Method for analyzing bisphenol

Abstract

Provided is a method for analyzing bisphenol by gas chromatography, the method involving introducing, into a gas chromatograph, a sample containing bisphenol and, as an additive, a hydroxy compound with a retention index being lower than that of the bisphenol and a difference in retention index from that of the bisphenol being 2,000 or less.

Description

Analytical methods for bisphenols

[0001] The present invention relates to a method for analyzing bisphenols.

[0002] Bisphenols with a phenol skeleton, such as bisphenol A and tetrabromobisphenol A, have two or more hydroxy groups in their molecules and are likely to be added to the list of restricted substances specified in the European REACH Regulation and the RoHS2 Directive. Therefore, the analysis and quantification of bisphenols is expected to become increasingly important in the future. Gas chromatography (GC) and gas chromatography-mass spectrometry (GC / MS) have traditionally been used as analytical methods for such bisphenols.

[0003] However, when bisphenols are quantified by these methods and a calibration curve is created using bisphenols with known concentrations, the reproducibility of peak areas in the chromatogram may be low, or the linearity of the calibration curve may be poor, resulting in problems such as low accuracy in the measurement of bisphenols.

[0004] One of the causes of this is the adsorption of bisphenols to the components of the instrument. Specifically, bisphenols injected into a GC instrument pass through the insert in the sample vaporization chamber and the column before being detected by the detector. During this process, some bisphenols adsorb to active sites (-Si-OH) such as silanol groups generated on the inner wall of the insert in the sample vaporization chamber or on the stationary phase in the column. This prevents the adsorbed bisphenols from reaching the detector, making it impossible to accurately detect the amount of bisphenols. While the inner wall of the insert and the stationary phase are sometimes deactivated with hydrophobic groups, the effectiveness of this deactivation treatment decreases with repeated use. Furthermore, contamination can sometimes cause silanol groups to adhere to the stationary phase in the column.

[0005] Therefore, methods have been disclosed that improve the accuracy of bisphenol measurement by derivatizing the hydroxyl groups of bisphenols with silyl groups, acyl groups, methyl groups, etc. and detecting the derivatized bisphenols (see Non-Patent Documents 1 and 2).

[0006] Tsuyoshi Ibaraki et al., "Analysis of Tetrabromobisphenol A in Environmental Samples," Journal of Environmental Chemistry, Vol. 12, No. 3, 585-591 (2002); Kaoru Takahata et al., "Analysis of Bisphenol A in Canned Seafood Using Solid-Phase Extraction and GC / MS," Nippon Shokuhin Kagaku Kogaku Kaishi, Vol. 48, No. 6, 437-443 (2001)

[0007] However, the methods of Non-Patent Documents 1 and 2 require additional derivatization and associated processing during analysis. In particular, the derivatization process requires multiple steps, making the process complicated and time-consuming. Specifically, these processes require heating (e.g., at 60°C for 60 minutes) for derivatization of bisphenols; solvent transfer from the derivatization solvent to the solvent used for chromatogram injection; and compound identification in cases where different isomers of the derivatized bisphenols exist. Therefore, a simple method for measuring bisphenols is desired.

[0008] An object of the present invention is to provide an analytical method capable of quantitatively determining bisphenols simply and accurately.

[0009] The analytical method of a first aspect of the present invention is a method for analyzing bisphenols by gas chromatography, in which a hydroxy compound having a retention index lower than that of bisphenol and having a difference in retention index from bisphenol of 2000 or less is introduced as an additive into a gas chromatograph in addition to a sample containing the bisphenol.

[0010] According to the analytical method of the first aspect, bisphenol can be quantitatively determined simply and accurately.

[0011] 1 is a schematic diagram of a gas chromatograph mass spectrometer used in a first embodiment. FIG. 2 is an enlarged schematic diagram of the sample vaporization unit of FIG. 1. FIG. 3 is a schematic diagram of a gas chromatograph mass spectrometer used in a second embodiment. FIG. 4 is a calibration curve created in Example 1, where the vertical axis represents the peak area of ​​the mass spectrum and the horizontal axis represents the concentration of the measurement sample. FIG. 5 is a calibration curve created in Comparative Example 1.

[0012] 1. First Embodiment The analytical method of the first embodiment of the present invention is a method for analyzing bisphenols by gas chromatography-mass spectrometry. In this analytical method, first, a measurement sample and an additive are prepared.

[0013] The measurement targets contained in the measurement sample are bisphenols. Specifically, these are bisphenol A (4,4'-isopropylidenediphenol), bisphenol S (4,4'-sulphonyldiphenol), bisphenol F (4,4'-methylenediphenol), bisphenol AP (1,1-bis(4-hydroxyphenyl)-1-phenylethane), bisphenol B (4,4'-(1-methylpropylidene)bisphenol), bisphenol BP (4,4'-dihydroxytetraphenylmethane), bisphenol C2 (4,4'-(dichlorovinylidene)diphenol), bisphenol E (4,4'-ethylidenebisphenol), bisphenol M (4,4'-ethylidenebisphenol), bisphenol P (4,4'-(1,4-phenylenediisopropylidene)bisphenol), and bisphenol TMC (4,4'-(3,3,5-trimethylcyclohexylidene)bisphenol). ), bisphenol A's such as bisphenol Z (4,4'-cyclohexylidenebisphenol) and bisphenol AF (4,4'-[2,2,2-Trifluoro-1-(trifluoromethyl)ethylidene]bisphenol); brominated bisphenols such as tetrabromobisphenol A, tetrabromobisphenol A dimethyl ether, tetrabromobisphenol A dibromopropyl ether, tetrabromobisphenol bis(allyl ether), tetrabromobisphenol bis(2-hydroxyethyl ether), brominated tetrabromobisphenol epoxy oligomer, tetrabromobisphenol carbonate oligomer, tribromobisphenol A, 3-3'-dibromobisphenol A, and 3-monobromobisphenol A.

[0014] The measurement sample is preferably a liquid sample diluted with a solvent such as isooctane, hexane, cyclohexane, toluene, ethyl acetate, acetone, dichloromethane, carbon disulfide, ethanol, acetonitrile, or water. From the viewpoint of ease of handling, acetone, hexane, or the like is preferred as the dilution solvent. The dilution ratio is not limited, but may be adjusted so that the concentration of the measurement target is 0.01 to 100 ppm, for example.

[0015] The additive is a hydroxy compound. From the viewpoint of adsorption to the column and the insert, the additive is preferably a polyhydroxy compound having a plurality of hydroxy groups (two or more), more preferably a polyhydroxy compound having three or more hydroxy groups.

[0016] The retention index of the additive is lower than that of the bisphenol to be measured. If an additive with a higher retention index than that of the bisphenol is used, when the additive and a measurement sample are injected into a gas chromatograph, the measurement sample will pass through the column before the additive, and there is a risk that the additive will not function to protect the bisphenol active sites (sites where bisphenol adheres) on the inner wall of the insert and the column stationary phase.

[0017] In addition, the difference between the retention index of the additive and the retention index of the bisphenol is 2000 or less. The difference is preferably 1500 or less, more preferably 1200 or less. The lower limit of the difference is, for example, 100 or more, preferably 500 or more, more preferably 800 or more, and particularly preferably 1100 or more. If the upper limit of the difference between the two retention indices is outside the above range, when the two retention indices pass through the column, the significant difference in retention indices will cause a large distance between the additive and the measurement sample, and there is a risk that the additive will already have detached from the bisphenol active sites on the insert inner wall or the like by the time the measurement sample reaches the active sites on the insert inner wall or the column stationary phase.

[0018] The retention index of the additive used is, for example, 1000 or more, preferably 1500 or more, and for example, 2500 or less, preferably 2000 or less.

[0019] The retention index is an index that represents the relative retention ratio of a linear alkane to a target component, based on the carbon number of the linear alkane, and is determined in accordance with JIS K 0123: 2018. An example of a column used to determine the retention index is SH-1MS (non-polar liquid phase: 100% dimethylpolysiloxane, film thickness 0.1 μm, length 15 m, inner diameter 0.25 mm).

[0020] Specific examples of such additives include D-sorbitol (retention index 1974) and L-gulone γ-lactone (retention index 1859), and a combination of these is particularly preferred. When D-sorbitol and L-gulone γ-lactone are used in combination, the mass ratio of L-gulone γ-lactone to 100 parts by mass of D-sorbitol may be, for example, 10 parts by mass or more and 1000 parts by mass or less.

[0021] In the first embodiment, a gas chromatograph mass spectrometer is used, which allows for easy identification and quantification of the measurement target. A schematic diagram of a gas chromatograph mass spectrometer (GC-MS device) 1 is shown in FIG. 1. This GC-MS device 1 includes a gas chromatograph section (GC section) 2 and a mass spectrometry section (MS section) 3.

[0022] The GC section 1 includes a carrier gas flow rate control section 4, a sample vaporization section 5, a column 6, and a column oven 7. A carrier gas cylinder 8 is connected to the upstream side of the carrier gas flow rate control section 4.

[0023] As shown in FIG. 2 , a sample injection port 9 for injecting a sample is formed at the end of the sample vaporizer 5, and an insert 10 is built into the sample vaporizer 5. The insert 10 prevents non-combustible materials in the sample from being introduced into the column 6 when the sample is vaporized, and is replaceable. The sample vaporizer 4 is equipped with a heating device (e.g., a heater; not shown) for vaporizing the sample. A syringe or the like is used to pierce a sealing part (e.g., a septum) located at the sample injection port 9 (see the dashed line in FIG. 2 ), and the sample and hydroxy compound are injected into the sample vaporizer 5 and, therefore, into the insert 10.

[0024] The column 6 may be either a capillary column or a packed column, but a capillary column is preferred from the viewpoints of good chromatogram peak separation and shortened analysis time. In a capillary column, a stationary phase is applied to the entire inner surface of a tube made of glass or the like. In a packed column, a large number of packing materials (particles whose surfaces are coated with a stationary phase) are packed inside a tube made of glass or the like. The stationary phase in the column is appropriately determined depending on the type of bisphenol to be measured, and examples include methylsilicone-based, phenylmethyl-based, cyanopropylphenyl-based, trifluoropropyl-based, and polyethylene glycol-based, with methylsilicone-based being preferred. Furthermore, the polarity of the stationary phase can be selected from nonpolar, weakly polar, moderately polar, and highly polar. Specific examples of such columns include the SH-I series, SH-1 series, and SH-5 series manufactured by Shimadzu Corporation.

[0025] The MS section 3 includes an ionization section 11, a mass separation section 12, and a detection section 13. The detection section 13 is connected to a data processing device 14.

[0026] Examples of the separation type of the mass separator 12 include quadrupole, magnetic sector, time-of-flight, ion trap, and ion cyclotron resonance. The mass separator 12 may also be a tandem mass spectrometry type consisting of multiple mass separators. That is, in the first embodiment, gas chromatography tandem mass spectrometry may be employed. Examples of tandem mass spectrometry types include triple quadrupole (Q-Q), tandem time-of-flight (TOF-TOF), quadrupole-time-of-flight (Q-TOF), quadrupole-ion trap (Q-IT), quadrupole-ion cyclotron resonance (Q-ICR), and ion trap-time-of-flight (IT-TOF).

[0027] Specific examples of such a GC-MS device 1 include the GCMS-TQ series and GCMS-QP series manufactured by Shimadzu Corporation.

[0028] In this analysis method, gas chromatography mass spectrometry is performed on a measurement sample. Specifically, the measurement sample and the hydroxy compound are introduced into the GC-MS device 1, and the measurement sample is analyzed. In this case, the measurement sample and the hydroxy compound are mixed in the sample vaporization unit 5, and then these are introduced into the column 6.

[0029] Examples of methods for introducing such a measurement sample include (1) a method in which the measurement sample and the hydroxy compound are mixed in advance and then injected into the sample vaporizer 5, and (2) a method in which the measurement sample and the hydroxy compound are separately injected into the sample vaporizer 5 and then mixed within the sample vaporizer 5. Method (1) is preferred from the viewpoints of ease of operation and the ability to more reliably mix the measurement sample and the hydroxy compound in the sample vaporizer 5. These introduction methods may be performed using an auto-injector that performs the above automatically. Specifically, an auto-injector function that automatically mixes the two and injects them into the sample vaporizer 5, or an auto-injector function that automatically collects the two separately in syringes and then co-injects them into the sample vaporizer 5, is used.

[0030] The amount (concentration) of the hydroxy compound mixed is, for example, 10 ng or more, preferably 30 ng or more, more preferably 300 ng or more, per 1 μL of the amount introduced into the sample vaporization section 5 (the amount of the mixed solution containing the measurement sample and the hydroxy compound injected), and is, for example, 10,000 ng or less, preferably 3,000 ng or less, more preferably 1,000 ng or less.

[0031] Examples of the carrier gas include helium, nitrogen, hydrogen, and argon, and preferably helium. The flow rate of the carrier gas may be set according to a conventional method.

[0032] The temperature of the sample vaporizer may be equal to or higher than the boiling point of the bisphenol to be measured, for example, 250° C. or higher, preferably 280° C. or higher.

[0033] The temperature of the column may be set by either a temperature-promoting method or an isothermal method. For example, in the temperature-promoting method, the temperature may be raised from an initial temperature of 100°C or lower to a temperature above the boiling point of the measurement sample (e.g., 250°C or higher).

[0034] As a result, in the GC section, the vaporized measurement sample is mixed with a carrier gas and passes through a column to separate the measurement sample. The separated measurement sample is then introduced into the MS section, where it is separated into predetermined ions (precursor ions, product ions, etc.) in the ionization section and mass separation section, and the ions are detected in the detection section.

[0035] The detection results include a total ion current chromatogram, multiple mass chromatograms (mass chromatograms), and multiple mass spectra. Since the mass-to-charge ratio (m / z) of the bisphenol to be measured is known, the bisphenol can be identified by comparing the m / z. Furthermore, the concentration of the bisphenol can be calculated by measuring the peak intensity or peak area of ​​the mass chromatogram or mass spectrum for the m / z. These measurements can be performed according to known methods.

[0036] The analytical method of the first embodiment enables accurate quantification of bisphenols. Furthermore, even very small amounts of bisphenols can be detected, improving measurement sensitivity. This is because a specific hydroxy compound added simultaneously with bisphenols can suppress unnecessary adsorption of bisphenols to the gas chromatograph (e.g., the inner wall of the insert or the active sites of the column stationary phase). Specifically, the hydroxy compound introduced simultaneously with bisphenols into the sample vaporization section adsorbs to the active sites (silanol groups) on the inner wall of the insert. Because the retention index of the hydroxy compound is lower than that of bisphenols and moves faster through the column than bisphenols, the hydroxy compound adsorbs to the active sites before the bisphenols reach and are adsorbed on the active sites, thereby inhibiting the adsorption of bisphenols. Furthermore, because the retention index of the hydroxy compound is within a predetermined range compared to that of bisphenols, the bisphenols can pass through the active sites before the adsorption of the hydroxy compound to the active sites is eliminated (i.e., detached). Thus, because adsorption of bisphenols to the active sites is reduced, the bisphenols pass through the column and are reliably detected by the detector while maintaining the initial injection amount. Therefore, this analytical method can improve the reproducibility of peak areas in mass chromatograms and mass spectra, and the variability of measurement results such as the standard deviation in calibration curves, resulting in accurate quantification of bisphenols. Furthermore, since it can detect low concentrations of bisphenols that are adsorbed at active sites and therefore cannot be detected, measurement can be performed with high sensitivity. Furthermore, since it is only necessary to mix the hydroxy compound with the measurement sample, and no heat treatment or other process required for derivatization is required, measurement can be performed easily.

[0037] 2. Second Embodiment An analytical method according to a second embodiment of the present invention is a method for analyzing bisphenols by gas chromatography.

[0038] A schematic diagram of the gas chromatograph 15 used in this method is shown in Figure 3. Examples of such gas chromatographs include Nexis GC-2030, GC-2014, and GC-2025 manufactured by Shimadzu Corporation.

[0039] The measurement conditions and method are the same as those in the first embodiment. A chromatogram is obtained by the analytical method of the second embodiment, and the concentration of the bisphenol to be measured can be calculated by measuring the peak area or intensity of the chromatogram.

[0040] 3. Aspects It will be appreciated by those skilled in the art that the exemplary embodiments described above are examples of the following aspects.

[0041] (Item 1) A method for analyzing bisphenols according to one embodiment is a method for analyzing bisphenols by gas chromatography, in which a hydroxy compound having a retention index lower than that of the bisphenol and having a difference in retention index from the bisphenol of 2000 or less may be introduced into the gas chromatograph as an additive in addition to a sample containing the bisphenol.

[0042] (Item 2) In the analytical method according to item 1, the hydroxy compound may have a plurality of hydroxy groups.

[0043] (Item 3) In the analytical method according to item 1 or 2, the retention index of the hydroxy compound may be 1,000 or more and 2,500 or less.

[0044] (Item 4) In the analytical method according to any one of Items 1 to 3, the sample and the hydroxy compound may be mixed in a sample vaporization section of the gas chromatograph and introduced into a column of the gas chromatograph.

[0045] (Item 5) In the analytical method according to any one of Items 1 to 4, a mixture of the sample and the hydroxy compound may be injected into a gas chromatograph.

[0046] (Item 6) In the analytical method according to any one of Items 1 to 5, a gas chromatograph mass spectrometer may be used.

[0047] The present invention will now be described in detail with reference to examples and comparative examples, but the scope of the present invention is not limited thereto.

[0048] Example 1 Six solutions (solvent: acetone) containing tetrabromobisphenol A (retention index: 2988) at concentrations ranging from 0.1 to 10 ppm were prepared. D-sorbitol (retention index: 1974) was mixed with these solutions to a concentration of 500 ppm. This mixed solution was injected into a gas chromatograph mass spectrometer (manufactured by Shimadzu Corporation, instrument name "GCMS-QP2020NX"), and gas chromatography mass spectrometry was performed under the following conditions. Each peak area was measured. This was performed three times, and a calibration curve was created based on the average value. The results are shown in Table 1 and FIG. 4.

[0049] <GC section settings> Injection mode: Splitless Injection volume (introduction volume): 1 μL Sample vaporizer temperature: 300°C Oven temperature: 80°C → (20°C / min) → 320°C (4 min) Column: SH-1MS with guard column (stationary phase: non-polar liquid phase, 100% dimethylpolysiloxane, film thickness 0.1 μm, length 15 m, inner diameter 0.25 mm, guard column 2 m) Carrier gas: Helium Carrier gas control mode: Constant linear velocity (52.1 cm / sec) Purge flow rate: 3.0 mL / min

[0050] Ion source temperature: 230°C Interface temperature: 320°C Measurement mode: Scan / SIM simultaneous measurement Scan event time: 0.15 seconds Scan mass range: m / z 50 to 1000 SIM event time: 0.30 seconds SIM monitoring m / z: 528.7 (for quantification), 543.7 (for confirmation)

[0051]

[0052] Comparative Example 1 A calibration curve was prepared by performing measurements in the same manner as in Example 1, except that D-sorbitol was not added. The results are shown in Table 2 and FIG.

[0053]

[0054] Comparing Tables 1 and 2 and Figures 4 and 5, the results in Example 1 were significantly improved over the results in Comparative Example 1 in terms of the linearity of the calibration curve, the detection sensitivity in the low concentration range, and the reproducibility of the peak area.

[0055] Example 2 Measurements were carried out in the same manner as in Example 1, except that L-gulon γ-lactone (retention index 1859) was mixed in place of D-sorbitol, and a calibration curve was created. As a result, in the calibration curve graph, the relative standard deviation was 6% or less at any concentration from 0.1 to 10 ppm (see Table 3), and the linearity (correlation coefficient) of the calibration curve was 0.99 or more.

[0056]

[0057] Example 3 A calibration curve was prepared by performing measurements in the same manner as in Example 1, except that not only D-sorbitol but also both D-sorbitol and L-gulon γ-lactone were mixed at 500 ppm each. As a result, the relative standard deviation in the calibration curve graph was 4% or less at any concentration from 0.1 to 10 ppm (see Table 4), and the linearity of the calibration curve was 0.99 or more.

[0058]

[0059] REFERENCE SIGNS LIST 1 Gas chromatograph mass spectrometer 2 Gas chromatograph section 3 Mass analysis section 4 Carrier gas flow rate control section 5 Sample vaporization section 6 Column 7 Column oven 8 Carrier gas cylinder 9 Sample injection port 10 Insert 11 Ionization section 12 Sample analysis section 13 Detection section 14 Data processing device 15 Gas chromatograph

Claims

1. A method for analyzing bisphenol by gas chromatography, comprising the steps of: introducing into a gas chromatograph, in addition to a sample containing the bisphenol, as an additive, a hydroxy compound having a retention index lower than that of the bisphenol and having a difference in retention index from the bisphenol of 2000 or less.

2. The analytical method according to claim 1, wherein the hydroxy compound has a plurality of hydroxy groups.

3. The analytical method according to claim 1, wherein the retention index of the hydroxy compound is 1,000 or more and 2,500 or less.

4. The analytical method according to claim 1, wherein the sample and the hydroxy compound are mixed in a sample vaporization section of the gas chromatograph and introduced into a column of the gas chromatograph.

5. The analytical method according to claim 1, wherein the mixture of the sample and the hydroxy compound is injected into a gas chromatograph.

6. The analytical method according to claim 1, which uses a gas chromatograph mass spectrometer.

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