemical analysis and increase operator-to-operator error.

3. Liquid waste resulting from wet chemical analysis should be safely disposed of in accordance with appropriate legislation.

4. Currently available test methods do not easily determine exceeding one irrelevant analyte in a single test.

5. Most handheld devices have data interpretation and storage capabilities, but most test results still have to be passed to the database manually.

Other methods using test strips have been widely tried for semi-quantitative analysis on many analytes. Here, quantitative results can be obtained with a one-time optical sensor element read by a photometer. In most cases, only a single analyte is determined by the optical sensor element. Because of the measurement of transmission absorbance, it is difficult to manufacture one-time optical sensor elements for tests without calibration.

Disposable chemical sensors are well known in the art. For example, US Pat. No. 5,830,134 discloses a sensor system that detects physicochemical parameters designed to compensate for many disturbance factors, such as those caused by using a partial one-time monitoring unit, thus eliminating the need for calibration steps. .

Another US Pat. No. 5,156,972 discloses a chemical sensor based on absorbance, light divergence, light scattering, polarization, and electrochemical and piezoelectric measurement parameters.

Optical scattering controlled emissions for optical taggants and chemical sensors are disclosed in US Pat. No. 6,528,318.

Sensor arrays using reference and indicator sensors are known and disclosed in US Pat. No. 4,225,410. Here, the sensors can be calibrated individually as if each analysis could be read directly.

U.S. Patent 5,738,992 discloses a method of correcting fluorescent waveguide sensor measurements utilizing a reference material. U.S. Patent 5,631,170 teaches a reference method for fluorescent waveguide sensors by labeling the waveguide with a reference reagent. Note that the internal absorbance standard method used in the present invention is fundamentally different from the prior art in several ways.

First, the multi-angle scattering induced absorbance detection technique used in the present invention is different from traditional attenuated total reflection (ATR) sensors using thin elements with a film thickness approximately the same as the incident beam wavelength. Such thin elements may include a fluorophore that serves for internal reference. On the other hand, the system does not require a thickness close to the incident beam wavelength and belongs to a thick film element that uses another internal reference based on absorbance.

Two wavelength or double beam methods are known for spectrophotometric analysis. "Referencing Systems for Evanescent Wave Sensors," (Stewart, G. et al., Proc. Of SPIE, 1314, 262 (1990)), proposes a two-wavelength method for compensating for contamination effects on sensor surfaces. US Pat. No. 4,760,250 to Loeppert discloses an optoelectronic system that uses a feedback controlled light source to measure environmental characteristics that minimizes problems associated with light source stability and component aging. Similar feedback controlled two wavelength methods are disclosed in U. S. Patent 3,799,672 to Vurek. Dual beam reflective spectrophotometers are disclosed in "Optical Fiber Sensor for Detection of Hydrogen Cyanide in Air," (Jawad, S. M. and Alder, J. F., Anal. Chien. Acta 259,246 (1991)). In the method of Jawad and Alder, two LEDs are alternately supplied with energy. The ratio of the outputs at the two wavelengths is used to reduce the error caused by the background absorption of the sensor element for detecting hydrogen cyanide. These two wavelength methods are effective in minimizing the long term stability problems of the light source and the errors caused by optical and mechanical component aging. However, it does not address the errors associated with variations in the effective optical path length of the one-time test element.

One-time sensor systems that include and further include disposable or one-time measurement devices are disclosed in US Pat. No. 5,114,859.

In addition, US Pat. No. 6,007,775 analyzes multiple analytes with microfabricated sensors.

In "Application of a Plastic Evanescent-Wave Sensor to Immunological Measurements of CKMB," (Slovacek, RE; Love, WF; Furlong, SC., Sensors and Actuators B, 29, pp. 67-71, (1995)), It has been demonstrated that sensors handled by critical surfaces can be manufactured with improved robustness. Such sensing elements were made as plastic cones that are insensitive to the end where the sensing chemicals are deposited. The sensing element was injection molded from plastic, making it commercially available.

As a result, known sensors have a number of significant drawbacks that limit their applicability for field analysis applications. Examples of these shortcomings are as follows.

1. Critical alignment of the testing strip is required on the sensor to perform precise readings.

2. There is a need to reduce errors caused by variations in testing strip quality (embedded reagent concentration, effective optical path length, and component aging).

3. When the testing element is exposed to the sample, there is a need to reduce errors caused by physical changes in this element, for example errors such as expansion, contraction, and / or crazing.

4. It is necessary to determine the steady state response in chemical sensor response for precise analysis.

5. Unable to collect dynamic sensor information from irreversible chemicals.

6. No real-time information can be collected from irreversible chemicals when exposed to samples.

7. It is not possible to analyze dynamic sensor information from multiple irreversible chemicals to provide improved quantification of the sensor system.

Because of the shortcomings in the prior art described above, it has not been possible to provide a low cost portability and calibration free sensor system. The sensor system of the present invention solves the aforementioned disadvantages. In particular, the sensors of the present invention can collect dynamic information by tracking the rate of change in the kinetic or dynamic response of irreversible sensor chemicals as the sample reacts with the sensor to quantify the concentration level.

In view of the foregoing, it is an object of the present invention to provide a portable one-time handheld sensor system for quantitative determination of analyte concentrations. It would also be desirable to provide a system that does not require calibration before each new set of assays. In this regard, the system uses dual light analysis on the same sensor element, where the sample response is compared with an internal reference, eliminating the need for calibration before each new analysis set. In addition, the use of internal references significantly reduces the optical and mechanical coupling requirements for the device, thus providing an advantage in the cost of the manufacturing and assembly process with minimal impact on the precision of the testing results.

Another object of the present invention is to provide a sensor capable of manipulating, transmitting or electronically storing analytical data by an information processing unit such as a pocket personal computer or a sensor capable of communicating with a wireless mobile phone or satellite. .

It should be noted that the present invention provides a general photometer and / or spectroscopic test method that does not require any liquid reagents. This not only simplifies testing but also reduces the cost and labor intensive requirements associated with handling and handling toxic reagent materials.

The present invention provides a portable one-time handheld sensor system for measuring analyte concentration in a chemical. The system provides a common photometer and / or spectroscopic test method that requires no liquid reagents and no calibration before each new set of assays. The main components of this system include a thin film sensing reagent fixed on a one-time test element, an adapter that mounts the test element in a renewable manner, and a light source that can cause a luminosity response from the test element. Accordingly, the system may include optical light sources and photodetector elements commercially available in combination with appropriate coupling devices, fixturing, power supplies, electronic circuitry, and the like to store data on a computer or other display, storage or processing unit. It can interface and transmit.

In addition, the system considers additional devices that support their primary functions, such as closures that separate test elements from ambient light during sensing measurements. In addition, the present invention provides a highly reactive sensor system that is scalable to measure multiple analytes with a single multi-compartment test element and can be easily delivered to virtually any location requiring on-site analysis of a chemical or biological sample. I can understand that. An example of such a location is a cooling tower on the roof of an isolated lake, a city, or a tall building.

Advantages of the invention over the invention and the prior art will become apparent by reading the following description and claims with reference to the accompanying drawings.

1 is a perspective view of a handheld system according to one embodiment of the invention.

2 is a front view of a multi-compartment one-time optical element in accordance with an alternative embodiment of the present invention.

3 is a perspective view of a one-time test element according to one embodiment of the invention.

4 is a perspective view of a handheld sensor system in accordance with an embodiment of the present invention utilizing a multi-compartment test element.

5 is a diagram illustrating an example of a dual wavelength response from a single analyte.

FIG. 6 is a diagram illustrating an example of a series of absorbance levels indicating a change in spectral response from exposure of different ink concentrations.

7 is a perspective view of another measurement configuration according to an example of the present invention.

8 is a diagram illustrating an example of a sample spectrum and a baseline spectrum obtained with a polycarbonate reflective element.

FIG. 9 shows an example in which sample spectra for 0.5 ppm NaOCl before reference correction and thus optical element position are strictly controlled.

10 is a diagram showing an example in which the sample spectrum for 0.5 ppm NaOCl after reference correction and thus the optical element position are strictly controlled.

FIG. 11 is a diagram illustrating an example of a calibration curve for reference corrected absorbance listed in Table 1. FIG.

FIG. 12 is a diagram illustrating an example in which the sample spectrum for 0.5 ppm NaOCl before reference correction and thus the optical element position are not strictly controlled.

FIG. 13 shows an example in which the sample spectrum for 0.5 ppm NaOCl after reference correction and thus the optical element position are not strictly controlled.

14 is a diagram schematically illustrating a measurement configuration used for Example 1. FIG.

FIG. 15 is a schematic illustration of a handheld sensor system used for Example 5. FIG.

16 is a perspective view of a handheld sensor used for Example 5. FIG.

It is a figure which shows the calibration curve obtained with the handheld sensor demonstrated in Example 5. FIG.

The present invention relates to a method and apparatus for measuring the concentration of a chemical by utilizing a reaction characteristic of a predetermined chemical, for example, the characteristic of a substance reacting with a selective analyte that is another chemical. A change is caused, and a change of the light absorption property of the original chemical containing material occurs. In operation, the present invention measures the test element response to a particular analyte through alteration of absorbance, luminescence, light scattering, or other light based response. The analytes described herein are species, but the invention may also include biological systems in which biological analyte interactions stimulate similar test element responses. For example, such a biological system can be a luminescent enzyme response to an immobilized enzyme, eg, etipiase (ATP), that stimulates the optical response in proportion to the analyte concentration.

Referring to the drawings, FIG. 1 shows a basic sensor system detachably mounted onto an adapter 4 and comprising a one-time test element 2 of approximately glass microscope slide size. The test element 2 is generally formed of any suitably transparent material such as glass or organic polymer material having a refractive index of greater than one. Part of the test element is coated on one or both sides of a thin, transparent polymer membrane containing the reagents needed to react with the analyte to have a color product. The reagent film may be immobilized on the test element by dip coating or spin coating the test element or by other means known in the art. In addition to coating a portion of the test element, the entire test element may be coated. In combination with the reagent materials described above, the reactive membrane coating also includes a reference die that provides an internal absorbance standard or internal reference, such that the refractive index of the reagent die membrane mixture n ₂ may be less than or greater than n. The reference die is mixed with the membrane coating to provide a reagent membrane composite with a constant internal absorption standard. In other words, the reference die component of the reagent film composite provides a first absorbance response and the reagent itself provides a second absorbance response such that the reagent film composite provides a dual light absorbance response (i.e., dual light response) to incident light energy. It can be provided. However, unlike the reagents themselves, the reference die does not react with the analyte. Thus, if the optical and mechanical properties of the test element have not changed, the spectral profile of the die is constant from one test element to another before and after the test element is exposed to the sample. In addition, since the reference die and the reagent have different absorption spectra, the spectral profile of the reference die can detect the target detection wavelength, or range of wavelengths, used to measure the test element response to the reaction between the reagent and the analyte. Not overlapping enough. By providing this non-overlapping benchmark response difference between the reference die and the reagents, the reagent membrane composite provides an internal absorbance standard or internal reference, thus eliminating the need for external calibration and device calibration before each new set of assays. Will provide a response. As will be described in detail below, it will be appreciated that internal reference also minimizes response variation from device to device, providing significant manufacturing and maintenance cost advantages with minimal impact on the precision of test results. As a result, the features and features of the present invention are suitable for cost-effective production, assembly, and miniaturization. The above internal reference is a colorimetric die, but this is only one of many possible embodiments. Any standard that does not react with the analyte detection chemical and has a spectral response outside the detection spectrum may function as an internal standard. This material can be an inorganic compound, pigment, die, or micro-nanoparticle that can be used to generate the required spectral response and correct errors due to film variation.

Referring to FIG. 1, the mounting adapter 4 comprises at least one light source 6, which may be any means capable of emitting light energy 21, such as an LED, a laser diode, or a small bulb. The adapter 4 may at least be capable of detecting light energy 22 and may be any means capable of converting this energy into an electrical output signal representing a test element response to a target analyte or a plurality of target analytes. It further comprises one photodetector 8. This electrical output signal is transmitted to the signal converter 5 via the circuit wire 14. It will be appreciated that the performance required may be achieved using many commercially available photodetectors well known in the art, such as photodiodes, micromachined light magnification tubes, or photocells.

The adapter 4 further comprises a fixing means 44 which aligns the test element 2 and places it in a suitable reproducible position with respect to the light source 6 and the photodetector 8. As will be described in detail below, the present invention does not require fastening means 44 in providing control and strict positioning of the test elements. Instead, it has been found that proper or suitable control of the test element 2 with respect to the light source and photodetector is effective in obtaining accurate and reproducible absorbance results, and thus in manufacturing, maintenance, and assembly requirements. Provide a cost advantage.

When the power switch 9 is activated, the light source 6 generates a light beam that is not collimated and out of focus. As shown in FIG. 3, the collimated and unfocused light beam collides with the test element at different angles, ie at angles greater than and less than the critical angle of the test element. As described in detail below, some of the incident light energy reacts with the reagent film composite immobilized on the test element. Once this incident light energy is delivered through the reagent film composite, the photodetector can detect a pair of light response spectra, i.e., the photodetector can detect the first light response from the internal reference die only, and from the reagent film itself. The second optical response is detected and the device is thus capable of detecting the dual optical response from the incident light test element interaction. In this way, any change in the test element optical response spectrum can be detected and measured without external calibration before each new analysis set. In addition, it can be seen that due to the collimated and unfocused nature of the incident light beam, the positioning and strict control of the test element by the fastening means 44 is not necessary to provide a relatively precise test result. . Instead, the fastening means 44 only provide proper or suitable position control of the test element 2, thus saving costs in the manufacturing process.

The adapter 4 further includes a battery 7 for powering the sensor system, and those skilled in the art will understand that many other means may be used to power the sensor system. It also provides a suitable electronic means by which the signal converter 5 can communicate with the signal processing unit 10 to process and electronically store the electrical output signal produced by the photodetector 8. It is described in detail above, including embodiments capable of communicating with an external processing unit 10, such as a handheld computer, a PDA, or other wireless transmission device, via an interface 12 utilizing many configurations well known in the art. It will be appreciated that the same performance as in one embodiment can be obtained. In addition, it is to be understood that embodiments including embedded processing units (not shown) may be used.

For example, the light source 6 is located near the edge of the detachable test element 2 such that the incident light wavelength 21 emitted from the light source impinges on the edge 23 of the test element, as shown in FIG. 1. Light beams from uncollimated and unfocused light sources impinge on the test element at a plurality of different angles, but are not limited to this example. It is widely known that the critical angle of the test element can be calculated from the refractive index of the substrate n ₂ and the refractive index of air n ₁ can be calculated from the equation (Θ _c = sin ⁻¹ (n ₂ / n ₁ )), where Θ _c is the critical angle. Referring to FIG. 3, the divergent light beam 21 is directed to the edge of the test element at about 45 °. Since the light beam 21 is not collimated and out of focus, some of the incident photons 21 impinge on the test element 2 at an angle greater than the critical angle, while other incident photons are smaller than the critical angle. Crash the test element at an angle. If the angle of incidence of the photons 21 is greater than the critical angle Θ _c , the light beams are all reflected at the membrane-air interface. This phenomenon is called total reflection. On the other hand, when the incident angle of the light beam is smaller than Θ _c , the incident light beam is partially reflected at the film-air interface. This phenomenon is called partial reflection.

In the case of total reflection, a portion of the light beam 21 is totally reflected at the film-air interface of the test element, but some of the reflected light energy may reenter the substrate as though it traveled a short distance parallel to the interface through the membrane. This energy is referred to as an evanescent field or evernetcent wave 20E as shown in FIG. Since the reactive film coating 18 is fixed on the surface of the test element, a portion of the Evernetcent Wave 20E is absorbed (attenuated) by the film coating 18 at the substrate-film interface. This phenomenon is called attenuation total reflection (ATR). In the case of partial reflection, the partially reflected photons of the incident light beam 21 can similarly form the Evernetcent wave 20E and can be absorbed by the film coating, while the remaining unreflected photons are directed to the surrounding environment. Can be lost. This phenomenon is called attenuated partial reflection (APR). In order to increase the effectiveness of the APR, the reflective coating 19 can be fixed on the end of the test element so that the unreflected incident light 20 through the body of the test element is directed against the reflective coating 19. It can be reflected and scattered back through the test element. As a result, some of these internally reflected photons 20 are given another opportunity, ie a second opportunity to react with the film coating 18 at the surface of the test element and form an Evernetcent wave. Thus, since the present invention includes components from both ATR and APR, it is possible to improve the efficiency of the incident light beam 21 without the need for expensive optics or coupling requirements, and thus the widely known ATR. It can provide an advantage over the system.

Referring again to FIG. 3, some of these energetic photons may react with molecules contained in the reactive film 18 as the Evernescent wave 20E runs along the surface of the test element. This interaction causes some of the Evernetescent photons to be absorbed by the molecular structure of the reactive membrane. Accordingly, absorption by the reactive film 18 can be sufficiently avoided, otherwise photons 22 which are not lost due to the environment can be transmitted from the test element which can eventually be detected by the photodetector 8. have. As a result, the number of photons 22 transmitted from the test element depends on the absorbance level of the incident light beam 21, so that the electrical signal generated by the photodetector can be utilized to indicate the percent absorbance of the reactive film. Once the relative intensity of the final light response is compared with known reference data, the analyte concentration of the sample material can be detected and determined.

As described above, when the power switch 9 is activated and the light beam 20 is projected onto the test element, the photodetector will receive a dual light response 22 from the test element. This response curve is shown in FIG. Here, line 100 represents the optical response of the membrane coating before the test element is exposed to the sample analyte, and line 200 represents the dual optical response of the membrane coating after the test element is exposed to the sample analyte. A ₀ represents the absorbance level of the film coating only at the wavelength λ ₂ . The first peak at A ₁ represents the absorption level of the internal reference die at the wavelength λ ₁ before exposure and A ₂ represents the absorption level of the internal reference after exposure. The A ₁ and A ₂ values are identical unless the optical and mechanical properties of the test element have changed during exposure. The peak at A ₃ represents the absorbance level of the film coating at wavelength λ ₂ after the test element is exposed to the sample analyte. If the sample material is known to absorb light in proportion to the concentration of the material present in the sample, it can be seen that the difference between the absorbance levels A ₃ and A ₀ is proportional to the analyte concentration of the sample material. By taking into account the absorbance levels A ₁ , A ₂ of the internal reference concentrated at λ ₁ , the absorbance levels of the reagent membrane coating can be corrected according to the general formula.

Where A _corrected represents the normalized absorbance level of the reagent film coating. It will be appreciated that many other procedures may be used to normalize the response curve, such as peak-to-peak ratio or area comparison under the curve.

To calculate the absorbance, the blank signal output at λ ₁ and λ ₂ of the test element must be known before coating the reagent film. The signal sensor response can be obtained by measuring the photodiode signal when loading the test element without the polymer film. The blank response can be stored in the processor. In the following description it will be clear that the final result (A _corrected ) is independent of the blank response. By knowing the blank response, the absorbance level of the test element before exposure can be expressed as an absorbance unit rather than the volts or amps measured by the photodiode.

In a preferred mode of operation, the polymer coated test element 2 is detachably mounted to the adapter 4 by means of fastening means 44. As mentioned above, the fixing means 44 align and position the test element at a position that is appropriately reproducible with respect to the light source and the photodetector. Tight control of the test element and incident light angles for the light source and photodetector is not necessary. To compensate for variable lighting conditions, the operator activates the light source at the sample test site to record the corresponding reflection intensity from the coated test element once. The optical response spectrum measured during this step is called baseline intensity.

After establishing the baseline intensity response, the operator exposes the coated test element to the chemical or biological sample material for a predetermined period of time, for example, 1 to 3 minutes, depending on the diffusivity of the membrane coating. Next, the operator removes the test element from the sample and removes excess liquid sample from the test element by dripping or flowing it. This step can be done for 0 to 5 minutes. After this period, the operator reactivates the light source to record the reflection intensity from the corresponding sample exposed test element. The optical response measured during this step is called sample intensity.

The analysis described above is continued to process cumulative data indicative of the blank, baseline, sample and internal reference response intensities and combine with known chemical reference data corresponding to the expected spectral response of the particular analyte under examination. As shown and described in more detail in Examples 1-5 below, analysis of the sample material by comparing the intensity of the optical response after exposing the test element to the analyte to the intensity of the optical response prior to exposing the test element to the analyte Object concentrations can be measured.

The system described above represents photometric measurements performed with conventional optical devices. As a result of the multi-angle scattering induced absorption measurement technique utilized by the present invention, accurate and reproducible absorption measurements can be obtained for the membrane with higher sensitivity than conventional transmission measurement techniques for the membrane. This is because conventional transmission absorbance measurement techniques can be characterized as one pass. That is, in conventional transmission techniques, incident photons can pass through the material under inspection once and have a single chance to react with the test element when they are passed through the substrate with minimal refraction and scattering. On the other hand, as shown in FIG. 3, the present invention utilizes a multi-angle scattering scheme whereby incident photons 21 scatter within the test element and reflect on the reflective coating 19, thus incident photons Some of them get multiple passes through the test element. This multi-angle scattering approach increases the likelihood that the Ebenesent photons 20E eventually react with the film coating on the substrate surface. As such, if an incident photon is lost at the substrate surface during its initial pass, it is likely that the same photon will scatter within the test element and eventually reflect back to the substrate surface, thus causing such photons to be lost at the substrate surface and eventually to coat the film. There is another chance to be absorbed by. Thus, a certain amount of light energy can obtain a larger proportion of absorption events compared to conventional transmission techniques, thereby increasing the relative absorption percentage of incident light and improving the final sensitivity of the sensing device.

Note that many configurations of the same main components can achieve the same performance as the above-described embodiment. For example, another embodiment of the present invention is shown in FIG. Here, a multi-compartment optical test element 2A is shown which comprises an isolation region 3 and a sensing region 5. The isolation region acts as a barrier between the sensing regions by absorbing scattered light that may be reflected in the various sensing regions, thereby reducing the interaction noise between the sensing regions. Each sensing area utilizes an independent reactive membrane coating that contains its own internal chemical properties. Each of these reaction membrane coatings and the resulting chemical properties are effective in providing a dual light (spectrum) response independent of the particular analyte of interest in the sample solution. Thus, multiple analytes can be tested simultaneously on a single test element. In addition, it has been found that the separation regions 3 can be penetrated for improved separation, thereby increasing the efficiency of the test element.

It is contemplated that an independent light source and photodetector pair may be provided for each of the independent sensing regions so that the operation of the multi-compartment test element is easy, so that each light and detector pair is appropriate from each of the various sensing regions. It can produce a dual optical response. Alternatively, a single light source and photodetector can be configured to generate and detect an appropriate dual light (spectral) response from each of the independent sensing regions. In this case, an independent electrical signal generated by each of the various sensing regions can be combined and multiplexed in a manner known in the art by the processing unit 10 to detect and quantify a plurality of analytes as a single one-time test element. .

4 illustrates an apparatus that facilitates multi-compartment test elements. The apparatus includes the same basic components as the system shown in FIG. The exemplary embodiment of FIG. 4 includes several pairs of light source 6 and photodetector 8 that can be mounted on both sides of adapter 4A. The multi-compartment test element 2A is mounted onto the fastening means 44. Here, the fixing means 44 is attached to the moving carriage of the miniature motion slide 66. The motion slide can retrieve the test element into the adapter and function to align the test element with the light source / photodetector pair for absorbance measurements. Appropriate electronic means 77 are provided to control the device to process and electronically store the electrical output signal generated by the photodetector.

The invention also relates to ambient atmospheric conditions such as temperature (e.g., using a thermistor), relative humidity (e.g., using capacitive humidity sensors), and atmospheric pressure (e.g., using MEMS pressure sensors). Consider the use of additional sensors that may be used to provide information and are well known in the art.

In another embodiment, the chemical sensor system considers a dynamic pattern recognition system to improve the functionality and quantification of the sensor array. The functionality of the sensor array is improved by including means for indicating the end of the required environmental exposure of the sensor. For example, the sensor is immersed in the water sample until an alarm (eg beep) indicates that the sensor is ready to be recovered and ready to provide quantitative information. The principle of operation of such a system is based on the use of dynamic signal analysis of sensor response. In particular, the sensor in the present invention can collect dynamic data for a particular period by tracking the rate of change in the response of irreversible sensor chemistries as the sample reacts with the sensor to quantify the concentration level. Thus, the sensor of the present invention has more information compared to a sensor that is only exposed to a sample and later retrieved when the signal after recovery is measured. The collected dynamic data can then be analyzed for known parameters such as initial slope, intermediate slope, and final slope of the signal during exposure. These dynamic parameters can be used to indicate when a steady state response is reached. If the steady state does not reach the appropriate period, dynamic parameters can be used to quantify the analyte concentration. In addition, the slope of the chemical sensor response may be more sensitive than the balanced endpoint, resulting in increased sensitivity for the sensor system described herein.

In another embodiment, the sensor includes another alarm indicating an analysis completion time after the sensor is withdrawn from the sample. This is provided by different signal recovery rates from different sensor regions, which depend on sensor chemistry, reversibility, and ambient atmospheric conditions. As will be appreciated by those skilled in the art, many suitable electronic, integrated circuit and / or microprocessor means can be configured to provide the sensor and timer alarm features described above to obtain a collection of dynamic sensor response data in the embodiments described above. In one embodiment shown in FIG. 15, a Visual Basic® computer program is developed to provide timers and alarm features and to control and read sensor systems.

It is well known that reversible chemical sensors often suffer from poor response selectivity, mainly due to noise or interference from unspecified signal changes. Thus, irreversible one-time sensors can improve the selectivity of chemical recognition. The irreversible sensor chemistry often provides a stronger and more selective interaction between the chemical species and reactants of interest, which can generally be seen as one of the advantages created by the irreversible sensor chemistry. However, if it is advantageous to improve the dynamic range of the sensor or to reduce chemical interference, it is possible to use a single analyte with multiple sensor regions containing different reagents, or complementary sensor elements that combine to improve the overall system response. It may be desirable to analyze. Despite the known disadvantages associated with reversible reagents, the inclusion of reversible reagents in multiple reagent detection techniques can improve the overall sensor response. This combination of reversible and irreversible platforms can create a system with improved functionality. A standard pH indicator is one example of a chemical commonly used in reversible sensors, while the chlorine reagent described in the following example is one example of irreversible chemistry. Combining a reversible pH sensor with an irreversible chlorine sensor can further define other chlorine-containing species present in the sample, but is not limited to this example.

Referring to the following examples, suitable or proper control of the coupling and positioning requirements of the test element and the optical component, as opposed to strict or critical control of these coupling and positioning requirements, is internally referenced according to the following equation: It has been found that if absorbance standards are used, they are effective in obtaining accurate and reproducible absorbance results.

However, it will be appreciated that using a single internal absorption standard does not eliminate all of the errors caused by alignment of the test element with respect to the incident beam and variations in film or substrate quality. This is because each error source has a different effect on the absorption band at different wavelengths. For example, the change in absorbance caused by the change in incidence angle is a function of wavelength rather than chemical nature because the optical path length depends on the wavelength. Thus, it is recognized in the present invention that precision is increased by using a reference system having more than one internal standard or by using a spectral profile of a single standard absorption band when measuring the entire spectrum. However, note that a significantly higher level of reproducible measurements was obtained by utilizing a single internal absorption band in combination with a suitable or appropriate mechanical control coupling between the one-time test strip and the adapter, as illustrated by the following examples.

Example 1

Painting the four edges of the Fisher brand, clear glass slides (dimensions: 3 "x 1" x 0.41 ", Fisher Catalog No. 12-549) with a white paint pen (Uni®Paint PX-20) as shown in FIG. The area near one end was also painted with a white paint pen The arrangement of LEDs and light cells is shown in Figure 14. The light source is a 5 mm, 3000 mcd red LED from RadioShack®, with a peak emission wavelength of 660 nm and an observation angle of 12 °. Absorbance levels of different concentrations of blue lines formed with permanent and fine point Sharpie® markers are shown in Figure 6. Here, during the initial time period (0 to 22 seconds), the light is blanked (i.e. without blue marking). Projected onto the glass slide, as expected, the corresponding absorbance level at line 50 is almost zero, after about 22 seconds, a single blue line was formed on the glass slide and the corresponding absorbance level was shown as shown. Equal Increased to line 51. After about 34 seconds, a second blue line formed on top of the first blue line to increase the concentration of the blue marking on the glass slide. Similarly, after about 45 seconds, a third blue line was added to further increase the concentration of the blue marking on the glass slide As again expected, the corresponding absorbance level increased to line 53. It is well known that this measured absorption is defined as follows.

Here, the output in the dark is the steady state response of the detector when the light source is turned off.

This example illustrates that photometric measurements can be performed in a very simple manner. However, many simple designs can be built with this simple setup. For example, an interference filter film may be coated in the area facing the photodetector or mixed in reflective paint to measure absorbance for a given absorption band. 2 shows an example of such designs.

Example 2

In this example, a polycarbonate reflective element of 3.7 "x 0.49" x 0.21 "was made. The end of the polycarbonate element was cut at an angle of about 51 °. The test for absorbance measurement used in this example. The element configuration is shown in Figure 7. Here, Ocean Optics P400-2 six optical fiber bundles were used to provide incident light from Ocean Optics tungsten-halogen lamps R400-7 Ocean Optics USB2000 Spectrometer with Ocean Optics Reflective Probe The reflected light was collected for: A poly (2-hydroxylethyl methacrylate) (PHEMA) film containing tetramethylbenzidine (TMB) was dip-coated on one side of the polycarbonate element and all wavelengths A blank spectrum with zero absorbance was established for the polycarbonate element, after coating the TMA film, into a configuration as shown in FIG. Baseline spectra were recorded first, then 0.06 ml 0.1 ppm sodium hyperchlorite solution was carefully unfolded to cover a 3 mm x 12 mm area with respect to the TMB membrane 1 minute on the TMB membrane. After a while, the NaOCl solution was carefully removed with a paper towel The NaOCl solution was spotted on the TMB membrane and the sample spectrum was measured for 4 minutes Sample Spectrum 110 and Baseline Spectrum 120 ) Are all shown in FIG. 8.

Example 3

In this example, the same Ocean Optics spectrometer system as in Example 2 was used. The microscope slide holder strictly controlled the positioning of the glass slides. The incident optical fiber probe was directed to one side of the glass slide at an angle of about 45 ° with respect to the glass slide surface. About half of the incident light illuminated the white paper just below the glass slide and the other half illuminated the edge of the glass slide. The detection probe was also taken at an angle of about 45 ° and the distance from the probe to the slide was adjusted so that the amount of light did not saturate the spectrometer.

PHEMA membranes containing small amounts of red pigment were recovered from permanent red Sharpie® markers. The red pigment solution was spin coated onto a glass slide using a spinner modified from a magnetic stirrer as in Example 1, which had no speed control or readout. Spinner acceleration, final spin speed, and spinning duration were not controlled. Red pigment is used as internal absorbance standard. It has an absorption band centered at λ _max = 535 nm and does not overlap the absorption band of the TMB response response to chlorine (blue reactant, λ _max = 670 nm).

Before immersing the slides in NaOCl solution, the baseline spectra for TMB were measured. After soaking for 90 seconds in NaOCl solution, the glass slide was removed and held in a vertical position for 2 minutes to allow the solution to flow down the glass slide surface. Here, the sample spectra were recorded for 150 seconds after the glass slide was removed from the NaOCl solution.

All 11 slides were used to measure absorbance values at three different concentration levels of NaOCl solution according to the procedure described above. Slides 1-4 were independently immersed in 0.10 ppm solution, slides 5-7 were independently immersed in 0.25 ppm solution, and slides 8-11 were independently immersed in 0.50 ppm solution. Absorbance values at λ = 650 nm before and after reference correction are listed in Table 1 below. Note that after performing the reference correction according to Equation 1, the standard deviation for each concentration level is significantly reduced.

Four spectra from slides 8-11 and their corresponding baseline spectra are shown in FIG. 9.

All 11 spectra after reference correction according to equation 1 are shown in FIG. 10. FIG. 10 shows reducing errors and confirming the results listed in Table 1 by normalizing the results according to the internal absorbance standard as described by Equation 1. FIG.

11 shows a calibration curve confirming the linear relationship between absorbance level and concentration level as known in the art.

Several conclusions can be drawn from the results of this example.

1. Proper position control alone cannot guarantee the required precision for low absorbance measurements.

2. Correct the spectrum according to Equation 1 using an internal absorption standard to reduce errors caused by variations in experimental parameters such as glass slide dimensions, film quality, and incident beam angle.

3. Multiple-angle scattering induced absorbance is more sensitive than transmission absorbance. When compared with the transmission absorbance value at λ = 535 nm (0.014), the absorbance is increased by 10 times by the multi-angle scattering induction configuration of the present invention. Note that the absorbance can be further increased at longer wavelengths.

Example 4

The membrane used in this example contained a slightly lower concentration of the internal reference die as compared to the membrane used in Example 3. These membranes were prepared by the same procedure used in Example 3, but were prepared in different batches. Similarly, the experimental setup is identical to the setup used for Example 3 except that the slide position was tightly controlled by aligning the slide with respect to two vertical lines drawn with a Sharpie® marker.

The spectral responses before and after the reference correction along with the baseline spectral responses are shown in FIGS. 12 and 13, respectively. According to measurements derived without maintaining proper control of the glass slide position, it is clear that more error margin occurs in spite of the reference correction from the internal absorption standard. Nevertheless, the absorbance values of 0.177, 0.185, 0.209 at 650 nm were well controlled with the average values of 0.1790 ± 0.003 obtained from Example 5, although the slide position was not strictly controlled and the films were prepared in different batches and from different polymer solutions. Note that it is correct.

This consensus is clear, in particular in view of one object of the invention. That is, one-time test elements can provide quantitative determination of analyte concentrations without additional calibration steps.

Example 5

Sensor building

15 schematically illustrates an example handheld sensor system used for Example 5. FIG. Here, the basic sensing unit 150 is connected to a digital bus switch 152 (Texas Instruments, SN74CBTLV) and a computer 151 (Dataq CF2, a Dell Axiom Pocket PC equipped with a C-cubed limited data acquisition card). Is shown. The digital bus switch 152 allows a computer to turn on and off the LED 6 while providing DC power to the photodiode 8 and reading the output from the photodiode. Visual Basic®, a computer program, is developed to control and read sensor systems.

A perspective view of an exemplary sensing unit 150 used for Example 5 is shown in FIG. 16. Here, the sensing unit 150 may be described as including a combination of three subassemblies (Part A, Part B, Part C).

Part A includes elements 160, 161, 162. Part B includes elements 6, 8, 163, 164. Part C includes elements 18, 19, and 167.

In building part (A), remove the threaded portion of the 1/2 inch instant tube to tube adapter 161 and place the 1/4 inch compression fitting nut 162 onto the face of the modified adapter 161. Glue. A 4 inch long 1/2 OD stainless steel tube 160 is inserted onto the rubber O-ring / compression fitting 161C of the modified adapter to provide a light dense compartment.

In constructing part (B), the male portion of the 1/4 inch tube to pipe compression fitting 163 was removed and the thin polycarbonate sheet 164 painted in black on one side was modified. The openings of the modified fitting secured by epoxy adhesive to the fitting are separated as shown in FIG. 16. A 5mm bicolor LED 6 (LC LEDN500TGR4D) was adhered on the polycarbonate sheet. The focal path of the LED 6 is approximately parallel to the vertical center of the fitting 163. The photodiode 8 (ToasTSR257) was attached to the other side of the polycarbonate sheet so that the collection lens of the photodiode was offset from the fitting axis at an angle of about 45 ° as shown in FIG. After the construction described above, the LEDs and photodiodes are sealed in a 1 inch diameter PVC tube (not shown in FIG. 16).

In constructing part (C), an acrylic rod (0.25 inches in diameter and 3.20 inches in length) was coated with a PHEMA membrane containing chlorine sensitive reagent 18 as used in Example 3. The end section of the rod was painted with reflective white paint 19.

Measurement procedure

The measurement procedure used in Example 5 includes the following steps.

1. (a) Load acrylic rod 167 (part C) into extrusion fitting assemblies (parts A and B) and place stainless steel tube 160 into instant tube to pipe adapter 161. (b) Click on the button on the Pocket PC screen. (c) Visual Basic & commat: Green light and red light are turned on while a computer program sequentially turns on green light (525 nm) and red light (630 nm) and takes each reading (Go and Ro) from the photodiode.

2. (a) Remove the stainless steel tube 160 from the adapter 161 and soak the rod 167 in the sample solution for 60 seconds. (b) Take the rod out of solution and wipe off any remaining solution as appropriate. (c) The rods are dried for 2 minutes in the atmosphere.

3. (a) Place the stainless steel tube 160 back onto the adapter 161. (b) Click the appropriate button on the Pocket PC screen to read each output (G, R) from the photodiode. Note that both green and red lights are sequentially turned on.

4. Calculation of absorbance by Equation 2

Note that Equation 2 is mathematically equivalent to Equation 1. The results from these measurements are listed in Table 2 and plotted as calibration curves in FIG. 17.

While the foregoing specification has been presented to include the best mode of carrying out the invention as required by the patent bylaws, the invention is not limited to this best mode or other specific embodiments in the specification. The spirit of the invention is limited only by the exact and equivalent constructions that apply to the claims.

Claims (14)

In a system for measuring the analyte concentration of a chemical or biological material, a. With mounting adapter, b. A test element detachably mounted to the adapter, c. A reagent film fixed on the test element, the reagent film comprising at least one internal reference standard, d. At least one light source attached to the adapter and capable of stimulating a dual light response from the test element and the reagent film and capable of emitting a divergent light beam impinging on the surface with a reflection angle greater than a critical angle to the surface; , e. At least one photodetector attached to the adapter, capable of detecting the dual optical response and generating an electronic signal response indicative of the dual optical response; f. Electronic circuit means for processing, storing, and transmitting the electronic signal response and controlling the light source System comprising. The method of claim 1, Further comprising integrated clock means for enabling the collection of dynamic data from said dual optical response for a particular period of time; system. The method of claim 2, Further comprising integrated alarm means indicative of said period; system. The method of claim 2, The test element is a multisectional test element comprising a plurality of separation regions and a sensing region. system. The method of claim 4, wherein The multi-compartment test element is a perforated multi-compartment test element. system. 6. The method of claim 5, The multi-compartment test element comprises between 2 and 500 of the sensing areas. system. The method of claim 6, The sensing area is irreversible system. The method of claim 6, Some of the detection zones are reversible and some are irreversible system. In the method of measuring the analyte concentration of a chemical or biological material, a. Providing at least one internal reference standard to the reagent membrane, b. Immobilizing the layer of reagent film on a test element to provide a film coated test element; c. Emitting optical energy onto the film coated test element such that internal reflection and multi-angle scattering within the test element are stimulated to dual reference light response from the film coated test element; d. Exposing the film coated test element to a sample material for a specific period and removing the exposed test element from the material to provide a sample test element; e. Emitting light energy onto the sample test element such that a dual sample light response from the sample test element is stimulated; f. Collecting and processing the reference and sample optical response data to calculate an absorbance response; g. Detecting and quantifying analyte concentration in the material by utilizing the absorbance response ≪ / RTI > The method of claim 9, Collecting dynamic data from the absorbance response for a particular period of time; Way. 11. The method of claim 10, Analyzing the dynamic data to determine an initial slope, an intermediate slope, and a final slope of the absorbance response during the period; Way. The method of claim 9, The absorbance response is error corrected by normalizing the absorbance response using the internal reference standard. Way. 13. The method of claim 12, The normalization is performed according to the formula A _corrected = A _sample -A _baseline + (A _baseline _ _at _λ _reference -A _baseline _ _at _λ _sample ) Way. The method of claim 9, The membrane coated test element is a multi-compartment test element capable of providing a plurality of the absorbance responses, The plurality of absorbance responses are processed and multiplexed to detect and quantify a plurality of analyte concentrations in the material. Way.

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