Method for determining formaldehyde in water-based adhesive for cigarettes

Abstract

The invention discloses a method for determining formaldehyde in a water-based adhesive for cigarettes, which belongs to the technical field of formaldehyde determination, and comprises the following steps: sample pretreatment: adding a water-based adhesive to be determined into an outer tube of a direct extraction sample introduction bottle, adding water, uniformly shaking and dispersing, then adding a derivatization reagent solution, carrying out vortex uniform mixing, then carrying out ultrasonic extraction, and simultaneously carrying out formaldehyde extraction and derivatization reaction, a to-be-detected sample is directly obtained after the inner tube is pressed down; and performing liquid chromatographic analysis: directly loading the sample to be detected on a machine for sample detection. According to the method, extraction and derivatization reaction of formaldehyde in the water-based adhesive are carried out at the same time, traditional centrifugation, filtration and solution transfer are not needed, jelly emulsification generated after acetonitrile is directly added into the water-based adhesive is avoided, the use amount of toxic 2, 4-dinitrophenylhydrazine serving as a common derivatization reagent is reduced, meanwhile, complete derivatization reaction of formaldehyde is ensured, and the yield of the water-based adhesive is increased. The sample pretreatment process is simplified, and the detection efficiency is improved.

Description

Technical Field

[0001] The invention relates to a method for determining formaldehyde in water-based adhesive for cigarettes, belonging to the technical field of formaldehyde determination. Background Art

[0002] Water-based adhesives are an important auxiliary material in cigarette production, and their safety has attracted much attention. Aldehyde compounds are often used as raw materials in the synthesis of water-based adhesives, and formaldehyde will evaporate during its production and use. Formaldehyde not only irritates the human respiratory tract and nervous system, but may also cause cancer and even deformity in severe cases. It has been included in the Class I carcinogen.

[0003] At present, the main methods for determining formaldehyde are spectrophotometry, gas chromatography and high performance liquid chromatography. High performance liquid chromatography is widely used to determine formaldehyde residues in adhesives due to its advantages of simple operation and high sensitivity. When using liquid chromatography for detection, since formaldehyde itself has no luminescent group, it cannot be separated by a reverse phase chromatography column or directly detected by a UV detector. It needs to undergo a derivatization reaction to generate a highly hydrophobic derivative with a luminescent group before it can be separated and analyzed on a chromatographic column. The method using 2,4-dinitrophenylhydrazine (2,4-DNPH) as a derivatization reagent is suitable for the determination of formaldehyde in complex matrices and is currently the most commonly used derivatization method.

[0004] The tobacco industry standard YC / T 332 also uses 2,4-DNPH to derive formaldehyde. The formaldehyde in the water-based glue is first extracted by water oscillation, and the supernatant is taken by centrifugation for derivatization. The whole pre-treatment process has the disadvantages of complicated handling, large consumption of organic solvents, and large amount of toxic 2,4-DNPH. The literature (Direct derivatization / HPLC analysis of carbonyl compounds in water-based adhesives [J]. Journal of Analysis and Testing, 2011, 30 (12): 1412-8) reported that the direct derivatization method used is prone to forming a colloidal emulsion after acetonitrile is directly added to the water-based adhesive, and cannot fully extract the formaldehyde in the water-based adhesive. Summary of the invention

[0005] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a method for determining formaldehyde in water-based glue for cigarettes, which simplifies the sample pretreatment process, improves the detection efficiency, and solves the problems of complicated sample pretreatment process, large amount of toxic reagents and incomplete formaldehyde extraction in water-based glue.

[0006] In order to solve the above technical problems, the present invention is implemented by adopting the following technical solutions: The present invention provides a method for determining formaldehyde in water-based adhesive for cigarettes, comprising: Solution preparation: Prepare formaldehyde-2,4-dinitrophenylhydrazone standard stock solution; Sample pretreatment: add the water-based glue to be tested into the outer tube of the direct extraction injection bottle, add water to shake and disperse, then add the derivatization reagent solution, vortex mix, then perform ultrasonic extraction to simultaneously extract formaldehyde and derivatize, press down the inner tube to directly obtain the sample to be tested; Liquid chromatography analysis: directly load the sample to be tested on the machine; Qualitative and quantitative analysis: Dilute the formaldehyde-2,4-dinitrophenylhydrazone standard stock solution into standard working solutions of different concentrations for sample analysis, establish a linear regression equation for peak area and concentration, directly measure the concentration based on the linear regression equation, and calculate the mass fraction of formaldehyde in the sample to be tested.

[0007] Furthermore, the solution configuration includes: Weigh 5.0 mg of formaldehyde-2,4-dinitrophenylhydrazone, dissolve it in acetonitrile and dilute it to a 100 mL volumetric flask to prepare a standard stock solution with a concentration of 50 mg / mL; Pipette 2.0 mL of the standard stock solution into a 10 mL volumetric flask and dilute to volume with acetonitrile to prepare a formaldehyde-2,4-dinitrophenylhydrazone standard stock solution with a concentration of 10 mg / mL.

[0008] Furthermore, the sample pre-treatment includes: Weigh 0.01 g of water-based glue into the outer tube of the direct extraction injection bottle, measure 150 μL of water and add it to the outer tube, then add the derivatization reagent dinitrophenylhydrazine acetonitrile solution, fix the inner tube with the filter screen plate at the mouth of the outer tube, vortex for 10 seconds, perform 350W ultrasonic extraction, and press down the inner tube. The extract is filtered through the screen plate and then enters the inner tube to obtain the sample to be tested.

[0009] Furthermore, the ultrasonic extraction time is 20 to 40 minutes.

[0010] Furthermore, the preparation of the derivatization reagent dinitrophenylhydrazine acetonitrile solution includes: taking 2,4-dinitrophenylhydrazine in a beaker, adding phosphoric acid, dissolving it with acetonitrile and fixing the volume to obtain a dinitrophenylhydrazine acetonitrile solution.

[0011] Furthermore, the concentration of 2,4-dinitrophenylhydrazine in the dinitrophenylhydrazine acetonitrile solution is 100 μg / mL.

[0012] Furthermore, the volume content of the phosphoric acid in the dinitrophenylhydrazine acetonitrile solution is 0.6% to 0.8%.

[0013] Furthermore, in the liquid chromatography analysis, the liquid chromatography conditions are: C18 liquid chromatography column, 250 mm×4.6 mm×5 μm; The injection volume was 10 μL, the column temperature was 30°C, the flow rate was 1.0 mL / min, the mobile phase was water / methanol, the UV detector was used, and the detection wavelength was 365 nm.

[0014] Furthermore, in the qualitative and quantitative analysis, the formaldehyde-2,4-dinitrophenylhydrazone standard stock solution is diluted into standard working solutions of different concentrations for sampling and analysis, and a linear regression equation of peak area and concentration is established, including: The formaldehyde-2,4-dinitrophenylhydrazone standard stock solution was transferred and diluted with acetonitrile to prepare five formaldehyde standard working solutions with different concentrations for sample injection and analysis, and a linear regression equation of peak area and concentration was established.

[0015] Furthermore, the formaldehyde-2,4-dinitrophenylhydrazone standard stock solution is taken and diluted with acetonitrile to form five formaldehyde standard working solutions with different concentrations for sample injection and analysis, and a linear regression equation of peak area and concentration is established, including: Pipette 50.0μL, 100.0μL, 250.0μL, 400.0μL, and 500.0μL of the standard solution into a 10mL volumetric flask, and dilute with acetonitrile to five formaldehyde concentrations of 0.007μg / mL, 0.014μg / mL, 0.036μg / mL, 0.057μg / mL, and 0.071μg / mL.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The invention avoids the emulsification of colloid generated after acetonitrile is directly added to the water-based glue, and is conducive to reducing the dosage of the commonly used derivatization reagent toxic 2,4-dinitrophenylhydrazine while ensuring the complete derivatization reaction of formaldehyde. The working curve established by using the formaldehyde standard working solution can be directly measured on the sample to be tested. The entire pretreatment and sampling process are carried out in the direct sampling bottle, and there is no need to extract formaldehyde separately and then carry out the derivatization reaction, thus avoiding centrifugation, filtration and solution transfer. The entire pretreatment step is simplified, the detection efficiency is improved, and the problems of complicated sample pretreatment process, large dosage of toxic reagents and incomplete formaldehyde extraction in the water-based glue are solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a flow chart of a method for determining formaldehyde in water-based adhesive for cigarettes provided by an embodiment of the present invention; Figure 2 This is a flow chart of the use of a direct extraction sampling bottle structure in a method for determining formaldehyde in a water-based adhesive for cigarettes provided by an embodiment of the present invention; Figure 3 It is a schematic diagram of the effect of the derivatization extraction time on the peak area of ​​the formaldehyde phenylhydrazone analyte in a method for determining formaldehyde in a water-based adhesive for cigarettes provided by an embodiment of the present invention; Figure 4 It is a schematic diagram of the effect of the derivatization extraction temperature on the formaldehyde phenylhydrazone peak area in a method for determining formaldehyde in a water-based adhesive for cigarettes provided in an embodiment of the present invention; Figure 5It is a schematic diagram of the effect of phosphoric acid content on the formaldehyde phenylhydrazone peak area in a method for determining formaldehyde in a water-based adhesive for cigarettes provided in an embodiment of the present invention; Figure 6 It is a schematic diagram of the effect of 2,4-dinitrophenylhydrazine concentration on the formaldehyde phenylhydrazone peak area in a method for determining formaldehyde in a water-based adhesive for cigarettes provided in an embodiment of the present invention; Figure 7 It is a chromatogram of an extract and a 0.5 μg / mL formaldehyde-phenylhydrazone solution in a method for determining formaldehyde in a water-based glue for cigarettes provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0018] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present invention. Example

[0019] like Figure 1 As shown, a method for determining formaldehyde in water-based adhesive for cigarettes comprises: Solution configuration: Prepare the standard stock solution of formaldehyde-2,4-dinitrophenylhydrazone, specifically: Weigh 5.0 mg of formaldehyde-2,4-dinitrophenylhydrazone, dissolve it in acetonitrile and dilute it to a 100 mL volumetric flask to prepare a standard stock solution with a concentration of 50 mg / mL; Pipette 2.0 mL of the standard stock solution into a 10 mL volumetric flask and dilute to volume with acetonitrile to prepare a formaldehyde-2,4-dinitrophenylhydrazone standard stock solution with a concentration of 10 mg / mL.

[0020] Sample preparation: Add the water-based glue to be tested into the direct extraction injection bottle, add water and shake to disperse, then add the derivatization reagent solution, vortex mix and then perform ultrasonic extraction to obtain the sample to be tested. Specifically: Take 2,4-dinitrophenylhydrazine in a beaker, add phosphoric acid, dissolve it in acetonitrile and make up to volume to obtain a dinitrophenylhydrazine acetonitrile solution; like Figure 2 As shown, 0.01 g of water-based glue was weighed into the outer tube a of the direct extraction injection bottle, 150 μL of water was measured and added to the outer tube a, and then the derivatization reagent dinitrophenylhydrazine acetonitrile solution was added; Fix the inner tube b with the filter screen plate at the mouth of the outer tube, vortex for 10 seconds, perform 350W ultrasonic extraction, and then press down the inner tube b. The extract passes through the screen plate and is filtered before entering the inner tube b to obtain the sample to be tested. The ultrasonic extraction time is 20-40 min; like Figure 3As shown in the figure, at 10-30 min, the formaldehyde phenylhydrazone content extracted by derivatization increased; at 30-50 min, the formaldehyde phenylhydrazone peak area decreased a little, which may be because the ultrasonic extraction time was too long, resulting in a serious matrix effect, and the detected formaldehyde phenylhydrazone peak area decreased a little; as shown in the figure, the formaldehyde phenylhydrazone content increased at 10-30 min; at 30-50 min, the formaldehyde phenylhydrazone peak area decreased a little, which may be because the ultrasonic extraction time was too long, resulting in a serious matrix effect, and the detected formaldehyde phenylhydrazone peak area decreased a little; Figure 4 As shown in the figure, at 20-30℃, the derivatization extraction was complete, and the formaldehyde phenylhydrazone content detection value did not change much; when the temperature was subsequently increased, the formaldehyde phenylhydrazone peak area decreased a little, which may be because the ultrasonic extraction temperature was too high, resulting in a serious matrix effect; Therefore, in this embodiment, the ultrasonic extraction was carried out at room temperature for 30 min; The volume content of phosphoric acid in the dinitrophenylhydrazine acetonitrile solution is 0.6% to 0.8%; If the acidity of the acidic derivatization reagent is too low, the carbonyl group cannot be fully protonated, resulting in incomplete derivatization; if the acidity is too high, 2,4-dinitrophenylhydrazine is easy to form salts, resulting in precipitation, inhibiting the derivatization reaction. Prepare 2,4-dinitrophenylhydrazine solutions with phosphoric acid ratios of 0.1%, 0.3%, 0.5%, 0.7%, 0.9%, and 1.1%, respectively, for derivatization extraction and liquid chromatography determination, such as Figure 5 As shown, the phosphoric acid ratio reaches 0.7% and the peak area is the largest; Therefore, the phosphoric acid ratio in this embodiment is 0.7%; Referring to the YC / T 332 standard, 2,4-dinitrophenylhydrazine solutions with concentrations of 10 μg / mL, 20 μg / mL, 50 μg / mL, 100 μg / mL, and 200 μg / mL were prepared, and the phosphoric acid ratio was 0.7%, and the derivatization extraction reaction was carried out, such as Figure 6 As shown, with the increase of 2,4-dinitrophenylhydrazine concentration, the peak area of ​​formaldehyde phenylhydrazone analyte detected by HPLC increases. After the concentration reaches 50 μg / mL, the peak area no longer increases. In order to ensure complete derivatization and extraction of the actual sample, the concentration of the derivatization reagent selected in this embodiment is 100 μg / mL.

[0021] Liquid chromatography analysis: Place the sample to be tested directly on the machine for testing. Specifically: The liquid chromatography conditions were as follows: the chromatographic column model was Acclaim Explosive E2 column, 250 mm × 4.6 mm × 5 μm, Thermo Fisher Scientific, USA; The injection volume was 10 μL, the column temperature was 30 °C, the flow rate was 1.0 mL / min, and the detection wavelength was 365 nm using a UV detector; like Figure 2 As shown, using a water / methanol mobile phase as the extraction solution, the derivative product formaldehyde-phenylhydrazone was well separated from the matrix within 30 minutes.

[0022] Qualitative and quantitative analysis: The formaldehyde-2,4-dinitrophenylhydrazone standard stock solution was diluted into standard working solutions of different concentrations for sample analysis, and a linear regression equation of peak area and concentration was established. After the concentration was directly measured according to the linear regression equation, the mass fraction of formaldehyde in the sample to be tested was calculated. Specifically: Pipette 50.0μL, 100.0μL, 250.0μL, 400.0μL, and 500.0μL of formaldehyde-2,4-dinitrophenylhydrazone standard stock solution into a 10mL volumetric flask, dilute with acetonitrile to five standard working solutions with formaldehyde concentrations of 0.007μg / mL, 0.014μg / mL, 0.036μg / mL, 0.057μg / mL, and 0.071μg / mL, respectively, and inject and analyze. Establish a linear regression equation for peak area and concentration. The corresponding linear equation is: y= 340.2016 x+ 0.0488; in: y Indicates the detected formaldehyde peak area, x Indicates the concentration of the substance to be detected; Verify the working curve of formaldehyde peak area and concentration, the results are shown in Table 1:

[0023] Table 1 As shown in Table 1, the analytes have a good linear relationship in a wide concentration range. The detection limit (LOD) and quantification limit (LOQ) were calculated according to the signal-to-noise ratio (S / N) = 3 and 10, respectively. The quantification limit (LOQ) of formaldehyde is ≤1.4 mg / kg, which can meet the actual detection requirements of the tobacco industry and water-based glue manufacturers.

[0024] Accurately weigh 0.01 g of the first water-based glue to be tested into the outer tube of the direct extraction injection bottle, wherein a low concentration of formaldehyde phenylhydrazone is added to the first water-based glue to be tested; Accurately measure 150 μL of water and add it to the outer tube of the direct extraction injection bottle, then add 300 μL of the acidic derivatization reagent dinitrophenylhydrazine acetonitrile solution, fix the inner tube of the direct extraction injection bottle with a filter frit plate to the mouth of the outer tube, vortex for 10 seconds, then perform ultrasonic extraction at 350 W for 30 min at room temperature, press down the inner tube, and the extract will be filtered through the frit plate and enter the inner tube to obtain the sample to be tested, and directly put the sample to be tested on the machine for testing; Accurately weigh 0.01 g of the second water-based glue to be tested into the outer tube of the direct extraction injection bottle, wherein the second water-based glue to be tested is added with a medium concentration of formaldehyde phenylhydrazone; Accurately measure 150 μL of water and add it to the outer tube of the direct extraction injection bottle, then add 300 μL of the acidic derivatization reagent dinitrophenylhydrazine acetonitrile solution, fix the inner tube of the direct extraction injection bottle with a filter frit plate to the mouth of the outer tube, vortex for 10 seconds, then perform ultrasonic extraction at 350 W for 30 min at room temperature, press down the inner tube, and the extract will be filtered through the frit plate and enter the inner tube to obtain the sample to be tested, and directly put the sample to be tested on the machine for testing; Accurately weigh 0.01 g of the third water-based glue to be tested into the outer tube of the direct extraction injection bottle, wherein the third water-based glue to be tested is added with a high concentration of formaldehyde phenylhydrazone; Accurately measure 150 μL of water and add it to the outer tube of the direct extraction injection bottle, then add 300 μL of the acidic derivatization reagent dinitrophenylhydrazine acetonitrile solution, fix the inner tube of the direct extraction injection bottle with a filter frit plate to the mouth of the outer tube, vortex for 10 seconds, then perform ultrasonic extraction at 350 W for 30 min at room temperature, press down the inner tube, and the extract will be filtered through the frit plate and enter the inner tube to obtain the sample to be tested, and directly put the sample to be tested on the machine for testing; The number of parallel determinations for each spike level was 6, and the recovery and relative standard deviation (RSD) were calculated. The results are shown in Table 2:

[0025] Table 2 As shown in Table 2, the average recovery rate of the spiked method proposed in this embodiment is 93.3%~96.7%, and RSD≤3.4%, which can meet the needs of formaldehyde determination in actual water-based glue samples. The method is accurate and reliable.

[0026] In order to demonstrate the superiority of the method proposed in this example, water-based adhesive samples 1#, 2#, and 3# were taken and measured by the existing standard YC / T 332 solvent extraction filtration method and the method proposed in this example, respectively. The results are shown in Table 3:

[0027] Table 3 As can be seen from Table 3, the RSD of the detection results of the method proposed in this embodiment and the current tobacco industry standard method solvent extraction filtration method is ≤3.0%, and the measurement results of the two are consistent. The results of this method are accurate and reliable. In addition, the method proposed in this embodiment reduces the amount of toxic 2,4-dinitrophenylhydrazine commonly used derivatization reagents while ensuring the complete derivatization reaction of formaldehyde, thereby simplifying the sample pretreatment process and improving the detection efficiency.

[0028] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for determining formaldehyde in water-based adhesive for cigarettes, characterized in that: include: Solution preparation: Prepare formaldehyde-2,4-dinitrophenylhydrazone standard stock solution; Sample pretreatment: add the water-based glue to be tested into the outer tube of the direct extraction injection bottle, add water to shake and disperse, then add the derivatization reagent solution, vortex mix, then perform ultrasonic extraction to simultaneously extract formaldehyde and derivatize, press down the inner tube to directly obtain the sample to be tested; Liquid chromatography analysis: directly load the sample to be tested on the machine; Qualitative and quantitative analysis: Dilute the formaldehyde-2,4-dinitrophenylhydrazone standard stock solution into standard working solutions of different concentrations for sample analysis, establish a linear regression equation for peak area and concentration, directly measure the concentration based on the linear regression equation, and calculate the mass fraction of formaldehyde in the sample to be tested.

2. The method for determining formaldehyde in water-based adhesive for cigarettes according to claim 1, characterized in that: The solution configuration comprises: Weigh 5.0 mg of formaldehyde-2,4-dinitrophenylhydrazone, dissolve it in acetonitrile and dilute it to a 100 mL volumetric flask to prepare a standard stock solution with a concentration of 50 mg / mL; Pipette 2.0 mL of the standard stock solution into a 10 mL volumetric flask and dilute to volume with acetonitrile to prepare a formaldehyde-2,4-dinitrophenylhydrazone standard stock solution with a concentration of 10 mg / mL.

3. The method for determining formaldehyde in water-based adhesive for cigarettes according to claim 1, characterized in that: The sample pretreatment comprises: Weigh 0.01 g of water-based glue into the outer tube of the direct extraction injection bottle, measure 150 μL of water and add it to the outer tube, then add the derivatization reagent dinitrophenylhydrazine acetonitrile solution, fix the inner tube with the filter screen plate at the mouth of the outer tube, vortex for 10 seconds, perform 350W ultrasonic extraction, and press down the inner tube. The extract is filtered through the screen plate and then enters the inner tube to obtain the sample to be tested.

4. The method for determining formaldehyde in water-based adhesive for cigarettes according to claim 3, characterized in that: The ultrasonic extraction time is 20 to 40 minutes.

5. The method for determining formaldehyde in water-based adhesive for cigarettes according to claim 3, characterized in that: The preparation of the derivatization reagent dinitrophenylhydrazine acetonitrile solution comprises: taking 2,4-dinitrophenylhydrazine in a beaker, adding phosphoric acid, dissolving it with acetonitrile and fixing the volume to obtain the dinitrophenylhydrazine acetonitrile solution.

6. The method for determining formaldehyde in water-based adhesive for cigarettes according to claim 5, characterized in that: The concentration of 2,4-dinitrophenylhydrazine in the dinitrophenylhydrazine acetonitrile solution is 100 μg / mL.

7. The method for determining formaldehyde in water-based adhesive for cigarettes according to claim 5, characterized in that: The volume content of the phosphoric acid in the dinitrophenylhydrazine acetonitrile solution is 0.6% to 0.8%.

8. The method for determining formaldehyde in water-based adhesive for cigarettes according to claim 1, characterized in that: In the liquid chromatography analysis, the liquid chromatography conditions are as follows: the chromatographic column is a C18 liquid chromatography column, 250 mm×4.6 mm×5 μm; The injection volume was 10 μL, the column temperature was 30°C, the flow rate was 1.0 mL / min, the mobile phase was water / methanol, the UV detector was used, and the detection wavelength was 365 nm.

9. The method for determining formaldehyde in water-based adhesive for cigarettes according to claim 1, characterized in that: In the qualitative and quantitative analysis, the formaldehyde-2,4-dinitrophenylhydrazone standard stock solution is diluted into standard working solutions of different concentrations for sampling and analysis, and a linear regression equation of peak area and concentration is established, including: The formaldehyde-2,4-dinitrophenylhydrazone standard stock solution was transferred and diluted with acetonitrile to prepare five formaldehyde standard working solutions with different concentrations for sample injection and analysis, and a linear regression equation of peak area and concentration was established.

10. The method for determining formaldehyde in water-based adhesive for cigarettes according to claim 9, characterized in that: The formaldehyde-2,4-dinitrophenylhydrazone standard stock solution is taken and diluted with acetonitrile to form five formaldehyde standard working solutions with different concentrations for sample injection and analysis, and a linear regression equation between peak area and concentration is established, including: Pipette 50.0μL, 100.0μL, 250.0μL, 400.0μL, and 500.0μL of the standard solution into a 10mL volumetric flask, and dilute with acetonitrile to five formaldehyde concentrations of 0.007μg / mL, 0.014μg / mL, 0.036μg / mL, 0.057μg / mL, and 0.071μg / mL.

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