Quantitative determination method for sulfur-containing compound

Abstract

To provide a quantitative determination method for sulfur-containing compounds that enables stable measurements over a longer period.SOLUTION: The quantitative determination method for sulfur-containing compounds uses rubber compositions containing alkylthiophene as a standard reference material.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for quantifying sulfur-containing compounds.

Background Art

[0002] When quantifying sulfur-containing compounds in a composition containing sulfur-containing compounds, for example, pyrolysis gas chromatography / mass spectrometry (pyrolysis GC / MS) is generally used. However, since the sensitivity of pyrolysis GC / MS varies daily, in order to compare samples measured on different days, it is necessary to correct the peak intensity with a standard substance and then compare them. Dibenzothiophene, which is stable to heat, is generally used as the standard substance (see Non-Patent Document 1).

Prior Art Documents

Non-Patent Documents

[0003]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] As described above, dibenzothiophene is generally used as the standard substance in the quantitative analysis of sulfur-containing compounds. Here, when analyzing a plurality of samples, it is usually necessary to use an autosampler for work efficiency. However, as a result of intensive studies by the present inventors, since dibenzothiophene has sublimability, when set in the autosampler, it volatilizes over time and the peak area decreases. It has been found that dibenzothiophene is not suitable as a standard substance when using an autosampler. Therefore, the present inventors examined whether alkylthiophene, which is stable to heat and does not have sublimability, could be used as a standard substance in the quantitative analysis of sulfur-containing compounds. As a result, when alkylthiophene was dissolved in an organic solvent and subjected to pyrolysis GC / MS measurement, it was found that there was a large variation in the peak area for each sample, indicating that there is room for improvement in using alkylthiophene as a standard substance in the quantitative analysis of sulfur-containing compounds.

[0005] An object of the present invention is to solve the above problems and provide a method for quantitatively analyzing sulfur-containing compounds that enables stable measurement over a long period.

Means for Solving the Problems

[0006] The present invention relates to a method for quantitatively analyzing sulfur-containing compounds, characterized by using a rubber composition containing alkylthiophene as a standard substance.

Effects of the Invention

[0007] Since the present invention is a method for quantitatively analyzing sulfur-containing compounds, characterized by using a rubber composition containing alkylthiophene as a standard substance, stable measurement over a long period is possible, and it is possible to compare the amounts of sulfur-containing compounds in compositions containing sulfur-containing compounds with different measurement timings on different measurement dates.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Modes for Carrying Out the Invention

[0009] The present invention is a method for quantifying a sulfur-containing compound, characterized by using a rubber composition containing alkylthiophene as a reference substance. By adopting such a method, stable measurement can be achieved over a long period of time. Therefore, it is possible to compare the amounts of sulfur-containing compounds in compositions containing sulfur-containing compounds, where the measurement timings are different due to different measurement dates.

[0010] The reason for obtaining the above-described effects is not necessarily clear. However, when alkylthiophene is kneaded into rubber to form a rubber composition and the rubber composition is used as a reference substance, for example, in the case of subjecting it to pyrolysis GC / MS measurement, the variation in pyrolysis for each reference substance (the rubber composition) becomes small. As a result, the variation in peak area also becomes small. Consequently, stable measurement can be achieved over a long period of time, and it is presumed that it becomes possible to compare the amounts of sulfur-containing compounds in compositions containing sulfur-containing compounds, where the measurement timings are different due to different measurement dates.

[0011] The rubber composition used as a reference substance in the present invention contains at least alkylthiophene and a rubber component. The alkylthiophene is not particularly limited as long as it is a compound in which at least one or more alkyl groups are bonded to thiophene. Examples thereof include compounds represented by the following formula (1).

[0012]

Chemical formula

[0013] In the above formula (1), R is an alkyl group having 1 to 30 carbon atoms, and the alkyl group may have a substituent. n is an integer of 1 to 4. A plurality of Rs may be the same or different.

[0014] In the above formula (1), the number of carbon atoms of R is preferably 2 or more, more preferably 5 or more, still more preferably 7 or more, and even more preferably 10 or more. Also, it is preferably 27 or less, more preferably 25 or less, still more preferably 23 or less, even more preferably 20 or less, and particularly preferably 16 or less.

[0015] Specific examples of R in the above formula (1) include, for example, branched or unbranched alkyl groups such as methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, sec-butyl group, t-butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, nonadecyl group, eicosanyl group, heneicosanyl group, tetracosanyl group, nonacosanyl group, triacontanyl group.

[0016] Examples of the substituents that the above alkyl group can have include, for example, alkoxy groups such as methoxy group, ethoxy group, butoxy group; alkenyl groups such as vinyl group, allyl group, butenyl group; aryl groups such as phenyl group, naphthyl group, biphenyl group; alkyl groups such as methyl group, ethyl group, butyl group, t-butyl group; ether bond, ester bond, and the like.

[0017] In the above formula (1), n is an integer from 1 to 4. Among them, 1, 2, and 3 are preferred, 1 and 2 are more preferred, and 1 is even more preferred. In addition, when n in the above formula (1) is an integer from 1 to 3, the bonding position of R to thiophene is not particularly limited.

[0018] From the viewpoint of obtaining better effects of the present invention, the compound represented by the above formula (1) is preferably, for example, the compound represented by the following formula (1-1).

[0019]

Chemical formula

[0020] In the above formula (1-1), R is an alkyl group having 1 to 30 carbon atoms, and the alkyl group may have a substituent.

[0021] R in the above formula (1-1) is the same as R in the above formula (1).

[0022] Among the compounds represented by the above formula (1), from the viewpoint that the effects of the present invention can be obtained particularly well, the compounds represented by the following formula (1-2) are particularly preferred.

[0023]

Chemical formula

[0024] The rubber components that can be used are not particularly limited. For example, diene rubbers and the like can be used. Examples of diene rubbers include isoprene rubbers, butadiene rubbers (BR), styrene-butadiene rubbers (SBR), styrene-isoprene-butadiene rubbers (SIBR), ethylene-propylene-diene rubbers (EPDM), chloroprene rubbers (CR), acrylonitrile-butadiene rubbers (NBR), and the like. Also, butyl rubbers, fluororubbers, and the like can be mentioned. These may be used alone or in combination of two or more.

[0025] The content of alkylthiophene in the above rubber composition is not particularly limited. However, from the viewpoint that the effects of the present invention can be obtained better, based on 100 parts by mass of the rubber component, it is preferably 0.1 part by mass or more, more preferably 0.5 part by mass or more, still more preferably 1 part by mass or more, and even more preferably 1.5 part by mass or more. Also, it is preferably 10 parts by mass or less, more preferably 7 parts by mass or less, still more preferably 5 parts by mass or less, and even more preferably 3 parts by mass or less.

[0026] The above rubber composition may contain components other than alkylthiophene and the rubber component as long as the effects of the present invention are not inhibited, but it is desirable that there are as few other components as possible. Specifically, the content of the above other components in 100% by mass of the above rubber composition is preferably 1% by mass or less, more preferably 0.5% by mass or less, still more preferably 0.1% by mass or less, and even more preferably 0.01% by mass or less.

[0027] The above rubber composition can be produced by using a known kneading method, for example, kneading each of the above components using a rubber kneading apparatus such as an open roll or a Banbury mixer.

[0028] In the present invention, the above rubber composition is used as a standard substance, for example, for pyrolysis GC / MS measurement. It is preferable that the rubber composition (standard substance) to be used is finely cut and its weight is accurately weighed. By using such a rubber composition as a standard substance, the variation in pyrolysis for each standard substance becomes small, so the variation in peak area also becomes small. As a result, stable measurement over a long period becomes possible, and it is considered possible to compare the amounts of sulfur-containing compounds in compositions containing sulfur-containing compounds with different measurement timings on different measurement dates. As the cut standard substance (rubber composition), 1 g or less is preferable, 100 mg or less is more preferable, 10 mg or less is still more preferable, 1 mg or less is even more preferable, 500 μg or less is even more preferable, and 300 μg or less is even more preferable. Also, as the lower limit, for example, 1 μg or more is preferable, and 10 μg or more is more preferable. The method for preparing the above cut standard substance (rubber composition) is not particularly limited, and it can be prepared by a known method such as cutting and slicing the rubber composition with scissors or a razor. The shape of the above cut standard substance (rubber composition) is not particularly limited.

[0029] In the method for quantifying sulfur-containing compounds of the present invention, it is preferable to use pyrolysis gas chromatography. Thereby, sulfur-containing compounds in a composition containing sulfur-containing compounds can be quantified. By subjecting a measurement sample (sample) to pyrolysis gas chromatography, sulfur-containing compounds can be quantified from the peak area or peak height of the obtained pyrogram. As a method for quantifying sulfur-containing compounds in a composition containing sulfur-containing compounds using pyrolysis gas chromatography, a known method can be adopted. Here, pyrolysis gas chromatography is a method in which a measurement sample (sample) is instantaneously pyrolyzed, the pyrolysis products are introduced into a gas chromatograph, and separation is performed based on the difference in retention time in a column.

[0030] As the pyrolysis device for pyrolyzing the measurement sample, generally, any device that can be used in the art can be used. The temperature (pyrolysis temperature) when pyrolyzing the measurement sample is usually in the range of 450 to 700 °C, preferably in the range of 550 to 650 °C.

[0031] The detector for detecting the separated components by the above gas chromatography is not particularly limited. For example, a mass spectrometer such as a time-of-flight mass spectrometer (Tof: Time of flight) or a sulfur flame photometric detector (FPD) can be used. Among these, since sulfur can be selectively detected, it is preferable to use a sulfur flame photometric detector as the detector.

[0032] Here, an example of the outline of a pyrolysis gas chromatography device (Py-GC device) that can be used in the present invention is shown in FIG. 1. The Py-GC device 10 includes a carrier gas container 12, a pyrolysis device 14, a gas chromatograph 16, and a detector 18. The gas chromatograph 16 incorporates a separation column 20. An output device 22 is connected to the detector 18. Although not shown, the gas chromatograph 16 generally includes a carrier gas flow rate control means and a temperature control means.

[0033] As an example of a usable Py-GC device 10, a device composed of a pyrolysis device "EGA / PY-3030D" manufactured by Frontier Lab, a gas chromatograph "7890" manufactured by Agilent, and a time-of-flight mass spectrometer "Xevo G2-XS" manufactured by Waters is exemplified, but it is not limited to these models.

[0034] The measurement sample to be subjected to Py-GC measurement is introduced into the pyrolysis device 14. The measurement sample is heated and decomposed in the pyrolysis device 14 to generate gas. This gas contains a plurality of components derived from the organic substances in the measurement sample as decomposition products.

[0035] The gas generated from the measurement sample is introduced into the separation column 20 by the carrier gas supplied from the carrier gas container 12. The separation column 20 separates the plurality of components contained in this gas. Each component separated by the separation column 20 is sequentially detected by the detector 18. The detector 18 converts the amount of each detected component into an electrical signal and outputs it from the output device 22 as a pyrogram. The horizontal axis of the pyrogram is the detection time, and the vertical axis is the signal intensity.

[0036] A plurality of peaks are shown on the outputted pyrogram. Each peak corresponds to a component in the gas generated from the measurement sample. The area or height of each peak correlates with the amount of each component. Although not particularly limited, as a method for calculating the amount of each component, an internal standard method based on the area or height of the peak is preferably used. In the internal standard method, the above standard substance (rubber composition) is subjected to pyrolysis gas chromatography together with the measurement sample, and the area or height of the peak corresponding to the alkylthiophene contained in the standard substance (rubber composition) is normalized by the amount of the supplied standard substance (rubber composition), and the area or height of the peak corresponding to the normalized alkylthiophene and the area or height of the peak corresponding to the sulfur-containing compound in the gas generated from the measurement sample are compared to quantify the sulfur-containing compound in the measurement sample.

[0037] The sulfur-containing compound to be quantified is not particularly limited, and any compound having a sulfur atom can be quantified by the quantification method of the present invention.

[0038] As described above, in the method of the present invention, by using a rubber composition containing alkylthiophene as a reference substance, stable measurement can be achieved over a long period of time, and it is possible to compare the amounts of sulfur-containing compounds in compositions containing sulfur-containing compounds with different measurement timings on different measurement dates.

Examples

[0039] Based on the examples, the present invention will be specifically described, but the present invention is not limited thereto.

[0040] The various chemicals used in the examples and comparative examples will be described below. 3-Hexadecylthiophene: manufactured by Tokyo Chemical Industry Co., Ltd. Rubber: BR150 (manufactured by UBE Industries, Ltd.) Organic solvent: acetone (manufactured by Yoneyama Pharmaceutical Co., Ltd.) Dibenzothiophene: manufactured by Tokyo Chemical Industry Co., Ltd.

[0041] (Preparation Example 1: Preparation of a rubber composition containing 3-hexadecylthiophene) 0.3 g of 3-hexadecylthiophene and 150 g of rubber were kneaded using a roll to obtain a rubber composition.

[0042] (Preparation Example 2: Preparation of a 3-hexadecylthiophene solution) 200 μg of 3-hexadecylthiophene was added to 1 ml of an organic solvent and stirred to prepare a 3-hexadecylthiophene solution.

[0043] (Preparation Example 3: Preparation of a target component) 0.3 g of N-cyclohexylbenzothiazole-2-sulfenamide (CZ, manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.) and 150 g of rubber (BR150, manufactured by UBE Industries, Ltd.) were mixed using a roll to prepare a target component.

[0044] (Example 1) 200 μg of the target component obtained in Preparation Example 3 and 200 μg of the rubber composition obtained in Preparation Example 1 were placed in the same sample cup, and Py-GC measurement was performed by the following method. The results (peak intensity ratio, quantitative value) are shown in Table 1.

[0045] <Py-GC Measurement> Under the following conditions, Py-GC measurement was performed, and from the obtained pyrogram, among the pyrolysis products, 3-hexadecylthiophene, dibenzothiophene, and benzothiazole were detected, and the area of each peak was determined.

[0046] (Conditions) Pyrolysis apparatus: Vertical microelectric furnace type pyrolyzer "EGA / PY-3030D" manufactured by Frontier Lab Co., Ltd. Pyrolysis temperature: 550 °C Gas chromatograph: Gas chromatograph "7890" manufactured by Agilent (the temperature of the interface heater and the temperature of the sample injection port (sample inlet end) were set to 250 °C, the oven temperature was held at 40 °C for 3 minutes, heated from 40 °C to 300 °C at 8 °C per minute, and measured with a temperature program of holding at 300 °C for 15 minutes. Note that the head pressure was 83 kPa in the constant pressure mode and the split ratio was 50:1.) Detector: Time-of-flight mass spectrometer "Xevo G2-XS" manufactured by Waters (the measurement conditions were a corona current of 2.0 μA and a cone voltage of 40 V.) Detector: Sulfur flame photometric detector "5380" manufactured by O·I·Analytical (measurement conditions: detector temperature 250 °C) Carrier gas: Helium Column: Capillary column "Ultra Alloy+-5(MS / HT)" manufactured by Frontier Lab Co., Ltd. (5% diphenyl 95% dimethylpolysiloxane, 30 m × 0.25 mm i.d. × 1.0 μm film)

[0047] (Comparative Example 1) Py-GC measurement was performed in the same manner as in Example 1, except that 200 μg of the target component obtained in Preparation Example 3 and 2 μl of the 3-hexadecylthiophene solution obtained in Preparation Example 2 were placed in the same sample cup. The results (peak intensity ratio, quantitative value) are shown in Table 1. The peak intensity ratio in Table 1 was determined from the following formula. Peak intensity ratio = Area of the peak of benzothiazole / Area of the peak of 3-hexadecylthiophene (In the above formula, the area of the peak of 3-hexadecylthiophene is the sum of the areas of the peaks (1) to (3) in the chromatogram of FIG. 2.) And the quantitative value was determined from the following formula. Quantitative value (wt%) = Amount of 3-hexadecylthiophene × Peak intensity ratio (In the above formula, the amount of 3-hexadecylthiophene is the amount (wt%) of 3-hexadecylthiophene in the rubber composition prepared in Preparation Example 1 or the amount (wt%) of 3-hexadecylthiophene in the solution prepared in Preparation Example 2.)

[0048]

Table 1

[0049] (Reference Example 1) Five sample cups containing about 200 μg of the rubber composition obtained in Preparation Example 1 were prepared, and Py-GC measurement was performed on each of them in the same manner as in Example 1 (measurement interval between samples: 50 minutes). As a result, a chromatogram as shown in FIG. 2 was obtained. Then, the coefficient of variation (CV value) of the area (peak intensity) of the peak of 3-hexadecylthiophene was calculated, and it was 3.9%.

[0050] (Reference Example 2) Ten sample cups containing 2 μl of the 3-hexadecylthiophene solution obtained in Preparation Example 2 were prepared, and Py-GC measurement was performed on each of them in the same manner as in Example 1 (measurement interval between samples: 50 minutes). The coefficient of variation (CV value) of the area (peak intensity) of the peak of 3-hexadecylthiophene was calculated, and it was 25%.

[0051] From the results of Reference Example 1 and Reference Example 2, it can be seen that when the 3-hexadecylthiophene solution obtained in Preparation Example 2 is used as a sample rather than the rubber composition containing 3-hexadecylthiophene obtained in Preparation Example 1, the area (peak intensity) of the peak of 3-hexadecylthiophene to be measured varies greatly among samples.

[0052] (Reference Example 3) 250 μg of dibenzothiophene was put into 1 ml of an organic solvent and stirred to prepare a dibenzothiophene solution. Ten sample cups containing 2 μl of the obtained dibenzothiophene solution were prepared, set in an autosampler, and subjected to Py-GC measurement in the same manner as in Example 1 in order (measurement interval between samples: 50 minutes). When the area of the peak of dibenzothiophene was determined, the graph of FIG. 3 was obtained. From the results of FIG. 3, it can be seen that the area of the peak of dibenzothiophene varies greatly among samples, and it can be seen that as a tendency, the area of the peak of dibenzothiophene decreases when the order of measurement is later, that is, when the holding time in the autosampler is longer.

[0053] (Reference Example 4) Five sample cups containing about 200 μg of the rubber composition obtained in Preparation Example 1 were prepared, set in an autosampler, and subjected to Py-GC measurement in the same manner as in Example 1 in order (measurement interval between samples: 50 minutes). Among the areas of the peaks of 3-hexadecylthiophene, the area of the peak (1) in the chromatogram of FIG. 2 was determined, and the graph of FIG. 4 was obtained. From the results of FIG. 4, it can be seen that the area of the peak of 3-hexadecylthiophene varies little among samples, and it can be seen that even when the order of measurement is later, that is, even when the holding time in the autosampler is longer, the area of the peak of 3-hexadecylthiophene does not decrease. In addition, even when compared with the areas of the peaks (2) or (3) in the chromatogram of FIG. 2, the coefficient of variation (CV value) was about 3 to 4%.

Explanation of Symbols

[0054] 10 Pyrolysis Gas Chromatograph 12 Carrier Gas Container 14 Pyrolysis Device 16 Gas Chromatograph 18 Detector 20 Separation Column 22 Output Device

Claims

1. A method for quantifying a sulfur-containing compound, characterized by using a rubber composition containing alkylthiophene as a reference substance.

2. The method for quantifying a sulfur-containing compound according to Claim 1, using pyrolysis gas chromatography.

3. The method for quantifying a sulfur-containing compound according to Claim 1 or 2, using a sulfur flame photometric detector as a detector.

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