JP2005214815A - Continuous flow analytical method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a continuous flow analytical method hardly generating background absorption caused by pH fluctuation when measuring an absorbance, enhanced thereby in precision, and allowing stable measurement even as to a sample containing a suspended matter. <P>SOLUTION: In this analytical method wherein an eluent is passed through a column adsorbing a measuring objective element to elute the element, and wherein a color-producing reagent and a buffer solution are added to the eluent (sample solution) containing the element to be guided to an absorptiometer, the pH fluctuation ΔpH of the sample solution added with the color-producing reagent and the buffer solution is regulated within a range expressed by Expression (1):-0.5≤äΔpH=log[(B-X)/(B-Y)]}≤0.5 to be eluted, where X is an acid concentration of the column adsorption solution adsorbing the measuring objective element, where Y is an acid concentration of the eluent, and where B is an alkaline concentration of the buffer solution, the background absorption caused by the pH change is thereby restrained, and the method preferably has a means for dissolving the suspended substance in the sample to introduce the sample solution with dissolved suspended substance into a measuring system. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a continuous flow analysis method that is easy to measure even when background absorption is caused by a coloring reagent, has excellent measurement accuracy, and can stably measure a sample containing a suspended substance.

  Conventionally known is a measuring method in which a coloring reagent is added to a sample solution to cause coloration by an element to be measured contained in the solution, and the concentration is quantified based on the absorbance or the like. In the measurement of absorbance using such a coloring reagent, when the coloring reagent has background absorption, the concentration is determined by correcting this absorption. Since the background absorption of the coloring reagent is affected by the salt concentration of the sample, the pH of the sample solution, and the like, it is necessary to consider these influences in order to perform accurate measurement.

  For example, lead in a sample is adsorbed on a weakly acidic cation exchange resin, a cleaning solution is passed through the resin to remove interfering components, lead is then eluted, and a color former is added to the eluent containing lead to absorb light. A method of quantifying the lead concentration in a sample by a photometric method is known (Patent Document 1). Since this measurement method is a manual analysis, it is possible to suppress fluctuations in the background absorption of the coloring reagent if it is introduced into the absorptiometer after adjusting the pH of the sample solution when adding the color former. Therefore, it takes time for pH adjustment and concentration measurement.

  In addition, in the determination of cobalt, prior to the determination of the sample to be analyzed, the background of only the color former is measured in advance, then the absorbance of the sample is measured, and the background of the color developer is subtracted from this measured value. A method is also known (Patent Document 2). However, this measurement method requires time and effort to measure the background of the color former in advance, and is not suitable for continuous measurement.

On the other hand, as an automatic measurement method, a sample reagent containing a measurement target element is added to the detector while the sample liquid flows through the pipe and introduced into the detector, and the concentration of the measurement target element is quantified by measuring the absorbance and the like. Flow analysis is known. For example, the sample solution is passed through a strongly basic anion exchange resin to adsorb the cadmium iodide complex contained in the solution, and after evaporating after repeated adsorption, the eluate containing this cadmium is masked. A method is known in which a cadmium concentration in a sample is measured by adding an agent, a buffer solution and a coloring reagent, measuring the absorbance by introducing the reagent into a spectrophotometer (Patent Document 3). In this method, since the color is developed under a strong alkali at pH 14, even if background absorption of the coloring reagent is present, it is not substantially affected by the pH change.
Japanese Patent Laid-Open No. 09-061416 Analytical chemistry: Vol. 41, 633-638, 1992 JP 07-333212 A

  In a measurement method in which a coloring reagent is added to a sample solution and the concentration of an element to be measured contained in the sample solution is quantified based on the absorbance or the like, if the optimum coloring region of the coloring reagent is in the range of pH 1 to 14, the pH change Since the background absorption band of the coloring reagent changes depending on the flow rate, the continuous flow analysis method such as the flow injection method may be unmeasurable due to the fluctuation of the baseline of the absorption band.

  For example, in a continuous flow analysis method incorporating an ion exchange reaction or a solvent extraction reaction, when a color reagent is used, a background absorption band is always generated if the optimum pH condition for the color reaction does not match the pretreatment conditions such as ion exchange. Therefore, base line fluctuations and ghost peaks appear, making measurement impossible. In this case, a buffer solution is usually used to adjust the pH. However, depending on the combination of the element to be measured and the coloring reagent, the molecular ions that make up the buffer solution mask the reaction element. Such a buffer cannot be used.

  In addition, when the suspended solids containing the element to be measured are contained in the sample solution, the conventional continuous flow analysis method requires the suspended solids to be removed in advance in order to avoid clogging of the pipeline, and the measurement operation Is complicated and the concentration of the element to be measured is low.

  The present invention solves the above-mentioned conventional problems in a continuous flow analysis method using a coloring reagent. In the continuous flow analysis method incorporating an ion exchange reaction or a solvent extraction reaction, the measurement is easy and the measurement accuracy is improved. The present invention provides a continuous flow analysis method that is excellent and that can stably measure a sample containing suspended solids.

The present invention relates to a continuous flow analysis method and apparatus having the following configuration.
(1) Based on a continuous flow analysis method in which a reagent is added while a solution containing an element to be measured flows through a pipeline and introduced into the detector, the sample liquid containing the element to be measured is guided to the ion exchange resin column by the carrier liquid. In the analytical method, after the element to be measured is adsorbed, the element is eluted through the eluent through the column, and a coloring reagent and a buffer solution are added to the eluent (sample liquid) containing the element to lead to an absorptiometer. When the acid concentration [X] of the column adsorbed solution that adsorbs the target element, the acid concentration [Y] of the eluent, and the alkali concentration [B] of the buffer solution, the pH variation of the sample solution to which the coloring reagent and the buffer solution are added [ The continuous flow analysis method is characterized in that the background absorption due to pH change is suppressed by elution while adjusting [Delta] pH within the range represented by the following formula (1).
−0.5 ≦ [ΔpH = log [(BX) / (BY)]] ≦ 0.5 (1)
(2) The difference between the acid concentration of the column adsorbent and the eluent is adjusted within the above range by controlling either the acid concentration [A] of the carrier liquid or the acid concentration [Y] of the eluent. Analysis method of (1) or (2).
(3) The method according to claim 1, wherein the pH fluctuation [ΔpH] of the sample solution is adjusted within the range represented by the following formula (2) and eluted.
−0.5 ≦ [ΔpH = log [(Cx−B + Y) / (Cx−B + Y)] + log [(BX) / (BY)]] ≦ 0.5 (2)
(Cx in the formula is the concentration of the buffer)
(4) In a measurement system in which a complexing agent solution is added to a carrier solution to adsorb complex ions of an element to be measured to an ion exchange resin column, the carrier solution in which the acid concentration of the column adsorbing solution is diluted with the complexing agent solution The analysis method according to any one of the above (1) to (3), wherein the acid concentration is as follows.
(5) The analysis method according to any one of (1) to (4), further including a means for dissolving the suspended substance in the sample, and introducing the sample solution in which the suspended substance is dissolved into the measurement system.
(6) A measurement system for continuous flow analysis and a sample dissolution unit connected to the measurement system, wherein the sample dissolution unit is a dissolution tank for adding mineral acid to a sample containing a suspension, and a sample solution for the dissolution tank Characterized in that it is equipped with a pipe that leads to the sample introduction part of the continuous flow analysis measurement system, a storage tank that receives the residual liquid of the dissolution tank, a pipe that communicates the dissolution tank with the storage tank, and a water supply pipe that supplies water to the dissolution tank. Continuous flow analyzer.

[Detailed Description of the Invention]
An example of a measuring apparatus according to the analysis method of the present invention is shown in FIG. The measuring apparatus of the present invention shown in the figure has a measuring system for continuous flow analysis and a suspended substance dissolving part A connected to the measuring system. The measurement system has a sample introduction part B, an adsorption elution part C, a reaction part D, and a detection part E. These sample introduction part B, adsorption elution part C, reaction part D, and detection part E are connected in series by a pipe line.

  As shown in FIG. 2, the measurement apparatus is preferably provided with a suspended substance dissolving part A so that a sample containing suspended substances can be analyzed. After the suspended substance containing the element to be measured is dissolved in the suspended substance dissolving part A, this sample solution is introduced into the sample introducing part B of the measurement system. The suspension substance dissolving part A is provided with a dissolution tank 60 and a storage tank 70. The dissolution tank 60 is charged in a heating tank 61. The dissolution tank 60 includes a pipe 62 for supplying a sample containing suspended solids, a water supply pipe 63 for adding water to the sample, and a pipe for supplying mineral acid. A channel 64, a pipeline 66 for sending the dissolved sample solution to the measurement system, and pipelines 67 and 68 leading to the storage tank 70 are provided, and a stirrer 65 is provided inside the dissolution vessel 60.

  The storage tank 70 is a part that pumps up the residual liquid and the cleaning waste liquid from the dissolution tank 60 and temporarily stores them. The suction pipes 71 and 73 and the drain pipe 74 are connected to the pipe 71, and a suction pump is connected to the pipe 71. 72 is provided. Valves V for opening and closing the flow paths are mounted on these pipe lines 62 to 74. The sample containing the suspended substance is supplied to the dissolution tank 60 through the pipe 62, and an appropriate amount of water is added to the sample through the pipe 63 while the sample flows through the pipe 62. Furthermore, the mineral acid is supplied to the dissolution tank 60 through the pipe 64 and stirred to promote dissolution of the element to be measured contained in the suspended substance. As for the type of mineral production, nitric acid, hydrochloric acid, sulfuric acid or the like may be appropriately used depending on the type of suspended matter. It is advisable to increase the temperature of the dissolution tank 60 by supplying warm water to the heating tank 61 so as to promote dissolution. A heater may be used in place of the heating tank 61. For example, in the quantitative analysis of lead, when lead is contained in the sample as a suspended substance such as hydroxide, nitric acid is added to the sample to dissolve lead.

  After dissolution, the sample liquid is sent to the sample introduction part B of the measurement system through the pipe 66. On the other hand, the residual liquid in the dissolution tank is pumped into the storage tank 70 by the suction pump 72 through the pipe lines 67 and 68. Next, water is supplied to the empty dissolution tank 60 through the pipe 63 to clean the inside of the tank. This washing waste liquid is sucked into the storage tank 70 through the pipes 67 and 68 in the same manner as the sample residual liquid. The drainage liquid accumulated in the storage tank 70 is discharged to the outside through the pipe 74.

  The sample introduction part B includes a valve 12 for injecting a predetermined amount of sample liquid into the measurement system, a pipe line 10 for supplying a carrier liquid to the valve 12, a heater 13 for heating the carrier liquid, and a carrier flowing through the pipe line 10 A pipe 11 for adding a complexing agent to the liquid and a metering pump 50 for feeding the carrier liquid and the complexing agent solution are provided. The pump 50 introduces the same amount of carrier liquid and complexing agent liquid into the measurement system through the pipes 10 and 11. The sample liquid is introduced into the carrier liquid flowing through this conduit. Specifically, the injection valve 12 is provided with a loop (not shown) for holding a certain amount of sample solution, and a certain amount of sample solution is introduced into the conduit 10 by switching the flow path of the valve 12. The The element to be measured contained in the sample solution forms a complex with the complexing agent, and the sample solution containing this complex is introduced into the column 20.

  When the sample solution does not contain suspended substances, it is not necessary to dissolve the suspended substances. Therefore, a certain amount of sample solution may be introduced into the loop of the valve 12 without going through the suspended substance dissolving part A. . Further, the pipe 11 may be omitted when it is not necessary to add a complexing agent.

  The adsorption elution part C includes a column 20 filled with an ion exchange resin that adsorbs an element to be measured, a pipe line 21 leading from the column 20 to the reaction part 30, a pipe line 23 for supplying an eluent to the column 20, the column 20 has a conduit 24 for supplying a cleaning liquid, and a drainage conduit 22 for the column 20, and a fluid feed pump 50 is provided in each of the conduits 23 and 24. The column 20 is filled with an ion exchange resin that adsorbs complex ions of the element to be measured, and the complex ions in the liquid are adsorbed to the ion exchange resin while the sample liquid passes through the column 20. On the other hand, the sample effluent that has passed through the column 20 is guided to the outside through the conduit 22.

  After the adsorption, the pipe leading to the column 20 is switched, the eluent flowing through the pipe 23 and the pipe 21 is introduced into the column 20, and the complex ions adsorbed on the resin are eluted into the eluent. By this adsorption elution step, impurities in the sample liquid can be removed without being adsorbed and complex ions can be concentrated. Thereafter, the flow path of the column 20 is switched, and a cleaning liquid is introduced into the column 20 through the pipe line 24 to clean the inside, thereby regenerating the resin. This washing drainage is discharged to the outside through the pipe line 22. After the column is washed, the flow path of the column 20 is switched again so that the column 20 and the conduit 10 are communicated to prepare for the next adsorption.

  The reaction part D includes a pipe line 31 leading to the detection part E, a pipe line 32 for adding a coloring reagent to the eluent (sample liquid) flowing through the pipe line 21, a pipe line 33 for adding a buffer solution, a coloring reagent and a buffer. A reaction pipe 30 through which the sample liquid to which the liquid is added flows is provided, and a liquid feed pump 50 is provided in the pipes 32 and 33. The reaction pipe 30 is formed in a coil shape so as to ensure a time for the coloring reagent and the element to be measured to react, and is formed so that a sufficient length of the pipe can be obtained in a limited space. ing. Further, the detection unit E is provided with an absorptiometer 40 for measuring the absorbance of the sample solution, and further, a drain line 31 is provided.

  A coloring reagent is added to the sample liquid containing complex ions of the measurement target element eluted through the pipe 32 while flowing through the pipe 21, and a buffer is added to the sample liquid through the pipe 33. The buffer is for suppressing the pH fluctuation of the sample solution, and an alkaline solution is generally used for the acidic eluent. By adding a buffer solution, the pH of the sample solution is adjusted to the optimum color development pH.

  The coloring reagent reacts with a specific metal complex ion contained in the sample solution, and has a specific color tone at the optimum coloring pH. This colored sample solution is sent to the detection unit E, the absorbance is measured by the absorptiometer 40, and the concentration of the element to be measured is quantified based on the calibration curve from the magnitude of the absorbance.

In the analysis method of the present invention, when the acid concentration [X] of the column adsorbed liquid that adsorbs the element to be measured is set, the acid concentration [Y] of the eluent, and the alkali concentration [B] of the buffer solution in the above measurement system, color development Continuous absorption characterized by suppression of background absorption due to pH change by eluting with pH variation [ΔpH] of the sample solution to which the reagent and buffer are added within the range represented by the following formula (1) It is a flow analysis method.
−0.5 ≦ [ΔpH = log [(BX) / (BY)]] ≦ 0.5 (1)

A specific embodiment for adjusting the pH fluctuation of the sample solution to which the coloring reagent and the buffer solution are added within the above range will be described below.
In general, there is an appropriate range of acid concentrations for adsorption of metal complex ions onto ion exchange resins. For example, in the case of lead iodide ions (PbI ₄ ²⁻ ), the concentration of nitric acid in the adsorbent is 0.1 to 0.1. A range of 1.0M is appropriate. If the acid concentration of the adsorbed liquid is too high, lead iodide (PbI ₂ ) precipitates, and if the acid concentration is too low, complex ions of lead are not formed. The eluent has an appropriate acid concentration range, and a nitric acid concentration of 0.1 to 2.0 M is appropriate for eluting lead iodide ions (PbI ₄ ²⁻ ). When the concentration of nitric acid in the eluent is high, the absorbance peak becomes sharp, but it becomes difficult to adjust the pH of the coloring reagent to an appropriate pH. On the other hand, when the concentration of nitric acid is too low, the sensitivity decreases.

  In the present invention, the acid concentration range is determined so as to be compatible with both the adsorbed solution and the eluent so that the pH fluctuation of the sample solution to which the coloring reagent and the buffer solution are added is controlled within a certain range. Adsorption and elution of the target element can be performed satisfactorily, and background absorption due to pH fluctuations in absorbance analysis can be suppressed, so that high measurement accuracy can be obtained.

  Specifically, for example, in the quantitative analysis of lead by the illustrated measurement system, 1.0 M nitric acid is used as a carrier liquid and 0.2 M potassium iodide liquid is used as a complexing agent, and the same amount of complexing agent as the carrier liquid is used. When the solution is introduced into the measurement system, the nitric acid concentration of the carrier solution is diluted with this potassium iodide solution to a nitric acid concentration of 0.5M, and the lead contained in the sample solution forms a lead iodide complex, Adsorbed on resin. Therefore, an adsorbent having a concentration of 0.5 M nitric acid remains in the column.

  An eluent (nitric acid solution) is introduced into the column in which the adsorbent having a concentration of 0.5 M nitric acid remains to elute lead iodide ions adsorbed on the resin. A coloring reagent and a buffer solution are added to the eluent (sample solution) containing these ions. It is preferable to use 0.002%-(--- compound name ----: TPPS) as a coloring reagent and 0.12M sodium tetraborate and 1M sodium hydroxide as a buffer solution.

In the above measurement system, the pH of the sample solution after adding the coloring reagent and the buffer solution is represented by the following formula (3).
pH = pKa + log (Cx / Cy) (3)
pKa: Buffer (acid dissociation constant of sodium tetraborate)
Cx: concentration of sodium tetraborate Cy: concentration of sodium hydroxide contained in the buffer (Cya = BX, Cyb = BY)
X: Acid concentration of adsorbed solution Y: Acid concentration of eluent B: Alkaline concentration of buffer

In the above pH formula (3), since Cx and pKa are constant, the pH fluctuation amount ΔpH is expressed by the following formula (4).
ΔpH = log (Cx−Cyb) −log (Cyb) −log (Cx + Cya) + log (Cya)
Therefore, ΔpH = log [(Cx−B + Y) / (Cx−B + X)] + log [(B−X) / (B−Y)] (4)
Here, when the acid concentration of the sample solution is significantly smaller than the concentration (Cx) of the buffer solution, the equation (4) can be approximated as the following equation (5).
ΔpH = log [(B−X) / (B−Y)] (5)

  The analysis method of the present invention controls the pH of the sample solution to which the coloring reagent and the buffer solution are added by controlling ΔpH within the range of −0.5 ≦ ΔpH ≦ 0.5 based on the approximate expression (5). Suppresses background absorption due to fluctuations. When the approximate expression (5) is not used, the pH variation (ΔpH) of the sample solution is expressed by the expression (4), and this is controlled within the range of the expression (2). By controlling the pH fluctuation (ΔpH) of the sample solution within this range, high measurement accuracy can be achieved. If this pH fluctuation is outside the above range, the background at the time of measurement becomes significant, and it is difficult to obtain a highly reliable measurement result.

  In order to adjust the pH variation of the sample solution to which the coloring reagent and the buffer solution are added within the above range, as described above, the method is not limited to the method using the eluent with the acid concentration [Y] adjusted. By adjusting the acid concentration [A], the pH variation of the sample solution to which the coloring reagent and the buffer solution are added may be controlled within the above range.

  Incidentally, when 0.2M nitric acid is used as a carrier solution and the same amount of potassium iodide buffer is added to the carrier solution and introduced into the column together with the sample solution, 0.5M nitric acid is used as the eluent as in the conventional case. Then, the pH of the sample solution deviates greatly from the optimum color development pH range of the color developing reagent, and the background absorption due to pH fluctuation is large at the time of absorbance measurement, and accurate measurement cannot be performed.

  In the analysis method of the present invention, the acid concentration range is determined so as to be compatible with both the adsorbed solution and the eluent so that the pH fluctuation of the sample solution to which the coloring reagent and the buffer solution are added is controlled within a certain range. Therefore, the adsorption and elution of the element to be measured can be performed satisfactorily, and the baseline fluctuation and the ghost peak due to the pH fluctuation in the absorbance analysis can be suppressed, and a highly reliable analysis result can be obtained. Furthermore, the analysis method of the present invention having a suspended substance dissolving portion can efficiently dissolve suspended substances containing an element to be measured and introduce it into a continuous flow analysis system. In addition, since the clogging of the pipe line is not caused, stable measurement can be performed. Therefore, for example, even when a large amount of suspended substances such as waste water and raw water at the intermediate stage of the waste water treatment process are included, it is possible to automatically measure the entire amount of the sample for these sample solutions.

  For example, for lead in wastewater, the 0.01 ppm level lead contained in the wastewater can be continuously measured according to the analysis method of the present invention. This makes it possible to respond quickly and contributes to environmental protection without contaminating the surrounding environment with lead. In addition, it is possible to constantly monitor lead in factory effluent, groundwater and river water.

  In the analysis method of the present invention, for example, the measurement target element shown in Table 1 can be quantitatively analyzed using the coloring reagent and buffer solution in the same table.

  Using the continuous flow analyzer shown in FIG. 1, quantitative analysis of lead contained in the waste water was performed. First, a sample containing a suspension of lead hydroxide or organic lead was placed in a dissolution tank and supplied with water. Nitric acid was added to a concentration of 1 M and stirred to elute lead. The lead-dissolved sample solution was led to the sample injection valve of the continuous flow analyzer, and 4 ml of the sample solution was injected into a 1.0 M nitric acid carrier solution (liquid temperature 100 ° C.). Further, a complexing agent (0.2M potassium iodide solution) was mixed while the sample solution flowed through the pipe to form a lead iodide complex. This sample solution is passed through a column filled with a strongly basic anion exchange resin (product name: Bio-Rad AG1-X8, 100mesh). After passing through the column, the solution is discharged to the outside, and the connection of the pipe line is switched. The eluent (0.5M nitric acid) was passed through the column. The eluent (sample solution) that has passed through this column is guided to the reaction section, and further, the color reagent (0.002% TPPS), neutralizing agent (1.0M NaOH), buffer solution (0.12M) while the sample solution flows through the pipeline. Tetraboron (Na-Na hydroxide) was added to the sample solution to adjust the pH of the sample solution to 9 to 11, and heated while passing through the reaction part to increase the solution temperature to 120 ° C. to promote the color reaction. . The colored sample solution was guided to the detection part to measure the absorbance, and the lead concentration was measured using a calibration curve prepared in advance. The results are shown in Table 2. In addition, the measurement result by the official method is shown in comparison.

Comparative example

  The lead concentration was determined in the same manner as in Example 1 except that 1M nitric acid was used instead of 0.5M nitric acid as the eluent. The results are shown in Table 2 (Comparative Example 1). Further, in the measuring apparatus of FIG. 1, the lead concentration was quantified in the same manner as in Example 1 except that the suspended substance was removed without using the suspended substance dissolving part. The results are shown in Table 2 (Comparative Example 2).

  As shown in the results of Table 2, according to the analysis method of the present invention, a result that is in good agreement with the measurement of the official method can be obtained, and the method of the present invention enables continuous measurement, compared with the official method. Measurement time is greatly reduced. On the other hand, in Comparative Example 1, the baseline was unstable, and the measured value of the low concentration sample was higher than that of the official method. Moreover, since the comparative example 2 did not measure the lead of suspended material injection, the measured value lower than the official method was shown.

The schematic diagram which shows the structural example of the measuring apparatus which concerns on the continuous flow analysis method of this invention The schematic diagram which shows the structural example of the suspension substance melt | dissolution part of the measuring apparatus which concerns on this invention.

Explanation of symbols

A-suspended substance dissolving part, B-sample introducing part, C-adsorption dissolving part, D-reacting part, E-detecting part,
10, 11-line, 12-injection valve, 13-heater, 14-line, 20-column,
21, 22, 23, 24-line, 30-reaction line, 31, 32, 33-line, 40-absorbance altimeter, 50-liquid feed pump, 60-dissolution tank, 61-heating tank, 62, 63, 64-pipe, 65-stirrer, 66, 67, 68-pipe, 70-reservoir, 71, 73-pipe, 72-suction pump, 74-pipe.

Claims (6)

Based on a continuous flow analysis method in which a reagent is added while a solution containing the element to be measured flows through the pipe and introduced into the detector, the sample liquid containing the element to be measured is guided to the ion exchange resin column by the carrier liquid, and the object to be measured In an analysis method in which an element is adsorbed after the element is adsorbed through the eluent through the column, and a coloring reagent and a buffer solution are added to the eluent (sample liquid) containing the element to lead to an absorptiometer. When the acid concentration [X] of the adsorbed column adsorbed solution, the acid concentration [Y] of the eluent, and the alkali concentration [B] of the buffer solution, the pH variation [ΔpH] of the sample solution to which the coloring reagent and the buffer solution are added is A continuous flow analysis method characterized in that background absorption due to pH change is suppressed by adjusting and eluting within the range represented by the following formula (1).
−0.5 ≦ [ΔpH = log [(BX) / (BY)]] ≦ 0.5 (1)   2. The acid concentration [A] of the carrier liquid or the acid concentration [Y] of the eluent is controlled to adjust the difference in acid concentration between the column adsorbent and the eluent within the above range. 2. Analysis method. 2. The analysis method according to claim 1, wherein the pH fluctuation [ΔpH] of the sample solution is adjusted within a range represented by the following formula (2) and eluted.
−0.5 ≦ [ΔpH = log [(Cx−B + Y) / (Cx−B + Y)] + log [(BX) / (BY)]] ≦ 0.5 (2)
(Cx in the formula is the concentration of the buffer)   In a measurement system that adds complexing agent liquid to the carrier liquid and adsorbs complex ions of the element to be measured to the ion exchange resin column, the acid concentration of the column adsorbing liquid is the acid concentration of the carrier liquid diluted with the complexing agent liquid. The analysis method according to any one of claims 1 to 3.   The analysis method according to any one of claims 1 to 4, further comprising means for dissolving a suspended substance in a sample, wherein a sample solution in which the suspended substance is dissolved is introduced into a measurement system. A measurement system for continuous flow analysis and a sample dissolution unit connected to the measurement system. The sample dissolution unit is a dissolution tank for adding mineral acid to a sample containing a suspension, and the sample solution in the dissolution tank is continuously flowed. Continuous flow characterized by comprising a pipe leading to the sample introduction part of the analytical measurement system, a storage tank for receiving the residual liquid of the dissolution tank, a pipe line connecting the dissolution tank and the storage tank, and a water supply pipe for supplying water to the dissolution tank Analysis equipment.

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