Determination of fatty aldehydes by dispersive liquid-liquid microextraction with low-viscosity hydrophobic deep eutectic solvents coupled with high performance liquid chromatography

Abstract

The invention discloses a method for determining fatty aldehydes by liquid-liquid microextraction of a low-viscosity hydrophobic deep eutectic solvent dispersion liquid-liquid microextraction HPLC, and its specific process is: under acidic conditions, 2,4-dinitrophenylhydrazine solution is added to water environment sample to be measured, fatty aldehyde and 2,4-dinitrophenylhydrazine derivatization reaction in water environment sample to be measured generate phenylhydrazone, using low-viscosity hydrophobic deep eutectic solvent as the extractant for liquid-liquid microextraction, phenylhydrazone in reaction solution is separated and enriched, phenylhydrazone in extraction phase is analyzed and detected by high-performance liquid chromatography, fatty aldehydes in water environment sample to be measured are indirectly detected, the low-viscosity hydrophobic deep eutectic solvent includes a hydrogen bond acceptor and a hydrogen bond donor, wherein the hydrogen bond acceptor is thymol, and the hydrogen bond donor is hexafluoroisopropanol. The present invention has the advantages of fast detection, simple operation, high sensitivity, low cost and environmental protection.

Description

Technical Field

[0001] The present invention belongs to the technical field of water environment sample analysis, and particularly relates to a method for determining fatty aldehydes by low-viscosity hydrophobic deep eutectic solvent dispersed liquid-liquid microextraction-high performance liquid chromatography. Background Art

[0002] Aliphatic aldehydes are ubiquitous in our daily lives. For example, gaseous aldehydes from industrial and automotive exhaust emissions fall to the ground with rainwater and enter environmental water bodies through surface runoff. During tap water disinfection, the use of chlorine substitutes such as ozone, chloramines, and chlorine dioxide produces a range of disinfection byproducts, including low-molecular-weight aliphatic aldehydes. Long-term exposure to aldehydes has been shown to affect human health and increase the risk of cancer. Therefore, a simple, rapid, and sensitive method for the determination of aliphatic aldehydes is needed.

[0003] Currently, common methods for detecting fatty aldehydes include gas chromatography, gas chromatography-mass spectrometry, high-performance liquid chromatography, and liquid chromatography-mass spectrometry. High-performance liquid chromatography is the most widely used method due to its high sensitivity and low cost. However, due to the complex matrix and low analyte content, sample separation and enrichment are required before instrumental testing.

[0004] Dispersive liquid-liquid microextraction (DL-ME) is widely used due to its advantages, including short extraction time, high enrichment multiples, simple operation, and low solvent usage. Commonly used extractants for DL-ME include chlorine-containing reagents such as chloroform, carbon tetrachloride, and carbon dichloride, which do not meet the requirements of green analytical chemistry. Therefore, the selection of a green extractant remains a key factor in DL-ME.

[0005] A deep eutectic solvent is a low-melting mixture of two or more compounds formed by hydrogen bonding in a certain stoichiometric ratio. It is usually liquid in the temperature range below 100°C. Deep eutectic solvents have the characteristics of simple preparation, low price, high atomic utilization rate and good biocompatibility. In recent years, they have been widely used as green solvents in dispersive liquid-liquid microextraction, effectively overcoming the shortcomings of traditional dispersive liquid-liquid microextraction using toxic organic solvents. Most of the low eutectic solvents reported so far are hydrophilic, and due to the formation of hydrogen bonds, the viscosity is also relatively high, which is not conducive to their use in aqueous environmental samples. Therefore, it is necessary to prepare low-viscosity hydrophobic deep eutectic solvents to expand their application in the separation and enrichment of pollutants in aqueous environmental samples. Summary of the Invention

[0006] The technical problem solved by the present invention is to provide a method for determining fatty aldehydes by low-viscosity hydrophobic deep eutectic solvent dispersive liquid-liquid microextraction-high performance liquid chromatography, which is simple to operate, fast to detect, low in cost, highly sensitive and environmentally friendly.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solution, which is a method for determining fatty aldehydes by dispersive liquid-liquid microextraction-high performance liquid chromatography using a low-viscosity hydrophobic deep eutectic solvent. The method is characterized in that the specific process is: under acidic conditions, 2,4-dinitrophenylhydrazine is added to a water environment sample to be tested, the fatty aldehyde in the water environment sample to be tested reacts with 2,4-dinitrophenylhydrazine for derivatization to generate phenylhydrazone, the low-viscosity hydrophobic deep eutectic solvent is used as an extractant for dispersive liquid-liquid microextraction, the phenylhydrazone in the reaction solution is separated and enriched, the phenylhydrazone in the extract phase is analyzed and detected by high-performance liquid chromatography, and the fatty aldehydes in the water environment sample to be tested are indirectly detected. The low-viscosity hydrophobic deep eutectic solvent includes a hydrogen bond acceptor and a hydrogen bond donor, wherein the hydrogen bond acceptor is thymol, the hydrogen bond donor is hexafluoroisopropanol, and the molar ratio of the hydrogen bond acceptor to the hydrogen bond donor is 1:1 to 1:5.

[0008] The method for determining fatty aldehydes by low-viscosity hydrophobic deep eutectic solvent dispersive liquid-liquid microextraction-high performance liquid chromatography of the present invention is characterized by the following specific steps:

[0009] Step S1: 5 mL of the prepared mixed standard solution containing fatty aldehydes was placed in a centrifuge tube, the pH was adjusted to 3.0, and the solution was placed in a 40°C water bath. 500 μL of a 2 g / L 2,4-dinitrophenylhydrazine solution was then added for a derivatization reaction for 15 minutes. A mixture of 100 μL of a low-viscosity hydrophobic deep eutectic solvent and 0.8 mL of acetonitrile was then injected, and the solution was centrifuged at 3000 rpm for 1 minute. The extract at the bottom of the centrifuge tube was aspirated with a microinjection needle for high-performance liquid chromatography analysis and determination, and a standard curve of the fatty aldehyde concentration versus the chromatogram peak area was plotted;

[0010] Step S2: Place 5 mL of the pretreated water environment sample to be tested in a centrifuge tube, adjust the pH to 3.0, and place it in a 40°C water bath. Then, add 500 μL of 2 g / L 2,4-dinitrophenylhydrazine solution for derivatization reaction for 15 minutes, and then inject 100 μL of a mixture of a low-viscosity hydrophobic low eutectic solvent and 0.8 mL of acetonitrile. Centrifuge at a centrifugal speed of 3000 rpm for 1 minute, and use a microinjection needle to aspirate the extraction phase at the bottom of the centrifuge tube for high-performance liquid chromatography analysis and determination. Compare the chromatogram of the water environment sample to be tested with the chromatogram of the standard working solution to achieve qualitative detection of fatty aldehydes in the water environment sample to be tested, and then quantitatively detect fatty aldehydes in the water environment sample to be tested based on the peak area of the chromatogram of the water environment sample to be tested and the standard curve of the chromatogram peak area corresponding to the fatty aldehyde concentration.

[0011] It is further defined that the fatty aldehyde is one or more of formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, valeraldehyde, hexanal or heptanal.

[0012] It is further defined that the water environment sample to be tested is drinking water or an alcoholic beverage.

[0013] It is further defined that the drinking water includes groundwater samples and tap water samples, and the pretreatment process of the drinking water is to filter the drinking water samples using a 0.45μm nylon water filter membrane and store them in the dark at 4°C for future use.

[0014] It is further defined that the alcoholic beverages include beer and alcoholic beverages, and the pretreatment process of the alcoholic beverages is to ultrasonically degas the water sample of the alcoholic beverage, dilute it with ultrapure water, and then filter it using a 0.45μm nylon water filter membrane, and store it in the dark at 4°C for future use.

[0015] It is further specified that the chromatographic column model used in the high performance liquid chromatograph in the high performance liquid chromatography analysis is an Agilent ZORBAX Eclipse XDB-C18 liquid chromatography column with a specification of 250 mm × 4.6 mm and a particle size of 5 μm. The column temperature is 30°C, the mobile phase is a mixture of acetonitrile and water in a volume ratio of 80:20, the flow rate is 1.0 mL / min, the injection volume is 20 μL, and the detection wavelength is 360 nm.

[0016] Compared with the existing technology, the present invention designs and synthesizes a new type of low-viscosity hydrophobic deep eutectic solvent, which is used as the extraction agent for dispersed liquid-liquid microextraction. After extraction, no dilution with an organic solvent is required and it can be directly analyzed and measured by instruments. This method has the advantages of rapid detection, simple operation, high sensitivity, low cost and environmental protection. DETAILED DESCRIPTION

[0017] The above contents of the present invention are further described in detail below through examples, but this should not be understood as limiting the scope of the above subject matter of the present invention to the following examples. All technologies implemented based on the above contents of the present invention fall within the scope of the present invention.

[0018] Example 1

[0019] Detection of fatty aldehydes in drinking water

[0020] 1.1 Main instruments and reagents

[0021] A Waters high-performance liquid chromatograph was used, equipped with a model 1525 pump, a model 1500 column oven, and a model 2998 photodiode array detector. The instrument used a ZORBAX Eclipse XDB-C18 liquid chromatography column (250 mm × 4.6 mm, particle size 5 μm) and a Sepax GP-C18 guard column (4.0 mm × 10 mm, particle size 5 μm). The mobile phase consisted of acetonitrile / water (80 / 20, v / v) at a flow rate of 1.0 mL / min. The column temperature was 30°C, the injection volume was 20 μL, and the detection wavelength was 360 nm. An analytical balance was also used.

[0022] The standard stock solution of fatty aldehydes (5 g / L) was sealed and stored in a refrigerator at 4°C away from light. 2,4-Dinitrophenylhydrazine was recrystallized in acetonitrile before use to prepare a 2 g / L acetonitrile stock solution. Ultrapure water was used in the experiments.

[0023] 1.2 Preparation of low-viscosity hydrophobic deep eutectic solvent

[0024] Thymol is used as a hydrogen bond acceptor and hexafluoroisopropanol is used as a hydrogen bond donor. The hydrogen bond acceptor and the hydrogen bond donor are placed in a round-bottom flask at a certain molar ratio (1:1, 1:2, 1:3, 1:4 or 1:5), and then placed in a water bath and stirred at a constant temperature of 30°C for 20 minutes to obtain a uniform, clear, transparent solution, namely a low-viscosity hydrophobic deep eutectic solvent.

[0025] 1.3 Sample pretreatment

[0026] The drinking water samples were filtered using a 0.45 μm nylon water filter membrane and then stored at 4°C in the dark until use.

[0027] 1.4 Standard curve drawing

[0028] 5 mL of a prepared mixed standard solution containing seven fatty aldehydes was placed in a centrifuge tube, adjusted to pH 3.0, and placed in a 40°C water bath. 500 μL of a 2 g / L 2,4-dinitrophenylhydrazine solution was then added for derivatization for 15 minutes. A mixture of 100 μL of a low-viscosity hydrophobic deep eutectic solvent and 0.8 mL of acetonitrile was then rapidly injected into the solution. The mixture was then centrifuged at 3000 rpm for 1 minute. The extract at the bottom of the centrifuge tube was aspirated with a microinjection needle for HPLC analysis. A standard curve was plotted comparing the concentrations of the seven fatty aldehydes against the peak areas of the chromatograms. The analytical performance of the method is summarized in Table 1.

[0029] Table 1 Analytical performance of the method

[0030]

[0031] 1.5 Determination of fatty aldehydes in drinking water

[0032] A 5 mL sample of pretreated drinking water was placed in a centrifuge tube, adjusted to a pH of 3.0, and placed in a 40°C waterbath. Derivatization was then carried out with 500 μL of a 2 g / L 2,4-dinitrophenylhydrazine solution for 15 minutes. A mixture of 100 μL of a low-viscosity, hydrophobic deep eutectic solvent and 0.8 mL of acetonitrile was then rapidly injected into the sample. The sample was centrifuged at 3000 rpm for 1 minute, and the extract at the bottom of the tube was aspirated with a microinjection syringe for high-performance liquid chromatography (HPLC). The presence of fatty aldehydes in the sample was determined by comparing the chromatogram of the sample to that of the standard working solution. The concentration of fatty aldehydes in the sample was then determined based on the peak area of the sample chromatogram and a calibration curve comparing peak area to concentration. Spike recovery rates for this method ranged from 92.3% to 104.8%, with relative standard deviations ranging from 0.4% to 5.6%.

[0033] Example 2

[0034] Determination of fatty aldehydes in alcoholic beverages

[0035] 2.1 Sample pretreatment

[0036] After ultrasonic degassing, dilute with appropriate amount of ultrapure water, filter with 0.45 μm nylon water filter membrane, and store in the dark at 4 °C until use.

[0037] 2.2 Determination of fatty aldehydes in alcoholic beverages

[0038] A 5 mL sample of alcoholic beverage water, after pretreatment, was placed in a centrifuge tube, adjusted to pH 3.0, and placed in a 40°C water bath. Derivatization was then carried out with 500 μL of a 2 g / L 2,4-dinitrophenylhydrazine solution for 15 minutes. A mixture of 100 μL of a low-viscosity, hydrophobic deep eutectic solvent and 0.8 mL of acetonitrile was then rapidly injected into the solution. The mixture was then centrifuged at 3000 rpm for 1 minute. The extract at the bottom of the centrifuge tube was aspirated with a microinjection syringe and analyzed by high-performance liquid chromatography. The chromatogram of the sample was compared with that of the standard working solution to determine the presence of fatty aldehydes in the sample. The concentration of fatty aldehydes in the sample was then determined based on the peak area of the sample chromatogram and a calibration curve comparing fatty aldehyde concentration to peak area. The spiked recoveries of this method ranged from 89.0% to 104.8%, with relative standard deviations of 0.8% to 5.6%.

[0039] The above embodiments describe the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for illustrating the principles of the present invention. Without departing from the scope of the principles of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of protection of the present invention.

Claims

1. A method for determining fatty aldehydes by dispersive liquid-liquid microextraction with a low-viscosity hydrophobic deep eutectic solvent and high performance liquid chromatography, characterized in that The specific process is as follows: under acidic conditions, a 2,4-dinitrophenylhydrazine solution is added to a water environment sample to be tested, a fatty aldehyde in the water environment sample to be tested reacts with 2,4-dinitrophenylhydrazine to generate phenylhydrazone by derivatization, a low-viscosity hydrophobic deep eutectic solvent is used as an extractant for dispersed liquid-liquid microextraction, the phenylhydrazone in the reaction solution is separated and enriched, and the phenylhydrazone in the extract phase is analyzed and detected by high-performance liquid chromatography to indirectly detect the fatty aldehyde in the water environment sample to be tested, wherein the low-viscosity hydrophobic deep eutectic solvent includes a hydrogen bond acceptor and a hydrogen bond donor, wherein the hydrogen bond acceptor is thymol, the hydrogen bond donor is hexafluoroisopropanol, and the molar ratio of the hydrogen bond acceptor to the hydrogen bond donor is 1:1 to 1:5; The specific steps for determining fatty aldehydes are: Step S1: 5 mL of the prepared mixed standard solution containing fatty aldehydes was placed in a centrifuge tube, the pH was adjusted to 3.0, and the solution was placed in a 40°C water bath. 500 μL of a 2 g / L 2,4-dinitrophenylhydrazine solution was then added for a derivatization reaction for 15 minutes. A mixture of 100 μL of a low-viscosity hydrophobic deep eutectic solvent and 0.8 mL of acetonitrile was then injected, and the solution was centrifuged at 3000 rpm for 1 minute. The extract at the bottom of the centrifuge tube was aspirated with a microinjection needle for high-performance liquid chromatography analysis and determination, and a standard curve of the fatty aldehyde concentration versus the chromatogram peak area was plotted; Step S2: 5 mL of the pretreated water environment sample to be tested is placed in a centrifuge tube, the pH is adjusted to 3.0, and then placed in a 40°C water bath, and then 500 μL of 2 g / L 2,4-dinitrophenylhydrazine solution is added for derivatization reaction for 15 minutes, and then 100 μL of a mixture of a low-viscosity hydrophobic low eutectic solvent and 0.8 mL of acetonitrile is injected, and then centrifuged at a centrifugal speed of 3000 rpm for 1 minute. The extract phase at the bottom of the centrifuge tube is aspirated with a microinjection needle for high-performance liquid chromatography analysis and determination, and the chromatogram of the water environment sample to be tested is compared with the chromatogram of the standard working solution to achieve qualitative detection of fatty aldehydes in the water environment sample to be tested, and then the fatty aldehydes in the water environment sample to be tested are quantitatively detected according to the peak area of the chromatogram of the water environment sample to be tested and the standard curve of the chromatogram peak area corresponding to the fatty aldehyde concentration; The HPLC analysis used an Agilent ZORBAX Eclipse XDB-C18 column with a size of 250 mm × 4.6 mm and a particle size of 5 μm. The column temperature was 30° C. The mobile phase was a mixture of acetonitrile and water in a volume ratio of 80:20, the flow rate was 1.0 mL / min, the injection volume was 20 μL, and the detection wavelength was 360 nm. The fatty aldehyde is one or more of formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, valeraldehyde, hexanal or heptanal.

2. The method for determining fatty aldehydes by low-viscosity hydrophobic deep eutectic solvent dispersion liquid-liquid microextraction-high performance liquid chromatography according to claim 1, characterized in that: The water environment sample to be tested is drinking water or an alcoholic beverage.

3. The method for determining fatty aldehydes by low-viscosity hydrophobic deep eutectic solvent dispersion liquid-liquid microextraction-high performance liquid chromatography according to claim 2, characterized in that: The drinking water includes groundwater samples and tap water samples. The pretreatment process of the drinking water is to filter the drinking water samples using a 0.45 μm nylon water filter membrane and store them in the dark at 4° C. for future use.

4. The method for determining fatty aldehydes by low-viscosity hydrophobic deep eutectic solvent dispersive liquid-liquid microextraction-high performance liquid chromatography according to claim 2, characterized in that: The alcoholic beverages include beer and alcoholic beverages. The pretreatment process of the alcoholic beverages is to ultrasonically degas the water sample of the alcoholic beverage, dilute it with ultrapure water, filter it with a 0.45μm nylon water filter membrane, and store it in the dark at 4°C for future use.

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