Analysis method for detecting n-butyl alcohol in water by headspace-gas chromatography

Abstract

The invention provides an analysis method for detecting n-butyl alcohol in water by headspace-gas chromatography, which comprises the following steps: volatilizing volatile components in a sample in a headspace bottle to a space above liquid under a certain temperature condition to generate vapor pressure, and detecting n-butyl alcohol in the sample after a gas phase and a liquid phase reach thermodynamic and dynamic equilibrium. Volatile organic compounds in a gas phase are separated through gas chromatography, a flame ionization detector is used for detection, the nature is determined through chromatography retention time, and the quantity is determined through an external standard method. The method disclosed by the invention is simple, rapid, sensitive and accurate to operate, lower in detection limit, wide in linear range and suitable for detecting the content of n-butyl alcohol in water and wastewater.

Description

Technical Field

[0001] The invention belongs to the field of detection technology, relates to the detection and analysis of n-butanol, and in particular to an analysis method for detecting n-butanol in water quality by headspace-gas chromatography. Background Art

[0002] The chemical formula of n-butanol is C4H 10 O, also known as 1-butanol or butanol, is a colorless liquid with a wine odor. Butanol has a wide range of uses. It is a solvent for a variety of coatings and a raw material for making plasticizer dibutyl phthalate. In addition, it is also used to make organic compounds such as butyl acrylate, butyl acetate, and ethylene glycol butyl ether. In the pharmaceutical field, it is used as an organic synthesis intermediate and an extractant or solvent for biochemical drugs. It is used to make surfactants and prepare edible flavors such as bananas, cream, whiskey, and cheese.

[0003] However, n-butanol is a low-toxic substance that is acutely toxic to organisms. For example, the LD50 (median lethal dose) of rats is 4360 mg / kg, indicating that it is acutely lethal to organisms at a certain dose. Long-term contact or ingestion of n-butanol may cause harm to human health, such as affecting the function of organs such as the nervous system, liver, and kidneys. This long-term toxicity may also apply to aquatic organisms, although the specific effects may vary depending on the species and exposure conditions.

[0004] The discharge of n-butanol into the environment can pollute water bodies, affecting water quality and the ecological environment. This pollution may be transmitted through the food chain, causing long-term impacts on aquatic organisms and the ecosystems that rely on these water bodies. It may have toxic effects on aquatic organisms, destroying their physiological functions and living environment. This impact may lead to ecological problems such as a decrease in the number of aquatic organisms and a reduction in biodiversity.

[0005] At present, studies have reported on the detection methods of n-butanol, such as gas chromatography, liquid chromatography, mass spectrometry, etc. However, the pretreatment method of gas chromatography is relatively cumbersome, requiring distillation, liquid-liquid extraction and solid phase extraction, with a high loss rate. At the same time, there are also some difficulties, such as poor selective affinity for the analyte, inaccurate analysis results for active compounds, high detection limit, and poor precision. Summary of the invention

[0006] In order to solve the above problems, the present invention provides an analytical method for detecting n-butanol in water quality by headspace-gas chromatography. The method of the present invention is simple to operate, rapid, sensitive, accurate, has a lower detection limit, and a wide linear range, and is suitable for detecting n-butanol in water quality.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A headspace-gas chromatography analysis method for detecting n-butanol in water quality, wherein the analysis method comprises the following steps: under certain temperature conditions, volatile components in a sample in a headspace bottle volatilize to the liquid head space to generate vapor pressure, and after the gas-liquid two phases reach thermodynamic dynamic equilibrium, volatile organic matter in the gas phase is separated by gas chromatography, and detected by a hydrogen flame ionization detector, and the chromatographic retention time is used for qualitative analysis and the external standard method is used for quantitative analysis; wherein the n-butanol concentration (mg / L) in the sample is calculated according to formula I;

[0009] Formula I: C = C1 × N;

[0010] C-mass concentration of n-butanol in the sample, mg / L;

[0011] C1-mass concentration of n-butanol in the sample obtained from the standard curve, mg / L;

[0012] N-sample dilution multiple.

[0013] As a preferred embodiment of the present invention, the specific steps of the analysis method are:

[0014] 1) Sample collection and preservation;

[0015] 2) Preparation of calibration curve: prepare a series of standard solutions with n-butanol concentrations of 0.2 mg / L, 0.4 mg / L, 1.0 mg / L, 2.0 mg / L and 4.0 mg / L, respectively, seal with a cover, and mix well; analyze in sequence from low concentration to high concentration, and record the retention time and response value of n-butanol; establish a standard curve with n-butanol concentration as the horizontal axis and its corresponding response value as the vertical axis;

[0016] 3) Sample pretreatment: Add sodium chloride to the headspace bottle, add the sample, seal it with a cap, shake well, and wait for testing;

[0017] 4) Determination: Samples were injected under the conditions of headspace-gas chromatography, and detection was performed using a hydrogen flame ionization detector. The qualitative analysis was performed using the chromatographic retention time, and the quantitative analysis was performed using the external standard method.

[0018] As a preferred embodiment of the present invention, in step 2), the preparation method of the standard series solutions is: add 3g sodium chloride and 10mL pure water to 5 headspace bottles, and add 1.0μL, 2.0μL, 5.0μL, 10.0μL and 20.0μL of 2000mg / L n-butanol standard solution in sequence.

[0019] As a preferred embodiment of the present invention, in step 3), the amount of sodium chloride added is 3 g, and the amount of sample added is 10 mL.

[0020] As a preferred embodiment of the present invention, the head space sampler conditions are: heating equilibrium temperature: 80°C; heating equilibrium time: 30 min; injection valve temperature: 100°C; transmission line temperature: 120°C; needle temperature: 100°C; injection volume: 1.0 mL.

[0021] As a preferred embodiment of the present invention, the gas chromatograph conditions are as follows: injection port temperature: 200°C; detector temperature: 230°C;

[0022] Column program: initial temperature 50°C, hold for 4 min; increase temperature to 80°C at 10°C / min; increase temperature to 200°C at 30°C / min.

[0023] As a preferred embodiment of the present invention, carrier gas: N2, constant pressure mode, column front pressure 48.6kPa; hydrogen flow rate: 40mL / min; air flow rate: 400mL / min; tail gas flow rate: N2, 30mL / min; split injection mode, split ratio is 10:1.

[0024] As a preferred embodiment of the present invention, in step 4), before sample analysis, a retention time window t±3S is established, wherein t is the mean retention time of n-butanol at each concentration level during initial calibration, and S is the standard deviation of the retention time of n-butanol at each concentration level during initial calibration.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1) The present invention establishes an analytical method for detecting n-butanol in water quality by headspace-gas chromatography.

[0027] 2) The method of the present invention is simple to operate, rapid, sensitive, accurate, has a lower detection limit, and a wide linear range, and is suitable for detecting the content of n-butanol in water and wastewater. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0029] Figure 1 It is the chromatogram of the standard product of the present invention.

[0030] Figure 2 is the calibration curve of the present invention.

[0031] Figure 3 yes Figure 2 Chromatogram of sequence number 4.

[0032] Figure 4 yes Figure 2 Chromatogram of sequence number 5. DETAILED DESCRIPTION

[0033] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] The invention provides an analytical method for detecting n-butanol in water by headspace-gas chromatography. The analytical method comprises the following steps: under certain temperature conditions, volatile components in a sample in a headspace bottle volatilize to the liquid head space to generate vapor pressure. After the gas and liquid phases reach thermodynamic dynamic equilibrium, volatile organic matter in the gas phase is separated by gas chromatography and detected by a hydrogen flame ionization detector. The chromatographic retention time is used for qualitative analysis and the external standard method is used for quantitative analysis. The n-butanol concentration (mg / L) in the sample is calculated according to formula I.

[0035] Formula I: C = C1 × N;

[0036] C-mass concentration of n-butanol in the sample, mg / L;

[0037] C1-mass concentration of n-butanol in the sample obtained from the standard curve, mg / L;

[0038] N-sample dilution multiple.

[0039] When the sampling volume was 10.0 mL, the detection limit of the method was 0.05 mg / L and the lower limit of determination was 0.20 mg / L.

[0040] In the present invention, the reagents and equipment used include:

[0041] Japan Shimadzu Nexis GC-2030 gas chromatograph, capable of split / splitless injection, with programmed temperature rise function, and equipped with FID detector.

[0042] Shanghai Star HS-27A automatic headspace sampler, the heating temperature range can be controlled between room temperature and 220℃, the temperature control progress: ±0.1℃.

[0043] Capillary column: DB-FFAP, 30m×0.32mm×0.50μm, or other equivalent capillary columns.

[0044] Ultrapure water preparation instrument.

[0045] Balance: accuracy is 0.0001g.

[0046] Micro syringe: 10μL, 50uL, 100μL.

[0047] Headspace bottle: 20mL precision screw headspace bottle, with blue PTFE / white silicone septa, 18mm magnetic precision threaded metal cap.

[0048] Commonly used instruments and equipment in general laboratories.

[0049] Reagent water that does not contain organic matter can be replaced by ultrapure water from the laboratory, and the solvent is methanol.

[0050] Sodium chloride: analytical grade, heat at 400℃ for 4h to remove organic compounds adsorbed on the surface, store in a clean reagent bottle after cooling, and store in a desiccator.

[0051] Carrier gas: nitrogen, purity ≥99.999%.

[0052] Combustion gas: hydrogen, purity ≥99.99%.

[0053] Combustion-supporting gas: air, which needs to be dehydrated and free of organic matter, and is provided by an air generator.

[0054] Sample collection and storage

[0055] Collect and store samples in accordance with the relevant provisions of HJ / T91, HJ / T 164, and GB 17378.3. Use brown screw-mouth glass bottles with polytetrafluoroethylene gaskets to quickly collect water samples, leaving no space or bubbles above the head during sampling. Store in a 4-degree refrigerator away from light without interference from other organic matter. All samples should be analyzed within 7 days after collection.

[0056] Example

[0057] This embodiment provides an analytical method for detecting n-butanol in water by headspace-gas chromatography, comprising:

[0058] 1) Sample collection and storage: Samples should be collected in brown glass bottles and stored away from light. All samples should be analyzed within 7 days of collection.

[0059] 2) Preparation of calibration curve: Pre-add 3g sodium chloride and 10mL pure water to 5 headspace bottles respectively, and then add 1.0μL, 2.0μL, 5.0μL, 10.0μL and 20.0μL of 2000mg / L n-butanol standard solution in sequence to prepare a standard series with n-butanol mass concentrations of 0.2mg / L, 0.4mg / L, 1.0mg / L, 2.0mg / L and 4.0mg / L, respectively. Immediately cover and seal, and mix. Inject and analyze in sequence from low concentration to high concentration according to the instrument reference conditions, and record the retention time and response value of n-butanol. Use the n-butanol concentration as the horizontal coordinate and the corresponding response value as the vertical coordinate to establish a standard curve.

[0060] 3) Sample pretreatment: Add 3 g of sodium chloride to the headspace bottle in advance, add 10.0 mL of sample, immediately cover and seal, shake well, and wait for testing.

[0061] 4) Determination: Samples were injected under the conditions of headspace-gas chromatography, and detection was performed using a hydrogen flame ionization detector. The qualitative analysis was performed using the chromatographic retention time, and the quantitative analysis was performed using the external standard method.

[0062] Headspace sampler conditions

[0063] Heating equilibrium temperature: 80°C; Heating equilibrium time: 30 min; Injection valve temperature: 100°C; Transfer line temperature: 120°C; Needle temperature: 100°C; Injection volume: 1.0 mL.

[0064] Gas chromatograph conditions

[0065] Inlet temperature: 200°C; detector temperature: 230°C; column program: initial temperature 50°C, hold for 4 min; increase temperature to 80°C at 10°C / min; increase temperature to 200°C at 30°C / min.

[0066] Carrier gas: N2, constant pressure mode, column head pressure 48.6kPa; hydrogen flow rate: 40mL / min; air flow rate: 400mL / min; tail gas flow rate: N2, 30mL / min; split injection mode, split ratio is 10:1.

[0067] Result calculation and presentation

[0068] Qualitative analysis

[0069] Qualitative analysis is performed based on the retention time of the target substance in the sample and the target substance in the standard series. Before sample analysis, a retention time window of t±3S is established. t is the mean retention time of n-butanol at each concentration level during initial calibration, and S is the standard deviation of the retention time of n-butanol at each concentration level during initial calibration. During sample analysis, the target substance should peak within the retention time window.

[0070] Result calculation

[0071] The mass concentration of n-butanol in the sample is calculated according to the formula: C = C1 × N

[0072] C-mass concentration of n-butanol in the sample, mg / L;

[0073] C1-mass concentration of n-butanol in the sample obtained from the standard curve, mg / L;

[0074] N-sample dilution multiple.

[0075] The chromatogram of the standard sample is shown in Figure 1 , calibration curve see Figure 2 .

[0076] Figure 2 For the chromatogram of sequence number 4, see Figure 3 , see the chromatogram of No. 5 Figure 4 .

[0077] The method validation status is summarized in Table 1.

[0078] Table 1. Verification status

[0079] Verify content Verify the results Calibration curve linearity r＝0.9994 Detection limit verification 0.04mg / L Precision Verification RSD is 2.8-8.5% Correctness Verification Recovery rate is 78.2-102%

[0080] Calibration curve drawing results

[0081] To 5 headspace bottles, add 3 g of sodium chloride and 10 mL of pure water respectively, and then add 1.0 μL, 2.0 μL, 5.0 μL, 10.0 μL and 20.0 μL of 2000 mg / L n-butanol standard solution in sequence to prepare a standard series with n-butanol mass concentrations of 0.2 mg / L, 0.4 mg / L, 1.0 mg / L, 2.0 mg / L and 4.0 mg / L, respectively. Immediately cover and seal, and mix well.

[0082] According to the instrument reference conditions, sample and analyze from low concentration to high concentration in sequence, and record the retention time and response value of n-butanol. Use the concentration of n-butanol as the horizontal axis and the corresponding response value as the vertical axis to establish a standard curve, such as Figure 2-Figure 4 The calibration curve test data is shown in Table 2.

[0083] Table 2. Calibration curve test data table

[0084]

[0085] Verification of detection limit

[0086] Take 7 headspace bottles, add 3g sodium chloride, 10mL pure water and 1.0μL n-butanol standard solution respectively, the n-butanol concentration is 0.2mg / L. Analyze on the machine and perform 7 measurements. Calculate the standard deviation of 7 parallel measurements, and calculate the method detection limit according to the formula MDL=t×S. The t value is 3.143 (n=7), see Table 3.

[0087] Table 3. Detection limit test data table

[0088]

[0089] Verification of precision

[0090] Take 18 headspace bottles, add 3g sodium chloride and 10mL pure water to each, and add 2.0μg, 10.0μg, and 30.0μg of n-butanol, respectively, so that the concentration of n-butanol is 0.2mg / L, 1.0mg / L, and 3.0mg / L. Six full-procedure parallel determinations were performed on blank water samples containing three different concentrations of n-butanol, low, medium, and high, respectively. The precision data is shown in Table 4.

[0091] Table 4. Precision test data table

[0092]

[0093] Verification of correctness

[0094] The laboratory conducted n-butanol spiking tests on the collected groundwater samples, selecting three different contents of low, medium and high. The spiked contents were 2.0μg, 10.0μg and 30.0μg respectively. Each spiked content was measured in parallel for 6 times throughout the whole procedure. The accuracy data can be found in Table 5.

[0095] Table 5. Correctness test data

[0096]

[0097]

[0098] The above is only a preferred embodiment of the present invention, and is not any formal or substantial limitation of the present invention. It should be pointed out that ordinary technicians in this technical field can make several improvements and supplements without departing from the method of the present invention, and these improvements and supplements should also be regarded as the protection scope of the present invention. Any technician familiar with this profession, without departing from the spirit and scope of the present invention, can make some changes, modifications and evolutions of the technical content disclosed above, which are equivalent embodiments of the present invention; at the same time, any changes, modifications and evolutions of any equivalent changes made to the above embodiments based on the essential technology of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for analyzing n-butanol in water by headspace-gas chromatography, characterized in that: The analytical method is that under certain temperature conditions, the volatile components in the sample in the headspace bottle volatilize to the liquid head space to generate vapor pressure. After the gas and liquid phases reach thermodynamic dynamic equilibrium, the volatile organic matter in the gas phase is separated by gas chromatography and detected by a hydrogen flame ionization detector. The chromatographic retention time is used for qualitative analysis and the external standard method is used for quantitative analysis. The n-butanol concentration (mg / L) in the sample is calculated according to formula I; Formula I: C = C1 × N; C-mass concentration of n-butanol in the sample, mg / L; C1-mass concentration of n-butanol in the sample obtained from the standard curve, mg / L; N-sample dilution multiple.

2. The method for analyzing n-butanol in water by headspace-gas chromatography according to claim 1, characterized in that: The specific steps of the analytical method are: 1) Sample collection and preservation; 2) Preparation of calibration curve: prepare a series of standard solutions with n-butanol concentrations of 0.2 mg / L, 0.4 mg / L, 1.0 mg / L, 2.0 mg / L and 4.0 mg / L, respectively, seal with a cover, and mix well; analyze in sequence from low concentration to high concentration, and record the retention time and response value of n-butanol; establish a standard curve with n-butanol concentration as the horizontal axis and its corresponding response value as the vertical axis; 3) Sample pretreatment: Add sodium chloride to the headspace bottle, add the sample, seal it with a cap, shake well, and wait for testing; 4) Determination: Samples were injected under the conditions of headspace-gas chromatography, and detection was performed using a hydrogen flame ionization detector. The qualitative analysis was performed using the chromatographic retention time, and the quantitative analysis was performed using the external standard method.

3. The method for analyzing n-butanol in water by headspace-gas chromatography according to claim 2, characterized in that: In step 2), the preparation method of the standard series solution is as follows: add 3 g of sodium chloride and 10 mL of pure water to 5 headspace bottles, and add 1.0 μL, 2.0 μL, 5.0 μL, 10.0 μL and 20.0 μL of 2000 mg / L n-butanol standard solution in sequence.

4. The method for analyzing n-butanol in water by headspace-gas chromatography according to claim 2, characterized in that: In step 3), the amount of sodium chloride added is 3 g, and the amount of sample added is 10 mL.

5. The method for analyzing n-butanol in water by headspace-gas chromatography according to claim 2, characterized in that: The headspace sampler conditions were as follows: heating equilibrium temperature: 80°C; heating equilibrium time: 30 min; injection valve temperature: 100°C; transfer line temperature: 120°C; needle temperature: 100°C; injection volume: 1.0 mL.

6. The method for analyzing n-butanol in water by headspace-gas chromatography according to claim 2, characterized in that: Gas chromatograph conditions were: inlet temperature: 200°C; detector temperature: 230°C; Column program: initial temperature 50°C, hold for 4 min; increase temperature to 80°C at 10°C / min; increase temperature to 200°C at 30°C / min.

7. The method for analyzing n-butanol in water by headspace-gas chromatography according to claim 6, characterized in that: Carrier gas: N2, constant pressure mode, column head pressure 48.6kPa; hydrogen flow rate: 40mL / min; air flow rate: 400mL / min; tail gas flow rate: N2, 30mL / min; split injection mode, split ratio is 10:

1.

8. The method for analyzing n-butanol in water by headspace-gas chromatography according to claim 2, characterized in that: In step 4), before sample analysis, a retention time window t±3S is established, where t is the mean retention time of n-butanol at each concentration level during initial calibration, and S is the standard deviation of the retention time of n-butanol at each concentration level during initial calibration.

Images