JP2000304736A - Quick analytical method for organic compound in stainless steel sulfuric acid pickle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a quick analytical method for an organic compound in a stainless steel sulfuric acid pickle, in which the organic compound such as an acid pickling promoter or the like in the stainless steel sulfuric acid pickle can be analyzed simply and quickly without the special pretreatment of the organic compound. SOLUTION: In this quick analytical method for an organic compound in a stainless steel sulfuric acid pickle, the stainless steel sulfuric acid pickle is changed preferably into a mobile phase so as to be introduced to the separating column of a high-performance liquid chromatograph, an eluate from the separating column is guided to a detector, and the organic compound in the stainless steel sulfuric acid pickle is quantitatively determined. The separating column is a graphite carbon column, and a liquid which contains a hydrophilic organic solvent is used as the mobile phase of the high-performance liquid charmomatograph.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for rapidly analyzing an organic compound in a stainless steel pickling solution, which is capable of simply and quickly quantifying an organic compound in the stainless steel pickling solution.

[0002]

2. Description of the Related Art In a sulfuric acid pickling treatment of stainless steel, in recent years, an organic compound is often added as a pickling accelerator for improving productivity. As the above-mentioned pickling accelerator, the addition of thiol is effective, and the thiol is exchanged with a compound having a disulfide bond (hereinafter also referred to as a disulfide compound) in the pickling solution to remove hydrogen during the nascent stage on the steel sheet surface. However, it is known that acid pickling is promoted (see JP-A-10-2655981).

In this case, thiol is easily oxidized by air and hardly exists in the pickling solution at the time of use. Therefore, in order to control the concentration of the pickling accelerator, it is necessary to quantify the disulfide compound in the solution. Good. As a method for quantifying disulfide compounds in a pickling solution, a method using nuclear magnetic resonance spectroscopy (NMR) has been reported so far, and this method has made it possible to appropriately control the concentration of a pickling accelerator ( See JP-A-10-2655981).

On the other hand, in the case of the above method, since it is necessary to separate sulfuric acid and metal ions contained in the pickling solution in a large amount from the disulfide compound which is a component to be analyzed, pretreatment of the sample such as solvent extraction or salting out is required. There is a need for a method for rapidly analyzing an organic compound in a stainless steel sulfuric acid pickling solution that requires an operation, does not require a pretreatment operation, and can easily and quickly quantify an organic compound such as a disulfide compound.

[0005]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art and removes an organic compound such as a pickling accelerator in a sulfuric acid pickling solution of stainless steel without special pretreatment of the sample. An object of the present invention is to provide a method for quickly and easily analyzing an organic compound in a sulfuric acid pickling solution of stainless steel, which can be analyzed quickly.

[0006]

SUMMARY OF THE INVENTION According to the present invention, a stainless steel sulfuric acid pickling solution is introduced into a separation column of a high performance liquid chromatograph, and an eluate from the separation column is guided to a detector. It is a method for rapidly analyzing organic compounds in a sulfuric acid pickling solution for stainless steel, which comprises quantifying organic compounds in the solution.

In the above-mentioned present invention, it is preferable that the separation column is a graphite carbon column (a first preferred embodiment of the present invention). Further, the present invention described above,
In the first preferred embodiment of the present invention, it is preferable to use a liquid containing a hydrophilic organic solvent as the mobile phase of the high performance liquid chromatography (the second preferred embodiment and the third preferred embodiment of the present invention). .

Further, in the above-mentioned present invention and the first preferred embodiment of the present invention, the organic compound is an organic compound having a carboxyl group and contains a hydrophilic organic solvent as a mobile phase of the high performance liquid chromatography. It is preferable to use a liquid to which an acid is added (fourth preferred embodiment and fifth preferred embodiment of the present invention). In each of the second to fifth preferred embodiments of the present invention, it is preferable that the mobile phase of the high-performance liquid chromatograph further contains water, and in this case, The concentration of the hydrophilic organic solvent in the liquid as the mobile phase is 3 to 30 v
ol% is more preferable (the sixth preferred embodiment to the ninth preferred embodiment of the present invention).

Further, the present invention and the first to ninth preferred embodiments of the present invention are characterized in that the sulfuric acid concentration of the stainless steel sulfuric acid pickling solution when introduced into the separation column is preferably 10 to 10. _{500g-H 2 SO 4 / l} , more preferably 50~500g-H ₂ SO ₄
/ l, more preferably is suitably used as a quick method for analyzing organic compounds stainless steel sulfuric pickling solution is _{100 ~500g-H 2 SO 4 /} l.

The present invention and the first to ninth preferred embodiments of the present invention are characterized in that the sulfuric acid concentration of the stainless steel pickling solution when introduced into the separation column is preferably 10 to 10%. _{500g-H 2 SO 4 / l} , 0.01~ iron ion concentration as Fe
5 mol / l, more preferably the sulfuric acid concentration is 50 to 500 g-H
₂ SO ₄ / l, iron ion concentration is 0.01 to 5 mol / l as Fe, more preferably the sulfuric acid concentration is 100 to 500 g-H ₂ SO ₄ / l, and iron ion concentration is 0.01 to 5 mol / l as Fe. It is suitably used as a rapid analysis method for organic compounds in a stainless steel sulfuric acid pickling solution.

In the above-mentioned present invention and the first to ninth preferred embodiments of the present invention, the above-mentioned eluent is determined based on a detection value obtained by a detector and a standard substance. Quantification can be performed from the calibration curve. In addition, each provision regarding the mobile phase in the second preferred embodiment to the ninth preferred embodiment of the present invention described above relates to the mobile phase (carrier liquid) before merging (mixing) with the stainless steel sulfuric acid pickling solution as the sample. Is shown.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. High performance liquid chromatograph (hereinafter also referred to as HPLC)
Is used as a device for separating and quantifying organic components in a solution. However, when using liquid chromatography for the purpose of quantification, it is common practice to extract only the target component by some pretreatment and then prepare a nearly neutral solution for measurement in order to avoid interference with coexisting components. In addition, there is no example applied to a sample which is strongly acidic and contains a large amount of metal ions, such as the pickling solution of the present invention.

The present inventors have conducted intensive studies to solve the above-mentioned problems of the prior art, and have found the following findings (1) to (5).
(3) was found, which led to the present invention. (1) By analyzing the stainless steel sulfuric acid pickling solution with a high performance liquid chromatograph, it is possible to quantify the organic compounds in the stainless steel sulfuric acid pickling solution without special pretreatment.

(2) By using a liquid containing a hydrophilic organic solvent as the mobile phase of the high-performance liquid chromatograph, the stainless steel sulfate pickling solution can be directly introduced into the high-performance liquid chromatograph without any pretreatment. It is possible to completely separate the analysis target component from coexisting components such as acid and metal ion, prevent acid and metal ion from remaining in the column, and use the separation column continuously and repeatedly. .

(3) In the quantitative analysis of an organic compound having a carboxyl group added as a pickling accelerator to a sulfuric acid pickling solution of stainless steel, a hydrophilic organic solvent is contained as a mobile phase in a high performance liquid chromatograph, and By using a liquid to which an acid is added, splitting of the elution peak and fluctuation of the retention time can be prevented, and the analysis accuracy can be improved.

That is, in the present invention, a stainless steel sulfuric acid pickling solution containing sulfuric acid and metal ions is directly introduced into a separation column of a high-performance liquid chromatograph without special pretreatment, and is then separated from the separation column. The eluent from (1) is led to a detector, and the amount of organic compounds in the stainless steel sulfuric acid pickling solution is determined. Further, in a more preferred embodiment of the present invention, by using a liquid containing a hydrophilic organic solvent as a mobile phase of high performance liquid chromatography, an organic compound such as a pickling accelerator in a pickling solution is pickled with an acid. Separates a large amount of acid or metal ion in the liquid and prevents adsorption of the acid or metal ion to the separation column.

In a further preferred embodiment of the present invention, a mobile phase of a high performance liquid chromatograph is used for quantitative analysis of an organic compound having a carboxyl group added as a pickling accelerator to a sulfuric acid pickling solution of stainless steel. By using a liquid containing a hydrophilic organic solvent and adding an acid, splitting of the elution peak and fluctuation of the retention time are prevented.

The separated and eluted eluate is introduced into a detector,
The content of the organic compound is determined using a calibration curve prepared with a standard substance. Hereinafter, the stainless steel sulfuric acid pickling solution, the separation column, the mobile phase, and the detector in the present invention will be described. [Stainless Steel Sulfuric Acid Pickling Solution:] The present invention is used as a rapid analysis method for an organic compound in a stainless steel sulfuric acid pickling solution containing an organic compound such as a pickling accelerator.

Further, the present invention relates to an organic acid in a stainless steel sulfuric acid pickling solution containing an organic compound having a disulfide bond (-SS-) and / or an organic compound having a mercapto group (-SH group) as a pickling accelerator. It is suitably used as a rapid analysis method for compounds. Further, the present invention is suitably used as a rapid analysis method of an organic compound in a stainless steel sulfuric acid pickling solution containing the above-mentioned pickling accelerator having a carboxyl group for the reasons described below.

The pickling accelerator according to the present invention includes the following:
The organic compounds of (1) and (2) are exemplified. (1): an organic compound having a disulfide bond (: a disulfide compound);
Examples thereof include one or more organic compounds selected from the aliphatic compounds represented by (1) and (2) and the dithiosalicylic acid represented by the following formula (3).

S ₂ (C _n H _2n COOH) ₂ ... (1) S ₂ (C _n H _2n OH) ₂ ... (2) In the formulas (1) and (2), n Represents an integer selected from 1 to 10,
More preferably, n is an integer selected from 1 to 5.

[0022]

Embedded image

The aliphatic compounds represented by the general formula (1) include S ₂ (CH ₂ COOH) ₂ (dithiodiacetic acid) and S ₂ (CH ₂
CH ₂ COOH) ₂ (dithiodipropionic acid). As the aliphatic compound represented by the general formula (2), S ₂ (CH ₂ CH _2
2 OH) ₂ (dithiodiethanol). The dithiosalicylic acid represented by the formula (3) may have a substituent such as an alkyl group.

In the present invention, the compound represented by the general formula (1), (2) or (3) before mixing with the pickling solution has hydrogen atoms of carboxyl group and hydroxyl group of Na, K and the like. May be substituted with an alkali metal or an alkaline earth metal such as Ca or Mg. (2): an organic compound having a mercapto group; examples of the organic compound include mercaptoacetic acid, mercaptosuccinic acid, 2-mercaptopropionic acid, and mercaptoethanol, which are formed from 2-mercaptopropionic acid in a pickling solution. Also included are disulfides of 2-mercaptopropionic acid.

In the present invention, the carboxyl group and the hydrogen atom of the hydroxyl group of the above compound before mixing with the pickling solution are
It may be substituted with an alkali metal such as Na or K or an alkaline earth metal such as Ca or Mg. As described above, the preferred specific examples of the organic compound having a disulfide bond (disulfide compound) and the organic compound having a mercapto group in the present invention have been exemplified.
Both a disulfide compound and an organic compound having a mercapto group may be used in combination, or two or more of them may be used in combination.

In the present invention, the sulfuric acid concentration of the stainless steel sulfuric acid pickling solution when introduced into the separation column is preferably 10%.
_{~500g-H 2 SO 4 / l} , more preferably of _{50~500g-H 2 SO 4 / l} , more preferably an organic compound of a stainless steel sulfuric pickling solution is _{100 ~500g-H 2 SO 4 /} l It is suitably used as a rapid analysis method. In the present invention, the sulfuric acid concentration of the stainless steel sulfuric acid pickling solution when introduced into the separation column is preferably 10 to
_{500g-H 2 SO 4 / l} , 0.01~5mol / l iron ions concentration as Fe
, More preferably the concentration of sulfuric acid _{50~500g-H 2 SO 4 / l} ,
A stainless steel sulfuric acid pickling solution having an iron ion concentration of 0.01 to 5 mol / l as Fe, more preferably the above sulfuric acid concentration of 100 to 500 g-H ₂ SO ₄ / l, and an iron ion concentration of 0.01 to 5 mol / l as Fe It is suitably used as a rapid analysis method for organic compounds in the solution.

According to the present invention, the pickling solution can be prepared without removing these coexistent components even in the case of the above-mentioned high-concentration sulfuric acid or even a stainless steel sulfuric acid pickling solution containing iron ions. This is because it is possible to quantify the organic compounds therein. If the sulfuric acid concentration and further the iron ion concentration exceed the above-mentioned preferred upper limit, the separability of sulfuric acid and iron ions from the organic compound is reduced.

[Separation Column:] The present inventors have selected a graphite column having high acid resistance as a separation column for separating the above coexisting components and organic compounds such as a pickling accelerator. Graphite carbon columns have excellent mechanical strength (pressure resistance) due to the structure of carbon.
It has the advantage that it can be used in all pH ranges and that it can be used in both reversed-phase and normal-phase modes depending on the choice of mobile phase.

As other separation columns, silica-based columns using silica gel as a base, polymer-based columns more stable to acids than silica-based columns, and the like can be used. Although the above separation column is inferior in durability in the analysis of the pickling solution as compared with graphite carbon, it does not hinder the use in the analysis. [Mobile phase:] The present inventors eluted a large amount of acid and metal ions in a pickling solution that interfered with measurement without first adsorbing them to a separation column, for example, thiol added as a pickling accelerator. An organic compound as a target analytical component such as a disulfide compound was adsorbed and retained on a separation column for a predetermined time, and a mixed solution of a hydrophilic organic solvent and water was used as a mobile phase for this purpose.

According to the present invention, the following excellent effects can be obtained by using a liquid containing a hydrophilic organic solvent as the mobile phase. (1) Even if stainless steel sulfuric acid pickling solution is directly introduced into the high-performance liquid chromatograph without pretreatment, acids and metal ions are quickly eluted from the column, and organic compounds such as dithiodiacetic acid, which are the target analytes, are analyzed. Is captured on the column, and excellent separation performance can be obtained.

(2) Further, since a large amount of acid and metal ions can be rapidly eluted from the column, it is possible to prevent the acid and metal ions from remaining in the column even after repeated analysis. (3) Since all organic compounds such as acid, metal ion, dithiodiacetic acid, and oil in the stainless steel sulfuric acid pickling solution are dissolved in the hydrophilic organic solvent, high-performance liquid chromatography It is possible to prevent dirt and blockage in the solution flow piping system in the graph.

As the hydrophilic organic solvent in the present invention,
Although not particularly limited, acetonitrile, ethylenediamine, nitrogen-containing organic compounds such as monoethanolamine, methanol, ethanol, alcohols such as ethylene glycol, dioxane, tetrahydrofuran,
And at least one selected from acetone.

Although the concentration of the hydrophilic organic solvent is not particularly limited, the concentration is set to 3 to 30 vol% in order to accelerate the elution of the organic compound. It is preferable to elute the organic compound, which is the target analytical component, after is completely eluted.
Many of the disulfide compounds and organic compounds having a mercapto group added as a pickling accelerator have a carboxyl group in order to have water solubility.

As a result, based on these acid dissociation equilibria,
Multiple species are generated depending on the pH of the liquid in the separation column,
The elution peak is split into multiple peaks, and the retention time fluctuates, which lowers the analysis accuracy. Therefore, in the present invention, when quantifying the organic compound having a carboxyl group, it is preferable to add a small amount of acid to the liquid as the mobile phase in advance to suppress acid dissociation.

The type of the acid to be added is not particularly limited, and any of an inorganic acid and an organic acid can be used. Sulfuric acid and / or
Or perchloric acid is preferred. The acid addition concentration is 0.1 to 10
A 0 mmol / l mobile phase (carrier liquid) is preferred. Since increasing the acid concentration increases the retention time of an organic compound such as a disulfide compound, the elution time is preferably adjusted according to the amount of the hydrophilic organic solvent.

In the present invention, when the organic compound to be quantified is an organic compound having a hydroxyl group such as dithiodiethanol or mercaptoethanol, dissociation does not occur as in the case of a carboxylic acid. Is not particularly necessary. [Detector:] According to the present invention described above, the target analytical component can be completely separated from the coexisting component in the separation column by the mobile phase used in the present invention.

For this reason, as a detector for a target analysis component, a general-purpose ultraviolet-visible absorption photometer detector, an electric conductivity detector, an electrochemical detector, a differential refractometer detector, a fluorometer detector, and the like are used. The detector is not limited as long as it can be used and can detect the target organic compound. According to the present invention, the acid and metal ions contained in the stainless steel sulfuric acid pickling solution do not remain in the separation column, so that the separation column can be used continuously and repeatedly.

[0038]

The present invention will be described more specifically below with reference to examples. Using the analysis method of the present invention, a stainless steel sulfuric acid pickling solution (sulfuric acid pickling solution for a hot-rolled stainless steel sheet, to which mercaptoacetic acid (HSCH ₂ COOH) is added as an acid pickling accelerating component.
Sulfuric acid concentration: 250 g-H ₂ SO ₄ / l) was quantitatively analyzed.

Since mercaptoacetic acid becomes dithiodiacetic acid (H00CCH ₂ SSCH ₂ COOH) in the pickling solution, dithiodiacetic acid was quantified. As a separation column for high-performance liquid chromatography,
Graphite carbon column: Hypercarb (trade name, 5
μm, 100 × 4.6 mm I.D., manufactured by Htpersil). As a liquid (carrier liquid) as a mobile phase, an aqueous solution to which acetonitrile concentration was 10 vol% and sulfuric acid concentration was 5 mmol-H ₂ SO ₄ / l was used, and 1 ml / min.
The liquid was sent at the speed shown in FIG. When introducing the sample into the separation column, the sulfuric acid concentration of the stainless steel pickling solution was 250 g-H ₂ SO ₄ / l, and the iron ion concentration was 2 mol / l as Fe.

The sample injection volume was 20 μL. An ultraviolet / visible absorptiometer equipped with a flow cell for HPLC was used as a detector, and the absorbance at 210 nm was measured. The calibration curve was prepared using dithiodiacetic acid as a reagent. An example of the obtained calibration curve and a chromatogram of the pickling solution are shown in FIGS. 2 and 3, respectively.

Table 1 shows the results of repeatedly quantifying dithiodiacetic acid in the pickling solution by changing the analysis date using the calibration curve of FIG. FIG. 1 shows a correlation diagram between the analysis values obtained by the analysis method of the present invention and the analysis values obtained by the conventional solvent extraction / NMR method. As shown in Table 1 and FIG. 1, according to the analysis method of the present invention, the stainless steel sulfuric acid pickling solution can be used without performing special pretreatment of the sample such as separation and removal of sulfuric acid and iron ions outside the system. It has been found that organic compounds such as pickling accelerators in the solution can be analyzed quickly and accurately with excellent accuracy.

[0042]

[Table 1]

[0043]

As described above, according to the present invention, the analysis of organic compounds such as a pickling accelerator in a sulfuric acid pickling solution of stainless steel, which has conventionally required a long time for sample pretreatment and measurement, is performed. Simple, fast, without the need for special sample preparation
Moreover, it has become possible to carry out with high precision and accuracy.

The present invention is also applicable as an on-site on-site analysis method. Based on the analysis results obtained by the analysis method of the present invention, an appropriate amount of a pickling accelerator is promptly added to a pickling solution. It can be added, and a remarkable effect is expected in terms of product quality improvement and stable production.

[Brief description of the drawings]

FIG. 1 is a correlation diagram showing a relationship between an analysis value obtained by an analysis method of the present invention and an analysis value obtained by a solvent extraction / NMR method.

FIG. 2 is a graph showing an example of a calibration curve.

FIG. 3 is a graph showing an example of a chromatogram obtained by the analysis method of the present invention.

Claims (4)

[Claims] 1. A stainless steel sulfuric acid pickling solution is introduced into a separation column of a high performance liquid chromatograph, an eluent from the separation column is guided to a detector, and the amount of an organic compound in the stainless steel sulfuric acid pickling solution is determined. A rapid analysis method for an organic compound in a sulfuric acid pickling solution of stainless steel, characterized by comprising: 2. The method for rapidly analyzing an organic compound in a sulfuric acid pickling solution of stainless steel according to claim 1, wherein the separation column is a graphite carbon column. 3. The rapid analysis of an organic compound in a sulfuric acid pickling solution of stainless steel according to claim 1 or 2, wherein a liquid containing a hydrophilic organic solvent is used as a mobile phase of the high performance liquid chromatograph. Method. 4. The method according to claim 1, wherein the organic compound is an organic compound having a carboxyl group, and a liquid containing a hydrophilic organic solvent and containing an acid is used as a mobile phase for the high performance liquid chromatography. Or the method for rapid analysis of organic compounds in a stainless steel sulfuric acid pickling solution according to item 2.