JP2634077B2 - Trace iodide measuring device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an apparatus for measuring a small amount of iodide, which is useful for quantifying a small amount of iodide in a material.

[Problems to be Solved by the Prior Art and the Invention] Iodine and waxes start from iodine tincture, pharmaceuticals on iodoform, photographic chemicals, analytical reagents, and catalysts for synthesizing organic compounds, such as methanol and carbon monoxide. It is widely used as a rhodium-iodine catalyst in the production of acetic acid as a raw material, methyl iodide as a cocatalyst, and the like. Quantifying such iodine or iodide is useful in wastewater treatment and in process control of the reaction. In particular, since a synthesis catalyst is generally used in a small amount, it is important for quality control to determine a trace amount of iodide present in a product.

The determination of iodide is generally based on the fact that iodide ion (I ⁻ ) acts catalytically on tetravalent cerium ion (Ce [IV]) and trivalent arsenic ion (As [III]), Cerium ion (Ce [III]) and pentavalent arsenic ion (As
[V]). A colorimetric method is known as a method for quantifying iodide using this reaction. In the colorimetric method, a predetermined amount of a sample containing iodide is added to a predetermined amount of a reagent in which Ce [IV] ion and As [III] ion are stabilized with sulfuric acid, and after the above-described oxidation-reduction reaction, iron complex coloring in red when adding a reagent containing a) ^- Ce (IV) ion of divalent iron [Fe (II)) to produce a Fe [III] ion was reduced by ion, thiocyanate ion (SCN that [Fe (SCN) ₆ ] ^3- is used.
More specifically, in this colorimetric method, for example, Ce of 0.02N
(IV) reagent 0.5 ml, 0.1N As (III) reagent 5 ml and sample 5 ml
Is mixed in a 25 ml volumetric flask, and then heated at a temperature of 50 ° C. for about 10 minutes to perform an oxidation-reduction reaction. Then 0.08N F
e [II] Add 1 ml of reagent, cool, leave at room temperature for about 15 minutes, add 1 ml of 1.0N SCN ^- reagent, make up to a predetermined amount with water, and store in a 1 cm optical path length cell And a wavelength of 488 nm
The iodine ion concentration can be quantified by performing colorimetry with this light beam. However, in this colorimetric method, it is necessary to manually perform many steps such as weighing, mixing, and heating.
Moreover, four types of reaction reagents are required. Accordingly, the analysis operation becomes complicated, and the analysis of iodide requires a long time of one hour or more, and the analysis accuracy is necessarily reduced. As described above, the conventional colorimetric method cannot quickly and accurately measure a sample containing a small amount of iodide, which hinders process control and quality control.

On the other hand, as a method for quickly quantifying a small amount of iodide,
The following Drex reaction Injection analysis (Flow Injecti) utilizing the fact that Ce [III] generated by
on Analysis, FIA) [Analytical Sciences, 2 , 197-198
(1986)].

FIG. 3 is a schematic view showing a conventional apparatus using FIA. This device is the first to send Ce [IV] reagent constantly.
And a second reagent sending line (32) that constantly sends the As [III] reagent and joins the first reagent sending line (31). Ce [IV] reagent
A mixing section (33) for mixing the As [III] reagent, and a water feeding line (34) for constantly sending degassed water and joining with the mixed reagent mixed in the mixing section (33). And a sample injection section (35) for injecting a sample in the middle of the water supply line (34). The degassed water referred to here is degassed water that does not contain impurities that hinder the oxidation-reduction reaction. Each of the lines (31), (32), (34) and the mixing section (33) is constituted by a tube or a coiled tube. The sample mixed with each reagent and mixed is sent to a reaction section (36), and heated to a temperature of about 90 ° C. in the reaction section (36) to produce Ce.
[III] and As [V] are produced and cooled in the cooling section (37). The reaction section (36) and the cooling section (37) are each composed of a tube or a coiled tube for sending the mixed solution and the reaction solution, and a heating bath and a cooling bath. Then, when the iodine ion ^- concentration in the sample is proportional to the generated Ce [III] concentration, and Ce [III] is excited by a light beam having a wavelength of 254 nm,
Utilizing the emission of 365-nm wavelength fluorescence, the fluorescence detection unit (38) detects the fluorescence, and measures the iodine ion concentration based on a previously obtained calibration curve. In the figure, the symbol (P) is a peristaltic pump that constantly supplies each reagent and the like. This report also reports that when an iodine solution is used as a sample, iodide with a detection limit of about 0.4 ppb can be quantified.

Compared to the manual method, the FIA method has the advantage that it does not require skill, has good reproducibility, has no individual differences, has a short analysis time, and can process and automate a large number of samples. Have.

However, since the detection limit by this FIA method is about 0.4 ppb, it is difficult to accurately quantify a trace amount of iodide. In addition, when applied to industrially produced organic compounds containing iodide, such as acetic acid, the detection accuracy is significantly reduced, probably because the sample is injected into the middle of the water supply line (34). It is difficult to apply to process control and quality control of manufactured products.

Accordingly, it is an object of the present invention to provide a highly reliable trace iodide measuring device capable of accurately and quickly measuring a trace amount of iodide.

Another object of the present invention is to provide a trace iodide measuring device capable of continuously and automatically processing a large number of samples.

It is a further object of the present invention to provide an apparatus for measuring trace iodide, which can be applied to industrially manufactured products while utilizing the FIA method.

[Means for Solving the Problems] A volume ratio (former / latter) of a tetravalent cerium Ce [IV] reagent having a concentration of 0.1 to 10 mM and a trivalent arsenic As [III] reagent having a concentration of 5 to 100 mM is 3 A reagent feed line for constantly feeding a mixed solution mixed at a ratio of / 7 to 7/3 in a stabilized state, and merging with the reagent feed line, and constantly sending degassed water. A water supply line, a sample injection part in the middle of the water supply line for injecting a sample containing iodide, a reaction part for performing an oxidation-reduction reaction between the combined reagent and the sample, A detection unit for detecting cerium, wherein the sample injection unit is a middle part of a water-soluble solvent feeding line where the water-soluble solvent is constantly fed, and merges with the water feeding line. The above problem is solved by a trace iodide measuring device characterized by being provided in is there.

[Operation] According to the present invention having the above configuration, the sample injection section is provided in the middle of the water-soluble solvent supply line, so that the sample
The water-soluble solvent feed line and the water feed line which are constantly supplied are sequentially merged. In the reaction section, iodide ion I ^-
Acts as a catalyst and Ce [II
I] and is and As (V) to produce a concentration of the generated Ce (III) is iodide ion I in the sample ^- is proportional to the concentration. At this time, the water-soluble solvent sent in the water-soluble solvent sending line has a buffering action, and the sample has a specific concentration of Ce [IV] reagent and As
[III] The detection unit can accurately detect a trace amount of iodide in a sample even for an industrially manufactured product or the like, probably because of a confluence with a mixture containing a reagent at a specific ratio.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the accompanying drawings. In this specification, ppb means parts per billion by weight.

FIG. 1 is a schematic view showing one embodiment of the device for measuring a small amount of iodide of the present invention, in which a tetravalent cerium Ce [IV] reagent and a trivalent arsenic As [III] reagent are supplied by a constant flow pump ( P1) and a first reagent delivery tube (t1) composed of a first reagent delivery tube (t1), a constant flow pump (P2) and a second reagent delivery tube (t2). The liquid is constantly supplied to the second reagent liquid supply line (1b). In addition, the first reagent solution sending line (1a) and the second reagent solution sending line (1b) merge with each other to form a reagent solution sending line (1). In addition, each reagent is a sulfuric acid solution for stabilization,
For example, it is used as a sulfuric acid aqueous solution of about 0.1 to 2M, preferably about 0.5 to 1.5M.

The concentration of the Ce [IV] reagent is 0.1-10 mM, preferably 0.5-5 m
M, and the concentration of the As [III] reagent is about 5 to 100 mM, preferably about 5 to 50 mM.

The inner diameter of the first reagent delivery tube (1a) and the second reagent delivery tube (1b) can be appropriately set according to the desired reagent delivery volume, but is usually about 0.5 to 5 mm, preferably about 0.5 to 5 mm. Is about 1 mm. The above-mentioned Ce [IV] reagent and As [III] reagent are sent at the same or different rates, respectively, when the supply ratio of the two is within the range of 3/7 to 7/3 (volume ratio). Yes, the first reagent delivery tube (1a) and the second
When the inner diameter of the reagent feeding tube (1b) is about 1 mm, the solution can be sent at a rate of usually about 0.1 to 1 ml / min, preferably about 0.3 to 0.7 ml / min.

This apparatus has a water feed line (2) composed of a constant flow pump (P3) and a water feed tube (2a), and the water feed line (2) is made of distilled water or the like. Degassed water is constantly fed and merges in the middle of the reagent solution sending line (1). This degassed water can be sent at an appropriate speed. For example, when the inner diameter of the water supply tube (2a) is about 1 mm, it is usually about 0.1 to 1 ml / min, preferably 0.2 to 0.1 ml / min.
The liquid can be sent at a speed of about 6 ml / min.

In order to stably and accurately detect iodide even in the case of a small amount of iodide contained in industrial products, it is composed of a constant flow pump (P4) and a water-soluble solvent feeding tube (3a). A water-soluble solvent feed line (3) is provided. The water-soluble solvent feed line (3) constantly feeds a water-soluble solvent, and merges with the water feed line (2). I have. A predetermined amount of the sample containing iodide is supplied to a sample injection section (4) provided in the middle of the water-soluble solvent supply line (3).
Injected from. The sample injection section (4) can be constituted by a conventionally used injection valve or the like. Therefore, the sample injected from the sample injection section (4) joins the aqueous solvent sending line (3) and the water sending line (2) sequentially, and further joins the reagent sending line (1).

The water-soluble solvent is not particularly limited as long as it is water-soluble. Examples of such a water-soluble solvent include alcohols such as methanol, ethanol, propanol, isopropanol, ethylene glycol, diethylene glycol, polyethylene glycol, methoxyethanol, ethoxyethanol, and glycerin; ketones such as acetone; dioxane, tetrahydrofuran, and diethylene glycol. Ethers such as dimethyl ether; formic acid, acetic acid,
Monochloroacetic acid, trichloroacetic acid, trifluoroacetic acid,
Organic acids and their derivatives such as thioglycolic acid, formamide, N-methylformamide, N, N-dimethylformamide, N-methylacetamide and hexamethylphosphoric triamide; amines such as pyridine and morpholine, and mixed solvents thereof Is exemplified. These water-soluble solvents are preferably the same type of solvent as the solvent in the sample, particularly preferably the same solvent.

The water-soluble solvent can be sent at an appropriate speed, but when the inner diameter of the water-soluble solvent delivery tube (3a) is about 1 mm,
The liquid is sent at a rate of about 0.2 to 4 ml / min, preferably about 0.5 to 2 ml / min.

The mixed liquid of each of the combined samples is sent to the reaction section (5), where an oxidation-reduction reaction is performed. The reaction section (5) is composed of a reaction coil (5a) for performing the above-mentioned reaction while feeding a liquid and a heating bath (5b) in order to increase the detection sensitivity. The inner diameter and length of the reaction coil (5a) are not particularly limited as long as they do not hinder the reaction time. The inner diameter of the reaction coil (5a) is the same as the reagent feeding tube (1a) ( It can be set as in 1b). Since the detection sensitivity increases substantially in proportion to the length of the reaction coil (5a) and the reaction temperature, the length and the reaction temperature of the reaction coil (5a) are appropriately determined according to the desired detection limit value of iodide. Can be set. The length of the reaction coil (5a) is usually about 0.5 to 10 m, preferably about 1 to 5 m. The reaction temperature of the reaction section (5) by the heating bath (5b) is as follows:
The temperature is about 30 to 110 ° C, preferably about 40 to 100 ° C, and more preferably about 50 to 90 ° C. When the length of the reaction coil (5a) and the reaction temperature are set as described above, iodide of about 0.1 ppb can be accurately detected. When the reaction temperature is about 80 ° C., a reaction time of about 1 to 2 minutes is sufficient.

The reaction solution reacted in the reaction section (5) is cooled in a cooling section (6) composed of a cooling coil (6a) and a cooling bath (6b). The temperature of the cooling section (6) is not particularly limited, but is usually about -10C to 30C, preferably about 0C. The inner diameter and length of the cooling coil (6a) are set within a range in which the reaction solution can be cooled. The inner diameter of the cooling coil (6a) can be set in the same manner as the reagent feeding tubes (1a) and (1b), and the length is usually about 0.1 to 4 m, preferably about 0.3 to 3 m.

Then, Ce produced by the reduction reaction in the reaction section (5)
[III] is detected by the detection unit (7). This detector (7)
Although the Ce [IV] reagent and the As [III] reagent may be used to detect the oxidation-reduction potential or the like after the reaction with respect to the oxidation-reduction potential,
In order to enhance the detection sensitivity, it is preferable to detect the fluorescence intensity of the generated Ce [III]. The Ce [III] concentration can be measured by irradiating a light beam having a predetermined wavelength to excite it and detecting emitted fluorescence. Therefore, it is preferable that the detection section (7) is constituted by a fluorescence detector. Note that Ce [II
Since the excitation and fluorescence wavelengths of I) differ depending on the water-soluble solvent, it is necessary to measure the optimum wavelength in advance. When the water-soluble solvent is acetic acid, the excitation wavelength is 260 nm and the fluorescence wavelength is 352 nm.

The data detected by the detection section (7) is recorded by the recording section (8) of the recorder. The reaction solution whose Ce [III] concentration has been detected by the detection section (7) is discharged.

According to the above-described measuring device, two kinds of reaction reagents may be used, while four kinds of reaction reagents are required in the conventional colorimetric method. In contrast to the conventional colorimetric method, which required one hour or more for measurement, the measurement can be performed in a short time of about two minutes per sample. Therefore, the measurement time can be shortened, and a large number of samples can be processed continuously. In addition, compared to the conventional FIA method, a trace amount of iodide can be measured with high accuracy, and the reliability is high. That is, the above measuring device can accurately measure iodide of about 0.1 ppb, and the coefficient of variation (CV value) of the analysis is about 3% when the number of samples is n = 3, so that the reliability is high. Furthermore, the present invention can be applied to industrially produced organic compounds.

In addition, in each of the above tests, the flow rate of water or a water-soluble solvent can be adjusted by a flow rate adjusting means such as a solenoid valve. Also Ce [IV]
The reagent and the As [III] reagent may be sent in a mixed state as necessary. Further, a mixing coil may be provided at an appropriate position of each reagent or a liquid sending line passing through a junction of degassed water and a water-soluble solvent in order to increase mixing efficiency. Further, the tube, the coil, and the connector for connecting these can be formed of a non-corrosive material, for example, stainless steel, polytetrafluoroethylene, ceramic, or the like. It is preferable to use a non-corrosive material, for example, ruby, sapphire, ceramic, or the like, as the material of the liquid contact portion of the pump.

Further, the Ce [III] concentration C Ce [I
II] is the Ce [IV] concentration in the reagent C Ce [IV], As [III]
It is affected by the concentration C As [III], the iodide concentration CI in the sample, the reaction temperature T, the reaction time RT, in other words, the flow rate.
That is, the iodide concentration CI in the sample is determined by the detection unit (7) C
e [III] concentration C is proportional to Ce [III] and this Ce [III] concentration
The relationship between C Ce [III] and each of the above factors is represented by the following relational expression.

C Ce [III] = f (C Ce [IV], C As [III], CI,
T, RT) Therefore, to accurately detect the concentration CI of iodide,
It is preferable to compensate the concentration of the reagent, the temperature of the reaction temperature, the reaction time, in other words, the flow rate. Such compensation,
This can be performed by obtaining a change in the detection value accompanying a change in each factor.

In addition, in order to quickly measure a large number of samples, it may be automated. FIG. 2 is a block diagram showing another embodiment of the present invention. In this device, a detection unit (17) for detecting the Ce [III] concentration in the same manner as described above, an A / D converter (18) for A / D converting detection data detected by the detection unit (17), A memory (19) for storing the converted data, and the following relational expression C Ce [III] = f (C Ce [IV], C As [III], CI,
(T, RT) Storage unit such as ROM for storing the program indicated by (20)
And the detection data stored in the memory (19) and the storage unit (2
An arithmetic unit (21) for calculating the Ce [III] concentration based on the program stored in (0) and a display unit (22) for displaying the calculation result. In addition, reagent sending line (11),
The water feed line (12), the water-soluble solvent feed line (13), the sample injection section (14), the reaction section (15), and the cooling section (16) are configured as described above.

Each of the liquid sending lines (11), (12) and (13) is provided with a flow rate sensor (not shown) for detecting a flow rate of a reagent or the like, and a temperature sensor is provided in the reaction section (15) and the cooling section (16). (Not shown) is provided. The memory (19) is provided with a data input unit (not shown) for inputting reagent concentration data. The flow rate sensor, the temperature sensor, and the reagent concentration data are A / D-converted by an A / D converter, respectively stored in the memory (19), subjected to an arithmetic operation based on the relational expression, and provided with a feedback control unit ( (Not shown)
Controls the flow rate and temperature.

According to the above apparatus, the calculating section (21) calculates and displays iodide concentrations in a large number of samples quickly and continuously on the basis of the data detected by the detecting section (17), and displays and prints as necessary. Can be out.

When measuring the iodide concentration in a sample under the condition that the reagent concentration and the reaction temperature are constant, the relational expression stored in the storage unit (20) is simply expressed as C Ce [III] = f (CI). Be transformed into

Further, in order to perform the process control with high accuracy, the supply amounts of the raw materials and the catalyst in the production plant may be automatically controlled based on the iodine ion concentration measured as described above.

[Effects of the Invention] As described above, according to the present invention, the sample injection section is provided with a water-soluble solvent that is constantly fed, and is located in the middle of the water-soluble solvent feeding line that merges with the water feeding line. In addition to the conventional FIA method, the sample is combined with a mixture containing a specific concentration of a tetravalent cerium Ce [IV] reagent and a trivalent arsenic As [III] reagent in a specific ratio. , A small amount of iodide can be accurately measured. In addition, two types of reaction reagents may be used, and the time required to measure one sample is 2
Because it is on the order of minutes, it can be measured quickly and has high reliability. Furthermore, while being able to process a large number of samples continuously and automatically, it is also applicable to industrially produced organic compounds.

[Experimental Examples] Hereinafter, the present invention will be described in more detail based on experimental examples.

Experimental Example 1 In the apparatus shown in FIG.
a), a water feeding tube (2a), a water-soluble solvent feeding tube (3a), a reaction coil (5a) and a cooling coil (6a) are formed of a Teflon tube having an inner diameter of 1 mm, and a detection unit (7). However, an apparatus having a fluorescence detector with an excitation wavelength of 260 nm and a detection wavelength of 352 nm was used. Also, changing the Ce [IV] concentration / 1 M sulfuric acid solution, under the following conditions, iodide concentration 1 ppb, 2 pp
b, 4ppb and 10ppb when the fluorescence intensity of the sample was measured,
The results shown in FIG. 4 were obtained.

Ce (IV) concentration: 0.325 mM, 0.65 mM, 1.3 mM, 2.6 mM, flow rate 0.
5 ml / min As [III] concentration: 25 mM / 1 M sulfuric acid solution, flow rate 0.5 ml / min Water: flow rate 0.4 ml / min Water-soluble solvent: acetic acid, flow rate 1.2 ml / min Reaction coil (5a) length: 3 m, reaction Temperature: 80 ° C. Length of the cooling coil (6a): 0.6 m, cooling temperature: 0 ° C. (ice water) From FIG. 4, the detection intensity increases as the concentration of the Ce [IV] reagent increases.

EXPERIMENTAL EXAMPLE 2 The same procedure as in Experimental Example 1 was carried out, except that the iodide concentration was 1 ppb, 2 ppb,
When the fluorescence intensities of the 4 ppb and 10 ppb samples were measured, the results shown in FIG. 5 were obtained.

Ce [IV] concentration: 1.3 mM / 1M sulfuric acid solution, flow rate 0.5 ml / min As [III] concentration: 6.25 mM, 12.5 mM, 25 mM, 50 mM / 1M sulfuric acid solution, flow rate 0.5 ml / min The fluorescence intensity of an acetic acid solution sample having an iodide concentration of 1 ppb, 2 ppb, and 4 ppb was measured in the same manner as in Experimental Example 1 except that the measurement was performed under the following conditions, and the results shown in FIG. 6 were obtained.

Ce [IV] concentration: 1.3mM / 1M sulfuric acid solution, flow rate 0.5ml / min Reaction temperature: 80 ° C (air bath), 60 ° C (hot water bath), 70 ° C (hot water bath), 80 (hot water bath) Fig. 6 Thus, the detection intensity increases as the reaction temperature increases.

Experimental Example 4 The fluorescence intensity of the samples with iodide concentrations of 1 ppb, 2 ppb, and 4 ppb was measured in the same manner as in Experimental Example 1 except that the apparatus shown in Experimental Example 1 was used under the following conditions, and the results shown in FIG. 7 were obtained. I got

Ce [IV] concentration: 1.3 mM / 1 M sulfuric acid solution, flow rate 0.5 ml / min Length of reaction coil (5a): 2 m, 3 m and 4 m From FIG. 7, the longer the length of the reaction coil, in other words, The longer the reaction time, the greater the detection intensity.

EXPERIMENTAL EXAMPLE 5 The iodide concentration was 0.1 ppb and 0.2 pb in the apparatus shown in Experimental Example 1 in the same manner as in Experimental Example 1 except that the following conditions were used.
The fluorescence intensities of the pb, 0.4 ppb and 1 ppb samples were measured, and the iodide concentration was calculated based on the calibration curve. The measurement was repeated three times (n = 3) for the same sample to determine the coefficient of variation.

Ce [IV] concentration: 1.3 mM / 1 M sulfuric acid solution, flow rate 0.5 ml / min Reaction temperature: 80 ° C. (water bath) The calibration curve under these conditions is shown in FIG.

The concentration of iodide in the sample was measured by a conventional colorimetric method.

 The results are shown in the table.

Comparative Experimental Example In the conventional apparatus shown in FIG. 3, an iodide concentration of 1 ppb acetic acid solution was used as a sample under the same conditions as in the above experimental example 1, and the iodide concentration was measured. , Iodide could not be detected. When an aqueous solution having an iodide concentration of 1 ppb was used, 1 ppb of iodide could be detected.

[Brief description of the drawings]

FIG. 1 is a schematic view showing one embodiment of a measuring device for a trace iodide of the present invention, FIG. 2 is a block diagram showing another embodiment of the present invention, and FIG. FIGS. 4 (A) to 8 are schematic diagrams respectively showing the results of the experimental examples. (1) (11) ... reagent sending line, (2) (12) ... water sending line, (3) (13) ... water-soluble solvent sending line, (4) (14) ... sample Injection section, (5) (15) ... reaction section, (5a) (15a) ... reaction coil, (6) (16) ... cooling section, (7) (17) ... detection section

Claims (3)

(57) [Claims] 1. Tetravalent cerium Ce [IV] having a concentration of 0.1 to 10 mM
A reagent and a trivalent arsenic As [III] reagent having a concentration of 5 to 100 mM,
A reagent sending line for constantly sending a mixed solution mixed at a volume ratio (former / latter) = 3/7 to 7/3 in a stabilized state;
A water feeding line that merges with the reagent feeding line, and constantly feeds degassed water, and a sample injection unit that injects a sample containing iodide at an intermediate portion of the water feeding line,
An apparatus having at least a reaction unit for performing an oxidation-reduction reaction between a combined reagent and a sample, and a detection unit for detecting the generated trivalent cerium, wherein the sample injection unit constantly supplies a water-soluble solvent. A trace iodide measuring device, which is provided in a middle part of a water-soluble solvent sending line which is liquefied and merges with a water sending line. 2. The reaction section according to claim 1, wherein the temperature of the reaction section is 30 to 110 ° C.
An apparatus for measuring a trace amount of iodide as described in the above. 3. The apparatus according to claim 1, wherein the reaction section has a reaction coil having a length of 0.5 to 10 m.