JP2018021902A - Plasma spectroscopic analysis method and plasma spectroscopy analyzer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasma spectroscopic analysis method which has a high analysis sensitivity and does not make a wrong analysis of a sample less frequently.SOLUTION: The plasma spectroscopic analysis method according to the present invention includes: a voltage application step of applying a voltage to a pair of electrodes under the presence of a sample; an enriching step of enriching an analysis target in the sample near at least one of the electrodes by the voltage application; and a detection step of generating plasma by applying a voltage to the pair of electrodes and detecting light emission of the analysis target caused by the plasma. In at least some intervals of the enriching step when the voltage is being applied, a current between the pair of electrodes is constant.SELECTED DRAWING: Figure 2

Description

  The present disclosure relates to a plasma spectroscopic analysis method and a plasma spectroscopic analysis apparatus.

  As a method for analyzing an analysis object in a sample, an analysis method using plasma emission is known. Regarding the analysis method, Patent Document 1 discloses a method of analyzing a sample using a high-frequency plasma mass spectrometer. Patent Documents 2 and 3 disclose a method of analyzing a sample by using a plasma generator having a narrow portion, generating plasma in the sample, and analyzing plasma emission. Further, Patent Documents 4 and 5 disclose a method of analyzing a sample by generating plasma in a liquid sample and analyzing plasma emission.

  However, the method of Patent Document 1 has a problem in that the analysis result changes due to mixing of other substances unless appropriate pretreatment is performed. Further, in the methods of Patent Documents 2 and 3, when a sample with contaminants is used, and when foreign matter or the like is mixed during pretreatment to reduce the amount of the sample liquid, the contaminants and the foreign matter are narrowed. There was a problem that it could not be measured due to clogging. Furthermore, the methods of Patent Documents 4 and 5 have a problem that analysis sensitivity is low.

JP 2009-128315 A JP 2011-180045 A JP 2012-185064 A International Publication No. 2006/059808 International Publication No. 2011/099247

  Therefore, the present disclosure provides a plasma spectroscopic analysis method that has high analysis sensitivity and suppresses generation of an analysis error during sample analysis, and a plasma spectroscopic analysis device for use in the plasma spectroscopic analysis method. Objective.

In order to solve the above problems, a plasma spectroscopic analysis method of the present disclosure (hereinafter also referred to as “analysis method”) includes:
A voltage application step of applying a voltage to a pair of electrodes in the presence of the sample, and a concentration step of concentrating the analyte in the sample in the vicinity of at least one electrode by the voltage application; and the pair of electrodes Generating a plasma by applying a voltage to, and detecting a light emission of the analyte generated by the plasma,
The current between the pair of electrodes at the time of voltage application in at least a part of the concentration step is constant.

The plasma spectroscopic analyzer (hereinafter also referred to as “analyzer”) of the present disclosure is
Including a pair of electrodes, a container, a light receiving part, and a constant current part,
The container includes a translucent part,
The pair of electrodes are disposed in the container,
Outside the container, a light receiving unit capable of receiving light emitted from the analyte generated by voltage application to the pair of electrodes through the translucent unit is disposed,
The constant current portion is connected to the pair of electrodes, and when a voltage is applied to the pair of electrodes, the current between the pair of electrodes is constant,
The plasma spectral analysis method of the present disclosure is used.

  According to the plasma spectroscopic analysis method of the present disclosure, analysis sensitivity is high and, for example, generation of analysis errors during sample analysis can be suppressed.

FIG. 1A shows a schematic perspective view of the analyzer in the embodiment of the analyzer of the present disclosure, and FIG. 1B is a schematic cross-sectional view seen from the II direction of FIG. FIG. 2 is a graph showing the correlation between the lead concentration and the count value in Example 1. FIG. 3 is a graph showing count values in each cycle in the second embodiment.

<Plasma spectroscopy method>
As described above, the plasma spectroscopic analysis method of the present disclosure includes a voltage application step of applying a voltage to a pair of electrodes in the presence of a sample, and the voltage application includes a voltage in the sample in the vicinity of at least one electrode. At least a part of the concentration step, including a concentration step for concentrating the analysis target, and a detection step for generating a plasma by applying a voltage to the pair of electrodes and detecting light emission of the analysis target generated by the plasma The current between the pair of electrodes at the time of voltage application during the period is constant. The analysis method of the present disclosure includes the concentration step and the detection step, and is characterized in that a current between a pair of electrodes at the time of voltage application in at least a part of the concentration step is constant, and other steps The conditions are not particularly limited.

  In general, in order to efficiently analyze an analyte in a sample, for example, the sample is subjected to a pretreatment for reducing the total volume (total liquid amount) of the sample by concentration, The amount of analyte per unit volume was increased in the total volume of the sample. In contrast, the present inventors concentrate the analyte in the sample in the vicinity of at least one electrode by applying a voltage to the pair of electrodes in the presence of the sample, that is, locally in the vicinity of the electrode. And the generation of plasma on the electrode side on which the analysis object is accumulated, whereby the analysis object having a locally high concentration can be efficiently analyzed. A new analysis method that does not require treatment was established. However, when this analysis method is used, the analysis results sometimes vary among a plurality of samples including the same concentration of the analyte. Due to the diligent research of the present inventors, for example, in the sample coexisting with an analyte such as lead and a specific coexisting substance of ethylenediaminetetraacetic acid (EDTA) which is a chelating agent, an error occurs in the analysis result. It has been found that the analysis results vary among the plurality of samples, that is, the occurrence of an analysis error due to the presence of the specific coexisting substance causes the variation in the analysis results between the plurality of samples. And although the mechanism is unknown, the present inventors make the current specified between the pair of electrodes constant during voltage application in at least a part of the concentration step, that is, by making the current constant. The present inventors have found that the generation of analysis errors can be suppressed even in the presence of coexisting substances, and have completed the analysis method of the present disclosure. Therefore, according to the analysis method of the present disclosure, for example, it is possible to suppress the generation of analysis errors during sample analysis. Moreover, since the analysis method of this indication can suppress generation | occurrence | production of the analysis error at the time of sample analysis, it can analyze the said analysis object with high precision irrespective of the kind of sample and the kind of said analysis object, for example. Furthermore, as described above, the analysis method of the present disclosure can efficiently analyze an analyte having a locally high concentration without performing the pretreatment on the sample, for example. The sample can be analyzed with

  In the analysis method of the present disclosure, the sample is, for example, a specimen. The specimen may be a liquid specimen or a solid specimen. As the sample, for example, an undiluted solution of the sample may be used as a liquid sample as it is, or a diluted solution suspended, dispersed or dissolved in the sample as a medium may be used as a liquid sample. When the sample is solid, for example, it is preferable to use a diluted solution in which the sample is suspended, dispersed, or dissolved in the medium as a liquid sample. The medium is not particularly limited, and examples thereof include water and a buffer solution. Examples of the specimen include biological specimens (samples), environmental specimens (samples), metals, chemical substances, pharmaceuticals, and the like. The biological sample is not particularly limited, and examples thereof include urine, blood, hair, saliva, sweat, and nails. Examples of the blood sample include red blood cells, whole blood, serum, plasma and the like. Examples of the living body include humans, non-human animals, plants, and the like, and examples of the non-human animals include mammals other than humans, seafood, and the like. The environment-derived specimen is not particularly limited, and examples thereof include food, water, soil, air, and air. Examples of the food include fresh food and processed food. Examples of the water include drinking water, groundwater, river water, seawater, and domestic wastewater. The sample preferably includes, for example, the metal and a chelating agent described later, and the metal is the analysis object.

  The analysis object is not particularly limited, and examples thereof include metals and chemical substances. The metal is not particularly limited. For example, aluminum (Al), antimony (Sb), arsenic (As), barium (Ba), beryllium (Be), bismuth (Bi), cadmium (Cd), cesium (Cs) , Gadolinium (Gd), lead (Pb), mercury (Hg), nickel (Ni), palladium (Pd), platinum (Pt), tellurium (Te), thallium (Tl), thorium (Th), tin (Sn) , Metals such as tungsten (W) and uranium (U). Examples of the chemical substance include reagents, agricultural chemicals, and cosmetics. The analysis object may be one type or two or more types, for example.

  When the analysis object is a metal, the sample may include, for example, a reagent for separating the metal in the specimen. Examples of the reagent include chelating agents and masking agents. Examples of the chelating agent include dithizone, thiopronin, meso-2,3-dimercaptosuccinic acid (DMSA), sodium 2,3-dimercapto-1-propanesulfonate (DMPS), ethylenediaminetetraacetic acid (EDTA), nitrilotri Examples include acetic acid (NTA), ethylenediamine-N, N′-disuccinic acid (EDDS), α-lipoic acid, and the like. In the present disclosure, “masking” means inactivating the reactivity of the SH group, and can be performed, for example, by chemical modification of the SH group. Examples of the masking agent include maleimide, N-methylmaleimide, N-ethylmaleimide, N-phenylmaleimide, maleimidopropionic acid, iodoacetamide, iodoacetic acid and the like.

  The sample may be, for example, a sample with adjusted pH (hereinafter also referred to as “pH adjusted sample”). The pH of the pH adjusted sample is not particularly limited. The method for adjusting the pH of the sample is not particularly limited, and for example, a pH adjusting reagent such as an alkaline reagent or an acidic reagent can be used.

  Examples of the alkaline reagent include alkali and an aqueous solution thereof. The alkali is not particularly limited, and examples thereof include sodium hydroxide, lithium hydroxide, potassium hydroxide, and ammonia. Examples of the aqueous alkali solution include those obtained by diluting an alkali with water or a buffer solution. In the aqueous alkali solution, the concentration of the alkali is not particularly limited, and is, for example, 0.01 mol / L or more and 5 mol / L or less.

  Examples of the acidic reagent include acids and aqueous solutions thereof. The acid is not particularly limited, and examples thereof include hydrochloric acid, sulfuric acid, acetic acid, boric acid, phosphoric acid, citric acid, malic acid, succinic acid, and nitric acid. Examples of the acid aqueous solution include an acid diluted with water or a buffer. In the acid aqueous solution, the acid concentration is not particularly limited, and is, for example, 0.01 mol / L or more and 5 mol / L or less.

  The electrode is not particularly limited, and examples thereof include a solid electrode, and specific examples include a rod electrode and a spherical electrode. The material of the electrode is not particularly limited as long as it is a solid conductive material, and can be appropriately determined according to, for example, the type of the analysis object. The electrode material may be, for example, a non-metal, a metal, or a mixture thereof. When the material of the electrode includes a nonmetal, the material of the electrode may include, for example, one type of nonmetal or two or more types of nonmetal. Examples of the nonmetal include carbon. When the material of the electrode includes a metal, the material of the electrode may include, for example, one type of metal or two or more types of metal. Examples of the metal include gold, platinum, copper, zinc, tin, nickel, palladium, titanium, molybdenum, chromium, and iron. When the electrode material includes two or more kinds of metals, the electrode material may be an alloy. Examples of the alloy include brass, steel, Inconel (registered trademark), nichrome, and stainless steel. The pair of electrodes may be made of the same material or different materials, for example.

  The size of the electrode is not particularly limited, and may be a size that can come into contact with the sample, for example. When the electrode is a rod electrode, the diameter of the electrode is preferably 0.02 mm or more and 50 mm or less, and more preferably 0.05 mm or more and 5 mm or less. For example, the length of the electrode is preferably 0.1 mm or more and 200 mm or less, and more preferably 0.3 mm or more and 50 mm or less.

  As described above, the concentration step includes a voltage application step of applying a voltage to a pair of electrodes in the presence of the sample, and the analyte in the sample is placed near at least one of the electrodes by the voltage application. This is a concentration step, and the current between the pair of electrodes is constant during voltage application in at least a part of the concentration step. The pair of electrodes are in contact (wetted) with the sample, for example. In the concentration step, “concentrate the analyte in the sample in the vicinity of the electrode” means to electrically attract the analyte in the sample in the vicinity of the electrode. The range in the vicinity of the electrode is not particularly limited, and examples thereof include a range in which plasma is generated in a detection step described later. In the present disclosure, the vicinity of the electrode includes, for example, a portion on the electrode, that is, a portion in contact with the electrode.

In the concentration step, “the current between the pair of electrodes is constant” means that the current between the pair of electrodes is a constant current. In the present disclosure, the “constant current” or “constant current” includes a case where the current value between the electrodes is substantially constant. When the current value is substantially constant, even if the current value varies with time from the set current value, the current value (A _c ) between the electrodes becomes equal to the set current value (A _S ) Within a range of ± 20% (0.8 × A _S ≦ A _c ≦ 1.2 × A _S ). For example, when the current value (A _c ) between the electrodes is maintained within the range of the set current value ± 10% (0.9 × A _S ≦ A _c ≦ 1.1 × A _S ) or set When the current value is maintained within a range of ± 5% (0.95 × A _S ≦ A _c ≦ 1.05 × A _S ), it can be said that the current is “constant” or “constant current”. For the set current value, for example, the description of the current between a pair of electrodes described later can be used.

  In the analysis method of the present disclosure, when the current between the pair of electrodes at the time of voltage application in at least a part of the concentration step is constant, generation of an analysis error during sample analysis can be suppressed. For example, when a sample containing a coexisting substance (for example, EDTA) and a sample not containing the coexisting substance are analyzed for an analyte (for example, Pb) having the same concentration by the analysis method of the present disclosure, the coexisting substance is used. It is possible to suppress a difference (error) between the measured value of the amount of the analyte in the sample containing the sample and the measured value of the amount of the analyte in the sample not containing the coexisting substance. Specifically, for example, the error can be suppressed to a range within ± 15%, preferably within ± 10%, more preferably within ± 5% with respect to the reference value. The reference value can be appropriately set by a known method.

  In the concentration step, for example, a part of the analysis object may be concentrated near the electrode, or the entire analysis object may be concentrated near the electrode.

  In the concentration step, it is preferable that the charge condition of the electrode is set so that the analysis target is concentrated on the electrode used for detection of the analysis target, that is, the electrode where plasma is generated, in the detection step described later. . The charge condition is not particularly limited. For example, when the analysis object has a positive charge, the charge condition may be set so that the electrode generating the plasma has a negative charge. For example, when the analysis object has a negative charge, the charge condition may be set so that the electrode generating the plasma has a positive charge.

  The concentration of the analyte can be adjusted by voltage, for example. For this reason, those skilled in the art can appropriately set the voltage at which the concentration occurs (hereinafter also referred to as “concentration voltage”). The concentration voltage may be, for example, 1 mV or more, or 400 mV or more. The upper limit of the concentration voltage is not particularly limited, and may be 1000 V or less, for example. The concentration voltage may be, for example, the same voltage throughout the concentration process or may vary during the concentration process. Further, the concentration voltage may be a voltage at which plasma is not generated, for example.

  The time for applying the concentration voltage (hereinafter also referred to as “application time” in the concentration step) is not particularly limited, and can be set as appropriate according to the concentration voltage. The time for applying the concentration voltage is, for example, preferably 0.2 minutes or more and 40 minutes or less, and more preferably 1 minute or more and 5 minutes or less. The voltage application to the pair of electrodes may be applied continuously or discontinuously, for example. Examples of the non-continuous application include pulse application. When the voltage application is discontinuous, the time for applying the concentrated voltage may be defined as the total time of applying the concentrated voltage, and the time for applying the concentrated voltage and the time for applying the concentrated voltage It may be defined as the total time with the time when the concentration voltage is not applied.

  In the analysis method of the present disclosure, the current between the pair of electrodes is constant during voltage application in at least a part of the concentration step. The period during which the current between the pair of electrodes is constant is preferably 50% or more, more preferably 70% or more with respect to the total time of applying the concentration voltage in the concentration step, It is more preferably 80% or more, particularly preferably 90% or more, and extremely preferably 100%.

  The voltage can be applied to the electrodes by a voltage applying means. The voltage application means is not particularly limited, and for example, it is sufficient if a voltage can be applied so that the current between the pair of electrodes is constant, and a voltage device or the like can be used as a known means.

  In the concentration step, the current between the pair of electrodes is, for example, preferably 0.01 mA or more and 200 mA or less, more preferably 10 mA or more and 60 mA or less, and further preferably 10 mA or more and 40 mA or less. Particularly preferably, it may be set to 10 mA, 20 mA, or 40 mA.

  In the concentration step, the voltage application to the pair of electrodes is preferably a non-continuous application because the analysis error can be further suppressed, for example. When the voltage application to the pair of electrodes is discontinuous application, the concentration step includes, for example, a voltage application step for applying a voltage to the pair of electrodes and a voltage for not applying a voltage to the pair of electrodes. Non-application process. In this case, the current between the pair of electrodes is constant during at least a part of the voltage application process.

  In the voltage application step, for example, the analyte in the sample is concentrated near at least one of the electrodes by applying a voltage to the pair of electrodes. For this reason, in the voltage application step, in the detection step described later, the charge condition of the electrode is set so that the analysis target is concentrated on the electrode used for detection of the analysis target, that is, the electrode where plasma is generated. It is preferable to do. In the voltage application step, the description of the concentration voltage described above can be used as the voltage applied to the pair of electrodes, for example. In the voltage application step, the current between the pair of electrodes is, for example, preferably 0.01 mA or more and 200 mA or less, more preferably 10 mA or more and 60 mA or less, and more preferably 10 mA or more and 40 mA or less. Further preferred. Particularly preferably, it may be set to 10 mA, 20 mA, or 40 mA.

The voltage applying step may be performed once or a plurality of times, for example.
When the voltage application step is performed a plurality of times, the current between the pair of electrodes is constant in at least a part of the period of at least one voltage application step. Preferably, the current between the pair of electrodes is constant throughout at least one voltage application step. The current values between the pair of electrodes in each voltage application step may be the same or different, and are preferably the same. More preferably, the current between the pair of electrodes during voltage application is constant (constant current) and has the same current value over a plurality of voltage application steps.

  In the voltage non-application step, voltage application to the pair of electrodes is not performed. For this reason, in the voltage non-application step, for example, the analyte does not concentrate near at least one of the electrodes. In the voltage non-application step, a voltage applied to the pair of electrodes is, for example, 0V. In the voltage application step, the current between the pair of electrodes can be set to 0 mA, for example. Examples of the voltage and current applied to the pair of electrodes in the voltage non-application step are, for example, examples of the voltage and current applied to the electrodes from outside the electrodes. For this reason, between the pair of electrodes, for example, a potential difference based on the material of the electrode, the type of sample, and the state of the sample may occur.

  The voltage non-application step may be performed once or a plurality of times, for example. Further, the voltage non-application step may be performed, for example, the same number of times as the voltage application step or a different number of times, but the former is preferable.

  The adjustment between the voltage application step and the voltage non-application step can be performed, for example, by adjusting the voltage to be applied. Examples of the adjustment of the applied voltage include a method of switching an electric circuit between a closed circuit and an open circuit.

  When the electric circuit is switched between a closed circuit and an open circuit, for example, the voltage application step and the voltage non-application step are alternately performed by switching the electric circuit between a closed circuit and an open circuit. The state of the closed circuit is the voltage application step, and a voltage can be applied to the pair of electrodes by making the electric circuit a closed circuit. Further, the state of the open circuit is the voltage non-application step, and by setting the open circuit, the voltage can be non-applied, that is, the voltage can be 0 volts (V). The voltage of the closed circuit is the voltage of the voltage application process, that is, the concentrated voltage, the voltage of the open circuit, that is, 0 V is the voltage of the voltage non-application process, and the voltage is applied to the pair of electrodes. Not. The voltage of the closed circuit is not particularly limited, and for example, the illustration of the concentrated voltage can be used.

  In the concentration step, when the repetition of performing the voltage application step and the voltage non-application step once is one set, the time for the one set is not particularly limited. Hereinafter, the one set time is also referred to as an application cycle. The lower limit of the application period is, for example, preferably 250 msec or more, more preferably 1000 msec or more, and more preferably 2000 msec or more, since analysis sensitivity is further improved, and 3000 msec. The above is particularly preferable. Further, the upper limit of the application period is, for example, preferably 600000 msec or less, more preferably 64000 msec or less, and further preferably 10000 msec or less. In addition, the range of the application period is, for example, preferably from 250 msec to 600000 msec, more preferably from 1000 msec to 600000 msec, further preferably from 2000 msec to 600000 msec, and 2000 m It is particularly preferably from 2 to 64000 ms, and very preferably from 2000 to 10000 ms.

  In the concentration step, when the voltage application step and the voltage non-application step are repeated once each as one set, the time of the voltage non-application step in the one set time is not particularly limited. Hereinafter, the time of the voltage non-application process is also referred to as non-application time. The lower limit of the non-application time is preferably, for example, 125 msec or more, more preferably 1000 msec or more, and further preferably 1500 msec or more. Further, the upper limit of the non-application time is, for example, preferably 300000 msec or less, more preferably 32000 msec or less, and further preferably 10,000 msec or less. The range of the non-application time is, for example, preferably 125 msec or more and 300000 msec, more preferably 1000 msec or more and 300000 msec or less, further preferably 1500 msec or more and 300000 msec or less, and more preferably 1500 msec. More preferably, it is 10000 milliseconds or less.

  In the concentration step, when the repetition of performing the voltage application step and the voltage non-application step once is made one set, the ratio of the time of the voltage application step to the one set time is not particularly limited. Hereinafter, the ratio is also referred to as duty. The lower limit of the duty is, for example, preferably 1% or more, more preferably 25% or more, and further preferably 50% or more. For example, the upper limit of Duty is preferably less than 100%, more preferably 85% or less, and even more preferably 50% or less. The duty range is, for example, preferably 1% or more and less than 100%, more preferably 1% or more and 99% or less, further preferably 15% or more and 85% or less, and 45% or more and 55%. It is particularly preferred that For example, the duty is preferably 50%.

  In the concentration step, the number of repetitions of the voltage application step and the voltage non-application step is not particularly limited, and is, for example, 2 to 9600 times, preferably 3 to 5 times.

Regarding the concentration step, conditions per one set of the voltage application step and the voltage non-application step are exemplified below, but the present invention is not limited to this.
Application cycle: 250 msec or more and 600000 msec or less Non-application time: 125 msec or more and 300000 msec or less Duty: 1% or more and less than 100% Current in voltage application process: 0.01 mA or more and 200 mA or less Current in voltage non-application process: 0 mA

  As described above, in the detection step, plasma is generated by applying a voltage to the pair of electrodes, and light emission of the analysis object generated by the plasma is detected.

  The detection step may be performed continuously with the concentration step or may be performed discontinuously. In the former case, the detection step is performed simultaneously with the end of the concentration step. In the latter case, the detection step is performed within a predetermined time after the end of the concentration step. The predetermined time is, for example, 0.001 to 1000 seconds, preferably 1 to 10 seconds after the concentration step.

  In the detection step, “to generate plasma” means to substantially generate plasma. Specifically, in detection of plasma emission, it means generation of plasma that exhibits substantially detectable light emission. To do. As a specific example, it can be said that plasma is generated when plasma emission can be detected by a plasma emission detector.

  Substantial plasma generation can be adjusted, for example, by voltage. For this reason, those skilled in the art can appropriately set a voltage (hereinafter, also referred to as “plasma voltage”) for generating plasma exhibiting substantially detectable light emission. The plasma voltage is, for example, 10 V or higher, preferably 100 V or higher. The upper limit of the plasma voltage is not particularly limited, and may be 1000 V or less, for example. The voltage generated by the plasma is, for example, a voltage that is relatively higher than the voltage at which the concentration occurs. For this reason, it is preferable that the plasma voltage is higher than the concentrated voltage. The plasma voltage may be, for example, the same voltage throughout the detection process or may vary during the detection process.

  The time for applying the plasma voltage (hereinafter also referred to as “application time” in the detection step) is not particularly limited, and can be appropriately set according to the plasma voltage. The time for applying the plasma voltage is preferably, for example, 0.001 seconds or more and 0.02 seconds or less, and more preferably 0.001 seconds or more and 0.01 seconds or less. The voltage application to the pair of electrodes may be applied continuously or discontinuously, for example. Examples of the non-continuous application include pulse application. When the voltage application is discontinuous, the time during which the plasma voltage is applied may be defined as, for example, the time during which the plasma voltage is applied once. It may be defined as the total time, or may be defined as the total time of the time during which the plasma voltage is applied and the time during which the plasma voltage is not applied.

In the detection step, the electrode from which the plasma is generated can be adjusted, for example, by setting the wetted areas of the pair of electrodes to different wetted areas. Specifically, plasma can be generated in the former by making the wetted area of one electrode smaller than the wetted area of the other electrode. For this reason, in the present disclosure, the pair of electrodes is a pair of electrodes having different liquid contact areas with the sample, and an electrode having a small liquid contact area with the sample of the pair of electrodes is generated by plasma generation. The electrode is preferably used for analyzing the analysis object. When wetted area of the pair of electrodes is different, the difference between the wetted area of the pair of electrodes, for example, it is preferably at 0.001 cm ² or more 300 cm ² or less, it is 1 cm ² or more 10 cm ² or less More preferred. In the present disclosure, the “wetted area” means an area in contact with the sample. The method for adjusting the liquid contact area is not particularly limited. For example, the electrode immersed in the sample has a different length, and the electrode in contact with the sample is covered with an insulating material. Etc. The insulating material is not particularly limited, and examples thereof include resin, silicone, glass, paper, ceramics, and rubber. Examples of the resin include polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyethylene terephthalate, polymethacrylate, polyamide, saturated polyester resin, acrylic resin, polybutylene terephthalate (PBT), polyether ether ketone (PEEK), polymethylpentene ( Examples thereof include thermoplastic resins such as registered trademark TPX), epoxy resins such as urea resin, melamine resin, phenol resin and fluororesin glass epoxy, and thermosetting resins such as unsaturated polyester resin. Examples of the silicone include polydimethylsiloxane.

  In the detection step, the light emission of the generated plasma may be detected, for example, continuously or discontinuously. Examples of the light emission detection include detection of the presence or absence of light emission, detection of the intensity of light emission, detection of a specific wavelength, detection of a spectrum, and the like. The detection of the specific wavelength includes, for example, detection of a specific wavelength that the analysis object emits during plasma emission. The light emission detection method is not particularly limited, and for example, a known optical measurement device such as a CCD (Charge Coupled Device) or a spectroscope can be used.

  The voltage can be applied to the electrodes by a voltage applying means. As the voltage applying means, for example, the above description can be used. In the detection step, the current between the electrodes is preferably, for example, from 0.01 mA to 100,000 mA, and more preferably from 50 mA to 2000 mA.

  The analysis method of the present disclosure may further include a calculation step of calculating the concentration of the analysis target in the sample from the detection result in the detection step. Examples of the detection result include the above-described emission intensity. In the calculation step, the concentration of the analysis target can be calculated based on, for example, a detection result and a correlation between the detection result and the concentration of the analysis target in the sample. The correlation is, for example, plotting a detection result obtained by the analysis method of the present disclosure and a concentration of the analyte in the standard sample with respect to a standard sample whose concentration of the analyte is known. It can ask for. The standard sample is preferably a dilution series of the analyte. By calculating in this way, reliable quantification is possible.

  In the analysis method of the present disclosure, the pair of electrodes may be arranged in a container including a light transmitting part. In this case, in the detection step, the light emission is detected by a light receiving portion arranged so as to be able to receive light emission of the analysis object through the light transmitting portion. For the description of the container, the light transmitting unit, the light receiving unit, and the like, for example, the description of the analysis device of the present disclosure described later can be used.

<Plasma spectroscopy analyzer>
As described above, the plasma spectroscopy analyzer of the present disclosure includes a pair of electrodes, a container, a light receiving unit, and a constant current unit, the container includes a light transmitting unit, and the pair of electrodes is disposed in the container. And a light receiving unit capable of receiving light emitted from the analyte generated by applying a voltage to the pair of electrodes through the light transmitting unit, and the constant current unit includes the pair of constant current units. When the voltage is applied to the pair of electrodes, the current between the pair of electrodes is made constant and used for the plasma spectroscopic analysis method of the present disclosure. The analysis device of the present disclosure is characterized by being used in the analysis method of the present disclosure, and other configurations and conditions are not particularly limited. According to the analyzer of the present invention, the analysis method of the present disclosure can be easily performed. For example, the analysis device of the present disclosure can use the analysis method of the present disclosure and the description of each other.

  An example of the analyzer of the present disclosure will be described with reference to the drawings. In the drawings, for convenience of explanation, the structure of each part may be simplified as appropriate, and the dimensional ratio of each part may be schematically shown, unlike the actual case.

  1A is a schematic perspective view of the analyzer of the present embodiment, and FIG. 1B is a schematic cross-sectional view as viewed from the II direction in FIG. As shown in FIGS. 1A and 1B, the analyzer 10 of the present embodiment includes a pair of electrodes 1 and 2, a container 4, a light receiving unit 5, and a constant current unit 6, and the container 4 includes a transparent electrode. A light receiving unit 5 including the light unit 3 and disposed outside the container 4 so as to be able to receive light emitted from the analyte generated by applying a voltage to the pair of electrodes 1 and 2 through the light transmitting unit 3 is disposed. ing. Further, the electrode 1 is disposed in the horizontal direction with respect to the bottom surface of the container 4, and the tip thereof is disposed so as to contact the translucent portion 3. The electrode 2 is disposed in a horizontal direction with respect to the bottom surface of the container 4, and is disposed so that a part of the electrode 2 is exposed in the container 4 on the side surface of the container 4. The electrode 1 is covered with an insulating material 7. The constant current unit 6 is connected to the electrodes 1 and 2. In the analyzer 10 of the present embodiment, the sample containing the analysis object is introduced into the cylinder of the container 4 so as to be in contact with the electrodes 1 and 2, for example. In the present embodiment, the analyzer 10 is a vertically installed analyzer, but the analyzer 10 is not limited to this embodiment, and may be a horizontally installed analyzer, for example.

  In the present embodiment, the constant current unit 6 is not particularly limited, and known means for controlling the current value to be constant can be used. Specific examples include a constant current source and a galvanostat.

  In the present embodiment, a part of the surface of the electrode 1 is covered with the insulating material 7, but the insulating material 7 may have any configuration and may or may not be present. Moreover, in this embodiment, although the electrodes 1 and 2 are arrange | positioned in the horizontal direction with respect to the same surface of the container 4, the arrangement position of the electrodes 1 and 2 is not restrict | limited in particular, For example, in arbitrary positions Can be placed.

  In this embodiment, although the electrode 1 and the translucent part 3 are in contact, this invention is not limited to this, For example, the electrode 1 may be arrange | positioned away from the translucent part 3. The distance in particular between the electrode 1 and the side surface of the container 4 is not restrict | limited, For example, it is 0 cm or more and 2 cm or less, Preferably, it is 0 cm or more and 0.5 cm or less.

  The material of the translucent part 3 is not particularly limited, and may be any material as long as it is a material that transmits light emitted by applying a voltage to the pair of electrodes 1 and 2, and can be appropriately set according to the wavelength of the light emission. Examples of the material of the translucent part 3 include quartz glass, acrylic resin (for example, polymethyl methacrylate (PMMA)), borosilicate glass, polycarbonate (PC), cycloolefin polymer (COP), and methylpentene polymer (TPX (registered trademark)). )) Etc. The size of the light transmitting portion 3 is not particularly limited, and may be a size that can transmit light emitted by applying a voltage to the pair of electrodes 1 and 2, for example.

In the present embodiment, the container 4 has a bottomed column shape, but the shape of the container 4 is not limited to this, and may be an arbitrary shape such as a bottomed cylindrical shape. The material of the container 4 is not particularly limited. For example, acrylic resin (for example, polymethyl methacrylate (PMMA)), polypropylene (PP), polyethylene (PE), polyvinyl chloride (PVC), polyethylene terephthalate (PET), polystyrene (PS). Volume of the container 4 may for example also be 0.2 cm ³ or more 3 cm ³ or less, or may be 0.3 cm ³ or more 0.5 cm ³ or less. When the container 4 has a bottomed column shape, the width and depth of the container 4 are, for example, not less than 0.4 cm and not more than 50 cm, preferably not less than 1 cm and not more than 5 cm. When the container 4 has a bottomed cylindrical shape, the diameter of the container 4 is, for example, not less than 0.4 cm and not more than 50 cm, preferably not less than 1 cm and not more than 5 cm. When the container 4 has a bottomed columnar shape or a bottomed cylindrical shape, the height is, for example, 0.3 cm or more and 50 cm or less, preferably 0.5 cm or more and 5 cm or less, more preferably 0.7 cm or more and 2 cm or less. is there.

  The light receiving unit 5 is not particularly limited, and examples thereof include known optical measurement devices such as a CCD and a spectroscope. The light receiving unit 5 may be, for example, a transmission unit that transmits the light emission to the optical measurement device arranged outside the analyzer 10. Examples of the transmission means include a transmission path such as an optical fiber.

  The manufacturing method of the container 4 is not particularly limited, and for example, a molded body may be manufactured by injection molding or the like, or may be manufactured by forming a recess in a substrate such as a plate. In addition, the manufacturing method of the container 4 or the like is not particularly limited, and examples thereof include lithography and cutting.

  Next, examples of the present invention will be described. In addition, this invention is not restrict | limited by the following Example.

Example 1
It was confirmed by the analysis method of the present disclosure that lead in urine samples can be analyzed in a wide range of concentrations with little variation.

(1) Plasma spectroscopic analyzer The analyzer of the above embodiment was prepared. Specifically, a bottomed columnar transparent PMMA container (height 35 mm × width 8 mm × depth 6.5 mm) was prepared. Quartz glass was disposed on the side surface of the container 4. The electrode 1 and the electrode 2 were disposed in the container 4. The electrode 1 and the electrode 2 were each connected to the constant current part 6 (galvanostat). The electrode 1 and the electrode 2 were disposed in the horizontal direction with respect to the bottom surface of the container 4. The tip of the electrode 1 was disposed so as to contact the quartz glass on the side surface of the container 4. The electrode 1 was a nichrome electrode rod having a diameter of 0.1 mm and a length of 25 mm. The electrode 1 was used by exposing 0.5 mm from the tip and insulating the other regions. The electrode 2 was arranged on the side surface of the container 4 so that a part of the electrode 2 was exposed in the container 4. The electrode 2 was a carbon electrode rod having a diameter of 4 mm and a length of 15 mm. Further, as the light receiving part, an optical fiber was disposed so as to face the tip of the electrode 1 through the quartz glass. As the optical fiber, a single core optical fiber having a diameter of 400 μm was used. The optical fiber was connected to a concave grating type spectroscope (self-prepared).

(2) Plasma spectroscopic analysis After EDTA was administered to two subjects by infusion, the urine of each subject was collected and used as a urine sample. Lithium hydroxide was dissolved in the urine specimen so as to be 2 mol / L. About the said urine sample, the density | concentration of each lead was measured by the atomic absorption method. As a result, the lead concentrations in the urine specimens were 2.7 ppb and 12.3 ppb, respectively. In addition, a 2 mol / L aqueous lithium hydroxide solution was used as a control (0 ppb sample). Next, three types of specimens were introduced into the container of the analyzer. A voltage is applied between the electrode 1 and the electrode 2 under the following concentration conditions so that the electrode 1 becomes a cathode (cathode) and the electrode 2 becomes an anode (anode). Concentrated. In the following concentration conditions, “application time” represents the total time of the time during which the concentration voltage is applied in the concentration step and the time during which the concentration voltage is not applied.

(Concentration conditions)
Current value when voltage is applied: 40 mA
Application time: 1200 seconds Application period: 4 seconds Duty: 50%

  Immediately after the concentration, a voltage and a current are applied between the electrode 1 and the electrode 2 under the following plasma generation conditions so that the electrode 1 becomes an anode and the electrode 2 becomes a cathode. The emission intensity (count value) at a peak near the wavelength of 368.3 nm was measured (Example 1, n = 2). In the following plasma generation conditions, the “application time” represents the total time of the time during which the plasma voltage is applied and the time during which the plasma voltage is not applied in the detection step.

(Plasma generation conditions)
Applied voltage: 500V
Application time: 2.5 ms
Application period: 50 μs
Duty: 50%

  The result is shown in FIG. FIG. 2 is a graph showing the correlation between the lead concentration and the count value. In FIG. 2, the horizontal axis indicates the lead concentration, and the vertical axis indicates the count value. As shown in FIG. 2, in Example 1, the count value increased depending on the lead concentration, and lead with a low concentration of 2.7 ppb was also detected. Moreover, the dispersion | variation in the count value between samples was suppressed. From these results, it was found that according to the analysis method of the present disclosure, it is possible to suppress variations in count values over a wide range of concentrations.

(Example 2)
It was confirmed that lead in urine samples can be analyzed with little variation at different application cycles.

  Example 1 except that the application period was 0.25 seconds, 0.5 seconds, 1 second, 2 seconds, 3 seconds, 4 seconds, or 8 seconds in the concentration conditions of Example 1 (2). The count value was measured in the same manner as (2) (n = 2).

  The result is shown in FIG. FIG. 3 is a graph showing count values in different periods. In FIG. 3, the horizontal axis indicates the application period, and the vertical axis indicates the count value. As shown in FIG. 3, the application period was effective from 0.25 seconds, and the count value increased as the application period increased. A higher count value was obtained in a long application period of 2 seconds or more. From these results, according to the analysis method of the present disclosure, it is possible to analyze the analysis object in a wide cycle, and in particular, a strong signal (high count value) can be obtained by setting the application cycle to 2 seconds or more. all right.

  As mentioned above, although this invention was demonstrated with reference to embodiment and an Example, this invention is not limited to the said embodiment and Example. Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention.

  According to the analysis method of the present disclosure, for example, it is possible to suppress the occurrence of analysis errors during sample analysis. Moreover, since the analysis method of this indication can suppress generation | occurrence | production of the analysis error at the time of sample analysis, it can analyze the said analysis object with high precision irrespective of the kind of sample and the kind of said analysis object, for example. Furthermore, since the analysis method of the present disclosure can efficiently analyze a locally high concentration analyte without performing the pretreatment on the sample, for example, the sample can be easily analyzed with high sensitivity. it can. For this reason, the analysis method of this indication is very useful for the analysis of the element etc. which used plasma generation, for example.

DESCRIPTION OF SYMBOLS 1, 2 Electrode 3 Translucent part 4 Container 5 Light receiving part 6 Constant current part 7 Insulating material 10 Analyzer

Claims (17)

A voltage application step of applying a voltage to a pair of electrodes in the presence of the sample, and a concentration step of concentrating the analyte in the sample in the vicinity of at least one electrode by the voltage application; and the pair of electrodes Generating a plasma by applying a voltage to, and detecting a light emission of the analyte generated by the plasma,
The plasma spectroscopic analysis method, wherein a current between a pair of electrodes is constant during voltage application in at least a part of the concentration step. The concentration step comprises
A voltage application step for applying a voltage to the pair of electrodes;
The plasma spectroscopic analysis method according to claim 1, further comprising a voltage non-application step in which no voltage is applied to the pair of electrodes. In the concentration step, the voltage application step and the voltage non-application step are performed once each as one set,
The plasma spectroscopic analysis method according to claim 2, wherein the one set time is 0.25 seconds or more. In the concentration step, the voltage application step and the voltage non-application step are performed once each as one set,
The plasma spectroscopic analysis method according to claim 2 or 3, wherein a time of the voltage non-application step in the one set time is 0.125 seconds or more. In the concentration step, the voltage application step and the voltage non-application step are performed once each as one set,
5. The plasma spectroscopic analysis method according to claim 2, wherein a ratio of a time of the voltage application step in the one set of time is in a range of 1% to 99%.   6. The plasma spectroscopic analysis method according to claim 1, wherein, in the concentration step, a current value between the pair of electrodes when the voltage is applied is in a range of 0.01 mA to 200 mA. The pair of electrodes are a pair of electrodes having different liquid contact areas with the sample,
7. The plasma spectroscopic analysis method according to claim 1, wherein an electrode having a small liquid contact area with the sample among the pair of electrodes is an electrode for analyzing the object to be analyzed by plasma generation.   The plasma spectroscopic analysis method according to any one of claims 1 to 7, wherein the voltage in the detection step is higher than the voltage in the concentration step.   The plasma spectroscopic analysis method according to any one of claims 1 to 8, wherein the voltage in the concentration step is 1 mV or more.   The plasma spectroscopic analysis method according to any one of claims 1 to 9, wherein the voltage in the detection step is 10 V or more. The pair of electrodes are disposed in a container,
The container includes a translucent part,
The plasma spectroscopic analysis method according to any one of claims 1 to 10, wherein a light receiving unit capable of receiving light emitted from the analysis object through the light transmitting unit is disposed outside the container.   The plasma spectroscopic analysis method according to claim 1, wherein the analysis object is a metal.   The metal is selected from the group consisting of aluminum, antimony, arsenic, barium, beryllium, bismuth, cadmium, cesium, gadolinium, lead, mercury, nickel, palladium, platinum, tellurium, thallium, thorium, tin, tungsten, and uranium. The plasma spectroscopic analysis method according to claim 12, wherein the method is at least one metal.   The plasma spectroscopic analysis method according to any one of claims 1 to 13, wherein the sample is at least one of a biological sample and an environment-derived sample.   The plasma spectroscopic analysis method according to claim 14, wherein the biological sample is at least one selected from the group consisting of urine, blood, hair, saliva, sweat, and nails.   The plasma spectroscopic analysis method according to claim 14, wherein the environment-derived sample is at least one selected from the group consisting of food, water, soil, air, and air. Including a pair of electrodes, a container, a light receiving part, and a constant current part,
The container includes a translucent part,
The pair of electrodes are disposed in the container,
Outside the container, a light receiving unit capable of receiving light emitted from the analyte generated by voltage application to the pair of electrodes through the translucent unit is disposed,
The constant current portion is connected to the pair of electrodes, and when a voltage is applied to the pair of electrodes, the current between the pair of electrodes is constant,
A plasma spectroscopic analysis apparatus for use in the plasma spectroscopic analysis method according to any one of claims 1 to 16.