69results about How to "Wide detection concentration range" patented technology

The invention relates to a synthesizing method of a functionalized AuNc (gold nanocluster) based on BSA (bovine serum albumin) and application. The synthesizing method is characterized in that HAuCl4 is used as a precursor of Au (copper) atom, the BSA is used as a reductant and a protectant, and BSA-AuNCs is synthesized by a one-pot synthesis method. The synthesizing method has the beneficial effects that the synthesizing method is simple, and the reaction conditions are wild; the synthesized fluorescent AuNc has the advantages of good biocompatibility and photostability, good fluorescent characteristics, high yield of quantum, good water solubility, non toxicity, little inference by outside and the like; the synthesized BSA-AuNCs has higher selectivity on Cu<2+>, and can be applied to the quantitative detection and analysis of Cu<2+>; the detection method is simple and quick, the sensitivity is high, the toxicity is avoided, and the real-time qualitative and quantative detection of Cu<2+> is realized.

The invention discloses a preparation method and application of a silicon-based spiny nanocone ordered array. The preparation method comprises the steps: preparing a tightly-arranged single-layer ordered PS sphere array on a silicon wafer substrate; heating the single-layer ordered PS sphere array on the silicon wafer substrate; then, carrying out etching by using a reactive ion etching method, and regulating an etching current at least once in the etching process; and then, after finishing the etching, removing the single-layer ordered PS sphere array on the silicon wafer substrate to preparethe silicon-based spiny nanocone ordered array. A layer of gold film is deposited on the surface of the silicon-based spiny nanocone ordered array serving as a template by using a physical depositionmethod to prepare a silicon-based spiny nanocone ordered array on which the gold film is deposited, and the silicon-based spiny nanocone ordered array can be directly used as a substrate material with surface-enhanced Raman effect. The preparation method is simple, convenient to operate, low in cost, economic and environment-friendly; and the prepared silicon-based spiny nanocone ordered array islarge in structure area, good in uniformity, clean in surface, high in sensitivity and good in detection property.

An analyzing and measuring method for chlorophyll a of phytoplankton in eutrophic water is a new method for extracting, analyzing and measuring the chlorophyll a of phytoplankton in eutrophic water and relates to the technical field of restoration of water environment in the environmental engineering. The method comprises the following steps of: filtering and freezing a collected water sample and then adding hot ethanol; after the water bathing and the ultrasonic treatment, extracting the water sample for a plurality of hours in dark, centrifuging the water sample, taking the supernatant and measuring the content of the chlorophyll in a water body by using the spectrophotometry. The invention has the advantages of simple and quick extraction and measurement of the sample, capability of extracting the chlorophyll in the phytoplankton to the most extent, high degree of extraction, low toxicity, good accuracy, low limit of detection and wide range of detection concentration; the problems that the traditional grinding method has high loss degree of chlorophyll and low extraction efficiency and the acetone extraction is toxic to human bodies to a certain extent are solved; and the invention is suitable for rapidly extracting and accurately measuring the chlorophyll of phytoplankton in the eutrophic water.

The invention relates to the technical field of chlorine dioxide disinfection sterilization, in particular to a method for evaluating a chlorine dioxide release rate. The method provided by the invention comprises the following steps: firstly forming a colorimetric card showing one-to-one correspondence between chlorine dioxide release rates and color spots, then detecting color spots of to-be-evaluated samples in the same test environment and comparing with the colorimetric card, thus the chlorine dioxide release rates of the to-be-evaluated samples can be directly read according to the colorimetric card. The method provided by the invention has the advantages that the to-be-evaluated samples only need to be placed in a test container for preset time after a color spot-release rate colorimetric card is formed, then chromogenic reaction is performed by using wet potassium iodide test paper, and reading is performed by comparing the colorimetric card, so that operation is simple and easy; and especially when the chlorine dioxide release rate of a to-be-evaluated sample needs to be tracked for a long time, only simple potassium iodide test paper chromogenic reaction and comparison with a pre-prepared color spot-release rate colorimetric card need to be performed, so that evaluation work is greatly simplified and evaluation efficiency is improved. The method provided by the invention is easy to operate, low in cost and quick in result and is applicable to popularization and application.

The invention relates to the technical field of electrochemical sensors and the field of electro-catalysis, in particular to a preparation method and application of a foam transition metal phosphide carrying noble metal. The preparation method comprises the following steps: putting a foam transition metal into a tubular annealing furnace, placing red phosphorus powder at an uptake, wherein under gas flow driving of protective gas, phosphorus steam can be in contact with a test sample and react with the test sample, thus generating a three-dimensional multihole transition metal phosphide carrier; by adopting a three-electrode system in which the foam transition metal phosphide, a Pt slice and a saturated calomel electrode are respectively used as a working electrode, an auxiliary electrode and a reference electrode, applying constant working voltage, and finally preparing a self-supporting three-dimensional foam transition metal phosphide carrying noble metal nano particle electrode which is used for performing enzyme-free detection on glucose and has high activity and low detection limit.

The invention discloses a preparation method of a silicon substrate array with nanometer gaps being controllable and application thereof. The preparation method comprises the steps that a silicon slice substrate single-layer polystyrene colloidal crystal array is prepared; etching is conducted on the silicon slice substrate single-layer polystyrene colloidal crystal array by adopting a reactive ion etching method, the single-layer polystyrene colloidal crystal array is removed after etching is completed, and a tapered silicon substrate array is prepared; and the tapered silicon substrate arrayis taken as a template, a layer of gold film with the thickness being 10-50nm is deposited on the surface of the template by adopting a physical deposition method, gold nanoballs are deposited and formed at the top of the tapered silicon substrate, the distances among the gold nanoballs are adjusted by controlling the deposition time, and the silicon substrate array with the nanometer gaps beingcontrollable is prepared by controlling the deposition time and adjusting the distances among the gold nanoballs. The silicon substrate array is large in structure area, clean on surface, high in sensitivity and good in detection performance, can directly serve as a substrate material which has long-term stability and a high-activity surface enhanced Raman effect, and can be used for conducting rapid trace detection on the concentration of saccharin sodium salt. The preparation method is simple, convenient to operate, low in cost and economical and environmentally friendly.

The invention relates to the technical field of liquor component detection, in particular to a method for simultaneous determination of lactic acid and acetic acid content in liquor fermented grains. The method includes: diluting fermented grains, performing extraction, conducting centrifugation, redilution and filtration, and finally loading the product to a liquid chromatogram for analysis. Through optimization of the fermented grain dosage, water adding dilution amount, extraction way, centrifugal condition, dilution condition of centrifuged supernatant, liquid phase analysis conditions and the like, a liquid chromatographic analysis technology based method for qualitative and quantitative determination of lactic acid and acetic acid in fermented grains is established. The method has the advantages of rapidity, simplicity and high sensitivity, and provides a way for simultaneous determination of lactic acid and acetic acid in liquor fermented grains.

The invention discloses a gold film covered high-density nano needle point array and application thereof. A preparation method of the gold film covered high-density nano needle point array comprises the following steps: preparing a glass substrate single-layer polystyrene colloidal crystal array; etching the glass substrate single-layer polystyrene colloidal crystal array by a reactive ion etching method; removing the single-layer polystyrene colloidal crystal array from the glass substrate to obtain a high-density nano needle point array; with the high-density nano needle point array as a template, depositing a layer of gold film with thickness of 10-50nm on the surface of the template by a physical deposition method to obtain a gold film covered high-density nano needle point array. The gold film covered high-density nano needle point array can be directly used as a substrate material of a surface-enhanced Raman scattering effect. The gold film covered high-density nano needle point array disclosed by the invention has the advantages of large structural area, high uniformity, clean surface and high detection sensitivity; moreover, the preparation method is simple and convenient to operate, low in cost and economical and environment-friendly.

The invention provides a composition for measuring peroxide content in solution or the content of a peroxide generated by reaction. The composition comprises a peroxidase, a buffer salt, a color-developing agent and two color stabilizers, wherein one color stabilizer has a higher reducing capacity than the color-developing agent, and the other color stabilizer has a reducing capacity which is between that of the color-developing agent and that of the first color stabilizer. The composition enlarges the test range of the tested materials and makes color-developing effect stable.

The invention provides an analysis method for determining potassium in potassium metavanadate and / or sodium in sodium metavanadate. The method comprises the following steps of: counteracting potassium metavanadate and / or sodium metavanadate so as to form a solution to be tested; preparing multiple standard solutions with different concentration values, wherein the standard solutions contain potassium and / or sodium and do not contain vanadium; sequentially determining the multiple standard solutions in a sequence that the concentration values are from low to high by using an inductively coupled plasma atomic emission spectrometer, and then drawing a calibration working curve; and determining potassium and / or sodium in the solution to be tested by using the inductively coupled plasma atomic emission spectrometer, and calculating the potassium content of the potassium metavanadate and / or the sodium content of the sodium metavanadate in combination with the calibration working curve. The method disclosed by the invention has the advantages of wide application, wide concentration detection range, strong anti-jamming capability, less man-made factors, convenient and rapid operation, short process, less steps, and excellent technical performance indexes such as accuracy, precision and recovery rate, and the like.

The present invention discloses an enzyme electrode and its producing method, which comprises: providing a substrate with a carbon surface; forming a gold surface on the carbon surface and thus forming an electrode; covalently bonding a mediator containing an aldehyde group to the electrode; and covalently bonding a glucose oxidase to the electrode.

The invention discloses a fluorescent aptamer probe based on Prussian blue nanoparticles as well as a preparation method and application of the fluorescent aptamer probe. The fluorescent aptamer probeis composed of Prussian blue nanoparticle complex modified FAM fluorophore aptamers. The preparation method comprises the following steps: incubating the Prussian blue nanoparticles and the aptamersmodified with the FAM fluorophore in an HEPEs buffer solution system in a dark place, and closing by adopting BSA, thereby obtaining the fluorescent aptamer probe. The fluorescent aptamer probe can beused for detecting various markers such as markers of tumor, breast cancer, blood glucose and Alzheimer's disease, has the advantages of strong signal, high specificity, high sensitivity, wide detection concentration range, good biological safety and the like, and is beneficial to popularization and application.

An economical and rapid type test pack for colorimetric determination of COD in a water body and a determination method are provided. The test pack and the method are characterized in that: an integrated agent solution and a set of standard colorimetric cards are adopted to establish the rapid and convenient method, determination of a sample is achieved by following three steps, namely a step of sampling, a step of digesting and a step of color matching, and a determination range is 0-150 mg / L. Only two agents are added in the whole process of the method. Operation is simple. The agents are common and easily available. The test pack and the method are capable of rapidly obtaining a determination result, free of use of any measurement instrument and low in determination cost, provide a novel manner for water COD determination, can be widely used in society after being developed into products, and further ensure water safety. The test pack and the method fill the gap that only laboratory standard determination methods are provided for water COD determination at present while no rapid potable colorimetric determination method is provided.

The invention discloses a preparation method of a glucosyl modified quantum dot fluorescent probe. The preparation method comprises: adopting D-glucose as a raw material, carrying out hydroxyl complete protection and terminal glycosylation, adding a N,N-dimethylformamide solution and potassium thioacetate to catalyze, removing the protection group through sodium methoxide / methanol to obtain mercapto derivatized glucose, and modifying the mercapto derivatized glucose on the surface of quantum dots through ligand exchange to obtain the glucosyl modified quantum dot fluorescent probe. According to the present invention, the prepared glucosyl modified quantum dot fluorescent probe is used for detecting the pesticide fenpropathrin content; and the glucosyl modified quantum dot fluorescent probe has the specific recognition ability of sugar and the special properties of quantum dots, and further has advantages of good water solubility and long stabilization time, and the preparation method has advantages of short synthesis route of the glucosyl modified body, simple synthesis operation, simple preparation method of the modified quantum dots, and rapid preparation.

The invention discloses a method for measuring depth and quality of plating of a galvanized plate through a glow discharge spectrometer and aims to provide a method for rapidly, accurately and efficiently measuring the depth and the quality of the plating of the galvanized plate. The method comprises steps as follows: an instrument is debugged, center positioning and curve calibration are performed, accordingly, the instrument is in the optimum state, a sample is cut into sample blocks with appropriate sizes, the surfaces of the taken sample blocks are flat and don't have defects, the sample is arranged in a spectrometer sample chamber after surface dirt is wiped and removed, intensity of spectral lines is measured, a changing curve of the intensity of each element with time is obtained, the curve is subjected to analysis and calculation, and the depth and the quality of the plating of the galvanized plate are obtained.

This invention discloses a high-efficiency liquid phase chromatography detection method for PDE-5 inhibitor in Chinese patent drug, health food and food. Diode array detector is adopted, and octadecylsilane chemically bonded silica is used as liquid phase chromatographic column of filling agent; the mobile phase is phosphoric acid triethylamine solution-methanol-acetonitrile system; the flow rate is 0.5 to 1.5 ml / min; the column temperature is 20 to 50 degrees centigrade; the pre-process of the sample uses acetonitrile or methanol for ultrasonic extraction; the sample is analyzed in the wavelength range from 200 mm to 400 mm. This invention has simple pre-process method, high accuracy, good specificity, short analysis cycle and wide detection concentration range; one analysis can detect eleven kinds of PDE-5 inhibitors; the invention is applied to qualitatively and quantitatively analyze PDE-5 inhibitor in Chinese patent drug, health food and food, which can greatly improve detection efficiency, save detection cost and meet the daily monitoring and detecting requirement.

The invention discloses a wide-concentration multi-component hazardous gas detector and an implementation method thereof, and solves the problems that a gas detector equipped by fire forces in the prior art often has false negative detection results, over-limit concentration and sensor poisoning conditions. The wide-concentration multi-component hazardous gas detector comprises a gas dilution sampling joint, a sensor integration module, an electrochemical sensor, an ADC circuit, an MCU single chip microcomputer, an audible and visual alarm, a 4-key keyboard module, an LED display module, an SD card data storage module, a power control and electric quantity display module, a high-performance lithium battery pack, a small air pump, a 433M signal transmission module and a remote command platform signal acquisition terminal. The implementation method provided by the invention is simple, smooth and efficient, can effectively prevent the poisoning and the misinformation of the electrochemical sensor, can detect various gases, and is wide in gas detection concentration range and accurate in detection result.

The invention relates to a preparation method and applications of a flower-like ferroferric oxide-molybdenum disulfide-manganese dioxide nano complex. The preparation method comprises the following steps: dispersing ferric chloride and ferric sulfide in deionized water, adding ammonia water, and aging to obtain ferroferric oxide; adding sodium molybdate and thiourea into deionized water, uniformlystirring, adding the ferroferric oxide, transferring into a high-pressure reaction kettle, and carrying out a reaction; centrifugally separating, cleaning with ethanol and deionized water, and dryingto obtain a ferroferric oxide-molybdenum disulfide finished product; dissolving a proper amount of the ferroferric oxide-molybdenum disulfide complex, manganese sulfate monohydrate and potassium permanganate into deionized water, uniformly stirring, transferring the mixture into a high-pressure reaction kettle, and carrying out a reaction; drying to obtain a flower-like ferroferric oxide-molybdenum disulfide-manganese dioxide finished product; and dispersing the flower-like ferroferric oxide-molybdenum disulfide-manganese dioxide nano-complex in a mixed solution of water, ethanol and perfluorosulfonic acid, and dropwisely coating the surface of a clean glassy carbon electrode with the dispersed flower-like ferroferric oxide-molybdenum disulfide-manganese dioxide nano-complex.

The invention discloses a kit for detecting immuno-gold synchronous scattering spectrum of human serum complement 3 and a use method thereof. The kit comprises three reagents, wherein the reagent 1 is a calibrator containing the frozen dry plasma protein reference serum of the complement 3, the reagent 2 contains 111.5-164.5mM of Na2HPO4, 17.5-45.0mM of citric acid solution and 50-70g / ml of PEG6000, and the reagent 3 contains gold-labeled goat anti-human C3 antibody and 0.03-0.06 g / L of PEG20000. The use method comprises the following steps: firstly preparing a C3 standard series, adding the reagent 1, reagent 2 and reagent 3 according to a defined ratio, performing constant volume process, incubating for 15min in a ultrasonic reactor, scanning the synchronous scattering spectrum with a fluorescence spectrophotometer to detect the synchronous scattering value, and calculating the C3 content according to the standard curve. The kit of the invention can be used to accurately and qualitatively detect the complement C3, be suitable for the clinical and scientific research analysis of complement 3 in samples such as serum and plasma, and have the advantages of convenient, fast and sensitive operation, low detection limit, wide linear range, simple phase separation process and low sample consumption.

The invention discloses a method for determining the content of all elements in a galvanized sheet substrate by a glow discharge spectrometer, so as to solve the problems that the operation of determination of all the elements in the galvanized sheet substrate in an existing method is complex, surface coating needs to be treated specially, more chemicals are used, and a process is long; the method disclosed by the invention is more quick, accurate and efficient to use; the method comprises the steps that an apparatus is debugged, centralized positioning and curve calibration are performed to achieve a best state of the apparatus, a sample needs to be cut into sample pieces, the selected sample pieces of which the surfaces need be smooth and defect-free, the sample pieces are arranged in a spectrometer sample room after the sample pieces are scrubbed to remove dirt on the surface, the spectral line intensity is determined so as to obtain changing curves of the intensity of all the elements along with the time, and analysis and calculation are performed on the curve to obtain the content of all the elements in the galvanized sheet substrate.

The invention provides a detection method of lactic acid in baijiu base liquor. The detection method comprises following steps: low temperature reduced pressure distillation is adopted for complete evaporation of a baijiu base liquor sample; a low concentration ethanol aqueous solution is added for redissolving of the evaporated sample; and then high performance liquid chromatography detection is carried out. According to the detection method, a simple pretreatment method is adopted; a high performance liquid chromatograph is used for direct sample injection; the content of lactic acid in baijiu base liquor can be obtained accurately; the detection method is rapid, is high in accuracy, and wide in detection concentration range; influences of compounds such as esters, other organic acids, and higher alcohols in baijiu base liquor can be eliminated; and the detection method is of important significance in scientific guidance on baijiu base liquor production.

The invention discloses a CRISPR / Cas12a-RCA electrochemical sensor detection system and application thereof. According to the present invention, the CRISPR / Cas12a-RCA electrochemical sensor detection system can be used for the detection of Escherichia coli O157: H7, has characteristics of simple operation and low cost, can accurately distinguish Escherichia coli O157: H7 from different bacteria, and has strong detection specificity; the detection concentration range is also wide, a good linear relation is achieved within the range of 10-107 CFU.mL <-1 >, the detection sensitivity is high, the lowest detection limit is 10 CFU.mL <-1 >, and the detection result is accurate and reliable. The detection method is not only suitable for detecting escherichia coli O157: H7 in food, but also has huge application potential in detection of other pathogenic bacteria or clinical diagnosis.

The invention relates to a preparation method and application of a rod-like nickel disulfide-molybdenum disulfide nano composite. The preparation method comprises the following steps: dispersing nickel nitrate hexahydrate and sodium thiosulfate pentahydrate in deionized water, adding hexadecyl trimethyl ammonium bromide, stirring, adding ethylenediamine, uniformly stirring, transferring into a high-pressure reaction kettle for reaction, centrifugally separating, cleaning with ethanol and deionized water, drying, calcining in a tubular furnace to obtain nickel disulfide, weighing ammonium tetrathiomolybdate and nickel disulfide, adding ammonium tetrathiomolybdate and nickel disulfide into an N,N-dimethylformamide solution, adding hydrazine hydrate, carrying out ultrasonic treatment, transferring the mixed solution into a high-pressure reaction kettle for reaction, centrifugally separating, cleaning with ethanol and deionized water, drying to obtain a rod-like nickel disulfide-molybdenumdisulfide nano-composite, dispersing the composite into a mixed solution of water, ethanol and perfluorosulfonic acid, dropwise coating on the surface of a clean glassy carbon electrode and naturallyair-drying to form a three-electrode system together with a platinum wire and a saturated calomel electrode, wherein the clean glassy carbon electrode is used as a working electrode.

An economical and rapid type test pack for colorimetric determination of sulfides in a water body and a determination method are provided. The test pack and the method are characterized in that: an integrated agent kit and a set of standard colorimetric cards are adopted to establish the convenient method, determination of a sample is achieved by following three simple steps, namely a step of performing a pre-chromogenic reaction, a step of performing a chromogenic reaction, and a step of comparing with the prefabricated standard colorimetric cards, and a determination range is 0-0.70 mg / L. Only two agents are added in the whole operation process. Operation is simple. The agents are cheap and easily available. The test pack and the method are capable of rapidly obtaining a determination result, free of use of any measurement instrument and low in determination cost, can be widely used in society after being developed into products, and further ensure water safety. The test pack and the method fill the gap that only laboratory standard determination methods are provided for water sulfide determination at present while no rapid potable colorimetric determination method is provided.

The invention discloses a method for visually and specifically detecting biomacromolecules based on effective assembly of aptamers and gold nanoparticles, which comprises the following steps: inoculating a nanogold solution and a target biomacromolecule aptamer together to obtain an aptamer@AuNPs compound solution; respectively inoculating an aptamer@AuNPs compound solution with a series of standard target biomacromolecule solutions with different concentrations, adding a NaCl solution, controlling the pH value of the solution system, and establishing a concentration and color comparison card according to the relationship between the concentration and color development of the standard target biomacromolecule solutions; and after the standard target biomacromolecule solution is replaced with the standard target biomacromolecule solution to be detected for reaction, determining the concentration range of the target biomacromolecule solution to be detected according to the color displayed by the NaCl solution in the concentration and color comparison card. The method has the characteristics of high specificity, high sensitivity, wide detection range and the like; and visual detection of biomacromolecules can be realized.

The invention relates to a detection method of surface fluoride ions of a non-ferrous metal material. According to the method, non-ferrous metal is heated through high temperature, the surface fluoride ions of the non-ferrous metal are enabled to be separated through surface hydrolyzation, a condensing method is combined to collect fluoride ion condensate, xylenol orange is used as a chromogenic reagent, and ultraviolet-visible spectrophotometry is used to determine the surface fluoride ion content of the non-ferrous metal. The detection method of the invention has the characteristics of obvious color development, stable absorbance, obvious working curve dominant-features, a low sample detection limit, a large detection concentration range and the like, can realize measurement and determination of a fluoride ion content of 0.5-50mg, and is suitable for use in detection of surface fluoride ions of non-ferrous materials such as titanium and zirconium.

The invention discloses an identification and evaluation method of sterilization effect of a disinfectant, and belongs to the technical field of measurement or detection of microorganisms. The methodcomprises the following steps: (1) marking 8 testing tubes; (2) adding physiological saline: No. 1- No. 5: 9 mL of physiological saline and No. 6- No. 8: 10 mL of physiological saline, in a 20 + / - 2 DEG C water bath; (3) adding 1 mL of bacterial solution into the No. 1 testing tube, taking 1 mL of solution from the No. 1 testing tube and transferring into the No. 2 testing tube, taking 1 mL of solution from the No. 2 testing tube and transferring into the No. 3-No. 5 testing tubes, and then the solution in the No. 6-No. 8 testing tubes is poured into the No. 3-No. 5 testing tubes, respectivelyand taking 10 mL of solution from the No. 3-No. 5 testing tubes and transferring into the No. 6-No. 8 testing tubes, respectively; (4) adding a disinfectant into the No. 3-No. 7 testing tubes as experimental samples; and the No. 8 testing tube without adding any disinfectant as control sample; (5) conducting qualitative and quantitative culture; (6) observing the results and calculating the bacteriostatic rate. The detection method of the invention can detect any concentration of disinfectant, can simultaneously detect the bacteriostatic effect of two or more batches of disinfectant, has a wide detection concentration range, and can save time.

The invention discloses a p-benzoquinone detection and analysis method based on a photoelectric cathode sensor, which comprises the following steps: constructing a photoelectrochemical three-electrode system comprising a xenon lamp light source, a Cu3SnS4 / ZnO / ITO working electrode, a platinum wire counter electrode and an Ag / AgCl reference electrode; the method comprises the following steps: adding p-benzoquinone solutions with different concentrations into a photoelectrochemical three-electrode system under the condition of switching on, and drawing I-T curves of the three-electrode system in the p-benzoquinone solutions with different concentrations under a set voltage range; and obtaining a p-benzoquinone quantitative detection standard curve according to the I-T curve, and carrying out trace analysis on an actual water sample. The photoelectric cathode sensor disclosed by the invention not only is low in preparation cost and convenient to operate, but also has the characteristics of high sensitivity and wide detection range on detection and analysis of p-benzoquinone, and can be applied to trace analysis of p-benzoquinone in an actual water sample.

The invention provides a composition for measuring peroxide content in solution or the content of a peroxide generated by reaction. The composition comprises a peroxidase, a buffer salt, a color-developing agent and two color stabilizers, wherein one color stabilizer has a higher reducing capacity than the color-developing agent, and the other color stabilizer has a reducing capacity which is between that of the color-developing agent and that of the first color stabilizer. The composition enlarges the test range of the tested materials and makes color-developing effect stable.